320 CE Cutting Out When Warm

[daclick]

Some help here please - this problem is driving me crazy.

My 320 CE (1993 with catalyst) has a tendency to cut out when warm - anything after around 10 minutes.

There is no set condition which will cause the cut out - it may happen in traffic or at 70 mph. I do however believe this is due to an elecrical component suffering a heatsoak problem because there is a strong likelihood of being unable to restart soon after turning the engine off.

The car will then start after around a minute or two of the ignition being off.

The problem may occur 2 minutes - or 2 weeks later, however is getting more frequent. The record is 9 times in one day

So far the investigative work has found the following:

Everything from the fuel pump relay backwards (to the pump) is ok

Just before cutting out the fuel pump relay clicks - something upstream of the relay is cutting the elecrical supply to the fuel system

The ECU had no fault codes stored and the fuel system functions perfectly - when the fault is not occuring

Fuel pressure is ok

If the ignition is left on without the engine running the car will most likely not start.


An auto electrician and various specialists have not been able to find the problem.

The worst feeling is in traffic when I have to hit the hazards for a couple of minutes with a multitude of horns sounding behind me.


Any ideas?

 

[Orlando 300E]

Hello daclick,
really hope this does not dilute any replies you get, but I am having a very similar (embarrassing) problem.

Just edited this, have posted my problem seperately to avoid confusion!
hope you get yours sorted
O

 

[Neilc]

Hmmm! Well has anyone looked at the fuel accumulator next to the fuel pump? The fuel accumulators jobs is to act as a resevoir and hold fuel pressure for up to 1/2hr after switch off - basically to avoid vapour lock issues. When it fails it can cause all sorts of fuel supply problems.

Has the fuel pump relay actually been replaced? These are notoriously unreliable - dry solder joints causing intermittant problems. If not, I would definitely replace it as a matter of course.

Have you checked for flooding? Try pulling the injectors with the ignition on, are they leaking?

You could also be flooding at the air flow meter courtesy of a malfunctioning fuel distributor or the control plunger being out of adjustment, seals failed etc.

HTH
Neil

 

[Spike]

Just wondering if the (automatic ) choke is still on. I dunno how this works on MB's but I had a similar issue on lesser marques before.

Another thing you could check is your filler cap vent....mebbe its blocked.

 

[daclick]

I thought this may have been a fuel lock at first - but does not seem to be.
Removing the filler cap will not ensure the car will start again straight away. Removing the cap causes a whoosh when the tank is nearly empty - normal apparently.

I don't think the fuel accumulator has been checked but can find out, would this not show up in a pressure test?

Flooding? Would this not cause petrol smell and black smoke on startup? Would it also not be difficult to flood the engine at around 70 mph?

The fuel pump relay has been replaced - I thought at £12 it was worth it.

What of the overload relay? Could this be the culprit?

Happened again 3 times yesterday - any idea what the clicking is before cut out? Could this be the oveload relay? It sounds like 3 or 4 clicks - car will cut out 2 seconds afterwards.

 

[Neilc]

Car will work with or without the Over-Voltage-Protector (OVP) relay so it won't be that. OVP can cause stalling but restarting problems I doubt it. If the car refuses to restart when it's warm then it must be ignition or fuel related. It could be a tuning issue, lamda incorrect or bad setup of the air flow meter plate.

You can flood an engine at any speed but yes it's unlikely it's just something else I'd check as a matter of course. If the injectors haven't been changed and it's a high mileage vehicle then it's a good thing to do anyway.

You may have a faulty ignition module. Have you checked your ground straps? Battery connections? Battery itself? This sort of thing can happen if one of the cells is dying. Get it to a mechanic to do a drop test.

Could also be the ignition coil, these fail under heat related conditions and will start working again when they cool down. Sounds suspiciously like an ignition fault to me.

As for the clicking, does sound like a relay but hard to know across Email..

 

[daclick]

Thanks for the help so far.

A few more thoughts have come to me which may clinch it:

The car has cut out quite a few times on hitting the horn - I also had the feeling for a fair while that the problem happens more often when the lights are on.

To re-start I wait between 1 and 2 minutes, set the alarm/immobiliser (which works on the ignition and another circuit I believe - not the fuel though) and then un-set the alarm. This seems to re-set the faulty component.

Does that help? I'm beginning to think more of an ignition problem here.