W123 200 intermittent starting problems...HELP!!

[thenaylortribe]

Evening all!

I am having a problem with an intermittent starting fault on my W123 200 2 litre petrol 1981 mercedes.
Smetimes it starts first time on the key, turn off, then sometimes won't start at all.
Believe it to be ignition related (transistorised system) as have had a plug out and checked for spark. When not starting, surprisingly, no spark.

When the car is running it doesn't cut out but runs without missing a beat.


Any ideas?

Lee

 

[Bolide]

When not starting, surprisingly, no spark

I'd have said unsuprisingly...

If none of the plugs have a spark on the occasions it doesn't start then it has to be the electronic ignition, king lead, distributor cap or coil

First I'd check you have volts on the LT side of the coil next time it doesn't start. If you don't, there may be a malfunctioning immobiliser on the car or some other fault. Next I'd check the king lead, distributor cap & rotor arm. If it has points & a condensor I'd check them

If none of these looks like the problem it probably is the electronic ignition unit. I'm not sure, though, how one of these can be intermittent and I suspect the problem lies elsewhere

It just might be related to the ignition switch - the "start" position feeds the starter and the coil so make sure the coil gets its feed in both ignition on & start. You can wire a bulb across the coil LT & earth to show when it has volts

Halfords sell a natty little neon tester that plugs into the HT lead at the spark plug. They're useful for diagnosis

Nick Froome
www.w124.co.uk