1991 Mercedes SL500 Intermitten No Starting When Warm????

[ron59b]

Good evening all

A friend of mine has a 1991 SL500 that I am considering purchasing. The car has 98,000 miles and ran great aabefore he starting issue. Hes narrowed it to possible issues with the coil or the ECU.

He said that when attempting to start the car, if the dash icons along the base of the cluster aren't on or lighted, the car will not start.

He also said that once the engine is warm, the car will not start intermittently. Can some tell me where to start? What might be the most likely culprit?

Thank you

Ron

[duxthe1]

Ignition switch.

[ron59b]

Good morning and thanks for the reply. Are you referring to the electrical connector for the ignition switch, or the entire lock assembly? How difficult is it to replace?

[97 SL320]

The dash lights not working helps but we need a bit more info.

Define " car won't start " in terms of:

Turn key, engine cranks but won't run.

Turn key, engine won't crank.

You could have a ignition sw problem for the no dash lights and a fuel system issue for a no run warm.

I bought a SL parts car a while back. In the car was a dealer receipt for repairs.

Service writer: Customer states , " Car won't start "

Tech : car started 2 dozen times over the day.

Service writer: customer states , " Key won't turn "

List of ig lock, other parts and labor.

[ron59b]

Thank you 97 SL 320 for your reply. When turning the key, the engine does turn over, but will not start. I hope this is helpful?

Ron

[97 SL320]

The next step is to attach a test light to the ignition coil power supply and see if it lights up.

I'd also probe other circuits that need powered up with key on or when cranking.

As post 2 states , maybe ignition switch needs replaced.

[ron59b]

Thank you

[Benzyne]

I too have had the same symptoms as this but without the dash lights not going. Mine was the Crank Position Sensor. I got from here and put it in. 30 minute job. Problem solved. Worth doing as it was under a hundred bux and it seems to be a common thing with all types of cars.

[ron59b]

The car is now running after replac ou ng the following items:

1. Ignition switch.
2. Crank sensor.
3. Fuel pumps.

Now the car is having an issue with intermittent high and low idle. The car surges on it's own. Sometimes the idle is so low the car cuts off. I also get the smell of fuel sometimes. Any suggestions?

Thanks

Ron

[ron59b]

I forgot to mention the car did sit for sometime before I purchased it.

[rsandor]

Ron, My 94 SL500 had a similar problem in that it would start very hard only when the engine was warm - no problem when cold or hot, only when warm. Problem was found to be bad camshaft seals. Condensation would form inside the distributor caps and mess up the ignition timing. I replaced both camshaft seals, cleaned the distributor caps and have had no problems since.
Good Luck
Bob

[ron59b]

Thank you Bob for that information. I hope you're enjoying your weekend? Also when I attempt to operate the convertible top with the switch, nothing happens? Any idea where I should start?