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MG MGB GT V8 Factory Originals Technical - V8 cuts out whilst driving

The other day I was driving along in medium traffic, 2nd/3rd gear stuff really, kind of slow but moving. I flashed my lights to allow another car to pull out, and the car stalled (as if power had gone) and would not restart. Eventually she started 30 mins later after I lifted the bonnet to let cool air in and wiggled every wire I could see and tapped every item in the engine bay (very technical, but it worked!). She fired up and we were on our way. The day was warm but not hot (early evening, top up, windows down) and I'd been driving for about 40 mins.and although I was in medium traffic we were not at any point sat totally still, and the temp guage was about half way between normal and hot, but lowered right back down whenever we got some empty road to speed up on. The engine bay (after we stalled) was not overheating as such, but the whole area seemed rather too warm.

Prior to this she had simply cut out whilst I was driving (a sensation exactly like running out of petrol - no revs available all of a sudden and we drifted to a halt). She again took 30 mins of trying to restart. That time we replaced the fuel pump (original unit) as we thought this was the problem.

The car has not overheated at all since I had my fans fixed last year (one of them was sticking and not coming on). The fans were spinning away as usual when these 2 recent incidents happened, and as the temp guage was only half way to hot this was not the overheating scenario I had become familiar with in a V8 prior to my fans being fixed. Also, she doesn't overheat (burble, steam, etc.) - she just simply cuts out. It's like a power cut or something.

The battery is new and when we cut out the wipers, stereo, lights and windows all work with full power, so it doesn't seem to be a battery drain issue. Plus she fires up at full capacity after a cool down - no jump start or anything needed. She just suddenly goes from being totally dead to totally alive. When she's not starting, there is nothing except a bright ignition light when I turn the key - no chugga-chugga straining, no clicking, nothing.

Any clues? I'm getting nervous to take her anywhere, which is a shame.
Sally

dodgy ignition switch barrel?
David

I had a similar problem a few years back. It took me weeks to track it down. It turned out to be a faulty ignition relay. Apparently the coil in the relay would go open circuit when it warmed up & would come good again when the temp.reduced.HTHs Barrie E
Barrie Egerton

Sally

Do you have a Lucas distributor with points and condenser or an electronic ignition system?

What is your induction system, carburettors, Holley or SUs? Is the car fuel injected?

Anyone with power windows deserves trouble!!! Not really!

We need answers to the above questions to help. If you have a standard distributor I would guess condenser, but really need to know more.
Ian Buckley

I experienced a problem with a vapour lock in the fuel, sitting in traffic, just died, would not restart, 30 mins later started. Thought the fuel pum had gone, but was clattering away.
Ian Sanders

The car is a standard 1974 factory V8 mechanically - SU's and not fuel injected. I have some extra power draining items but to compensate have a bigger, modern day battery and uprated alternator. But this doesn't appear to be a power drain thing - lights, wipers, etc. all at 100% when I turn the ignition when we're stopped, it's just that the car won't start! The ignition light is very bright when I turn the key, not dimmed or flickering.

I had new a ignition relay when we changed the fuel pump, so I don't think it's that as the problem has occurred both before and after that was replaced. I do have an uprated alternator, but that was fitted last summer and this is a recent problem. The distributor is standard (as far as I'm aware). I don't know enough about the job of the distributor or the condenser to think it's anything to do with them. Anyone care to enlighten me?

There is absolutely no turning over of the engine once we're stopped, so I don't think it's a fuel vapour lock. It feels like a heat related problem with the ignition electrics. But why would the car just die mid travel? Surely an ignition problem would only show itself when I tried to start the car from ignition off?

Thanks for all your suggestions so far - please keep them coming! I want her in good shape for the Brighton Run in May.

Sally

I suspect the ignition Sw. It is the common factor in both your starting and stopping problems. Either that or you have two problems. One causing the stopping and one preventing turning over. I say this because the power to the starter is direct from the battery, switched by the ignition. If the engine is not turning over at all then there is either a solenoid problem or there is no actuator power from the ig. Sw. Equally a faulty Sw. could cause the cutting out. Does the ig. relay pull in Sally? Try shorting the solenoid pull in circuit to +12v. to see if it turns over (easier said than done I know). I would not describe a sudden cut out as a fuel problem as you do because fuel problems are more gradual - as the float chambers empty or the blockage comes and goes. Sudden cut outs are more likely to be electrical. These sort of problems are ******* becuse you have to wait until they occur before you can fault find - and this is often at the side of the road. And even then you don'y know if you can trust your findings as the problem might just have gone away - again. Happy hunting and keep us posted on what happens.

Ian T.
ian thomson

Sally,

I would check earth straps and wire from alternator to starter (at starter end). May be a vibration problem rather than heat but I'm sure the wires at starter pick up road salt corrosion during winter.

Paul
Paul

Ian - although the most recent time this happened it was a sudden stop (a rev dip when I flashed my lights caused me to stall), the many previous times were exactly like running out of fuel. The car would suddenly have no revs. I would stomp on the gas and there would by nothing, and we would drift to a halt, with the ignition light on but no power. This was preferable because I usually had enough juice in the system to steer and pull over to the side of the road. Once again though this was fixed by a brief rest (15 - 30 mins usually) and then we were off again.

After the first bouts of this (last Novemeber, happened 4 or 5 times in 2 days) we replaced the fuel pump, and the car didn't have this problem in 4 months (although it started having the other problem, see below). Then the exact same thing happened one more time (in March), so we replaced the fuel pump with an original unit (the previous replacement had been a compatible but not original unit and we thought maybe we had fried it). I've not had the 'running out of fuel' experience since we had the 2nd new pump fitted, but I had this thing on Saturday which, although brought on under different circumstances, had the same end result. No restarting until she's cooled down.

In addition, between Dec and March I've had basically the same thing, different circumstances. Sometimes where the car's been fine, started great, run great, and we've parked up and I've tried to start her up again soon after (ie: had to move to a different space within a few minutes) and when I've tried to restart her she's been dead. Not battery dead (lights etc. all 100%) but not turning over at all. Most times this has been fixed by just trying and trying until she suddenly wakes up, although one time a jump start did the trick (even though the battery was fully charged and powering everything but the engine ok).

It's such a difficult problem to trace, but the key factor in all these situations has been when I'm trying to restart immediately after switiching off( (or cutting out), with a warm engine. In all instances giving her time to cool down has done the trick, and it works faster with the bonnet up. It's just not always very practical!

So far we've replaced:

battery (twice)
ignition relay
fuel pump (twice)
immobiliser (I was blaming this for a while)

I'm not even sure if these 2 problems are connected, it just seems weird that although they both come about differently, the end result is the same, as is the 'fix' (albeit just until next time).
Sally

The next time it happens when driving, before you do anything with the ignition switch, clutch or gears, look at the tach and the ignition warning light.

If the tach is still registering then the problem is ignition HT or fuel. Carry a timing light with you, clip it on, and watch for flashing while you crank it. No flashing, no HT. If it is flashing, and on all leads, then it is fuel.

If removing the filler cap causes a loud 'gasp' and the car restarts straight away then either you have thre wrong cap or the vent has become blocked. You need a vented cap. But be aware that the vent has a spring-loaded valve that causes a small 'gasp', this is normal.

If the ignition warning light is on as well then you have lost the 12v supply off the white near the steering column. This could be the switch, or the multi-way plastic connector there, but I would expect problems there to be more intermittent and erratic.

If the tach has dropped to zero but the ignition warning light is *not* on, even though the motion of the car is still spinning the engine, then the problem is ignition LT. Whire wires around the fusebox, loom ballast, coil, points or wiring between. But the usual cause of stopping and not restarting for some time is the coil getting an intermittent open-circuit. With the ignition on and the points open you should have 12v both sides of the coil. With the points closed you should have 6v or so on the coil +ve (white/blue) and 0v (i.e. ground) on the coil -ve.
Paul Hunt

Crossed in the ether. V8s didn't have an ignition relay, you probably mean the starter relay. While that would account for not cranking it wouldn't account for cutting-out. Your first post I took to mean that it was cranking normally but just wouldn't fire up. Now you seem to be saying it isn't cranking at all when you try to restart. The starter motors themselves are a known issue with heat, I spent all day yesterday changing mine. Heat affects connections, and bad connections can affect the operation of the solenoid. When you turn the key to 'start' you either get the starter motor turning the engine, a loud click from the solenoid but no motor, a quieter click from the relay but no solenoid, or absolutely nothing at all. Which is it - or is it something else? Whichever, does the ignition light dim at all when you do it?
Paul Hunt

Something else that causes intermittent running problems, which mean that the cra suddenlt appears 'strangled' but comes back to life after a rest is the fule filter; this once foxed an AA Patrolman. I phoned Geoff Allen (known to many V8ers as 'The Guru') and he diagnosed the fault staright away. Maybe worth a look.
David Knowles

for 'cra suddenlt' read 'car suddenly'!
David Knowles

Sally
This is a quote from RPI if your distributor is electronic it could be the problem:-

"Lucas 'Opus system 35DE8, used 1976 through 82 With its amplifier and circuitry mounted internally this system has produced the most problems with complete failure of ignition sparks but problems normally lasts many months as the engine will normally re-start and behave again for some time. The failure is temperature related and can normally be identified by observing the rev counter because it will fail at the same instance due to loss of signal from the distributor"
Mick
Michael Black

Sally,
Way back I had an early roadster, which on it first long run(to the west country)kept cutting out, and restarting 15/20mins later-at the time I was less mechanically minded than I am now(thanks to running MG's)finaly called out the AA who found points closing/closed up- probably not your problem but I think check all the basic items first

good luck
bewdleyboy

Thanks Paul. My posts covered this, but to save you trawling through them:

- engine not turning over at all (no clicking, no thud, no anything).

- ignition light bright and steady when key is turned

I remember from last time that as soon as it happened, I looked down at the ignition light and it was lit up solidly, like it is when you turn the key but don't engage the engine, ie: to power the radio or something without starting the car. Does that help with any theories?
Sally

Ooh - thanks everyone else too! I took so long posting I missed a bunch of replies.

David, after the first day of 'running out of fuel' experiences, the fuel filter was checked and was full of gunk. We replaced it, and now I keep a spare in the car, although ever since that first change the filter has stayed clean. This is something I now look at when the car plays up, probably because I have a spare filter and have a fantasy of fixing the car myself by the side of the road!

bewdleyboy, I'm sure my MG mechanic will assure me that he's checked all the points, but perhaps another good cleaning would help.

Michael, I will look into that, thanks. Mine's a '74 so I don't think it applies, but then I really don't know what items were replaced by previous owners. The symptons certainly seem to fit.
Sally

I don't know what a factory car has for a fuel evaporative system,if any,but if the fuel tank is no longer vented properly the car will act as though it has run out of fuel(cannister plugged,lines plugged,faulty gas filler cap).I removed the cannister from my '77,thereby creating my own problem that was solved by venting the gas cap.
Dale

Factory V8 had conventional points.

OK Sally, on the face of it it looks like you have two problems. Diagnosing the non-starting should be the easiest and may well lead to the reason for cutting out as well.

The ignition switch sends 12v to the starter relay on a white/red. Check for this at the multi-plugs at the steering column as well as at the relay. The relay also needs a ground connection, check this as well. Measure the voltages with the wires connected to the relay as a voltmeter on its own will not reveal a high-resistance connection, which might be bad enough to stop the relay operating, unless the wire being tested is under load i.e. connected to the relay. If you can measure 12v between the white/red and the black when they are connected to the relay then the relay should be operated. The contacts have a brown on one side (12v unfused, so don't short it to ground!) and a white/brown to the solenoid on the other. If the relay is not connecting 12v from the brown to the white/brown (measured with respect to ground) when the white/red and black have 12v across them, the relay is bad. Make sure the spades on the relay are clean, also put your head near the relay when you turn the key (RHD remember ...) to make sure it really isn't clicking, they are quite quiet.

If the relay *is* putting out 12v on the white/brown then you are going to have to get underneath. The wiring, and there is a two-pin connector down there as well, suffers badly from water, salt and heat. BT, DT. If those are OK then the solenoid is bad, BT, DT also.
Paul Hunt

Paul
I believe Sallys non starting is it turns over but wont fire (am I right Sally )I believe you are thinking the car wont crank over
Mick
Michael Black

Michael, just 4 posts back -
>>>"My posts covered this, but to save you trawling through them:
- engine not turning over at all (no clicking, no thud, no anything)."
David

I agree with Paul that the most productive way of tackling this is through the "starter not turning" route, hoping that on the way you will come across the reason that the engine cuts out. At least that way you have something concrete and limited to look for i.e. power to the starter and solenoid. You may have to temporarily run wires into the car from the two starter connections and wait until the fault occurs. Then the presence or absence of +12v on these wires (permanently on the starter proper and only when the key is turned on the solenoid) will allow you to eliminate the starter. If the engine cutting out and the lack of cranking are from the same source then I can't see it being the starter itself as it has nothing to do with keeping the engine running. Concievably an earth/bonding problem could cause both problems, so it is worth checking them all for completeness (block to chassis, battery to chasis, gearbox to chassis - I expect Paul knows where they are better than me). An ordinary meter is not good enough for this as high starting currents can have effects which it will not pick up. Examine them physically. I know how difficult this one is as reproducing it is difficult, only occurring on the road (will it restart, can I get home - and I'm in a hurry). The worst part is probably living in London (Traffic jams and blocked junctions are not the place to cut out). Can you reproduce the symtoms without driving it - does it occur when ticking over. Am I right that you have to work on the roadside? I hate neighbours knowing that I have problems with my "silly old cars". Good Hunting.
ian thomson

Michael and everyone:

The car is NOT turning over. Not at all. It says this in my first post.
Sally

Hi Ian

Yes, it has once been reproduced by not driving it. It was at the garage, and my mechanic left the engine running to try and replicate the problem. He didn't get it to cut out, but he did swicth the ignition off and then try and restart immediately and it wouldn't (not until it had cooled down). It appears to be very much heat related, but I don't have to get it 'over-heating' hot, just quite warm.
Sally

Well, you do have two problems then, and the not starting is nothing to do with the cutting out. Therefore even if you fix the 'not cranking' problem you may well not be able to start the car, even though it is cranking, until the fault that caused it to cut out in the first place has 'repaired' itself. Someone competent with a voltmeter and a circuit diagram should be able to find the 'not starting' in a few minutes, then we can concentrate on the cutting out. I hope you are remembering to look at your tach and ignition light the next time that happens ...
Paul Hunt

It was simply a bad earth from the starter relay.
Sally

Paul, would a bad earth on the starter relay cause the cutting out? The non starting yes, but has Sally got another problem lurking? There was some question earlier about whether it was a starter or ignition relay. Can you put us right on this Sally. I can't remember if yours is a factory car or a conversion but if a conversion it could have an ig. relay. It still puzzles me as to how a relay of either type cause could cause both faults/symptoms. One symptom yes, but both?Concievably an intermittent earth _could_ cause interference with an electronic ig. system but I doubt it as they cope with the RF from the plugs etc.
ian thomson

It's a factory car. It has an electronic ignition system. The wiring is original (28 years old), and so it's not surprising that it's no longer at it's best.

The earth wire in question was shorting out in the heat, consitently after 40 mins of driving in normal London stop/go traffic. When it happened yesterday, 2 mins from my mechanic's (right on cue!) I called him and suggested that he come and check it out in it's current condition, rather than me getting her started up only for the 'mystery' to be gone by the time I reached the garage.

Whilst leaning over the engine bay to check things out by the starter relay, he realised that the earth wire was in fact live. He told me to put the key in full-on ignition position, and grounded the earth with a screwdriver, at which point the engine began to try and turn over. During the very very short (but slow) drive to the garage, the ignition light kept glowing, but plenty of revs kept her going until we got there.

He replaced the wire (well, a couple of them) and made new earth points for them. And I think that's done it. I will take her on a long, hot drive this weekend to make certain.
Sally

Good Luck. I hope it's fixed it.

I.T.
ian thomson

I spoke to soon! The car has been fine, but this morning when I went out to start it (from cold), there is no power to the engine at all. SO this time it hasn't cut out whilst driving, it's simply not letting me start it up.

First few turns of the key I hear the fuel pump clicking, then once that's done it's job I can distinctly hear something in the near right corner of the engine bay clicking as I turn the key on and off (ignition relay? starter motor?). Wiggling all of the wires around the starter relay area and then trying again to turn the key got a very brief (maybe 2 seconds) of engine-trying-to-turn noise. But then I tried and tried again and nothing happened. Have given the starter motor a good few taps and pushed all wiring connections firmly into their homes.

This time it's certainly not related to anything getting too warm as the car has not been driven.

Once again, all other power is good (wipers, windows, lights, etc.) and I can hear the key is activating something (clicking when I turn) but that something is failing. I'm suspicious that it's wiring to a unit rather than the unit itself because it's so intermittent.

Please help me crack this before the 12th!

Sally : (
Sally

Sally,

Do you have a tester? The wires can break up internally and the wire to starter can be a problem area.

Paul
Paul

I think Paul's on to it there. If wiggling the wires caused the starter to try, then it sounds like a corrosion problem either at connectors or within the insulation. Use an analog ohmmeter, the kind with the indicating needle, and long test leads, to test disconnected wires in the starting circuit end to end while shaking to see if you get changing indications. Easier said then done, I know. Maybe one of the B system experts can be more specific about where to disconnect and test.
Joe Ullman

If sally is getting a clicking in the right hand corner wont this be the starter solonoid which proves the wires to the starter it sound like a starter motor stuck to me could it be coincidence that it turned a bit after wiggling wires just my 2p worth
Mick
Michael Black

Paul, I was planning to pop to Halfords today (in my husband's Mini) and get a wire tester. The MGB Haynes manual has explained what wires are what. One wire I was suspicious of (one I wiggled before she attempted to turn over) was a greyish blue wire (could be that colour from old age, maybe it used to be white) that's insulation was worn/cut in a small place and I could see bare wires. This can't be good!

Michael, the absence of punctuation in your post made it difficult to understand but I was interested in what you had to say. Can you repost?

Another train of thought is that it could be the lumenition optronic ignition. Perhaps the LED or the optical eye is dirty?
Sally

Phew you have to watch your P&Qs here :-).what I was trying to say was. A starter circuit is a very simple circuit, power goes straight from the battery to the starter motor, via either a starter relay or if it is a prengaged motor there is a solonoid on the top that pulls in the starter gear before switching the power to the motor.the solonoid or starter relay is swiched by your ignition switch .I believe yours will be a pre engaged starter which has a solonoid mounted on the top.If the starter is jammed in the ring gear,then the battery cannot overcome the fricton in the engine and cannot turn or turns very slowly. All that you will here is the starter solonoid clicking, usualy if you rock the car in gear the starter will jump out and the car will start. If the solonoid is clicking it proves the electrical circuit and points to a faulty starter motor. I would discount anything on the distributor etc until the engine is turning over.hope that makes sense.
Mick
Michael Black

Thanks Mick! : ) That made sense.
Sally

Tried rocking the car backwards (in 4th gear, handbrake off) and nothing happened. The car is post '67 though (solenoid integral with the starter motor) so from what I've read and heard, this little trick wouldn't help in my case.

Also did a test to see if the headlights dimmed when the ignition was turned, but they didn't.

Sally

Incidentally, this time I am definitely getting a loud click (solenoid?) and a quieter click (start relay?) when I turn the key.
Sally

Sally
It souds like a starter motor fault to me. The cliking is probably the solonoid pulling in,it should make a pair of contacts on the back of the solonoid which puts power to the motor maybe these contacts are burnt.The best thing to do would be to remove the starter motor and get it tested.I know on mine that simple task would be a nightmare. the other thing would be to remove the solonoid I have manged this on mine when I had a problem. Anyway this post gets you back to the top of the list you may get some better ideas
Mick
Michael Black

Next time I have a problem I am using Sally's name. There must be a small place around here called London I can move to!!
Ian Buckley

You may have to bite the bullet on this one Sally and remove the starter motor to have it tested. See Paul Hunt's earlier posting for the horrors of doing this small job. Michael rightly called it a nightmare. Before going all the way down this route I would take a few minutes to confirm it as the problem before dismantling that manifold. Short the small connector on the solenoid (the smaller lump on the side/top of the starter) to a known good +12v - the fuse box connector would do. You will probably have to crawl underneath to get to it! If all is OK the starter should turn at normal cranking speed. If not you probably have a starter problem. If you can get the solenoid off it may be that bit easier. Solenoid mechanisms stick so that they do not actually switch the power to the starter proper. A removal and clean/oil may help.
ian thomson

This may sound silly amongst all this technical stuff but could it be that all this messing about has flattened the battery? It's a big engine to turn and if the battery is not up to scratch you will get fuel pump etc working but no turn over. I would be inclined to check before dismantling starter. Just a thought.
Martin

Sally - I've been following this thread since it started and didn't think there was anything I could say. I really can't comment on the cutting out problem but these things are usually so simple that we overlook the basics (they are nevetheless very frustrating as we all know). With regard to the failure of the car to restart after it has cut out. I once had this problem with a VW and it took ages for us to diagnose the coil overheating. I notice you say you have Lumenition. I fitted this on my factory car about seven years ago and have had no problems but I do remember that I had to fit a high performance coil at the same time. Is your coil compatible with the electonic ignition? It may be an idea to ask your tame mechanic to return to the points for a while and see if this cures it. As everyone else has said this appears to be an electrical problem and I would suspect it somewhere in the LT cicuit and not the HT.
I'll probably be shot down for this but everyone seems to be running out of ideas so I may as well throw
something else into the ring.
On subject of getting back to basics I once had a Le Mans Singer 9 which stopped on the top of the Yorkshire Moors whilst on a first date with a lady I particularly wanted to impress. After spending an hour taking the whole fuel system apart ('won't take a minute love!') a passing Samaritan diagnosed an empty fuel tank and a faulty guage. Since then I never take anything for granted. Success!
Martin

Thanks for all the posts (again)!

The update is that I was, strangely, able to start the car on Sunday by jumpstarting it. I figured "you never know..."

However, all usual battery tests on Saturday had led me to believe the battery was fine (lights full on, windows at full speed, lights not dimming when starting attempted). I didn't drive the car at all after getting it started on Sunday, so although it had no time to recharge (if it had indeed been flat), it started first time this morning (Tuesday). All very weird.

Could there simply be a lose connection from the battery? The battery itself is brand new (it has already been replaced within 6 months to make sure it wasn't causing the problem before). I'm not sure of the battery rating, but it is a single 12V and more powerful than a usual MGB battery.

Even though I have an uprated (75amp) alternator because of my rather excessive stereo, could there be some problem that the alternator is not producing enough charge for the battery to replace what's being used when I'm driving? The stereo cuts out (briefly) when I use the electric windows. I was planning to get a capacitor (car stereo kind) to rectify this problem - this stores a little charge so that when the stereo is cranked and I want to lower the windows or flash my lights or whatever, the cap releases the extra juice needed and nothing cuts out (in theory!). Perhaps I should get this fitted and see if it helps the battery situation?...

In the meantime, my Jumpstart 500 (www.machinemart.co.uk) is charging up ready, for it's new home in the boot of my MG.
Sally

Early on the question was raised, do your symptoms indicate you have one problem or two. It appears you had two and solved the one causing your car to cut out, but still have a second problem that didnít make itself apparent until the first one brought it to your attention. Your car no longer cuts out since fixing the ground or earth to your ignition relay. When your car died, you found it wouldnít start and noticed the car was hot and after cooling it would start. You also said your car wouldnít start when hot even when it hadnít died on its own. My MGB V8 does start when itís hot, but the starter can barely turn the motor over in this condition. A weaker starter wouldnít be able to turn the motor over, but may during a jump when additional current is applied. A hot motor is harder to turn over because the internal friction is increased and a cold motor is hard to start because no oil has circulated. A hot starter motor (they get very hot in these cars) will bind up some also and in the cold, the battery has less cranking capacity. This sounds like your starter is marginal and cannot handle the additional strain of turning over a hot motor when it is hot as well and is also losing its ability to turn the motor over when itís cold without additional current from a jump. One other thought is that the positive battery cable is attached to the same terminal on the starter solenoid as all the brown wires that source current for the rest of the electrical system. This could provide good current to the ignition switch, ignition relay and all the accessories that you note work well, but if the current isnít getting into the terminal due to corrosion or if the connection is broken inside the solenoid that would also prevent the starter from turning over.
George Champion

Thanks George. What kind of starter motor do you have? Is there a power output rating on those things?

I have just been out to the car, with the idea of removing the battery and charging it up overnight with the recharger I have in the house (just in case a weak battery is the problem). However, when I removed the battery bin lid, I noticed that the negative cable from the battery has a very large gash in it, with the internal wires visible. Could this be the source of the trouble I had on Sunday? Am I correct in presuming that a car will not start if the neagtive/earth cable is not properly connected? (sorry if that seems a stupid question, I'm just learning)
Sally

Side note: a 1 farad capacitor (the stereo kind) will supply 1000 watts of power for 1 second. So if you have a 500 watt stereo, it's only going to bail you out for 2 seconds at a time.

Food for thought,
Justin

p.s. Can a starter solenoid be tested while in the vehicle? Has the alternator been tested? A dead battery, a bad earth wire, power failures when using lots of accessories and a starter that won't crank when cold or hot, but can crank when being jumped... If it looks like a fish, and smells like a fish... What the hell is it?
Justin

Dodgy earth, most definately. After i converted my car to V8, had intermittant starting problems, caused by loose earth connector on battery, it was just clicking, some times would start ok though, tightened battery terminal up, fine after that.
Ian Sanders

Sally,

I have a conversion using the early Buick version of the motor and so I have a GM starter. A gash in the positive cable would be a problem because it could short. A gash in the other cable does not have that hazard, but could allow corrosion inside the cable that could lower its current carrying capacity. The starter is the most current demanding component in the car so it needs all the current it can get.

The GM solenoid can be removed so I would expect he Rover type MG solenoid could be removed for testing also, but this work is very difficult on MGB V8s because of the proximity of the exhaust. This heat also causes premature failure of the starter so a heat shield or aftermarket starter blanket would be a good idea. I clearly should get one, but have procrastinated because so far it hasnít prevented a start, just been a bit embarrassing when it looks like it may not start.
George Champion

Battery cable turned out to be fine (my apoligies - I was working by torchlight and had obviously started seeing things!) However the conenction was a bit loose and has now been firmly tightened. She's starting fine for now, but I am still getting a glowing ignition warning light if the revs are low, which cuts out the car if I don't keep the revs up. Alternator? Justin?!

The alternator is less than a year old (replaced standard one with 75amp monster), but perhaps it has reached a premature death?

Just to add insult to injury (or injury to insult in this case), the cable to the fan relay decided to pop out of place this morning as I was stuck in traffic for 15 minutes. No place to pull over, heat gauge shooting towards and ultimately past the 'H' mark... eventually pull over and, having experienced a free facial sauna courtesty of the steaming engine bay, I get splattered with explosive bright green anti-freeze and water as the radiator plug shoots off in my face. Honestly! After adding some water and replugging the fan relay, she cools off and we're on our way, but really.... Sometimes I think I'm driving 'Carrie'. Is this her way of telling me she doesn't approve of the brand new MX-5 I've ordered?.. I keep telling her it's not a replacement, just another member of the family so that she can be kept off the street in the winter. Why is she so upset?!
Sally

>>> Why is she so upset?!
Obvious! while prone to get hot under the collar in summer, the V8s rather like tooling around in the cool of winter :-) (pah - MX5 - whadda you expect?)
David

The 2200 watt stereo in my honda accord has a tendancy to eat alternators alive (and that's with dual deep cell batteries in the car.) I would be tempted to have the alternator tested. (Can be done on the car when a good battery is known to be in the car.) The battery has gone dead a few times right? If the alternator is not performing up to spec, and the battery is being forced to supply current for silly little things like SPARK PLUGS and tail lights, and what not, it's not going to last long before you physically kill the battery and it too can no longer hold a charge. This may explain why the starter is having such a hard time turning over, yet when you jump it it's fine. My last battery to die was only holding 7.5 volts of current. If I could get the car to start, the alternator would be fine keeping me going, but after about 2 days of sitting, the battery would be dead, and if I shut the car off and restarted it more then a few times during the day it would die too.


Oh I did a little research too, your mac 6 channel amp will draw 65 amps of power, so a 75 amp alternator isn't going to be sufficient to run the stereo, the crossover, the cd player, and the normal car accessories and required equipment. I would think minimum 100 amp if not even a 130 amp so you have a little head room.

Hope some of this might help, or might spark some ideas in someone elses's head,

Justin
Justin

Replaced the alternator this morning (still under warranty) and this seems to have fixed things for now. : )

Thanks for the Mac research Justin. That's an eye-opener for me (I feel stupid not figuring that one out, but this is my very first car audio experiment). It would also explain why the alt. was sufficient when I first fitted it last August but has since wound down. I will see if I can track down a larger alternator. Any clues where to get a 130amp one that would fit without too many adjustments? Or maybe I should just get a less greedy amp. That would probably be the easier route.

David, I too had a "pah!" attitude about those "fake MGB's" - until I drove the new model (2002 sports variant). Obviously it's not the pure torque thrill of a V8, or even the charm of a standard B, but I'm not shopping for an MG replacement here. Where this car shines is the handling. It is quite literally like driving a go-kart (way more so even than my husband's (original design) Mini Cooper), and having experienced that I just had to have one. This is exactly how I felt after I'd experienced driving an MGB V8 for the first time: "Here is a car that will make me happy every time I drive it!" Now there's a great reason to buy a car, whether it was built in 1974 or 2002.

If I had to chose between the two I would keep the V8, no contest. I just have to make her understand that!
Sally

Any decent 6 channel amplifier will draw at least 45 amps of power. Keep the mac and upgrade the alternator. State side the ac delco small case alternator is regularly rebuilt to 150 amp spec and best I remember, only costs around $200.00 US (£135) Finding one of those might be a bit of a stretch over there, but I don't see a reason why a bosch alternator cound't be fitted with a more tightly wound core to increase the amperage output. Before checking with stereo shops (usually more expensive) check with an alternator rebuilding shop and see what they say.

Hopefully you've got the problem beat, and a lot of other small issues have been resolved along the way!

Justin
Justin

Nice idea Justin. How easy is it to get a delco alt (150 amp rebuilt spec) in the US? I am actully going to be in Texas for a month from next week, so I'm thinking I could pick one up whilst I'm over.

Sally
Sally

Here is a company in Ohio that should be able to do it without any problems:

http://www.egrproducts.com

Things worth considering: Will the alternator bolt up in your existing alternator bracket? Will it line up?

Hope you're ready for some good ole Texas HEAT!
Justin
Justin

Been away for a few days. Permit me to differ but if the ignition lights stays at full brightness when Sally tries to start the car and all she gets is silence, a quiet click or a loud click but no cranking then it ain't the battery hence it ain't the alt. Neither is the starter jammed with the flywheel as this will dim the ignition warning light when trying to start the car. In the latter case (solenoid does click) it *could* be the starter, but the factory V8 differs from anything else in that the battery cable terminates on a stud underneath the RH toe-board together with the brown cables up to the alt and the rest of the electrics. The short cable from this stud to the starter has its own nut, so this nut, either of the lugs on the short cable, or the nut on the starter, could be making a bad connection and cause the problem. When you can reproduce the problem you need to test the voltage on the starter stud (not the cable lug). If it doesn't show 12v to begin with, or drops to zero when trying to start, it is the connections. If it is at 12v but the motor still doesn't crank then it is the motor or the solenoid contacts.

I've just had to changed mine and it wasn't as bad as I feared. I could do it quite easily without having to touch any of the exhaust (tubular manifolds, down-pipe round the back of the sump) except loosen and move the clamp on the RH manifold to make removing the heat shield easier. I did have to pull the rack to get at the top motor bolt but I believe a 1/4" drive with a long extension and possibly a UJ makes even this unnecessary.

Just a minor nit-pick but if the relay ground wire was showing 12v then it wasn't shorting out but was open-circuit, hence replacing wires/cleaning grounds fixed that particular problem. However, as someone pointed out many years ago, "Just because you have found *one* problem don't think you have found the *only* problem".

Factory V8s never had an ignition relay, but if yours has an aftermarket ignition system this could have picked up a ground from anywhere, like the one for the starter relay and may even have been the cause of this ground point failing.

Even a good alternator will stop charging (warning light comes on) if the revs drop to about 600 or less, maybe at higher revs if a very heavy load is switched on. Correct idle speed is 800, but I have mine set to about 900 so when the fans come on (high-ish electrical load) I still get a reasonable idle.
Paul Hunt

Just to close the thread:

After a fine drive on Sunday and then suddenly not being able to restart at all (except by a bump start or by shorting between the battery wire and starter motor), my Dad (a mechanic, albeit not an MG 'specialist') ran some quick tests and disgnosed the starter relay. We replaced is and everything is 100% great again. I had already had a new starter relay in March, but it obviously died before it's time.

The new alternator was needed anyway, I think I was just very unlucky and had 3 or so things all go wrong at once.

I have listed my car's audio set up to some car audio experts, one of whom has a stack of stuff in a 1960's V8 Rover, with a dynamo rather than alternator, and even he said my 75a alt. should be more than powerful enough for my system.
Sally

This thread was discussed between 29/04/2002 and 14/05/2002

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