380 SEL cranks, has spark will not start
 

Hello, I have a '82 380 SEL which just up and quit running at a stop light. The motor cranks just fine, has a fairly strong spark, timing chain seems OK, fuel pump is working. Last night I removed one injector (left it on the fuel line) and cranked the engine. Injector puffed one nice cloud of gas then nothing but maybe a dribble. I would quite cranking, wait just a moment to crank again and again the injector would puff one time and then no more nice puffs. Any ideas? The plug (only checked one but it was a different one than the tested injector) seemed very dry. I appreciate any advice.

You need to go through the basics. The possibilities are: jumped timing left bank, fuel pump relay, fuel pump, main computer. I would pull all plugs, ground the coil, and check compression starting on the left bank. Then I would jumper the pump relay and do a volume and pressure test according to the manual. That car should have a frequency valve. If the compression test is good, you could unplug the freq valve and throw it into open loop and see what that buys you. Keep me posted on progress.

Peter

Thanks for the advice. I am taking the afternoon off and will do what I can. In the past a friend showed me how to place a jumper to make the fuel pump be constantly on. I could hear it running and a ticking sound on top of the motor. I find it interesting that the injector just seem to produce one good puff of gas and then nothing (or barely nothing). Seems like a pressure problem. I do not have a fuel pressure tester, however I am willing to buy one. Any other advice before I leave for the afternoon?

If I'm not mistaken, the pump comes on via the relay and then the relay has an rpm sensor in it that keeps the relay closed. I would try jumpering the relay first based on your description of the one shot from the injector.

I have jumpered the relay which controls the fuel pump. When jumpered I can hear what I think is fuel flowing through and back to the tank. Would jhte fuel pressure regulator be something I should test and if so how do I test?

Again as a professional MB mechanic, I would run a compression check first. It is quick and easy and eliminates one possibility right away. If you find no compression on the left bank, you know in a half hour what your problem. If compression is good, then you can start doing all the fuel delivery checks. The choice is yours, but I don't have time to waste, so I have to approach every diagnostic situation in an orderly fashion.

Good luck,
Peter