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So, the saga with my '90 F250, 5.8L, E4OD continues. I have totally rebuilt the power train, replaced all the sensors and recently replaced the PCM. Everything run fine when dry, but not after rain. The engine cranks and spins freely, but the fuel pump runs continuously. I did manage to start it once by holding the gas pedal to the floor, but after today's very heavy rain it cranks and cranks but does not start. I suspect that when it dries out everything will be fine.
I noticed all the wires around the PCM are wet. The engine wiring harness connectors are wet. The relays are wet.
I would suspect the ignition system if the fuel pump was not running. I would suspect the PCM if it did not fix itself when dry. What am I to do? It does seem odd that everything gets so wet, but I'm not sure where the water from the back of the hood is supposed to go.
Well, to be honest, the seal is not in good shape. I did not have this problem before the rebuild, so I guess I was really just searching for a sanity check that the wiring harness getting wet is a problem. Should it be this sensitive?
Fuel pump running constantly is a sign that the PCM is not healthy, if water is getting into it that is not good obviously.. water and electronics don't mix well.
The rain stopped and it was a sunny day, so when I got home from work everything was perfect. I examined the hood - cowl seal, and what I don't understand is that even if the seal were new, it ends before the computer and other wiring. What is supposed to protect this from the water that will run at the gap at the top of the hood? Am I missing something?
it's hard to tell from this pic ... but I went out and checked mine .... it looks like that pcm connector MAY not be seated properly. even if it is, I don't recall that area ever being wet ... and it rains here a LOT.
Just an update. I pulled the cowl, put seam sealer on the joints, and cleaned out the drains -- I got a bunch of "top soil" out of the driver's side. I put new weatherstrip under the cowl, and I also put dielectric grease on the PCM connector. So far, so good. I'm not yet ready to declare victory, but I am sure less water is getting in the cab and more water is going out the drain onto the ground. This was work that needed to be done.
A couple of hints for others looking to do this. You should be able to get to the drains from the bottom if you just remove the bottom screw holding the plastic inner fender and push the inner fender out of the way, however, you will get a bunch of crud falling on you so keep your mouth closed! I also just used large gap self adhesive weatherstrip from Lowes under the cowl along the firewall edge which seems to direct water into the newly cleaned out drains.
I started to celebrate too soon. Today, she wouldn't start and the fuel pump would just run and run. While troubleshooting, I switched from front to rear fuel tank and back a few times, then the fuel pump stopped and she started. So, does anyone know what tells the PCM to turn off the fuel pump? Does it run a particular amount of time or does it need to build a certain pressure? I have not paid a lot of attention to this in the past, but it does seem to run longer when the truck has been sitting for a while.
08-07-2017, 08:36 PM
