Just about had enough! I have replaced the fuel pump, the FPR, sealed the distributor cap, replaced the coil, replaced the plug wires, had a complete tune-up and STILL, when it's raining or extremely humid my '91 740 will not start. I have not replaced the CPS. The fan relay and noise suppression relays have been swapped with each other. I have searched the forum over and nowhere does anyone come up with a conclusion as to what they finally did to correct their no-start problems. Any and all ideas are welcomed.

 

I'd try diagnosing it rather than throwing random parts at it.
Next time it won't start, check to see you have spark, injector pulse etc.

 

Thanks Typhoon but everything that's been done has been done by my mechanic and his recommendation. (except for switching the two relays on the passenger side strut). I definitely have spark. I don't know why but the problem is with fuel delivery. I cannot even hear the fuel pump turn on prior to starting. I guess Im gonna go buy one of those test lights and see if I have power to the fuel pump wires prior to them entering the tank. I have put two new fuel pumps in that tank so far.

BTW, I have a Regina system and I've also replaced the coil pack. There is only one fuel pump on the car.

 

You have "sealed" the distributor cap? I am not sure how you did that but you may have done something to prevent moisture from escaping and caused your wet condition problem...

 

+1 wet under the cap does weird things.

My car had a problem where on wet days when you would turn on the high beams the engine would short out and die. The problem was a less-than-solid ground connection. Make sure that your lights are off when you are trying to start. Check the grounds on the intake manifold (don't over tighten them), and check the grounds on the fenders behind the headlights. Make sure that the ones near the battery don't look all blackened and maybe loosen and tighten the bolt that bolts the whole plate of spade connector to the fender. I really don't know if it will help, but it seems like a possibility. With my car, the high beam headlight ground on the drive's side was corroded and gave me this whole problem.

 

Thank God it's over. Here's the scoop. I started having problems about two years ago when there was a down-pour where I worked. Went to start the car after work and no start. Two days later, it started. Had this problem intermittently for about a year. Mechanic replaced all wires and did a complete tune-up and he sealed everything so that moisture could not get in. After moving to Houston, another down-pour and she won't start. Checked FP relay. Shot, or so I was told. Replaced ($$80.00$$) and two days later (waiting for part to come in) she fires right up. Took car back to old hometown and no start after coming out of store. (Beginning to get pissed). Mechanic says to change fuel pump so I agree. One week later...no start again. Pulled fuel pump and replaced again and one week later...no start. Today I replaced the engine speed sensor...no start. (really pissed and ready to call the tow truck). But wait, I talked to the mechanic where I work and he asks two simple questions..."is it getting fuel?" No, I replied. "Why not?" Then I remembered last night I was reading on the Brickboard about there being a connector in the left side rear wheel well so I go out to look as a last resort; just prior to calling the tow truck. Pulled back the trunk liner and viola, what do I see??? A connector that leads to the fuel pump. I wiggled the wires, got in the car, turned the key and she starts as if she was brand spankin' new. Moral of the story, ANYONE HAVING COLD START PROBLEMS, CHECK THAT PRIMARY FUEL PUMP ELECTRICAL CONNECTOR!!! Now I understand why it was happening when it was humid outside...all that moisture collecting in the trunk was probably encouraging some sort of decay on those connectors.

Now in order to be official, I'll have to start the car for at least a month before I can trust her again. But I'll be back in a month, if nothing more but to tell you how good the Alpine stereo sounds. I wouldn't install it until I knew for sure that I was going to keep the car.

Thanks to everyone for your support.