I have a 99 F350 7.3L with almost 310,000 miles on it. The manufacture date on the door is July 98.

Now onto the problem. We had a really bad wind storm here in the southeast corner of Wyoming during Christmas for about 2 days and it packed snow into the engine compartment as my truck is parked outside. This has happened before with no issues of starting or anything.

When I went out to fire it up to let it idle and warm up on Christmas it started up fine and was idling but when I went out later it had died. I went and tried to crank it over again and when I had turned the key on to allow the glow plugs to warm, I noticed the "wait to start" light didn't come on. I left the key on for a few and tried cranking it and it cranked fine but wouldn't fire up. I ended up not messing with it any more that day and went back a couple of days later and when I turned the key on, same thing of no "wait to start" light. I pulled out the Ford service book to look for a glow plug relay fuse, but I didn't find one, but after reading my repair manual I realised it could be the PCM. Sure enough that fuse was blown. I swept all of the snow away from the glow plug relay thinking that may have been shorting things out. I replaced the PCM fuse and it fired right up, but right after it fired up it blew the fuse right away. I decided to just leave it and allow things to hopefully dry out as I figured that might have been the issue.

Today I went out and replaced the fuse and it fired up with no problems but then I noticed it started to surge when it idled and right when it surged, it blew the PCM fuse. I then replaced the fuse, fired it up again, and then just kept the throttle down and had it reving somewhat. It stayed running fine, but then after about a minute, I allowed it to go back down to idle and then it started idling irractically (surging) and right after that, blew the fuse again. I did not try to restart it as I am at a loss as to why once it goes to idling, it idles like it is surging and then blows the fuse.

Is this something indicative of the PCM going bad or being bad or could it be something else? One of the guys at the auto parts store had mentioned to me last night about the glow plug relay mounting bracket as being broke and an issue of blowing the PCM fuse but I looked at it and it is not broke. At this point I do not think it is something with the glow plug relay portion of starting as that is with start up and not with an engine staying running.

If this is a PCM issue, who has the best prices for ordering? That same guy from the auto parts store told me to look on Ebay for one if it is the PCM.

Thanks for any help you can give me on this as I haven't run into this before and I am stumped.

 

If you know someone with a heated shop or garage, see if they will let you park it in for a day or two. Once everything is thawed, locate the PCM, then remove and clean the connection.

 

Everything is thawed out now and I did not notice any moisture in the engine compartment yesterday. When I looked in the manual I did notice that the plug in portion for the PCM is behind the wheel well fender apron and the PCM module is actually on the driver's side wall inside the cab.
Also in reading the emissions section of my manual I got to reading about the MAP sensor and I am wondering if that might be the issue since it is located on the right side in the engine compartment by the AC system and it mentions about it controling fuel delivery as well as ignition timing and with it idling and surging and blowing the fuse, that almost sounds to me like a fuel and ignition timing problem.
Trying to figure this out so I don't spend a ton of money replacing stuff I don't need to.

 

like the ram said you might bring it in a heated shop to let it really warm up so any water or condensation will evaporate or heat the engine compartment up to do the same thing and also welcome to diesel bombers good luck

 

Well problem solved. Another guy on another forum mentioned about unplugging the fuel filter heater as there is a heater in the fuel filter bowl. I unplugged it and started the truck and it has been running fine for the last 10 minutes or so. That heater is one the same fuse as the PCM.

 

im glad the problem was solved