@ 3rdrock. the coolant temp sensor is used by the PCM to help determine fuel mixture. at colder temperatures more fuel is needed to start and run the engine. my old B5 had a temp sensor go bad and give a false reading of -274 F and it never even gave me a code for it, i hooked up my scan tool and went though the datastream and came across that crazy reading, i dont often see them fail like this but it happened to me. this caused the PCM to richen up the fuel mixture so much that it flooded the engine with fuel. it simply caused the air-fuel mixture to be thrown off far enough that the engine couldnt start.

@millerS4. im going to see if i can find you a good power distribution diagram when im at work tomorrow. i usually start with checking for poor connection in the connector then im move on to splices since the power wire that powers the pump may also power other things as well and splices are always weak links that when it comes to corrosion. also and im asuming that you already know this but im going to say it anyhow, so please dont take offence if you already know this. the fuel pump relay will only stay energized for a few seconds of it doesnt detect the engine running or cranking over, so if the key is just turned to the on position it will shut off in a few seconds. i hope this all made sense, as i have had a few drinks lol.

 

mikeresnit,
Thanks for the info, it's always good to share your knowledge because some people may not know what you know and it never hurts to hear it again.

 

no problem always happy to help.

 

I had the exact same problem with my Mercedes C240 a year ago. It turned out to be the crank shaft position sensor. I replaced it and it solved the problem. The CPS is located on the bell housing bewtween the engine and transmission. It took me longer to find it than to replace the darn part.