Peugeot 504 Stalling

[aquinian]

Hi guys,

Currently we have a 1981 Peugeot 504 with a TMIMA carburetor engine. Recently we had the carburetor rebuilt and tuned, but the car still will not run properly - it runs roughly at idle and stalls when you push the accelerator down too fast - or when you try to move the car (i.e. under load). Once you get the revs up it runs nicely though.

It does not have a choke but still exhibits this behaviour even when the choke is manually fixed on. Also I have tried adjusting the ignition timing but doing so (either way) only results in it backfiring (more) than it does now.

I have linked to a couple of videos showing the problem - any pointers as to what to troubleshoot would be much appreciated please!

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Kind regards,
Michael (John's son)

[Beano]

If you had not had the carby rebuilt, I would have said that the symptoms match the accelerator pump diaphragm being kaput.
Perhaps they dislodged something which has clogged up one of those passages underneath the diaphragm ? Or (more likely) a linkage is not working.

What the accelerator pump does is squirt a small amount of petrol directly into the carby throat, so that when you push down the pedal, the fuel mixture does not suddenly become too air-rich, causing the engine to starve of fuel. The carby gets a quick kick of fuel. It's primitive, but then so are carbies.

Perhaps one of the linkages was put on improperly ? This is more likely, and easier to diagnose.

The accelerator pump is in/on the passenger side of the carby, towards the front. Externally, it is a small piece (about 3 centimetres square, and with a screw in eack corner) out of which you can see a small lever protruding from the middle and going downwards under the carby. When you push down the accelerator you should see the lever moving. If it is not, then a linkage has been put back wrongly.

But before you do anything, take a look down the top of the carby. You will see a couple of tiny brass tubes which come out horizontally, then go downwards. There is one in each throat. Now, with the engine OFF, turn the accelerator drum the way you did in the video.....so it's the same as pushing down the pedal.
Can you see a tiny stream of petrol go down into the carby from ONE of them ? The one on the passenger side ? ? If so....then your accelerator pump is working. But I doubt it will be...

[aquinian]

Hi Beano,

Thanks for your quick reply and advice. Yes, the accelerator pump does work. I think it's squirting out both though?

The other thing is that it is running quite smoky (weird as I would have thought backfiring indicated lean) and is a bit rough at idle (if you're lucky you may hear this in the video - apologies for the quality) so it couldn't only be the pump anyway.

Kind regards,
Michael

[pugwash]

Is it possible that the base gasket isnt sealing ,letting air in ,the idle mixture screw is adjusted way rich to compensate ,therefore the problem transitioning from the idle to main jet ,that would explain the rich running at idle then lean as throttle is open ,other things i would be checking is float height and blocked jets ,both of which should have been covered when it was rebuilt, pugs

[aquinian]

Thanks pugs, might give it a spray with start ya bastard and see if it leaks there.

Also, this car refuses to start when it's in neutral, only in park works. Is this a simple fix - I cannot see an obvious switch on the lever? As you can imagine this is a particularly fun problem combined with it's penchant for stalling...

[Beano]

Petrol will squirt out both little accelerator pump brass jets in both throats, but it will do it first from the one on the passenger side as that is the primary one.

The inhibitor switch which prevents the car starting in gear is located on the gearbox. If it is the same as on 505s, it will be a small screw-in brass switch with two wires going to it. (My 504s were all manual).
In 505s it often wears out, but if it eventually won't start in PARK, it is possible to short out the wires to circumvent it. In 505s you can do this without getting under the car as there is a relay in the engine bay. Not sure where in a 504.
Not advisable to do this long-term though....it is then possible to absent-mindedly start the car in gear, and have it surge forward. Quite dangerous.
I think you'll find it will be fine to start in PARK for a long time.

Can't think of what your carby problem might be, then...

We do have a couple of members in WA......if you aren't in the outback, they might be able to look at it..

[dacia4x4]

hi Michael, have you looked at ignition points/condenser for pitting on points or bluing due to condenser not doing it,s job and spark jumping across ign points.coil lead or distributor cap for cracking.carbon brush in distributor cap for wear,rotor button for condition.I have also come across coil negative to condenser/points wire breaking down.spark plugs gap/condition and insulator condition,spark plug leads would be worth checking as well.just a couple of ideas that may cause backfiring/rough idle.......jim

[Pug72]

My 2 cents worth - check ignition as per Jim's post. I suspect the points. Petrol 504's thrive on clean and properly adjusted points.

[robmac]

Also check the points rubbing block is l well lubricated with a couple couple of drops of oil.

[driven]

Take the car back to the carbie place that did the rebuild and tune.
They have stuffed something up badly.

Need to pull apart again and see what is missing when the work experience kid did the job

[Stuey]

I agree with the above. However, as an additional thing to pugwash's comments and along the same line, it could be the needle valve wasn't replaced and is grooved (or it's not installed properly) and not shutting off fuel, so the fuel level is too high.

[Beano]

I suspect the points. Petrol 504's thrive on clean and properly adjusted points.

True. It could just be the condensor mounted on the outside of the distributor. If that is stuffed, the points will get dirty very quickly. Or the vacuum advance may be stuffed.

It is quite possible that dirty, daggy points may produce those symptoms. And it's best to check the simple things first.

If you have a Ducellier distributor, as is most likely, the points will no longer be self-cleaning if the vacuum advance capsule has a split diaphragm. Crap will build up on them quickly. The easiest way to tell if the vacuum advance works is :

1) Remove dizzie cap.
2)At the carby end, pull off the rubber tube going from vacuum advance to carby.
3)Suck on that end and watch to see if the movable section of the points does in fact move. If it does, fine. If not, it's stuffed. They cannot be repaired....get a new one or secondhand dizzy.

The way Ducellier points self-clean is that as well as opening and closing, the moveable section goes back and forth across the fixed section. This needs to happen or the points will get dirty fast. And when they do, they do not work.

There are two other brands of distributor found in Australian 504s which do not use this procedure. They are Bosch and Paris Rhone, and people have a very low opinion of them. The brands are stamped on the side, and if you have one of them, either replace it with a Ducelllier one, or maybe just get a new condensor.

A word of caution : never push the lever going to the vacuum advance by hand....you can damage the diaphragm. The only way to test them is to suck on the other end, as that is how they are meant to operate.

PS....it may be possible that the people who repaired your carby simply forgot to plug in the vacuum advance tube at the carby end. Or (more likely) they plugged it back onto the wrong place on your carby.

[Peter Chisholm]

From the videos it doesn't seem like a condenser problem to me. Assuming the timing is okay, as Beano suggests, the first thing I would check is the vacuum advance on the side of the carby. Suck on the vacuum tube and see if it maintains suction.

Just wondering why you had the carby rebuilt in the first place? Was the engine exhibiting similar symptoms?

[Stuey]

A word of caution : never push the lever going to the vacuum advance by hand....you can damage the diaphragm. The only way to test them is to suck on the other end, as that is how they are meant to operate.

That'd be very tiring on a long trip.

FWIW, I had to replace the capsule on my R12's Ducellier distributor and I'd expect most to have to have it done, so this is good advice. The rubberised cloth stuff just gets stiff and tears. I seem to remember I had issues with starting then too.

[Skellibert]

I know very little so this might not even be worth the 2c, but if your spark is weak then it will miss under load.
I had visible spark on my old cruiser, but it had a miss as soon as we tried to rev.
In our case the alternator was not charging properly.
Have you checked the coil?
It could be that on the way out.
But as I say, I am far from an expert.

[edgedweller]

helped to broaden the common understanding Skellibert
good post


ed

[Armidillo]

Just to provide another example of how many causes there could be, our 504 started missing and backfiring horribly while on a trip towing a trailer in 1986.

Cause turned out to be a pinhole leak in a radiator hose, which directed a fine spray of coolant over the distributor!

Cheers

Alec

[edgedweller]

woohoo 2 2 2 2 oops 3

[driven]

Well, the 504 must be on the way out, time for a burial.
Tell it sternly that you will be going to SIMS Metal if you don't perk up
If doesn't come good, shred it and get a BA Ford for towing

[aquinian]

Lol - trying desperately not to let this car become a victim of its own behaviour.

Thanks for all the advice guys - my feeling is that it is a fuel / air issue rather than an ignition issue.

So had a look tonight at the plugs - all sooty and black. Plan is to take it back to the mechanic tomorrow and get him to look at the carby tuning - will keep you posted.

Kind regards,
Michael

[julian c b]

From my experience it seems like an ignition problem .Try reving in the dark and look for sparks from leeds ,spark plug extensions ,dissy cap etc .Check points gap is ok and check timing and advance when revved with a timing light ,and replace condenser and coil just to be sure .

[julian c b]

Did it run like this before the carby rebuild?

[aquinian]

Cheers Julian - been playing with it in the dark and not seen any sparks jumping. Will change the coil next if the carb tweak doesn't help.

Previously the air filter had disintegrated and turned into yellow grainy dust - hence it ran very very badly before the rebuild as everything was gunked up with ex-airfilter.

Kind regards,
Michael

[Beano]

everything was gunked up with ex-airfilter.

Presumably also the carby. The problem may well be that.

[Peter Chisholm]

Being a 1981 504 there will be a number of rubber tubes connecting up this to that, and this to this etc. My 1980 504 has much the same setup as an early carby 505. I wonder if the pipes have not been connected back up correctly after the carby rebuild?

If so, it would probably be not beyond the realms of possibility that the rubber tube that is connected to the distributor vacuum advance has not been connected to the right thing at the carby end.

Others please feel free to chip in here but black and sooty plugs mean that there is either too much fuel, not enough spark or not enough spark at the right time. A distributor vacuum that isn't connected properly, and thus not working correctly, may well be the answer.

Maybe someone can upload the appropriate diagram so you can give all those tubes the once over.

Having said all this, I assume that the TMIMA is the carby that was originally fitted to your 1981 504!