Engine cuts out randomly (1993 W124 E280)

[Alan J]

I wonder if anyone can suggest an answer...? The engine cuts out randomly: this can happen at high cruising speed (in which case it sometimes restarts on its own), at low/idle speed, when trying to restart whilst warm. The effect is just like the ignition being switched off.

It will restart after 3-20 attempts and then behave normally for anything between a few minutes and a few weeks without recurrence. When trying to restart, the engine will start 'normally' and then cut out after a second or so.

After enough tries, instead of cutting out it will give a cough and run happily - until the next time!

Also, when coming to a halt, the engine revs sink almost to stall (about 500) before recovering to 700. Idle wanders between 500 and 750.

I'm tired of being told to wait until what ever it is fails completely! It's often embarrassing and occasionally dangerous and it's taken away my confidence in the car...

Thanks,

Alan J

 

[justin1820]

this is an engine with a hfm injection and ignition system which is diagnosable with suitable diagnostic equipment to see if there are any stored faults in the system, this would be my first port of call. this obviously isnt a cure but if i does not come up with any faults then an air flow meter is a good bet cause it doesnt always show a fault in the system

 

[mjtray]

This is one of the most common problems on the m104 engine and the odds on favourite will be the OVP relay (Over Voltage Protection) relay.

Sits up behind the battery and behind the plastic cover that protects the ECU's and to the right of the ECU. It's 3 inches high, silver, with a fuse on the top.

The original relays had a design fault on them, which causes the soldering to break down internally. This will cause random shut downs as you have explained.

Replacement is easy....10 minutes and the relay costs about £45.

Do this before you do anything else.

 

[Alan J]

Thanks for this! I've ordered an OVP relay and will fit it over the weekend....

Watch this space....

Best wishes

Alan J

 

[Alan J]

Engine cuts out randomly

Hi

I've fitted the new OVP relay and (I hardly dare write this...fingers firmly crossed) have had three trouble free days. Still a long way to go, but I'm beginning to hope!

Best wishes,

Alan J