1990 928 GT - Failure to start following rain...

BTW Wally, Howard chuckled when I told him what you said. He likewise, spoke very highly of you.

Wet plugs can be too much fuel, or too little spark.

To test the "too much fuel" possibility, the next time that the problem happens, hold the throttle down and try to start the engine. When/if it fires and runs for a few seconds, then clears up at least partially, you have diagnosed that the problem is too much fuel. If the engine doesn't run at all, pull the fuel pump fuse, hold the throttle down and try to start the engine. If the engine then tries to run, or runs for a few seconds and dies, replace the fuse, hold the throttle down and try again. If you can get it running, you have diagnosed "way too much fuel".

If none of the above helps at all, and the engine doesn't even fire, you may have just diagnosed "no fire at the plugs" instead. That diagnosis sounds a lot less likely, after what has been done to the car.

Ok kent, I would say howard covered all the tune-up basics.
You maybe on the right track at the MAF sensor, they will do strange things but I do not know if moister on the resister wire would do it.
What you can do to test that theory is whan its nice out and it starts and runs fine. shut it off, use a spray bottle and fith the air cleaner off give about 5 good sprays in and on the MAF. let it sit for 3 min and then start it. if it acts like it dose when it rains you hit the problem, if not then lets move on.

There was a comment earlier about water running down onto the (CP)central electrical panel. Make sure that moister is not getting onto the electronics that way. remove and check the LH connector for moisture of water stains is another thing to look at.

I hope you find it so look close at everything and let us know.

Brad

Fellows, this issue continues to plague me. I could sure use some help. I have been stranded 3 times with a car that would not crank, recently. In every case, I had to just call someone to get me, & then return hours later to a car that cranked up fine.

The symptom that I think we need to focus on is this:

When the air is damp (day of rain, or day or two following rain), the car intermittently will not crank. But the really strange thing is the 'PUFFFFFF' (like a gasp) that sounds like it tries to fire only on the first attempt to turn over, & then after that it the starter only turns over and over, with no fire nor further gasps. However, you smell fuel strongly, as you attempt to continue turning it over. I have found that if I hear that PUFFF, I just need to back off attempting to start it, because it works like flooding symptoms. The longer I attempt to start it, the longer the delay before it will restart hours later.

I troubleshot it in my garage for hours, over the weekend (while it was rainy and wet outside, might I add). I thought it might be Mass/Airflow related, so I unplugged the plug from the MAF, & it still won't crank. I replaced my plugs (Bosch Standard Copper Core), and the old plugs looked fine still. I pulled both distributor caps and all is crystal clear in there, with no moisture. Wiped all down again with a dry cotton cloth, but no change after reassembly. I pulled the central fuse/relay panel and inspected all. No moisture that I can see anywhere (the car has been stuck in garage for 3+ weeks now, due to it leaving me stranded). No lines showing possible water intrusion on or around the LH connector. I pulled the (new Beru) coil wires, and checked for water intrusion/moisture; and saw none.

I am stumped!

I also want to say, once it does finally start - it runs perfectly. No hesitation, degradation in power, etc. Of course on real cold mornings it idles high (swinging up and down slightly) for a few minutes until warm, and then settles out smoothly after a few minutes. But I am figuring that is normal.

Thanks in advance for any help on this!

Could my Fuel Injectors possibly be plugged, & pissing instead of atomizing? I could possibly see a straight stream not firing properly, & flooding things out. But why then would it fire up later, perfectly. And why would fuel injection be prone to any issues related with moisture in the air?

I think you still need to isolate whether this is a fuel or ignition issue. Remove the fuel pump fuse. This also shuts down the injectors on your car. Pull the cover off of the air box and spray starting fluid onto your filter for a just a few seconds. See if the car hits on the ether. If so, then this is a fuel problem. If not, then it is an ignition problem. If you're still not sure, remove one plug wire from each distributor cap. Hook up a spare spark plug and have a helper turn the car over. Lay the plug threads over one of the bolts for the engine cross brace. Observe for spark. Do this on one wire from each distributor cap.

Report back. Also, there is a two pin plug for your ignition trigger units at the passenger footwell slightly above the CE panel. One wire is white and the other is green, so it's easy to identify. Check its condition and look for moisture traces.