Merc 1982 500SEC No spark

There is a very expensive relay under the bonnet on the nearside (IIRC). My 500 SEL needed one shortly before I bought it.

There is a hand full I'll check them out, would make sense if the unit was not getting power.

The unit has two connection plugs.

A double wire going to the distributor - and the distributor is pulsing so I am making the assumption that is OK.

Then there is another set of 4 wires coming from somewhere else, this may go to that relay. Should find a wiring diagram to check for feed voltage to the unit.

I found a similar problem when I had a 230TE. The ignition system is such that you can easily be fooled by looking for the fault in the wrong place. In my case I noticed that the fuel pump mounted under the rear, which usually runs for a couple of seconds when you turn on the ignition, wasn't.

I tracked it down to a relay which, on the 230, was behind the battery. Fortunately it was a dry joint where said relay attaches to the PCB, which was an easy repair for me. Finding it wasn't though.

Rob

You could try posting the same question to alt.autos.mercedes where there are a lot of people who really know Mercedes cars, especially the older models.

Richard See

I did check for spark and here was none. As for petrol I could smell that.

The control unit, when I took the lid off, smelt of over heating.

Just don't know hoe one goes about checking electronics.

Nothing there someone advertising an auto blog and another money making scheme.

Unless it comes up when the whole group has downloaded. Bot very active at present.

I've posted it anyway.

Thanks

Rob

I typoed, it's alt.auto.mercedes, I didn't realise that .autos. existed until you mentioned it.

Apologies for the error.

Richard See

So thats why there has been no response, have now subscribed to alt.auto. and posted again.

That group is actually showing at present 105 unread headers which is much better than the other one, at least its active.

Lets see what happens now.

thanks

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Rob saying something like:

Simplest way is to take a known good unit and a multi-meter. Cross-check resistances on all leads on the good one and make a table then do a comparison with the suspect unit. It might not tell you the exact fault (it will if you are familiar with them) but it identifies a dud one.