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MG Midget and Sprite Technical - Another infuriating starting problem

For those of you who don't remember I have a 1098cc rebuilt engine to stage 2 spec which was done last year. Work was done via owners club. All I know is that the head has been ported and flowed to "stage 2 spec" and the cam was replaced with a fast road cam with the rest of the engine being rebuilt where necessary.

Standard twin SU carbs
SU electronic fuel pump
Normal points and dizzy - no electronic ignition

I got my car back late last year and we had 2 or 3 short runs out covering about 100 miles before putting her away for the winter. I have started her up periodically over the winter and let the engine run until warmed through. The battery is kept on a trickle charge and the car started first time most times.

Two weekends ago I decided the weather had improved enough to get back out on the road. My wife wanted to pop to the supermarket for a couple of things so we went in the midget. Started first time, drove to the supermarket without incident. Engine showed no sign of a problem and was running as I would expect it to. Good pressure and temp, nice response to the throttle. Parked up, did the shopping, got back in the car, turned the key and nothing. She turned over fine, electrics were all working but no sign of firing up at all, not even a little cough. At this point I thought I couldn't hear the fuel pump but it was difficult with the traffic noise to be sure. I wasn't dressed for getting under the car and I had no tools with me anyway - won't make that mistake again. When it was obvious the car was not going to start I gave up and called my recovery service. Whilst waiting for them I kept trying the key. After about 30 mins she fired up. So I headed off home whilst the going was good but unfortunately it was short lived and after about half a mile she started spluttering as if starved of fuel and if I eased of the throttle she recovered again but then eventually died and we coasted to a halt. After 5 mins she started again. We limped in this fashion all the way home with one push needed when we got stuck at some lights. I concluded I probably had an intermittent fuel pump problem, bad earth or perhaps crap in the fuel line.

This weekend I have had a chance to have a look to see what is going on. Started first time on choke idled until warm and off choke. Idles at around 1000 rpm. Revved fine. I left her running to see if she would stop but after 15 mins there was no sign of that happening, so I revved the engine and at that point it died and would not start. Same scenario everything turning over, no ignition. I checked for a spark and I had one, the fuel pump ticks for a few ticks when the ignition is first turned on and stops when the carbs are primed as it always does. I checked the carb pistons and they appear to move up and down ok although the front one doesn't drop as smoothly as the back one. Having flipped them up and down a bit to make sure the needles weren't stuck I tried again but no joy. After standing for 5-10mins however, she starts up just fine.

The next time it died I left the ignition on and carefully released the fuel line from the carb - fuel pumped from the free end suggesting that the pump is working ok at least when there is no resistance.

I also tried removing the petrol cap from the tank in case there was a vacuum in the tank but there was no release of air and the car still didn't start with the cap left off.

So now I'm stuck. Any ideas. Could it still be the fuel pump? Sticky pistons on carbs? Should I put a filter in the fuel line. Help?

Stuart K

Sounds like a fuel pump to me.
Brad (Sprite IV 1380)

what did the tach do when it died...did it go straight to zero,or did it flutter to zero


how old is the coil?

prop
Prop

I had the same thing on a Fiesta many years ago, turned out to be the capacitor. Changed that as a last resort, after changing everything else. Car was never a problem again until it rusted away.

Dave
Dave Barrow

Fluttered and died. The coil could be pretty old, it came with the car. I have a fancy Lucas sports coil sitting around somewhere.
Stuart K

change the coil
and in these instances i always change the pionts and condenser
they cost almost nothing and can give all sorts of nasty errors (have a 123 electronic waiting)
and
check all the fuel hoses even the overflow hoses!!!!
they may look fine from the outside but can degrade and block up
Onno Könemann

>>> I had the same thing on a Fiesta many years ago, turned out to be the capacitor. Changed that as a last resort, after changing everything else. <<<

There for a while, some of us were getting laughs by diagnosing any and all Midget problems as being caused by the condenser. But there was a firm ring of truth, all the same. Right about that time, a lot of people started having ignition problems that they eventually traced to faulty condensers. I could myself among them, and yes, it was very frustrating. The condenser was the last thing I thought of. I eventually hurled it and converted to a pertronix.

All of this to suggest that you should keep the condenser in mind when troubleshooting ignition woes.

Cheers, and good luck,

-:G:-
Gryf Ketcherside

Also check (by giving it a light tug) the small braided earth lead that connects the points base plate to the distributor body.

Years back I had an Austin A60 Cambridge stolen, and it was recovered quickly cos that fly lead had gone open circuit and the car had broken down somewhere conspicuous.

I also had a Morris 1000 that had this lead fail. It would start fine, but cut out at random revs, then as the engine nearly died it would pick up again as the distributor base plate swivel back to some position where the earth could work.

Roly
Roly Alcock

whoa

I thought we werent allowed to use the capacitor tale anymore...

If fuel is flowing it is almost certain to be an ignition problem

some people have never had a faulty condenser, lucky them

I had to replace hundreds of the things on breakdown duties, they can't ALL have been figments of my imagination

can they?

even fresh new points can stop switching due to oily residues on their faces (wipe the faces clean with card or tissue)and condensers can stop storing charge if the earth path is dodgy as well as if the live feed is poor or broken

Do check your ignition circuit from the switch, through to the coil and down to the points

and make sure the pigtail earth wire on the dizzy faceplate is good as Roly advises
bill sdgpm

Next time it conks out feel the coil. If it's really hot it could be the voltage regulator has gone AWOL.
F Pollock

Stuart,
Prop didn't explain, but if the rev counter needle flickers rather than just dying as the engine revs drop, then it indicates an electrical rather than a fuel problem. Its quite a good diagnosis first step. But this sounds like an electrical one.

You could try replacing the rotor arm. There are poor quality ones around that work fine for a while, then break down as they warm up and then magically "recover" again when they cool. There have been reports of these for several years now and someone else on here had this problem not so long ago.

Guy
Guy Weller

Thanks all. I'm going to replace points and condenser first, then stepwise through the other parts until it works. I'll feedback when I've done.
Stuart K

Stuart while you have the cap off swap the rotor arm too

There really are duff ones out there, someone will have the link for the "Good" ones that are about now

(I cant find it but it was only a few days ago)
bill sdgpm

rotor arm is the easiest to start with! Perhaps you are not convinced!

The only other thing I would say is just do one change at a time.
Guy Weller

Whilst I am at it. Am I correct in thinking I can remove the distributor altogether and so long as I don't loosen the collar/pinch bolt and the engine is not disturbed then I won't lose the timing? It would save my back to be able to sort the points and condenser out on the bench and I could give the whole unit a look over at the same time.
Stuart K

OK, first update. Changed the condenser only. Starts up fine as always, idled and happy to rev for about 10-15mins after which the first attempt to rev caused the engine to die and wouldn't restart. Drat.

Checked the coil immediately afterwards and it was red hot. Voltage regulator?
Stuart K

no just a defective coil
Getting to hot causes them to fail a little cooling and it works again but when it heats up it fails again.
has to do with old age and the oil (cooling liquid) leaking out or going bad

when removing the distributor just mark the block and distr with a bit of paint
Onno Könemann

It's not unusual for a regulator cut outs to suffer over a winter layoff - in the same way electric pumps sometimes need adjusting with a broom handle to kick them into life again. If the cut outs are working outside the normal limits they can be cleaned up or adjusted back. Much over 14 volts and the coil gets too hot and gives up the ghost - only to work when it's cooled again. You can try swapping it for that sports coil you have, but my money is on the regulator.
F Pollock

i must admit i assumed you have an altenator.
if you have a dynamo and reg give that a whack

if your coil has badly over heated it might be fried from that
so when you checked the voltage (as F says) and it is okay again (or stil) change the coil
Onno Könemann

I have an alternator and a voltage regulator as far as I can tell. You'll have to excuse my limited knowledge of this electrickery. They can both be seen in the picture below with a close up of what I presume to be the regulator. Which bit needs a whack?


Stuart K

if you have an alternator the the regulator should be a fake
it is just used as an connection box since an alternator has a (much more robust) regulator built in.
just measure the power on the batery when the engine is running.
the should not go over 14/14,5 volts

my bet certainly is on the coil now
Onno Könemann

Well I changed the coil and the car ran at idle for over 45 mins with no protests when revving so I risked it and went out on the road. Only managed half a mile before conking out again. Stutters, picks up and dies then won't restart. Same scenario as the first time when we were out at the supermarket. I've abandoned it and I'll go back later when it has cooled down. I'll take a rotor arm with me as that is the next swap. Frustrating as hell. As soon as it gets hot it dies on me. Oh and the new coil was very hot to the touch too. I measured the voltage across the battery terminals at idle before I set off and it was reading a steady 13.88v - good or bad?
Stuart K

rev the engine a bit when measuring and see what happens
Onno Könemann

Will have to wait until I recover it!
Stuart K

Went back to it after an hour and started first time. Replaced the rotor arm and drove home. Still stuttering on the way back so not the rotor arm.

Volts on revving remain steady at 13.88v

Stuart K

con
den
ser
?
breaking down under load?

the second coil got hot too...

I still suspect the condenser

breaking down insulation can cause this

13.5 or above up to about 14.5 is OK with an alternator
bill sdgpm

The condenser was the first thing I replaced. Are you saying I have 2 faulty ones?

Then the coil, then the rotor arm.

Haven't done the points yet.
Stuart K

Are you measuring the voltage as the engine is starting to stutter? - hold it at 2000 rpm and then measure voltage at the coil.
F Pollock

brand new faulty condensers hav been known to happen...
Onno Könemann

Mh, although propably discarded as a cause, I can tell from my own experience that it could be the fuel pump.
The points in there may be burned, wich will cause the same symptoms.
Fuel flowing freely with the fuel line not connected is not the same as a fuel pump working against a closed needle valve.

I had a fairly new su pump in my MG1300 and was happily touring in the south of france when the same symptoms occured.

If the pump is the culprit, it will be stinking hot and will tick when wacked.
Alex G Matla

But would that cause the coil to get so hot? I'm useless at the electric side. What are the likely causes of an "overheating" coil? What should I look for?

I'm going to take out the dizzy and strip everything down, new points, another condenser, replace the low tension lead and insulator block. The cap looks in very good order and the carbon thingy at the top moves freely up and down but I have a spare I could swap over.

I do have a new fuel pump so may change that over too. Where is a good jacking point at the back?
Stuart K

Stuart

Have you checked the points gap. It's not unknown for the heel to wear down quickly leaving virtually no gap, it'll start fine and run until warmed up then start to stutter, then fail totally, then start fine when cooled.
David Billington

Nope, David, haven't done that. That was the next task in the sequence. I'm going to take the dizzy out to do it though as it is a bear with it in place.
Stuart K

Stuart,
have you checked that you have the LT connections to the coil the correct way round?
Guy Weller

Stuart my mistake sorry

I did the stupid not "reading properly all of the thread" thing

the coil wired the right way round question is important as is checking the contact gap

modern plastic heels on points can wear down very quickly if the lobe isnt lubricated on reassembly with new points

I usually drip a spot of oil off the handy engine based dripper (the dip stick) onto the cam inside the dizzy when I change points

bill sdgpm

Bill
lubricating the heel of the points is a great tip I am sure it was part of my not starting problem. See other thread Messed up my timing.
I Pickering

The coil is wired correctly I think. The car is negative earth and the distributor is wired to the negative terminal and there is a white wire to the positive which I presume goes to the starter according to the wiring diagram in Haynes. There is also a black/white wire to the negative terminal which is new and I think goes to the new tacho I had fitted.

Today was put aside for putting the engine back in my Morris so no work on the Midget. May get to sort out the points tomorrow. I'll report back when I've done that.

Frustrating. Best 3 days of the year so far and no classic on the road. Ho hum.



Stuart K

OK. The points were in good condition - they were new only 200 miles ago, but the gap was barely 9 thou!

I put new points in anyway, reset the gap, installed a new low tension lead and insulator block, another new condenser, and new rotor arm. Checked the plugs for good measure and she has been running now at idle for 15 mins and the coil feels quite hot. So far no sign of dying on revving. Does the coil get hot during normal running anyway? I've never had cause to feel it before.

Stuart K

it can get a bit hot but you should not burn you hand
Onno Könemann

Update - ran for 35 mins without a problem and no sign of a hiccup when revved. Too late to go on a test drive this evening but looking promising. Fingers and toes crossed.
Stuart K

It's always something simple, but not always simple to find!

That's why I gave up on points & condensers years ago...replaced with Hall Effect triggers (Pertronix)since the early '90s

Good Job!
Dave Rhine ('78 1500)

Dave, do you have shares in pertronix? 8^P
If you do, could you get us a discount?
Alex G Matla

Stuart,

bit of a long shot this but the symptoms you describe match perfectly with those I had with a Metro a few years ago. Runs then dies, wait a while runs again then dies - and repeat ad nauseum. Turned out to be water in the fuel tank which mixed with the fuel when moving and caused the engine to die; then separated enough to allow the engine to fire after a briefish stop only to give a repeat performance a few minutes later. One of the fuel lines had an almost invisible crack which was allowing water in...
Otherwise Roy's suggestion rings true as I had the same thing with a Wolseley 1500 and it took me a week to find it!
Good luck,
Jeremy
Jeremy 3

I am very happy to report that since fixing the points gap everything seems to be running as it should. Just back from a test drive with no issues (other than the sticky gearbox, but that's another problem!). I let the car idle for 45 mins before I took her out on the street. At that point the coil was very hot but after the drive it was just warm so I'm hoping that isn't an issue.

It's always the simple things that go wrong. I'm kicking myself for not installing that electronic ignition I had promised myself last year. Seriously thinking about it again now!

Thanks for all the help guys!
Stuart K

letting it idle for 45 minutes is never a good idea.
a lot of things depend on driving wind cooling so warming up the engine is best done with just easy cruising.

good to hear all is well now
drive it for a while that gearbox might get better.
have fun!
Onno Könemann

This thread was discussed between 06/04/2010 and 13/04/2010

MG Midget and Sprite Technical index

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