1992 300E 3.0 L stalls when warm
 

My 1992 300e 3.0L starts fine, runs very smoothly and well - it would run at road speed all day long. But once up to operating temperature, if I stop at a light or whatever, letting it idle, it stalls and won't start at all again until the engine has cooled off. Then it starts.

When it won't start, it has spark, so I don't think it's an ignition module. The fuel pump runs then shuts off when keyed, so I think the MAP relay is fine. I replaced the crankshaft position sensor - problem not solved. Changed out the 4 pin water temperature sensor that controls fuel and spark at the computer - problem not solved.

How to I check the engine for fault codes?? Is there a place I can plug in a code reader?

Any ideas?

Thanks!

Dave

I would check the rotor button and distributor cap common issue with that motor. Visual inspection would let you know their condition.

Thanks - I'll check that out tomorrow night. Hope that's it.

Dave

don't forget to check your plugs/wires.. i mean plugs arn't even that expensive :) but make sure you get the oem brass ones..

i had a friend with an e420, he had simillar symptoms all he needed was a tuneup

Have you changed the distributor rotor? If it's old or a cheap replacement, get the best you can - MB - and try it.

Same symptoms for me and even the original, 17 year old rotor solved it.

RayH

crank position sensor
 

Had the same issue and found out it was the crank position sensor. It's an easy fix. You likely have the original one on the car. Good luck.

Al

I had the same problem 4 years ago. Fuel pump relay. Easy and not very expensive.

The first thing I checked out was the fuel pump relay. I ordered a replacement, but my car is fitted with a MAS relay instead, so it wouldn't fit. Instead I turned on the key and listened for pump activity with the door open - I could hear the pump spool up and then shut down when up to pressure, but still, when it was warm, it wouldn't start. So, I re-checked for pump sound and it's there, so I made the assumption the relay is ok.

Then I replaced the crankshaft position sensor, and still the same problem persists.

Then I replaced the 4 pin temperature sensor that sends engine temperature information to the ecu. Still the same problem.

I have yet to check out the rotor and cap as suggested, since I think they are the originals. In the meantime, does anyone know if there is a way to read trouble codes (fault codes) on this vehicle??

Thank you all for your time and good advice!

Dave

With the greatest respect ...
 

Need I say more?

RayH

Well, off came the cap and rotor - after careful inspection, it seems the cap is intact with no cracks. The contact posts are greenish with brown scale, and the center graphite contact post looks somewhat worn, but the rotor is terrible!!

I'll order fresh parts, install them, and see how far down the road the car takes me this time.

Thanks again folks! I hope to post a success story soon!

Dave

I wish you every success. PLEASE buy quality (pref. MB) parts. I once tried cheap and the rotor was dead in 18 months.

RayH

aermotor, at least clean the distributor cap contacts if you don't want to spend the money to buy a new Bosch cap. Buy a Bosch rotor.

Well, I replaced the cap and rotor and took the car for a little ride. It ran and didn't fail!! Drove about 20 miles, starting and stopping to check it all out. Cleaned the spark wire ends and lubed with dielectric grease, both ends.

THANK YOU EVERYONE for your help!!

You saved me and ended my frustration. This is my daughter's car and we've traded so she can get back and forth to college. My regular car is a '93 300D and I prefer the diesel, frankly. She does not, however. :) I've been driving my wife's CLK430 and, while it's a nice car, it's just not for me.

Dave