MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Begins to Stall after 1/2 hour running?

1974 MG midget 1275CC. I am really stumped on this one and could use some help. Maybe this exact symptom has plagued someone else. The car starts and runs fine for about a half an hour, then will just cut out for no apparent reason. It acts and feels like the ignition switch was just turned off. It
M Moment

something like this comes up often

wait for someone to start a logical diagnostic by asking you a question then moving on based on your answer rather loads of scattered ideas

if you look at the Archives a read the WHOLE threads you may see this already gone through in a logical diagnostic - and many scatter approaches

I've already two guesses but I'm not the best for logical diagnostics or really have the depth of knowledge

On rereading four guesses
Nigel Atkins

I will go for a faulty ignition switch.
The internals on the steering column type tend to wear so giving the symptoms you describe, next time it happens try holding it in the on position and see if this helps or stop and try something that normaly works with the ignition on and if it doesnt work you have cracked it.
As you drive over any bumps this will jolt the key from the on position.
Give it a try, hope this helps
Rob Newt

Rob
- that's a scatter suggestion rather than logical diagnostic, it could turn out to be correct but so could one of loads of other suggestions - your a naughty boy

M
- keeping all earth and electrical connections clean secure and protected (including the battery) is always good

but

first question will be Ė when you get your problems does the rev counter, tachometer needle jitter?
Nigel Atkins

Nigal is exactly dead on.

What is the tach doing just before it dies.... its behavior will tell you if its fuel or electrical

But i still love to play .... guess what it is ?

Concidering the engine just dies instantly and no warning ...im gueswing electrical.... so im thinking 3 areas....

1. The rotor.. is it the good red one or the problem plagued black on ?

2. Is it a hairline fracture in the dissy cap thats opening up when the engine get warmed up and hot.... ive never seen this on a lucas, but had 2 fords do this.

3. Im really hoping this isnt the issue...damaged wiring harness .... naamely a cut a where it passes passes thur the fire wall... yeah this board has stories to tell...

Is the coil extremely hot when this happens ?

If it is fuel related .... the most common area that would creat this situation is the fuel cap.... its vented... if that vent in the cap is no longer funtional... it will take about 15 to 20 minutes on a half tank of fuel before the vacume has increased to over come the force of the fuel pump to deliver fuel.....

think drinking a strawbarry milkshake thur a straw haveing a big wad of strawbarry at the buttom of the cup being sucked into the straw

Let us know what the tach is doing before dieing and how hot the coil is when it dies.. and if there is a swoosh sound when you remove the gas cap the next time this happens the way you discribe it.

Prop
Prop

Just another fast thoght thats easy to look at...

Pop the dissy cap off and look at the 2 wires on the pertronix chip... right where the 2 wires go into the chip... check for a break down and cracking in the wire insallation where the wires meet the chip...if the wires are hinging at that location from the back and forth advancing of the dissy... it can create somw shorting out... but id thnk you would have other signs of this happening long before itw dieing.

Anyway just a thought to make you worry a little extra.... besides its not like you purchased a midget for the piece of mind did you ? Lol.

Prop
Prop

Well, now that you mention it, I did notice that the tach needle was swinging rather erratically before the car stopped the first time. I didn't connect the two because (a)I have seen the tach do that before without consequence and (b) I didn't notice it happening the next few times it happened. That doesn't mean it wasn't; I might have just missed it. I am at work now and have a 30 mile ride home this afternoon. I will watch the needle more closely for erratic swings on the way home. I did feel the coil when I had the series of stalling the other day and it did not feel hot, only warm. But, I have switched out the coil and the problem remains so it is likely something else (unless both are going bad -unlikely). What does the "swinging needle" point to (pun)?
Matthew
M Moment

Prop
- there's no way of stopping you from guessing -

you've covered three of my four initials guess but I've got loads more, as you will - guesses that is

until M returns with the answer to the first question a logical diagnostic can not even be started

Prop did you ever check out all the links to Jam sketches I put up
Nigel Atkins

Matthew sorry I missed your last post

unlikely it's the coil and both being faulty too

but it could be LV or HT wires to/from coil

but that just another guess until you check needle movement - check that it's swinging before we move on

plus I'm off to get some high quality real ale tonight so the more knowledgeable will hopefully take you through things
Nigel Atkins

To answer Mathew's last question, an erratic tach needle means something electrical on the LT side.
I had a hired B out a couple of weeks back and was driving along quite happily diagnosing all the faults I was going to put on the feedback form! One being the faulty tach which started bouncing around. 10 mins later, driving over some very quaint Scottish cobbled streets (not good in a B with hard Koni's!) it died! No volts from battery to power anything. Turns out it was a broken battery earth lead.

check everything!

MGmike
M McAndrew

OK, well I made it home but barely. It happened again 3-4 times on the way. First time at about the 15 mile (20 min) mark. Did not see the needle swinging. Definately not the fuel cap because it stalled out while I was running it with the cap off. Checked power on the LT pos lead to coil and had power to coil even while it wouldn't start back up. Took about ten minutes to get going again. Then it was fine for about 15 more miles then cut out again; no needle swing. Tried turning key off then back on while coasting towards side of road and it came back to life (with a small backfire). Happened again a mile later, same result, came back on with the switch on and off. Stalled as I approached my driveway and this time the key trick didn't work but it did start within a minute or so.
My real problem here is the dangerous conditions test driving is putting me in. Stalling at 60 mph on a 2-lane parkway with narrow grass shoulders with traffic behind is SCARY!
M Moment

Hi Mathew

If you think it could be the switch then simply run a live (hot) wire to the coil direct from the battery. When you do this the ignition will be live all the time so the only wy to stop the vehicle will be to disconnect this wire.

Also the earth is a good point. Whilst the main engine earth is possibly very remote (after all the starter motor works fine) I have seen on one occassion that the distributor was not clamped in a manner that earthed the dissy to the engine. This of course interups the LT circuit and will stop the engine. Again that is a little remote but one never knows.
Robert (Bob) Midget Turbo

Sorry nigal..
My laptop is on the fritz so im mainly using my smartphone.... and it wont load certiqn videos... unfortantly the ones you posted but ill have a look in a few days


M. i agree with robert... run that jumper wire and see.what happens
Prop




Prop

Prop:
Just tried pulling the car into the garage; was hard starting (unusual) so I tried the jumper from battery to coil. While it did start, I think that was coincedental as it stalled again fairly quickly I guess effectively eliminating the switch as the problem. At this point I would prefer it didn't start at all; that would be easier to diagnose!
M Moment

Prop - I think you'll like the sketches

Matthew
- I'm no, no NO expert by a million miles but you make need the two man wiggle test with multimeter to check all connections LV side - that one guy checking the meter whilst the other wiggles the wire and connections to test for intermitents breaks, probably need to do this once the car is fully warmed up as it could be the breaks occur with heat

start from what's know other this side as "the ble*ding obvious" all electrical connections - like Mike suggests starting at the battery - all connectoins being clean, secure and protected (even the battery itself being secure and not moving around)

other side is (guess work from me now) rotor, dissy cap HT leads - as it happens when warm it possibly suggests HT lead or HT lead connection affect when warm

I don't know what they're called in USA (or even over here at the moment) but the old Sun diagnotic machines that can test for faults it HT leads etc. that you'd miss with your eyes would find this

don't drive a car that puts you at risk

obviously more investigation is needed but I've got a feeling it will be something quite simply but not necesarily simple to trace
Nigel Atkins

Well i think you made alot progress today...

you determined it was electrical, its not the ignition system at the key...its not the wiring harness shorting out

i think your down to the smaller stuff.... like nigal said... when you find it, it w ill be.somethi
ng stupid... but will take some time to find

Did you look at the wires where they attach. to the pertonix chip to see if they are hinging and shorting....

another idea... put the car in a super pitch dark garage...like zero light... fire up the car and watch for the blue light show
Prop

Augh... i hate the internet... lost half my last message


So to continue

Do you have the good red rotor, the black ones are bad right out of the box.. even tho they look good.

Try re installing the points and condensor and see what that does.

Check your grounds like robert said.... they need to be manually removed for a real look... make sure that braided line from the transmission to the body is in good shape

Put on new electrical connections on your coil leads..esp on the end of the pertonix conections.... if there crimped they can come loose over time un-less your using a kline crimping tool.

Im not sure what this would look like on the tach... but i wonder if an exhaust valve is sticking.... that would take 20 minutes for the exhaust valve to heat up to start sticking. My guess is it would memic a electrical issue on the tach... esp if it was biting fast and hard.

Any way there are a few ideas to keep you busy

Prop
Prop

Next time it happens feel whether the fuel pump is hot and listen if it still rattles.
You say SU solid state, but I've never heard nor can I find an SU solid state pump. Never to old to learn though.
Alex G Matla

Yeah alex...

its those new electronic SU pumps... appeartly there a little dodgy... david debois does a great rebuild to electronic with no issues, but these china made ones are not dong the job from what i hear.... no experiance my self, but thats what ive read.

To be honest ... im not sure what the differance is between these and a faucet pump is. As i dont think the electronic / solid state pumps have diaphrams and what not.

Good catch on that... i didnt see that being posted
Prop

Prop I donít think the problem has been confirmed as definitely electrical although thatís the path weíve followed

>>put the car in a super pitch dark garage...like zero light... fire up the car and watch for the blue light show<<

quite by chance I found a faulty HT lead when I lifted the bonnet (hood) one Xmas eve night, wasnít that dark as there were street lights around, so yes it can happen, if you just happen to be looking when when it occurs

Iím surprised Prop didnít add spray with water mist !! Ė with or without water mist it still may not show up the faults thatís why I suggest the proper (Sun?) diagnostic machine
Nigel Atkins

Couldn't risk driving the car into work again this morning - too dangerous. Will have to reserve test drives to afternoons after work (or weekends) on small local roads. Took the TR6 in this AM. I will look at the following tonight when I get home:
Pertronix wires where they attach to chip as well as connectors.
Various grounds (I replaced the braided line to trans a couple years back but I'll check it anyway).
I ordered a red, "premium" rotor from Moss as well as the little ground wire for the distributor points plate, they should arrive tomorrow.
If none of the above change anything, I'll try putting the points / condensor assy back in instead of the Pertronix. I will also try touching the fuel pump to see if it is getting hot.
I will report back any results as I collect them.
M Moment

If you want know the cause - and you may not, you may just want away with the problem - but if you want to know the cause then it's replace or test one thing at a time

If you do more than one test or replacement at a time then you wont know which resovled the issue - but as I say you might not care about that

A Sun(?) type diagnostic machine may find the cause in one session

If you don't resolve the problem after going through your list then, depending on what you report back, don't dismiss the two person wiggle and mutimeter test, covering the 'ble*ding obvious' testing all relevant curcuits, wires and connections starting from the battery onwards

Loose or poor connections or cracked wires that work for a while then don't can be awkward to find - not that this is necessarily your problem

Also be aware that new parts and components can sometimes be faulty so prepare, check and test them - I've particularly known new points to play up, hateful litle things they can be
Nigel Atkins

Yes, I am familiar with the Scientific Method and I will try to follow that line as long as my patience holds out. I would feel much better knowing what the source of the problem was and, it will be more helpful to future owners whose cars develop similar symptoms. I always prefer being a mechanic to being a "parts replacer" when possible as well.
On a different thought, I occured to me in the shower this AM that this kind of problem is likely to be the beginning of a future "barn find" car. Guy loves car, car develops weird, hard to trace problem, guy gets fed up and frustrated so he sticks it in the shed for a break... the rest is history.
M Moment

>>On a different thought, I occured to me in the shower this AM that this kind of problem is likely to be the beginning of a future "barn find" car. Guy loves car, car develops weird, hard to trace problem, guy gets fed up and frustrated so he sticks it in the shed for a break... the rest is history.<<

I read about exactly this quite recently so yes it does

and an engine rebuild that found after reinstallation it was a just a blocked pipe to/from engine which is why people need to be thorough with checking before moving on to next stages

a simple test that most youngsters who had been on electronic courses failed to find when tested for general electric equipment installation - I simply took the fuse out of the power cord plug - and no one thought to test the wall power socket either

they were thinking at the next level so overlooking the basics
Nigel Atkins

Hi Matthew
Follow this link from another forum for something which sounds familiar.
http://www.oldclassiccar.co.uk/forum/phpbb/phpBB2/viewtopic.php?t=8225

John
J Street

A couple of things Mathew

I just want to describe the bad earth again as you have not recognised the problem I described. The poor earth on the occassion I saw a difficult problem was the Distributor BODY to the ENGINE BLOCK. It was not the plate to dissy although that too could be at fault.

The rotor arm could indeed be faulty but if it was the rotor arm then the Tacho would NOT be scrambled about and would be steady in unison with the engine revs.

The tacho is extremely important in finding this problem and it can not be streed that it's behaviour must be observed intently and understood.

When the low tension circuit becomes faulty (the rotor arm is part of the high tension circuit) the tacho demonstrates this perfectly by dropping to zero long before the engine stops or indeed goes bananas and fluctuates all over the place.
Robert (Bob) Midget Turbo

The flickering tachometer needle is a good guide to electrical problems, but it does need to be watched carefully and interpreted properly. The tachometer is electronic, fed off the Low Tension part of the ignition circuit, so a break down in that circuit causes the tach to switch off. The needle just drops to zero. If the fault is partial or spasmodic, the needle flickers around as the ignition impulse comes and goes. But this is quite different to a needle that either "bounces" as the car hesitates or kangeroos, or a needle that drops in line with a fall in the engine revs if the problem is with fuel or some other cause.

Prop mentions that sticking valves could make the tach needle flicker - well yes it would flicker as engine revs drop, but it isn't the same at all as the tach effectively being switched off, or off and on again.

Guy

Hey guy,

.thank you.for mentioning my comment about the sticky valve showing up in the tachy... ive been kicking that around today.... any ideas what that would look like on the tachy... i wonder if the same tach signiture would be the same for other mechanic bindings... just an interesting thought to kick around
Prop

Prop,
I really don't know. I wasn't trying to say I know better than you, just pointing out the difference that an electrical fault makes with the tachometer when it is literally switching it off. I would guess that a mechanical "stuttering" of the engine from sticking valves or fuel starvation is going to be much less instant than one caused by a LT circuit failure. But the main point is that they are not having a direct electrical effect on the tach
Guy

John

I like your link - I link directly to the Distributor Doctor site in many of my posts - http://www.distributordoctor.com/red-rotor-arms.html

but I think I've covered this under >>Also be aware that new parts and components can sometimes be faulty so prepare, check and test them<<

which I also put in many of my posts - not because I'm clever but because it's so often relevant
Nigel Atkins

As well as checking the connections on your Pertronix also check the whole length of the wire inside the distributor in case a cam lobe has chaffed the insulation and is shorting at times. I have come across this with a points setup causing the same problems you are having and the break was so small it was not immediately obvious.

Trev
T Mason

So whats the latest news ?

Prop
Prop

The new (red) rotor, distributor plate ground wire (I know Bob, body to block) and fuel filter arrived yesterday afternoon. I did not have a chance last evening to work on the Midget as I was trying to get the TR6 brake lights working again since that's what I am currently driving (I must be insane). I hope to do the Pertronix and LT wire inspection tonight and maybe start off by popping the rotor in because its the easiest. It is time to change my fuel filter and fuel hose (reg maint), so I thought I might put in a "T" fitting and connect my fuel pressure gauge just for more information while I'm test driving. I am also going to connect the "coil to bulb on seat" line so I can watch the electrical side at the same time. I need to minimize my test drives as much as possible. Stay tuned (ha-ha).
M Moment

just FYI

if the TR6 has the white brake light switch that fits just behind the pedal then 4/5 years ago I found new ones used to spring themselves apart after a short time, thing might be different now but if the stock is from around that time beware
Nigel Atkins

Nigel: Thanks, it is a white one, but some jiggling and cleaning got it working again (for now).

Just for clarification; when I connect the fuel pressure gauge, I plan to route it into cockpit so I can see if anything weird is happening with fuel pressure when symptoms start. While I do think it probably is electrical, I just don't want to blindly chase electrics until I am certain it is electrical. Might as well eliminate any doubt.
M Moment

Matthew, I wonder if this will actually eliminate doubt

You'll need another person in the car with you as you drive to watch for momentry movements of fuel pressure gauge and/or rev counter

I'm not mechanical or technical at all but to me if you have an electrical fault that stops the engine the the fuel pressure drops at the same time(?) and if the electrical fault is from key ignition or fuse or something that could also include electric power to fuel pump too(?)
Nigel Atkins

Hmmm,

dedicted 2nd car battrey and a jumper wire in the passanger seat to power the fuel pump... hahaha

Good luck.... looking forward to what happens


Prop
Prop

Took a look a the Pertronix chip last night. Prop, you'll enjoy this; the negative lead was apparently just slightly contacting the spacer ring below the rotor enough to cause some wear (see photo- click on "Image" below)on the insulation. It did not wear all the way through; but it would have eventually - good call! I cut off the connectors, slipped on a piece of heat shrink tubing, resoldered new connectors and put it all back together. I also noticed some wierd insulation "flashing" near where the wires enter the chip but no cracks; it is nice, soft wire insulation - almost rubbery. I don't believe that was the problem, but in the name of scientific method, I resisted the temptation to install the new red rotor when I buttoned it back up. I have the coil test light hooked up, the fuel line is proving to be a challenge finding a hole to pass it through in the firewall. The weather is supposed to be crappy for several straight days starting tonight so testing may be delayed. I going to shoot for a window of clear weather this afternoon if possible.

M Moment

That's not totally uncommon

usually these igniter head leads are held secure by one or two small, cable wraps (ties) but allowance has to be made for movement

and as the wires are so thin their route outside the dissy has to be considered to keep them undamaged

why not forget the fuel pressure gauge for now and come back to it if necessary
Nigel Atkins

Im not totally convinced thats the issue....i cant see any break thur on that black wire... but if it is...wow congrats and i hope that fixes it .... might be carefull soildering those chip wires.... if its to close to the chip the heat can damage them....

Now just try to avoid what id do... pinching the wire between the cap and the dissy body on re-insallation.....lol.


I really hope it works for you


Prop
Prop

What does this mean " I also noticed some wierd insulation "flashing" near where..." and where is the picture? Could be the key to all.

FRM
FR Millmore

Frm,

I think what he means by "wire flashing" is the wire insulation closest to the chip ... looks like cricket/grass hopper rear leggs... spikey/rose bush thuorny

My guess its a by product of the manufacturing process....it does it about 2 inches up on both wires

Prop
Prop

Yes, that is what I meant Prop,; sorry FRM if I wasn't clear. By flashing I meant extra areas of rubber insulation from the wire production process that can be seen (a little) in the image posted. I'll post another photo that may make it clearer (although moot).

Prop, I did not mean to give the impression that the problem had been found. As a matter of fact, after this afternoon's test drive, I know that is NOT the case. I pulled out of my driveway and stalled within a mile of my house. Now heat is not appearing to be as big a factor as once thought. In addition, the coil-power-indicator light I installed remained illuminated the entire time; even through the ten minutes it took to restart. Since I had already determined that repairing the Pertronix wires had not cured the problem, it was fair to pop in the new red rotor just to see if she would now fire right back up. No dice. Also, there was clearly fuel reaching the carbs as my fuel filter is only 3" from the front carb and fuel was clearly visable in the filter.

Carburettor float sticking closed?



M Moment

I get it, thought maybe you meant some discolouration on the wires, which could indicate arcing.
I don't see anywhere that you have checked for actual spark from the coil or plug leads when it is dead. That's the first thing I'd check. I am suspicious of the Pertronix, as this is the typical way electronic ignitions fail.

FRM
FR Millmore

Nigel addressed this possibility above when he said;

"...a simple test that most youngsters who had been on electronic courses failed to find when tested for general electric equipment installation - I simply took the fuse out of the power cord plug - and no one thought to test the wall power socket either

they were thinking at the next level so overlooking the basics."

You're right, I haven't done a spark test from the coil or plug leads when dead. First thing, next stall.
M Moment

In anticipation of the coming week of rain for my area, I just grabbed my son to go for a test drive. We got to the end of my driveway and the stalling started. While it was not re-starting, I pulled the #1 plug lead and connected it to a spark tester and had my boy crank it over; it was sparking. Then, just to do something different, I decided to pull the tops off the float bowls and take a look. Both bowls were about 1/2 to 3/4 filled with fuel. They looked very clean with only a few small particles on the bottoms which were quickly and easily sucked out with a syringe / hose tool. The floats / needles seem to be operating normally with no obvious sticking. Not sure what I going to try next. Getting frustrated.
M Moment

Check for a split diaphragm in the fuel pump. It will still pump some fuel, but not enough once you build up the revs. It will also steadily deteriorate with time so the problem will become gradually more serious.
Guy

So your getting a nice blue spark when the car is stalled and dead ?

Sorry BUT I really thought this test had been done already .

A side from the spark plugs being fouled or way WAY wrong heat range then the ignition would be in good order. Provided there is a nice blue spark at the end of the spark plug cables and the car still wont start.

Obviously we need to recheck fuel system and compression...we know it will run fine for 20 minutes minume so its not timming related

At this point im leaning heavly towards a sticking valve and im also in love with guys thinking concerning the fuel pump diaframe going bad

Prop
Prop

"So you're getting a nice blue spark when the car is stalled and dead?"

Well, I am gonna check this again periodically because this afternoon, as it was "dead" it kept alternating between starting very briefly and then dying again. Also, I used a clip-on spark tester (that's the unit clipped to the thermostat housing in photo attached). It is basically a spark plug mounted to a grounding clip but the gap is very large, I guess to verify high spark energy? The gap is like 5mm from center electrode to sidewall. I get a narrow whiteish spark with it. So I didn't know if that was a good test, maybe I'll button the carbs back up and try it again with a new plug held against the head?

The motor has miles on it but on last compression was 170,180,180,170.

I had a sticking valve once and the motor just went from running on 4 cylinders to running on 3 when that cylinder's valve stuck.

The deteriorating nature of this condition makes me interested in the pump diaphram as well. Although, the fuel filter was full today when it happened and it WAS stalling in my driveway with basically NO revs involved.

I forget, how much am I going to hate pulling the fuel pump?



M Moment

Hmmm,

It would appear that we have gotten ahead of our selfs and out of sink... do we know for a fact that it is electrical related...that needs to be the 1 st thing that needs to be established.... if not then Perhaps we need to go back to basics and try agian.

Id start with the electrical system and run the car until it dies in the shop/driveway and find out if the plugs in the head are each delivering a nice crisp electric blue spark... before hand pull each plug inspect , clean, re-gap and reinstall. After that if its still dying 20 minutes later ... put in the points and condensor and see what that does ... you always want to keep a back up set just incase.... esp with electronic ignition cause if the pertonix chip fries in bumfreak oklahoma, im betting they wont have a pertonix chip at the local autozone.

If there is no crisp sharp electric blue flashing for each of the 4 plugs...dont move on till you do. Dont test just the #1 plug.... do all 4

Once you know the sparking part is perfectly good. And no issue ...and the car is still dieing then you can move on to the ignition and wirring.

Prop
Prop

SU fuel pumps rarely if ever have bad diaphragms.
If they do gas runs out on the ground.
You say it does not act like fuel - running out of gas.
There was fuel in the carbs when you looked.
Did you hook up the pressure gauge?

It does act like electrical.
It is clearly intermittent.
one test of one plug doesn't make it.
Prop is infected with "sense virus" OMG
Use your spark checker on the coil wire and watch for drop out or intermittent sparks. Take the plugs out so you can spin the engine for a bit with no compression and without sucking fuel in and flooding it.
Any inconsistency, throw the Pertronix away.
If sparks are constant and consistent, use the spark check on each plug lead. Differences here from preceding means bad cap or rotor.
I have no idea what effect loaded vs unloaded spark has on the Pertronix, but I'd be putting points in long ago.

Re the turning the key off & on earlier. This produces odd high voltage spikes in the whole system, which could trigger the (dying) Pertronix. In fact, if the alternator is at high load when you do it, such spikes can damage electronic components like alt/reg and Ign. You will note that the episodes are on average happening at shorter intervals - "this is the typical way electronic ignitions fail" to quote myself.

FRM

FR Millmore

Viz: "check fuel pump diaphragm" sorry l had lost track (long thread) l thought it was a 1500 until the photo appeared.

But l assume you have checked it isn't just a sticking fuel pump (common su fault).
Guy

Matthew not my original posts:

>>wait for someone to start a logical diagnostic by asking you a question then moving on based on your answer rather loads of scattered ideas<<

you've been sidetracked by Prop and his guesses then even he's forgot how far and what he's guess at

Bob, guy and FRM have the more logical approaches, each with their own methodology

go back to the start of the thread and read through again and I'd suggest go back to the start of logical diagnostics

you were lead to the quick (possible) solution aprroach rather than the long but thorough problem solving approach

testing for a spark is fine but you only tested one plug there are three others and 5 HT leads and so on and so on
Nigel Atkins

sorry not is supposed to be note
Nigel Atkins

A brief break in rain this morning may allow another quick testing session. I'm going to button the carbs back up and go back out and test all the spark plugs. As far as the 5 HT leads themselves, I don't have a Sun diagnostics machine at my disposal (still looking) in the mean time, what is considered to be a reliable / dependable "home" test for them?
M Moment

This time, do take a carefull and accurate look at what the tach needle does when the fault occurs.
Guy

as Guy says tacho test first

as far as HT leads go - well I don't need to suggest cleaning them!

look at them for good condition

are they firmly seated at both ends?

look at their condition, are they brittle, pinched, scuffed - if you take them off make it one only at a time so you don't lose firing sequence

coil lead - as with other HT leads but you may need to 'burp' the coil end if the cover is tight (like burping' Tupperware, ask wife or mother)

with my present Midget I've had the coil end of a HT lead feel as if its firmly on but the vacuum of the cover had lifted under the cover so causing me starting problems - but I don't think this is common

as Prop has previously suggest you could try running the engine in the dark and see if there "a fiework display"

- but

- again you're going out of logical diagnostic orreder here

Nigel Atkins

If it stalls it and the tacho goes crazy, maybe check the power to the coil!
a.o. arnold

Much to everyoneís relief (including me), I think this thread may finally be over, at least for now.
Hereís what happened. I went back to zero. Started the car, and watched the tach. And watched the tach, and watched the tach, and watched the tach, and watched the tach. I definitely watched the tach THIS time. After about 20 minutes of watching the tach and the engine running perfectly with a steady tach needle, I had to relieve myself and only got about 5 feet from the car when it stalled. WTF? I didnít see the tach do anything.
While the car was ďdeadĒ, I checked all spark plugs for spark Ė all dead. No spark. Every one, all four. No spark.
Good opportunity to try swapping out the Pertronix for the good ĎOl original pointís set-up.
Took a while, but once all parts were exchanged, the car then ran for Ĺ hour idling in the driveway followed by a very spirited 15 minute romp through the mountain roads, followed by 15 more minutes of idling in the driveway.

No stalling.
Iím going to go out on a limb here and declare the Pertronix ignition chip the failure in this case.
Time will tell.
This has gone on so long that I donít even care what the problem was, as long as itís over. This one was draining for me as Iím sure it was for all of you.
Thank you for all your diligence and support; I promise to let you know if this turns out to NOT be the solution to a very long and winding road.
M Moment

Good news as you say time will tell

I think quite a few would have had a small bet on the igniter head or it's leads or connections

let us know if it's not

another way to test it is to put it on another car that you know is working well and see if it happens

any volunteers ???
Nigel Atkins

You can always put the electrohasslegubbin back in whenever you are bored.

Or send it back to Pertronix for tests - might give you a new one. Allison used to be very good about this, even if you told them what the DPO had done to the wiring 5 years before. (it was wired to partly include the dead Lucas electronic system, run for an unknown time, then wrecked and parked. I got it running for the new owner, but it would not go past 2000rpm, though it was perfect on starts and up to 2000. I called Allison and they said send it back, no papers, many years, new owner, and bad installation. Got a new one -FREE- in the mail in a few days and a report saying yes it was dead, unknown if the Lucas crossfeed caused it. THAT is service!!!)

"this is the typical way electronic ignitions fail" to quote myself. Again.

FRM
FR Millmore

Yes, I think a return of the unit to Pertronix is certainly worth a try.

I once receceived a brand new ($$$) fly rod from from a VERY reputable company (I think it was Sag.. something?) even after I told them that I had closed the car door on the rod tip and the wonderful young lady kept saying "What?.. I'm sorry, I didn't hear that, but I'm so sorry that our product failed during normal use... we'd be glad to send you a replacement free of charge. Needless to say, I'll never hesitate to buy a fly rod from Sage (oops, I meant "that" company) again!
M Moment

That's good news. Well done! Most solutions are simple once you have got to them. It's the getting there - especially with intermittent faults - that is difficult!
Guy

that is great news pertronix really is a good company to work with if it's not real old they probably will send you 1 the just a note if you do you keep the pertronix always keep a set of points and condenser close by you will never know when you need them

again great job, finding a random fault is tough like you mentioned its easiest if it doesn't run at all

Prop
Prop

Interesting updates:
The car has been running well without stalling for about ten days now. The other day, I discovered very much by mistake (and surprize) some voltage leaking from the distributor cap where the HT coil wire goes in. As I moved a wire around while the engine was running, I felt a few sharp ZAPS when my hand ran across the top of the dizzy cap (side mount type). Every time I touched the top of the cap near the wires - Zap! I pulled the coil wire from the cap, trimmed the end a 1/8" and reinstalled it. I think the set screw may have been cranked down too hard into the cap? I'm not sure. The situation was improved greatly although it is hard to continuously subject yourself to that potential zapping to check it. With no rubber boot to seal the wire where it enters the cap, I guess I'm not surprized it can leak there. Does anyone ever silicone those wires / holes?

As per several recommendations, I did send the PerTronix Ignitor back to them for testing. What is wierd though is that the report I got back from them was that the module tested "good". The tech guy said that it wasn't unusual, that often that will happen with the electronic modules if there is bad /weak grounds or low voltage in the system. When I told him that the car car had now been running fine for a week, he said that also was not unusual because points/condensors will often operate fine with low voltage and/or weak grounds, whereas electronic ignitions will not. I am going to continue poking around and checking for weak / bad grounds just to be sure.

Just thought I'd share.

Matthew
M Moment

Thanks for the update....might try a childs hand instead of yours... just tell them its a video game...hahaha
Prop

would not getting a new dissy cap and if required HT lead (or lead set) solve your probelem and get yor electronic unit back in

replacing dissy cap and HT leads are always on my usual advice
N Atkins

This thread was discussed between 09/05/2011 and 28/05/2011

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.