300E start drive 3-5 miles won't start until cools
 

I have a 1987 300E that starts, then if you stop before it warms up good (3-5 miles) it will not start until it cools, does not do this all the time, sometimes it goes for months with out this problem. It is becoming harder to start now also. Sometimes when driving slow or coming to a stop light before it warms up good it cuts off and won't start until it cools, if I drive at highway speeds until it warms up completely it goes all day with no problem. I have changed the cold start valve, the ECU computer, fuel relay, spark plugs, and wires, none of those cured the problem, any suggestions. Thanks, Steve

possibly a crank sensor?

Well, the symptoms dont seem to match, but until someone with more knowledge posts,

do a search on the OVP (Over Voltage Protection relay)

300-E hard start problem
 

When was the last time the car was tuned up? I would check the ignition systems first. It may be a bad coil . Second fuel pump may be going. Check the OverVoltage Protection relay under plastic cover behine battery. check to see if fuses are still good on top unscrew the relay and shake if it rattles its bad.

Wish I could help you further.

Bob Geco

I don't think that rattling is absolutely indicative of a problem. I wondered how these buggers worked, so I took one apart (and I put it back together again, and it still worked...). It's pretty ingenious - a Zener diode (probably at 12 volts or so) powered through a resistor operates a relay coil. If voltage is under 12 volts, the Zener shorts the whole thing to ground and nothing gets through to power the coil. If the voltage goes significantly higher than that, the coil is energized enough to pull the main 12V (usually going to high-value electronics) to ground and blow out the fuse.

But the rattling in my case was a piece of phenolic insulation thrown between the bottom of the printed circuit board and the metal case of the OVP unit. Because rattling generally is associated with "bad", I'll bet later units are built not to rattle.

These symptoms sound very much like what just happened with my 2000 C280 where there is a failure with either the camshaft position sensor or crankshaft position sensor. It starts with an non start after having driven sometimes a short distance, sometimes a longer distance. Then it spread to the first start of the day and then progressed to the car shutting down while coming to a stop. It happened during a hot spell and it did seem to be heat related. Simply waiting awhile and it would restart. First I tried replacing the front camshaft sensor but it turned out to be the rear crankshaft sensor.

glenmore
1991 300CE
2000 C280
1990 LS400

Thanks to each of you for taking time to respond.

My car is a 1987 300E with 160,000, I have driven it for 8 years. Fist time it failed to start I took it to the MB dealer, they replaced the fuel pump and OVP relay. I left the shop and got about three miles before it cut off at a stop light. They came to pick up my car and it cooled down and started before they loaded it up. They kept the car for two weeks and said they could not get it to repeat the problem.

It has happened (drive a short distance and fail to start) about a dozen times since 2003, sometimes 8 months between episodes. In the last week or so it has become hard to start, and cut off once about a mile from home. I have replaced plugs, wires and cold start valve in the last six months.

Where is the crank position sensor and OVP relay located and what do they look like? Thanks, Steve

Not sure if your car has a FPR or if it is integrated into some other relay, but I would check that out. When the car stalls, jump your FPR and see if it starts right up. Check out one of my old threads, different car but similar symptoms: http://www.peachparts.com/shopforum/tech-help/155624-1985-380se-w126-stalling-fuel-pump-relay.html

Parts of this is sounding more like my problem. My car died once in the middle of traffic, and a AAA tow truck happened by so he picked me up and dropped me off around the corner on a side street. The car then started right up. I've read that the cold start valve is very hardy and not prone to failure. Your hard to start problem sounds different though. When my car would start, it would start. When it wouldn't start, nothing would help except waiting an arbitrary amount of time. Check out Fastlane under "engine electrical" and further under "reference sensor" and see what these things look like. You should have no problem finding it on your car. On my newer 2000 C280, it is just a sensor clipped to the harness, on the front of the engine and the rear one is by the firewall by the brake booster down in the bell housing. On my 1991 300CE the front one is right in front and I've never had to mess with the rear one. The front ones are just plug and play, very easy. The rear ones take fiddling time but still quite easy. I was also told to check the fuel pump relay, but this was not the problem.

glenmore
1991 300CE
1990 LS400
2000 C280

are you saying the syptoms he describes don't match crank sensor failure? if so what are they in your opinion?

I think what he is saying is that the symptoms don't really match the OVP relay failing but until someone else posts.... That's how I read it anyway. And I'm following this thread (and my own) trying to fix a similar problem in an '89 300E. After looking at gmercoleza's old thread it looks like I'll be taking a close look at the FPR this weekend.
Thanx to all.
Chuck.

I had the same symptoms that you describe. It was like chasing a gremlin. I could never nail it down. I replaced , fuel injectors, fuel distributor, throttle pot, OVP, fuel relay, ignition wires, and a host of other stuff I have forgotten. I have chased this devil for 2 years. One day it had the problem in my driveway. It would not start, I checked fuel and spark and it was getting both. It took a tow behind my pickup to get it going. It's a manual transmission. Once it got running it would die if the RPM dropped to less than 2500. It would not idle until it was warmed up. Took about 20 minutes before I could idle. It then drove and ran normally. Guess what it turned out to be?

The rotor and distributor cap!

High voltage was leaking & arcking all over the inside surface of the cap. Here is proof and a picture of the evidence.

http://www.davidpetryk.net/imagepages/image727.html
http://www.davidpetryk.net/imagepages/image729.html

I cleaned up the cap and things were fine for a few months. Then it started again. I finally replaced the cap and rotor and it runs like a new car. Based on the symptoms I had, I would have never guessed that was the problem.

Today I removed the idle control valve and cleaned it with brake fluid, replaced it and the car did the same, all the related hoses were in good condition. It was very hard to start, 4-7 tries, but after you get it running it runs smooth above 1500 rpm. I took "dpetryk's" advice and removed the distributor cap and it's in really bad shape, after seeing the cap and rotor I am amazed it started at all. I'm ordering a new rotor, cap and some other parts tomorrow. I am going to try the cap and rotor before I tackle the CPS. I will let you know later this week what improvement the cap and rotor make, but after reading a bunch of post I think I have two problems. I feel the cap and rotor will fix the starting but I may need a crank position sensor also. Thank's again to everyone for your help. This is a great site, I'm buying my parts here!!

crank or rpm sensor
 

just-n-time here,look up my post's you will find one with pic's,just finished the job on a 420sel.

crank or rpm sensor
 

just-n-time here,look up my post's you will find one with pic's,just finished the job on a 420sel.:behead: :silly: