1989 300E Follow Up

Hello: I posted back some time about some problems about my 300E cutting out. I replaced a whole bunch of parts and went to the mechanic who discovered fuel odor in the crankcase. The 02 sensor, and the cat were
replaced, all the header gaskets are tight and sealed with the oxygen getting in brofe the 02 sensor. The car runs for a while then cuts out. When the OVP relay is dissconnected the car runs fine after being warmed up, as it is running in a leaner mode. It is certain that the motor is getting flooded after the initial warm up. But with the relay DCd, it runs. I bought the 02 sensor to the mechanic and he tested it, stating it was sound. WHat is making my motor flood out?- Charlie, Monmouth COunty NJ
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Given your description one can only suspect the OVP relay - even though it was replaced not too long ago.
If you do choose to replace this OVP relay be sure you buy the right one for this car.
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Hi,
In the course of my "travels" on Usenet a kind soul posted this explanation of the OVP relay. I don't know enough about electronics to opine on its truth but you may.
The OVP relay protects the sensitive electronic circuits, i.e. your ECU from high voltages.
It basically consists of a fuse, followed by a relay energized by a small circuit, which has a zener diode built-in. This relay feeds the the SRS, ECU and ABS (any others?). If the voltage goes too high, the zener conducts, and shunts the circuit to ground, cutting out the relay, and if very high, blows the fuse.
These relays get tired, as basically, it has to activate continuously when the engine is running. 10 years is about the lifetime.
When it cuts out, your engine reverts to "dumb" mode, and won't compensate for temp, O2, timing, etc.
SRS, ECU and ABS, that's all. And depending on model and/or # of systems that are protected, there are different versions of OVP relay, between 5 - 9 pins, and 1 or 2 fuses.
A cross-cable during a jump start can easily kill this relay.
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Tom: I know that parts can go bad..... I did repalce the OVP back in October of 05....--c
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If it's not the OVP then maybe the air flow meter is bad (I can't recall if it was mentioned in your original post way back when). Wasn't it T.G. who was successful at cleaning his with some electronics parts cleaner and a pipe cleaner a while back? I was not as fortunate and had to replace mine a couple of weeks ago and these are quite pricey so I'm hesitant to throw (expensive) parts at your problem, but it may be worth a couple of bucks to try cleaning it (the risk is that if you break it you'll need to buy a new one whether it was bad or not). BTW, one free thing to check is for obstructions in the air intake ahead of the air filter. If the car has sat for any length of time who knows what might have nested in there... ;>
Josh
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good sugestion.....but i think the car keeps flood out, becuase if the OVP is hooked up, the car will cut out after a few minutes and then if it sits for about 5 - 10 minutes, it will start back up...and the plugs were getting a little fouled up...
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Make sure to change out your oil, as all that gas leaking down will ruin it!
Marty
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I had a similar problem with my 1985 380SE. It turned out to be the ignition control unit (ICU). Depending on where you buy this and whether it is rebuilt, it could cost $150 - $400.

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