Newbie with dead W124 needs help please

[nsundby]

Hi, my first experience of Mercedes ownership is turning into a bit of a 'mare. Any help would be much appreciated. It's a '93 E220 W124 TE with the 16V M111 engine, 170k up.

The car turns over on the starter fine, but won't start. There are no sparks at the plugs, and no fuel smell from the cylinders.

Until recently it ran fine apart from a fast idle issue already reported here.

Is there a way of testing that the ECU is OK?

Nick Sundby

[pascal]

Unusual that you have no spark & no fuel. I would re-check for a spark in darker conditions.

If you indeed have no spark then, I would suggest the coil or crank position sensor.
A longshot. On my 300 the cast iron drive that the rotar sits on broke (unusual). This is easy to check though. Have you tried all the plugs/ht leads and the dis cap/rotar OVP relay.

Regards the fuel, first thing comes to mind is the fuel pump relay (behind battery) Its a twin relay. Also there could be a problem with the idle valve.

Did the car just stop or was it going badly first?

Pascal

[nsundby]

I took out the OVP relay fuse, which was intact, and replaced it back in the relay. Bingo! Car starts and runs perfectly. Idle speed problem also solved.

Many thanks to all who posted suggestions - I'm really impressed by the people contributing to this forum.

For others encountering the same problem on a W124, the OVP relay is behind the battery, to the right of the ECU. It's about 3 inches high with a fuse on the top.

Thanks again

Nick Sundby

[marshie001]

nice 1, glad it was a cheap easy fix, those ovp relays have a lot to answer for!!

[nsundby]

I A few observations made by my MB dealer regarding the OVP relay:

- The main purpose is to protect the ECU from voltage spikes or aberrations. This can happen when the car is jump started.

- If the fuse blows, it may put the ECU into 'limp home' mode, where the ABS light is lit and the engine runs like a dog.

- MB said that the OVP relay itself rarely fails, and a new fuse was usually enough to sort the problem. Removing and replacing an intact fuse should have the effect of resetting the relay.

- The original OVP relay in my car (0005405245) has been superceded by 0005406745. One of these is £55 from MB or about £20+VAT from Mercman.

Nick

[pascal]

Good man Nick.

I suppose with all the possible solutions I posted, one had to be right

This fuse has caused problems before on these forums. The usual diagnostics was to remove and clean all contacts, then replace. The MB guys info on the reseting of the relay is interesting, but when he says the relay rarley fails, he is not totally accurate.

Pascal