W124 280E - Intermittent shutdown of the engine.

[PFIJ]

Can anyon eplease help with this problem? Intermittent shutdown of the engine. There is no warning at all, and no obvious pattern as to when this occurs, ie it makes no difference wnether the car is waiting in a traffic quue, moving slowly, or cruising quickly. Equally this has happened both during warmup when the engine is fairly cold and also when the engine is fully warmed up during a lengthy drive. The loss of the engine is sudden and total; it is not total loss of electrics in the car because all the normal warning lights appear on the dashboard; equally I am not convinced it is a fuel flow issue as there is no evidence of rough running prior to shutdown as might be the case if fuel flow was poor. In a similar way, it is unlikely to be partial loss of cylinders problem as there is no lumpy running as would be the case if one or more cylinders had failed. Just prior to the problem occurring, the engine is running normally; when th eproblem occurs normal cold and hot start porocedures do not work, I just have to wait up to four minutes then the engine restarts as though nothing had happened and runs perfectly normally until the next occurrence which may be an hour later, a day later, or a week later. Very frustrating - can anyone please offer any advice? Replies please to paul_fi_jackson@lineone.net

 

[Richard Moakes]

On my 1989 W124 300E, the exact same symptoms were caused by a faulty fuel pump relay.

I had a spare one, so swapped it and the problem went away and has not come back.

As it happened, not long after this I replaced both my noisy fuel pumps, so it may well have been overcurrent drawn by the pumps or bad solder joints in the original relay.

Of course, your mileage may vary, but it worked for me.

Good Luck,

Richard

 

[mjtray]

I would almost guarantee (99.9% sure ) its your Over Voltage Protection relay (OVP) which is located to the right of your ECU. Costs about £50 and takes 10 minutes to change.

The symptoms are exactly the same as what happened to my E280 and another members C280 using the same engine.

This unit had a design fault in it from new and with age the internal soldering breaks down causing the car to stall etc.

If yours is still on its original OVP, its guaranteed that it will fail with age.

Good luck.

ps: let us all know the outcome......you could also do a search on OVP or MJTRAY or MYROS.

 

[television]

Check under your car in front of tank to see if you have 1 or 2 pumps and let me know please. the relay as Richard say's is a major cause.

Malcolm

 

[mercw126man]

I've just solved my fuel problem (severe but only at high engine speeds) by replacing one non-operational fuel pump, and fuel pump relay. The relay caused the symptom of a huge misfire/kangarooing, and someone had had a go at repairing (presumably because of the high cost) and had fitted the wrong relay for the car (see earlier threads).

Hope it helps you to solve yours!!

 

[television]

Well at least yours is OK and you did not have to buy anthing that you did not
need. I know some can argue the point but I did say it was a fuel problem, the fact that the relays turned the fuel off still meant that it stopped as no fuel. Is there any chance that you could let me have your old relay, if I can repair you can have it back free of charge.

Malcolm

 

[mercw126man]

Yes no probs, if it's of any use you are welcome. I've had the lid off to have a look, but other than that (and the faint smell of hot/burnt electrics) it is intact. No visible signs of individual component failure.

Send me a PM with your address and I'll post it on.

Thanks once again Malcolm.

 

[PFIJ]

From PFIJ 27 Dec 2005
My thanks to those who replied to my original question - it looks as though the over voltage protection relay was indeed at fault - it was replaced 2 weeks ago and the car has run well ever since with no re-occurrence of the problem - will continue to monitor the car in case the issue does resurface.

 

[velosolex50]

re intermittent cutting out

Interested to hear the saga. My lpg converted 1990 420 se has exactly the same symptoms, and does it whether its on petrol or gas. What is the function of the ovp relay? Could it also cause rough running (only on petrol) & intermittent failure of the cruise control? Also where is it?
Thanks
Huw

 

[television]

Interested to hear the saga. My lpg converted 1990 420 se has exactly the same symptoms, and does it whether its on petrol or gas. What is the function of the ovp relay? Could it also cause rough running (only on petrol) & intermittent failure of the cruise control? Also where is it?
Thanks
Huw

the OVP relay is a device to protect the ECU's in the engine management.
when it goes it normally start going intermitent.
Poor running and running rough are all of the symptons, its normally near the battery, small square box with fuse on top. on some cars they disintergrate on others it is possible to resolder them, tapping with engine running would normally show up the fault. If your battery is in the boot I thinks it is just in front of it.

Malcolm

 

[velosolex50]

Thanks Malcolm
I was just about to advertise the car as the unreliability was getting me down, but I think I will give it a go with a new relay. Fingers crossed!

 

[television]

Thanks Malcolm
I was just about to advertise the car as the unreliability was getting me down, but I think I will give it a go with a new relay. Fingers crossed!

Before you buy a new one you have nothing to lose by resoldering the old one, all joints must be bright. the plastic box may be welded up, you can re glue with plumbers pipe solvent.

Malcolm

 

[velosolex50]

Thanks again- something for the weekend as they say. Can't get a new one for a few days anyway.
Huw

 

[velosolex50]

OVP replaced with new-----better but not entirely fixed. I will start a new thread.
Thanks for suggestions.
Huw