Confusing random no-start issue...

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Feb 25, 2010 | 05:44 PM

#16

ToaDisco

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From: Around

Quote:

Originally Posted by 3000 FPS

The prints I have show that when the ignition switch is in the start position 12 volts goes through the ignition switch to a digital transmission range sensor or saftety nuetral switch then to a starter motor relay. The ignition switch is what energizes the starter motor relay. The contacts then close and bring 12 volts to the starter solenoid that then closes. When the solenoid closes it's contacts then takes 12 volts straight from the battery and applies it to the starter motor. I would check for corrosion also around the battery junction box under the hood. I would also check the fire wall inside the truck for any kind of moisture. There are many electrical parts mounted to the firewall inside the truck and corroison could be building up there also. The starter motor relay is located under the hood on the passenger side on top of the fender well.

I swapped out the ignition switch and there was no change. I have water getting into the cab somewhere, and it is accumulating in the passenger side "sill" area near the door. So, I'm really leaning towards some corrosion inside the cab somewhere. Are all of these modules located on the drivers side of the firewall?

I only have about 30 minutes of daylight each day to work on this thing, and can't get it inside the garage so it really limits the time I can really look at it. I will see if I can take some more time and really look at it tomorrow afternoon. I have to be moved up to PA by Mar 15th(at the latest) for a new job, so I really need to get this figured out.

Feb 26, 2010 | 02:20 PM

#17

ToaDisco

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From: Around

Well I was able to take some more time and see if I can figure this out. I removed the fuse panel and what I believe was the GEM module(was attached to the backside of the fuse box) and again, I didn't see any obvious signs of moisture or corrosion. I even popped the cover on the GEM module and I didn't see anything. We have had a lot of rain here recently and I would think I would have at least seen something.

From searching around here I found another post claiming the fuse box will often times be affected by moisture much more than the GEM module(It was pretty well sealed). I couldn't actually see inside the fuse box to tell if anything looked out of the ordinary, so I gave all of the fuse locations a small shot of WD40. I removed all of the fuses and none of them were blown. The fuse blades were a little dirty, but overall looked acceptable.

So, do you think it would be worth buying a new fuse box and GEM module? Any new ideas?

Also, is there any way I could get this thread moved to the Gen. SuperDuty section? I originally thought this was related to the V10, but I'm doubting that now. I may be able to get more eyes on this thread over there.

Thanks

Feb 26, 2010 | 03:23 PM

#18

ToaDisco

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By the way, I'm comparing my GEM module to this guys(taken from a post here)

Mine looked pretty much factory new... I would think if I've been having moisture problems for over a year(from my original post), I think I would be able to see some signs of water entry similar to the picture above.

I haven't checked the plugs that connect the harness through the firewall. From following the wires, I found what I believe to be a group of connectors mounted on the engine side of the firewall under the master cylinder. They aren't exactly the easiest things to get to, so I have been saving them for last. I will check those out and see what I find.

Any other ideas or opinions?