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MG Midget and Sprite Technical - Starting Problem

I would be grateful for help on a problem that has me totally baffled.

Briefly, the midget's head gasket blew between cylinders 2 and 3. I had the head checked and faced. When I tried to start the car after refitting the head, it would barely turn over, as if the battery was flat, starter jammed etc. I diagnosed a dodgy starter circuit able to cope with two cylinders but not four at full compression.

So far I have:

checked, cleaned and tightened all the connections in the starter circuit;

replaced the solenoid to starter, battery to earth and engine to earth cables and fitted another earth from the starter to earth;

swapped the battery for a known good one, which shows 12.8 volts between the terminals, fitted a new solenoid and starter.

None of these has produced any improvement. I have also tried turning the engine over with the plugs removed to try to ensure that I didn't do anything particuarly stupid like leave a rag in the bore. It turns over freely, though not with a lot of enthusiasm. When trying to start with the headlights on they dim but not, I think, excessively.

One more point to mention is that while the head was away I fitted an electric fan, but I don't see how that might effect starting, and if I disconnect it the starting problem persists.

I have now done everything I can think of or can find in the archives. Obviously I am barking up the wrong tree, or missing something obvious. Any guidance would be very much appreciated.

Cheers

Mart
Mart

Mart have you got the firing order correct?
Bob Turbo Midget England

Sounds like you've swapped absolutely everything in the starter circuit.

Are you sure the replacement starter is ok? You could take the strap off it and check the brush length. If they are worn out and only just touching the comm it will still turn over but not get the current through for proper cranking.

If you short the terminals (big screwdriver) on the solenoid does it crank any better? This bypasses the contacts in the solenoid.

Whats the battery voltage under crank? It should be 10+ if it's below then it will crank slow. If it's above this it should still be cranking ok.

You can check for dodgy starter cables. Put a multimeter on volts put lead on each end of same cable and crank. Meter will read volatge drop through the cable. It should be no more than 0.1 volts for each cable.

But if you've replaced the whole starter circuit then perhaps something else.

Timing could be advanced too far. If the engine kicks back when you stop cranking this is an indicator.

So you looked through the plug holes to make sure there wasn't a rag in there?

Got the car out of gear? :)
Greg H

I'm with Bob on this. The engine is fighting itself, so there's a timing problem.
JM Morris

Firing order is 1,3,4,2 so you might as well double check that anyway. Then check your static timing.

However, you said ---
"I have also tried turning the engine over with the plugs removed ------ It turns over freely, though not with a lot of enthusiasm"

If this is the case, then you have still either got a stater circuit issue, 2 relatively flat batteries, or some other issue preventing the engine spinning.

If it won't even spin freely with no plugs, it doesn't sound like a timing/firing order issue. --- only ---.


Lawrence Slater

Any chance you might have disconnected the ground strap...the large braided wire from the transmission to the slave cly.

Are the battery cables okay...look inside the cable .. they can look fine from the outside....look for greenish with corrsion inside the insulation

And of course... The most obvious... Are the cables tightened lol. Laugh but it happens more then you think.

Prop
Prop

Prop,

>>replaced the solenoid to starter, battery to earth and engine to earth cables and fitted another earth from the starter to earth<<
N Atkins

Thanks guys, this is all very useful advice but I think I've covered it all.

I've replaced everything except the battery to solenoid cable and I've bridged that with a jump lead.

I have cable ties on the plug leads to make sure they are in the right order, and the dizzy cap marked as well. If the firing order was out or it was a timing issue I'd expect it to turn over OK, but refuse to run. Is that right?

I've checked the cylinders through the plug holes, and cranked it and pushed it to and fro in gear with the plugs out without causing any unpleasant noises so I don't think there's any mechanical obstruction.

At the moment it just turns over very slowly in a classic flat battery way, and can't get going enough to fire, but before the head came off it started fine, though not running very well because of the HGF. So either it's the increased compression beating the starter or I've done something myself.

I've been reluctant to believe that a replacement component would be faulty in just such a way as to reproduce the old fault, but given the quality of modern components that's probably a bit trusting.

One thing I haven't tried is jump starting, but our other car is modern and I'm a bit worried that all those electronics could go awry. Am I being too cautious there? If we end up with two dead cars ther'll be blood on the carpet.

I guess the only thing is to go through the circuit again, and if that does no good, have the head off and start again.

Thanks again for your interest, and if anyone can put their finger on what stupid thing I've done I would be very grateful.

Cheers

Mart
Mart

I'd try jump starting off your modern. At least that way you can rule out a weak battery, and getting the thing actually running might give you some other pointers. I don't think you will be risking frying your modern's electronics if you follow the usual jump starting rules. It does sound a bit like timing though. I'm presuming you didn't mess with the cam timing when you had the head off?
Matt1275Bucks

Thanks Matt

You're quite right, I should stop worrying and get on with jump starting to rule out another fault.

I simply removed the head, had it checked over, and converted to unleaded, and put it back. I didn't touch anything inside the engine, nor even disturb the distributor.

The problem I've got with timing being the problem is I can't see why it should effect the speed at which the engine cranks over on the starter. Surely the problem would only show once the engine was running (uless the cam was so far out the valves were hitting the pistons, which would be pretty obvious when the engine cranked with the plugs out)? But I am a very amateur mechanic so my understanding is perhaps wrong.

Cheers

Mart
Mart

Assuming that the cam-to-crank timing hasn't been altered (no reason that it should have with just a cyl head swapout), I'd be inclined to remove the low tension coil lead and/or king lead (HT coil to distributor) and remove all four plugs. Also remove the alternator belt and disconnect the alternator plug. Assuming good battery, cables, solenoid, starter - when cranking (no choke!) with the engine in that state, the engine should proverbially spin its nuts off. If it does not furiously turn over, then you either have a starter/battery/solenoid/cable/wiring fault or a very peculiar clutch/gearbox fault (highly unlikely).

If the engine does spin furiously, then do a cylinder compression check (might as well as the plugs are all out). If they look good, reconnect the plugs only and do another starter test. Engine cranking speed should only be a bit slower than before.

Reconnect the alternator plug and belt. Try the starter again. If the engine is very much slower, then you've got a (unlikely) fault with the water pump and/or alternator.

Obviously, it's all a process of elimination, but do recharge the battery after each session of cranking.
Andy Hock

Even easier than that,

just remove the plugs, and loosen fan belt.

Is engine easy to turn now on battery?
Is fan (water pump) free to turn by hand?
Is Alternator free spinning by hand?

Lawrence Slater

(Lawrence, from a safety standpoint, not a good idea having an HT circuit 'live' with open cylinders whilst cranking the engine. And, yes, a good idea to hand spin the alternator and water pump (to check for friction) before replacing the alternator belt. Thanks.)
Andy Hock

It's fine to jump start a midget from a modern car - nothing happens to either, except it starts! Of course, you then have to run it to charge, and it's probably easier and quicker in the long run to change the battery!

If it was running fine before the cylinder head, then, it's probably safe enough to assume that it's the battery for now - or at least, that's a darn good place to start, rather than taking everything to pieces and ending up in a ruddy great big mess and never finding out what the problem is ........

Where in Cambridge are you? Bring it along to Milton on the first Wednesday of next month - it's always good to have other midgets there :)
rachmacb

Hi Andy.

I've been doing it for years and years and years with a live HT, and the worst that has ever happened is a shock or several from the HT if I've got a plug hangiong out of the end of a cap. Mini ouch, but far from dead. lol.

If worried, then you can always leave the ignition off and spin it on the solenoid from under the bonnet. But really I can't see the risk. No plugs in, so I can't see how a spark from the HT is going anywhere to cause a problem. :)
Lawrence Slater

Lawrence, it is not so impossible under certain circumstances.

I once disconnected the carb and dizzy cap and assorted gubbins in order to remove the cylinder head on a Viva.

The head wouldn't lift off so a mate of mine (doing the job at night in slack time between beakdowns) suggested cranking it over to break the grip of the gasket on the head.

What we both forgot was to plug the petrol pipe.

A couple of turns on the & starter had the desired effect, the head lifted.

Sadly a single "blob" of petrol was pumped in an arc into the air above the engine

It landed IN the dizzy while the engine turned over

You will have guessed by now that we had not bothered disconnecting the LT because it was only "a quick top off, gasket, and bolt back on" job on my dad's old HB Viva

The resulting fire was interesting to say the least, as were our immensely brilliant fire control efforts.

Praise to the magical fire extinguisher

Dad never did mention the signs of overwarmness under his bonnet


" I learned about..."
Bill 1

I'm with rach - battery (and it connections)

I helped someone who'd put on a known good battery and it wasn't good enough

I've also spoken with someone that spent ages trying to sort the starting problems on his Sunbeam Alpine only to find what he thought was a good battery wasn't good enough and he'd done the same as you

so I'd remove the battery from the car and check the electrode level in all the cells then trickle charge the battery to full with a charger

before reffiting I'd clean the lugs and lead clamps then protect and firmly connect

as you've renew the connecting and earth leads along with the solonoid and starter unless those two are faulty it should at least turn over well

to do this loses you and costs nothing except a little time
N Atkins

As mentioned by Greg in post #3, you need to measure the battery voltage while cranking the engine. This will give you an idea of how good the battery really is.
Dave O'Neill 2

yes but you do need multi-meter and with clips or a second person to do that

which reminds me where can you get sets of clips and attachments now, I need them for my ultra cheap digital multimeter that only came with the two spikes (probes?)
N Atkins

Mart,

I have found on more than one occasion that a rebuilt engine can be impossible to start unless the car is tow - started. There are a number of explanations for this but generally the reason is that tight engine will not turn over fast enough to create the necessary venturi effect at the carb to get that first ignitable charge of fuel/ air mixture into the otherwise dry cylinders.

I know yours is not a fully rebuilt engine, but it could be the same effect. Actually an engine doesn't need to spin fast for it to start, it should only need to turn over past a compression stroke. But that is setting aside the need to draw in atomised fuel which does need a bit more engine speed. Unless you go to fuel injection!

Anyway, if the issue is in fact the lack of venturi suction at the carb, then in theory the use of one of the aerosol "easy start" products just might help.
Guy

A thimbleful of petrol down t'ole in each carb might just be all it needs

I draw the line at using Easystart (ether) myself, I've seen far too many engines become dependant on the stuff, for whatever reason, but a tad of the stuff it would run with might be OK...


Note that for safety reasons I am stating M I G H T rather than "go on, go on you know you want to!"

Loose petrol isn't good to have around but given with small carefully considered doses I HAVE had reasonable number of successes.

Simply take care

Bill 1

Maybe, Bill,
But the problem with neat petrol is that it really needs to be atomised - or do I mean vaporised? - to become combustible.

A tale - I remember in my early teens going to visit a friend's grandfather on his farm. He demonstrated the non-combustability of petrol by throwing lighted matches into a brim-full baked bean can of petrol. He claimed that as long as the can was full and there was sufficient air movement to take evaporating petrol away, it wouldn't ignite. In hindsight, from an adult's perspective, he really was a foolish old man. Not because his demonstration might have gone wrong but because he was showing a stupid trick to two impressionable teenagers just for his own edification.
Guy

At work

(in the good old'bad old days)

I very rarely used easystart (mostly because I AM half Scots and would have had to buy it for myself, it wasn't on a parts / spares / consumables list so that I could get it from a spares depot free)

I always used dear ol' gasoline

Another flammable (and very viable substance) is Carb Cleaner Aerosol, a squirt down a cranking inlet tract usually got an engine running

It may be the propellant that catches, never worried me as long as we got the punter back on the road :)
Bill 1

Mart,
Is a tow start a possibility ?
Guy

If you shove atomised fuel, of any type down the throat of the carbs, or directly into the combustion chambers, and it does then start, it will do so with no oil pressure, until it builds it. When my engine has sat for a while, I always prefer to spin the engine to build oil pressure first, --- before I start it.

Anyway, I think this is all getting too speculative. So far the only thing established is that the engine won't spin fast enough, ---- without knowing why.

So my advice, is yes, give it a tow, or -- establish a definitely good battery, and spin the engine with no plugs, then with plugs. IMO of course.:)
Lawrence Slater

Yegods, has everybody on this thread been sniffing carb cleaner? :-)

Mart's problem is very sluggish engine cranking after having only overhauled the head - and he's assailed with stories of old men throwing matches into baked been tins full of petrol, theories about atomised fuel, tow starts, modern cars' electrics etc etc.

Even if he jump starts his MG, he'll still have the problem 2 miles down the road.

Mart - just follow the advice in my earlier post (and subsequent post by Lawrence Slater). Be systematic and you'll find the problem.

Bear in mind that your "known good battery" might not be good - leave it on charge over night and get your trusted local motor factors to do a discharge test on it (or even Halfords!).

My money is on a stuffed battery.





Andy Hock

Not quite everybody, I wasn't sniffing carby cleaner! As I said very early on in post 3, crank engine and check battery voltage when cranking. :)
Greg H

Mart, just a thought on reading through this (as you state you only removed the head and then put it back together), did you remember to reset the valve clearances?

Trev
T Mason

we all agree

whatever the cause is the problem will best be solved with a fully charged battery in good condition at each attempt

the battery could well be the cause of the problem but even if it's not a battery that isn't in good condition and fully charged at each attempt will hinder the diagnostic and repair

lots of other good information on here, I like Trev's but I'm certainly no mechanic or electrician

Mart,
how bright the headlights seem isn't a good indication of the battery's engine starting power as they can look bright even when the battery has quite got enough in it to start the engine

good luck, let us know the outcome please

and if you set light to the engine, no don't do that it's not was's meant by firing up the engine :)
N Atkins


Setting the engine alight won't make it turn over any quicker but at least you'll be nice and warm while you're thinking of your next step.
Greg H

ha ha ha :)
Lawrence Slater

Mart,
sorry in my previous post I meant

>>how bright the headlights seem isn't a good indication of the battery's engine starting power as they can look bright even when the battery has NOT quite got enough in it to start the engine<<

bad habit of mine missing out that important word (not) when typing, wonder if I can get pills for it
N Atkins

Stupid question time... you DID put the pushrods back in, didn't you?

;-)

-:G:-
Gryf Ketcherside

(Gryf asks>> you did replace the pushrods, yes?)

That is a brilliant observation, Gryf. I wish I'd thought to ask it. No pushrods would obviously be an answer to Mart's problem.
Andy Hock

...although it should spin quickly with plugs removed, in fact even quicker with no pushrods.
Dave O'Neill 2

Thanks guys. Lots of useful ideas and I'll work through them. Damned if a lump of metal is going to beat me, the ultimate product of evolution (along with a good few millions others, of course).

Just for the record, the battery is a new one and I charged it overnight. The pushrods are in (clearly recall reading off the numbers as I took them out of the bit of cardboard) and I set the tappets.

I haven't had time to work on it over the last few days, first because it's been damned cold, and second because our son got married on Wednesday, but I'll get back when and if something happens.

Mart

Mart

probably doubt that it might be the battery then, possibly,

but

just because a part or component is new doesn't always mean it's in good condition so never discount a part or component just because it's new

and others have previously reported faulty new(ish) batteries so some sort of test required to discount it

and, I'm not so sure about the ultimate part of the product of evolution based on myself and some others I've met

good luck anyway

PS you should have got your son to sort it out before Wednesday as you've now handed over his control :)
N Atkins

Well, let that be a lesson for me - never jump to conclusions.

I decided to ask myself the garage mechanic's first question 'what have you done to it?' Answer, fitted an electric fan. What does that involve? Removing the old fan which is the only thing I've fiddled with that affects the lower engine. I had, of course, replaced the retaining bolts and ring. So I loosened the screws, tried the starter and she span away and fired up happy as Larry. Obviously the screws were fouling something and stopping the engine turning over properly, though not jammimg it entirely.

So I need to fit some spacers to the screws to ensure clearance and all should be OK (I never said that).

Thanks to all for your advice. The more suggestions are made the more it helps defines one's thoughts, so nothing is wasted.

Cheers

Martin
Mart

unless you mean the pulley bolts I'm lost but well done on find the problem by proper diagnostics
N Atkins

Mart. You said you fitted a new starter. Has the new starter got paint on the mating surface where it fits to the back plate? If so, it could be causing a bad earth and no matter how good the engine earth strap etc are, the current won't complete the circuit.

Bernie.
b higginson

Mart wrote>>I had, of course, replaced the retaining bolts and ring. So I loosened the screws.

>>AH asks>> Er, what "retaining bolts, ring and screws" are you referring to?
Andy Hock

Yup that would do it.

In removing the regular fan, the bolts were then too long, and when you tightened them up they fouled on the water pump I'm guessing.

Lawrence Slater

Sorry, euphoria made me babble!

By retaining bolts and screws I mean the same thing, the fittings that secure the fan etc. Technically they are machine screws (threaded all the way down) and that's what Moss calls them. My car had a metal ring behind the fan, through which the screws passed before securing the pulley to the pump. I assumed it reinforced the join as the pulley is not a massively built component.

Can't see that ring in the Book of Moss, maybe it's part of the pulley, or been added so a different pulley could be used. The car has obviously been round the block a few times as many of the components belong to earler model Midgets. Even the head is from a 12C engine, it appears.

Incidentally I had to use shorter bolts and an extra washer before the pulley would spin freely. That fan must be pretty thick. Like me.

Well done Andy and Lawrence for suggesting a test regime which would have located the fault. I am comforting myself that the battery was years old, the starter had been hanging up on the ring gear now and then and the new solenoid and cables look lovely and shiny. I'll be happy if someone benefits from my experience in the future.

Rach - I'm on the other side of the A14 from Milton and the car will hardly be warm when I get to the White Horse (that's where you meet I take it). May I be cheeky and ask what kind of group it is? On the one hand I don't want a session where people just gather with their special mates around tables of four and eat, like the local MGOC, on the other hand I don't fancy an evening crooning over a camshaft. Presumably my other half would be welcome?

Cheers

Mart

Mart

ahhh, yes, the fan spacer - Piece-distance AEG 560

keep that/sell/give away the fan as I dont't think you can get that part new (true those with macines and know how could make one but they still need to know thickness)

just out of interest to me Mart,

on my '73 1275 I've got a Revotec cooling fan kit with the thermo-switch that splices into top hose, works fine but if I was doing it again I'd have a deeper fan than the one that comes with the kit

if you have a different set up I wonder how you find it (when you're using the car again)
N Atkins

I've got a 73 as well N. Have put 'show the profile' but it doesn't seem to work (yet). I am keeping most of the original parts that I and the previous owner have changed, even the section I hacked out of the cross-member when I fitted the 5-speed (though I did manage to sell the old gearbox - even in the garage my wife has certain limits to the stuff I can keep).

Once I get the Revotec operational I'll tell you what I think, though I believe it's a bog standard kit.

Mart
Mart

Mart,
be interesting to see if you use the same setting on the thermo-switch dial

For the show your profile bit you’ve just missed one step

to get your ‘View vehicle profile’ to display

click on mine or someone else’s ‘View vehicle profile’

then scroll down to the bottom of the page the link takes you to for instructions

it’s easy otherwise I’d not be able to do it
N Atkins

I thought it was just me.

I too kept the section of chassis I cut out to fit the type 9 box.

I also kept all the other bits too, including the gearbox, which drained of oil I carried up step ladders, and now lives in my loft with numerous other bits and bobs, spiders, squirrels, and god himself only knows what else:)
Lawrence Slater

Thanks N, I see it's now working. I also note that, like me, you've dumped the black sills lettering etc from your Midget. I've always preferred the uncluttered look of the pre-facelift Sprites, have even lost the bootlid badge. I've never bought that 'Abingdon magic' stuff. They're just brilliant little cars and, in my view, extremely handsome for such a small vehicle.

Mart
Mart

told you it was easy or I couldn't have done it

some will use it to see what model you have, some wont

a photo if you wanted would also help

I got my car minus badges and sill colour I think I prefer it that way . . . until I see some with sill colours then I'm not sure :)

personally I wouldn't rush to drill holes to put badges on although I've not had trouble with them before
N Atkins

This thread was discussed between 19/10/2011 and 23/10/2011

MG Midget and Sprite Technical index

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