Over the last few days it's been cold and rainy. My 91 300E has struggled to start first thing during the day over the past few days, would run rough for about 30 seconds, and then would idle fine. However, this morning, it would not start. Typically it is one crank and an almost start, turn it off, crank it again and good to go. This morning it just cranked and didn't even attempt to turn over. After letting it sit for an hour at a time, I went out and tried again to no avail. I could tell the battery was draining. I decided to take out the plugs and clean them, inspect for gasoline wetness (which some of them had) and sprayed some starter fluid into the plug holes. I let it sit for an hour, reinstalled plugs and it fired right up. Anyone have any idea why? I drove to the auto parts store and got some 108 Octane booster and also filled halfway with 91 octane. I've changed out water temp sensor, ignition coil, plugs, rotor, and distributor cap. could it be my idle valve getting stuck in the morning? Does the moisture in the air have anything to do with it?

I honestly don't know the answer but I'll bet you'll find it if you do a search here and read up on all the similar problems experienced by other M103 owners. I'm still trying to completely figure my 88 300E's problems. I've got my 88 about 75% back to good now.

Please post your outcome.
Regards, Eric

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89 300E "Benzer1" 15.924 Uncorrected
93 400E "Benzer3" 14.200 U.C.
95 E420 "Benzer4"
92 300E "Benzer5" 16.299 U.C. Future turbo CNG
87 300D "Benzer7"
87 300D "Benzer8"
87 300D "Benzer9"
87 300D/70 AMC Javelin "Sidewinder-Benzer"
87 300TD "Benzer11"
06 E320 CDI "Benzer12"
05 E320 CDI "Benzer12A"
71 AMC Javelin AMX 401 "Sidewinder"
74 AMC Hornet 401 "C.K.10" 13.63 U.C.
74 Bricklin SV1 "Presto" AMC 360 pwrd.

check for a voltage on the cold start plug, lack of it means the OVP is not functioning correctly, resolder or best replaced.
mak

Bad gas....

El Sea,

Suckin Sludge & Havin a Gas

I do have a new OVP in there (new plugs also) but where is the cold start valve located? I'll test it. I haven't had a problem since I did the above and it has started on the first crank every day until today this afternoon, when it was actually warmer out. I did get it to start after several attempts at it trying to catch. Almost seems like it's not getting enough voltage but feels nice and strong when it cranks. Sounds like it's flooding and barely tries to catch when trying to start and having difficulty. BTW...my daughter has an 88 300E and it blows my engine away in idle, take off power, and high end power. Runs like a champ!

Pull a wire from a plug, put a new plug on the wire and have someone turn the ignition. Look at the spark at the plug. If it gives a blueish red spark, it is probably time for a new coil. The spark is supposed to be white and bright and you supposed to hear the spark. I'm not an expert, so if someone has any other ideas on how to check the coils, I would like to know also.

About three years ago, my 90 300E would not start. I play with it so much that I flooded the intake manifold with gas. I messed up the lambda adjustment so bad that became impossible for me to start the car. Finally I towed it to Mercedes, cost me a bundle to troubleshoot, because of my fixing and turned out was the coil.

Lately I had similar problems with the 92 300TE. At times was hard to start and other times would not start at all. Checked the spark and noticed that when the spark was bright the car started. When the spark was dim the car would not start. I believe the inconsistencies was from the distributor cap, rotor and coil. Changed it all and the car know starts normal.

Good luck
Michael

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1990 300E 264,000 miles
1992 300TE 188,000 miles

...Interesting. I was wondering if that could be it. I have recently replaced the coil and the rotor but not the cap since it looked so good. I will have to try the spark plug test. I had also messed with the Lambda since it wasn't idling well and got it to idle nicely with a solid start (on second attempt). When it starts now, it struggles and then catches up and goes fine. After stopping and turning it off for a while. It starts right back up like it's brand new. Sound familiar?

the cap is one weak point ,the carbon connector breaks off and there exists a gap between the rotor and cap .The engine does runs but has starting issues
mak
300se

I might as well replace the cap then. Today I noticed a "click" "click: noise when I raised the hood and noticed it was coming from the #1 spark plug wire. As I pulled it while it was running, I saw it was arcing to the manifold. I placed it back on and repositioned it so it wouldn't arc anymore but maybe I need to replace the plug wires now along with the cap? I don't know how old they are. Do I need to get special MB plug wires?

pulling a live spark wire off of a running engine? I would be very careful doing that

I would not do that at all....

...I used insulated pliers. What's the difference if you do that or pull the plug wire, insert a spark plug, start it up to see if you're getting a spark? Your still holding a live plug wire but now with a plug sparking....both are just as risky to me but I will definitely head the advice next time. Thanks