[takviator]

Hi there,

1991 Mercedes- Benz 500SL V-8 engine. Its only around 100000km.
Started few month ago, the engine won't start, did crank it but won't fire after drive while( around 1 hour or more). If its sit at parking spot more than 3 hours and start and drive normally.

Beginning had only once a month this problem, but has almost every two days recently.

The problem has all of sudden doesn't mutter weather and engine's temperature. But most likely happen this right after diving stop and try engine start it.

Sometimes happen sit the car after few hours.

Never happen engine stall it so far.

Every time I heard fuel pump is working.

Do anyone have same problem or some one knows solvent?

Thank you for your help

[TxGreaseMonkey]

I suspect the Ignition Control Module (ICM) is intermittently failing. Replacements are incredibly expensive, so shop carefully. Try and get a warranty, especially if you go salvage. Another possibility is that the coil is breaking down--this is less likely, however.

If you are Eastern European, try some of the shops around Stuttgart, Germany for a replacement ICM.

[takviator]

Now I had same problem in the morment.
No spark during cranking, same time seem like no injecting the fuel. No smell gas at exhaust muffler.
Is this still ICM problem?
I give little shock to ignition coil, and looks like ICM and fuse box with rely, then engine fire up.
Thx.

[TxGreaseMonkey]

I'm not sure I follow all of that. At this point, here's what I would do:

. Clean main ECM (computer) ground.

. Check ICM and coil connections, ensuring they are clean and tight.

. Check all under hood and under dash fuses with a test light or multimeter.

. Check for codes.

. Check the ignition switch for wear or pitting.

. Test reference voltages to several sensors, if possible, to verify the ECM is likely okay.

. Replace the ICM and coil.

At this point, I still think the problem likely involves the ICM and/or coil. Try to substitute these parts and see if it solves the problem. ICMs, regardless of manufacturer, are prone to failure. Heat is their enemy and they should be replaced every 200,000km or 10 years, whichever comes first.

[takviator]

Now this car is totally won't start at all. I can't just buy ignition module and change to check how it goes...
Its feels like no spark and no gas.
I check the price it, the price is way too expensive.

I don't see any engine light, even when I turn key is on. Looks like does not have engine light.

Is there any way to check error code on board? I don't have diagnosis scan tool for this. I only have OBD2 scanner.
If its possible I'd like to know how can get the error code.

Thank you for your help.

[TxGreaseMonkey]

If you checked everything I suggested in the last posting, I don't have any other ideas. You will have to contact a Mercedes manual on how to read codes.

[takviator]

What I changed is crank position sensor.

This engine mechanically injection pump using.

Ignition timing control by ICM (ignition control module) and crank position sensor.

Checked crank position sensor by OHM meter.

I found crank position sensor has open circuit.

It runs good after replace crank position sensor.