1992, 300SL, Stall, No Wam Start

[Sean19]

Hello everybody,

I am new here. I have been reading your posts for few nights and I think I need to give you the exact picture so you can help me out better. Sorry to make it so long.

I just bought a 1992, 300SL, with only 62K miles two weeks ago. It is beatiful. I drove it home smooth and nice that night. Few days later again I drove it for about 50 miles again at night with no problem. Finally I decided to take it work and just about 7 miles on a hot day engine started to sputter and stalled at the cross sectionwhen taking off from the stop light. I was able to strat the engine and make it to my work place parking lot few blocks away. This short run took few more starts. Then in the parking lot it started few more times and stalled every time shortly. I was able to go high RPM for very short time about few seconds each time but finally it died and didnt start again. After few hours the engine started normally. I didn't drive it and left it there untill I took off from work and drove it home at nihgt with no problem (7 miles). Few days later I drove it to grocary shop 3 miles away (around noon). After 15 to 20 minutes back from shopping the car did not start again. Did start couple times but stalled right away. Left it there and went back at night and drove it home with no problem. Yesterday I decided to take it to my friends house and check it out. It died few blocks away from home and was towed there. It started again after few hours and made it from drive way into the garage and died.

From my research here and your experiences with similar temperature related problems, I have narrowed it down to Crank Position Sensor, Fuel pump/fuel pump relay and OVP relay. But I need more help specific to my car make and model.

To be honest, I could not locate any of them. I looked under and behind the engine. I have the photo but couldn't find the CPS any where close to the bell house.

Also please let me know where the Fuel pump and fuel pump relay are so I can listen to the pump. Could the pump be so sensetive to temperature away from the engine and stop working after few miutes in day time?

BTW, check engine light never came up after all this. Bulb is OK. So no codes.

Please advise. I make my next messages short. I promise.

Thanks. Sean.

[tecqboy]

There really isn't enough diagnostic information in your question for anyone to say "change part X and it'll solve your problem." The crank position sensor is notorious for failing, and is a fairly cheap item if you find yourself in the shot gun mode. The fuel pump is on the right rear side ( near the filler cap ) and can usually be heard to run for a second or two when you turn on the ignition to presurize the fuel line. After the engine starts, it will run continuously, but you won't be able to hear it. The fuel pump is cooled by the gas flowing through it. Before a fuel pump fails, the bearings usually get VERY VERY loud. I don't believe that a bad OVP fuse will prevent the car from starting. You can find it under a plastic cover in the right rear engine compartment near the strut mount. You may have other electrical issues from something as simple as corroded fuses to a faulty engine control module, ignition components ( rotor / distributor ) or wire loom insulation breakdown. Intermittent problems are the WORST to find, but I don't think you problem will turn out to be heat related. Good Luck and keep us informed.

[Sean19]

Distributor cap seems brand new. I guess the previous owner replaced it before selling the car. Wiring harness shows minor defects only on the outer shell. Wire insulations close to the plugs are flexible. Engine always starts and runs for at least 5 to 10 minutes after a cold start and works fine when driving at night.
I ordered the CPS today. Thanks for comments on OVP and the fuel pump.

[tecqboy]

It's the part about being "OK" at night that is weird. A vampire SL? My 1991 300SL has 105K miles and although it's had a few electrical issues, nothing as strange as your problem. Be sure to post back if the CPS fixes the problem.

[Sean19]

I sure will. Thanks.

Hi,

I have a 1990 300SL with M103 engine and having difficulty starting when warm and would dies off after some time. We have changed the ignition module and now working on the MAS which also control the fuel pump. We did a by-pass on the MAS and the car run fine but the fuel pump will run continuosly. So at the moment looking for the MAS replacement.
Hope this help.

[Sean19]

Today engine didn't start even cold without help from sparying into the intake. Then stayed running for few minutes until I pushed on the gas pedal and it died. Long story short: I started with opening the distributor cap which seemed brand new. Well it was not!! It had a good amount of depotits on each pole inside the cap. More than what I had ever seen before. There was a layer of moisture inside. Very thick and visible. I'm not sure if it was water or oil. I should have paid more attention before I wiped it off.

Cleaned, washed and dried in sun and put it back. Guess what? Problem is gone. It started over and over, cold or warm. I let it run for about 20 minutes. Turned off and acranked again in betweem so many times every time started and idled smoothly. Drove it to work in a warm outside temperature and came back after work at night. No problem or any signs of it.

Thank you all for your valuable comments. I have other issues which I will post soon. Not so serious though.

I think I will change the distributor cap, seal, and rotor anyways. So far so good.

I need to check later if it was oil in the cap wether it accumulates again over time or not.

Thanks again.
Sean

SL300 1992
VW Cabrio 2001
VW Beetle 1968