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Issues starting after sitting during damp or wet weather

96AWD5.LOL

Elite Explorer
Joined
March 14, 2012
Messages
77
Reaction score
44
Location
Austin, TX
City, State
Austin, TX
Year, Model & Trim Level
91 XLT 4x4 - "Red Velvet"
I've recently moved and now the explorer sits outside until my garage is organized. Most days after rain or heavy dew in the morning I'll go out to crank it and it wont start. No matter how long you crank it wont start. I usually just turn the key to on and off several times and eventually it will come to life. Once running there are no issues starting throughout the day. I first started having this issue on a recent road trip. I came out to the explorer on a rainy day 2k miles from home and it would crank but not start. It wasn't till recently that the problem resurfaced. If its stored in a garage it doesn't seem to have the issue.

I've recently replaced the CPS, EEC Relay, & Fuel Pump Relay as they were all original. I've kept the replaced parts just in case.

I came across a thread here that mentions when the check engine light stays on durring a crank that its not receiving a signal from the CPS. This is what I'm experiencing. The check engine light is staying on while cranking. I know it will start when the light goes out when cranking. Is there any more theory and operation on this? It has a new fuel pump as of last July. Anyone have an idea on this?
 



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Maybe check fuel pressure, just to eliminate that issue. Some aftermarket fuel pumps, especially the cheap ones, just are not reliable.

If that does not resolve it, begin checking your electric connections … one by one by one. You might begin with the primary wiring harness and CPU connections.

Good luck.
 






Will do. My brother and I recently checked the fuel pressure but I'll need to get a gauge and re-check. I edited my post to include the fact my check engine light is on during crank.
 






Updates: Fuel pressure seems to be normal at about 38 PSI. Ive noticed that not all of the relays click when I turn the keys to the on position when the issue arises. I'm now just waiting till I hear all of the relays before cranking. I had this ECU/M out within the last year and it was pristine inside, no distended caps. I'll check power to the relays next time it wont start.

I also bought a code scanner and did both KOEO and KOER self tests. Its a 91 so I received 11 on both tests which via the book seems to be an all clear.
 






Just because an electronic item looks good doesn’t mean it is. A lot more to go wrong than the caps.

this is free. Try this:
 






Check grounds too. They are often overlooked. On a dry day, throw water at different portions of the vehicle until you have an issue starting. You might be able to narrow in on the area causing the issue.
 






Quick follow up:

TLDR: It seems to have been the PCM.

Finally had time to sit down and examine what was happening. Oddly, in a positive way it had been getting worse lately. Makes it easier to diagnose when the issue is consistent. I started with checking relays. All checked out fine. I noticed that when the ignition was in the on position the fuel pump would kick on and not turn off. Went back to the relays and checked +12v signal to the fuel pump relay and sure enough it was constantly on. Typically, it should cycle on then off. I pulled the PCM relay and verified the +12V to the fuel pump relay was removed. I so happen to have two extra PCM's for this vehicle So I replaced it. With everything connected I turned the key to the on position and all the relays clicked like normal. Truck started right up. I had to wait for a different replacement part to come in so the truck was sitting about three days. Decided to start it up and turned on just fine and has ever since. I went back to the old PCM and took it apart. The caps were fine at the base and were not distended. However, there seems to be some lifting of the PCB clear-coat material at the base. I can only imagine a trace may have come apart. It almost looks like there was water ingress on the board. The foot-well where the PCM lives seemed quite dry. After a recent rain, I checked the area again and didn't see any moisture in the area. We'll see how long this PCM lasts.:dunno:
 






This seems to be the third PCM issue in the last 2 weeks or so. Interesting..
 






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