Hi there everyone,
Well, my problem with the PCM fuse is back in my 2000 Excursion w/ 7.3. After a couple successful weeks relacing the PCM fuse under the hood, it is now blowing every time I turn the key to the "on" position.

I naturally assumed it was the PCM, so I replaced it. At least the good news is that I got a db-tuner flashed PCM without complaints from the wife.

But after replacing the PCM, still no luck, and these engines don't un reall well without them

Apart from pulling the fuses from all non-required items in order to try to isolate an electical issue, I'm pretty much at a loss for a way to proceed. Has anyone ever had a similar problem, or have any advice for troubleshooting this sort of problem?

I should add that I blew this fuse about two weeks ago, but put about 300 miles on the truck since then, so obviously this is a problem that came on somewhat gradually.

As always I appreciate any help.

Mike

 

On our 7.3s, the fuse you're referring to is for the PCM, but also for the fuel bowl heater (this is a little wire that gets hot when you turn the key to RUN, and is located at the bottom of the fuel bowl, underneath the filter). This heater will short out and cause the fuse to blow every time you turn the key to RUN, which then kills the power to your PCM (you probably notice that there is no Wait to Start light when you turn the key.

You can replace the fuel bowl heating element to solve it, but in the mean time, unplug the little connector going to the back of the fuel bowl, which powers the heating element. This way it won't have power to short, and you can drive until you can repair or replace the heating element.

That's my best guess, anyway.

PS - Moving the thread to the 7.3L section, where it'll get better replies.

 

lol... beat me too it. as i was reading that voice in my head ws screaming "fuel bowl heater, fuel bowl heater"...

 

I unplugged the connector at the base of the fuel bowl, but no joy. I continue to blow the PCM fuse (the under hood fuse, not a blade fuse inside the truck).

I had really high hopes for that one too. Thanks guys for the advice. Any other suggestions, either an idea of what the problem might be, or any troubleshooting hints?

I really don't want to take my car to the dealer!!

Mike

 

What's the fuse number? You need to figure out what else is on that circuit.

 

under the hood in the high current box the fuse for the PCM also does the fuel pump motor #19 so check the wiring on the fuel pump you may have a chaffed wire some where that is shorting out

on edit: # 24 does PCM power as well ( i turned the page and kept reading) and is not shared with anything

 

hey guys - it appears that the fuel heater is a very common problem. After reading a couple threads I'm wondering if I disconnected the correct wires. The connector I removed is at the base of the fuel bowl, directly at the rear. Some other post mentions it having a hood on it, but mine does not. Huh?

 

The fuse I'm blowing is #113 in the underhood box. The #30 fuse inside is just fine. I've tried unplugging the fuel bowl - no help unfortunately. I've already replaced the PCM, and that was no help either. Troubleshooting tips, anyone?

 

there is no #113 fuse under the hood??

 

Isn't that the WIF light?....

 

Yes there is a #113 under the hood of a 2000 Excursion and it is listed as a 20amp maxi fuse for PCM Power. No other feeds listed off of the fuse. Try unplugging your PCM and turning the switch to the on posistion ans see if it blows. Then you will need to start tracing wires from the Power Dist. Box to the PCM and find the short. Keep us posted. The fuel bowl heater shows to be fed off fuse #30 under the dash.

 

zx250 - good advice and not beyond my skill level...! I'll try it out today.

 

I really hope this is a good clue, because it's really confusing.

If I disconnect the harness from the PCM outside the firewall, then put in a good fuse, fuse #113 still blows!! As a sanity check to be sure I'm reading the fuse diagrams correctly, I removed fuse #30 inside the truck, and as you might expect, fuse #113 did not blow at key - on after that.

Using my very average powers of automotive deduction, I'm assuming this points away from a problem with the PCM harness, right?

Thanks for the help.

 

Try to trace the wires from the harness to fuse 113. It's not going to be easy. Fuse 30 inside feeds the PCM relay, I guess without the relay powered the PCM circuit is dead. Sounds like the short is between the harness plug and Power Dist. Box.

 

i never heard of that before, i wonder why the X has it and the SD doesn't? always learning. does the X also list #19 and #24 as PCM power as well or is it all different