Intermittant No Start -88' 560 SEL

[waylifeshouldbe]

Have searched but can't find anything similar and having benefitted from this forum recently thought I'd ask....

I have, on a few occassions, during the last three weeks, had problems starting (cold) my 88 560. Two days ago, I turned the key, engine cranked but did not fire. While the key was in the furthest position without engaging the starter, I saw the tach "dance" between 0 rpm and 1000. I watched this for a minute or so. Turned the key to off and retried to start - it fired up, idled fine, and later drove fine.

Does anyone know what I was witnessing and am I seeing something that could be telling me of a defective component leading to my intermittant starting issue?

I have replaced the rotor, cap, plugs, wires, coil, and fuel relay from a previous episode. My car still has some issues (ball joints, accumators, power steering hose leak) and am looking forward to the warmer weather to tackle. Would like to resolve anything electrical or fuel related now however.

Thanks ahead of time!

[spriro]

I have a 1999 C280 that did exactly the same thing like yours. I don't know if the solution will be the same, but I had my mechanic lube the starter drive gear and the flywheel about a month ago, so far (knock on wood) the problem hasn't come back.

There is a TSB on this:
DDAF15_30-U-640 Starter Occasionally Does not operate.
The starter stops running before the engine is running due to lack of grease on the starter drive gear.

I had that done with 2 hours labor. $120. Cheaper than changing the starter.

I hope this will work for you.

[delucat2]

My 88 560SL did the same thing. I think my problem was the cold start air valve. It was sticking and not opening when cold. The engine simply would not start - cranked well though. I left the key in the "run" position while I went to check on the fuel pump and finally opened the hood. I could hear the solenoid in the valve "sing" as it was energized, but it was stuck. I pulled the electrical connector off and confirmed that it was the source of the noise. When I put the connector back on, I heard the valve snap open. The car started immediately when I turned the key. This was really scarry as there was no sign of life from the engine until that valve opened. Try cleaning it w/ gumout. I was looking at the fuel injection relay, etc.. Simple fix.

Not sure on th tach bounce. Stray current from somewhere.

[waylifeshouldbe]

Thanks gentleman - I'll take a look at both suggestions and let you know what I find. Go Pats!

[BobK]

I have seen this sort of problem be a coil going bad. Cranks but no fire. Easiest way to test is to swap in a coil from another 560. My SL coil worked for testing in my SEL, just the terminals were backwards.

[ejsharp]

If your check engine light comes on then the problem is the over voltage protection relay... available from parts shop

[cgoodwin]

If I am not mistaken the tack gets its feed from the ignition, cant remember but I think it is from a pickup on a plug wire??? At any rate I would look at the cap and rotor, moisture in the cap will cause arcing and that will make the tach dance and the engine not start. That is the first thing I would look at, unfortuneately I am at home with no manuals and it is simply too cold to go out to the garage and look at my 560 to see.

I may be wrong, anyone else care to comment?

chris

[porkface]

the tach drive is from the td terminal on the ezl unit. and so it goes, chuck.