Help! Pcm fuse keeps blowing.

[mymustang44]

First off, I've searched and searched before making the thread without any luck.

About a month or so ago I left my car idleing in my driveway for about ten minutes and when I went back outside it was dead, my theft light was flashing and my odo was showing dashes. After looking around I found out the 30 amp pcm fuse under the hood was blown. Tried replacing it and it just blows when I turn the key over, not trying to start it. I put a new ccrm in it and that didn't help. Traced all the wires, with the help of ford's wiring diagrams, but didn't find anything that looked remotely like it would cause a short. It's not the pcm cause it still shorts when it's unhooked.

We're at a loss of what to do now. Anyone have any ideas or have had this problem before?? Any help would be greatly appreciated.

And the car does have a new enigine, but it's been in for about 10k now.

 

[TwinTurbo4vGT]

i would check to see if the ECU is still good.

 

[DOHCTER]

Disconnect the coils and see if that works. I have had coils cause problems like this before. Also check the 02 heater wires.

 

[99Cobra_vert]

Seems like any blown fuse that keeps blowing (assuming no major electrical modifications to the circuit) is due to a short.

 

[99Cobra_vert]

i would check to see if the ECU is still good.

In theory, it should be okay, right? The fuse blows prior to a power spike reaching the computer, so the computer isn't feeling anything abnormal.

In theory.

 

[Parts-is-Parts]

I had the same problem and it was a frayed wire on the passenger side ignition noise isolator thingy (touching the cam cover)

 

[mymustang44]

I had the same problem and it was a frayed wire on the passenger side ignition noise isolator thingy (touching the cam cover)

Yeah, I've seen that while I was searching this site. Where exactly are they on the covers??

Thanks for the help guys. I should have a chance to work on it a little tomorrow afternoon so keep throwing out suggestions.

 

[006]

See the wire below where the # 38 is? (and on the opposite driver's side)

I think that's what he's referring to.

 

[mymustang44]

Thanks man. That picture helps a lot and my passenger side one is definitely not hooked up so maybe that'll turn out to be my problem.

 

[Bite Me]

My friend had this problem, but only under hard acceleration.

Only thing he changed was removing his STB, so after replacing fuel pump, tracing wires, etc, etc, I checked the maf and noticed the wire had shorted against the firewall. Since he removed his STB the car flexed enough to rub that wire and short it. There is all of 1/8" of space there to begin with. Taped it up, checked it and worked perfect. Not sure if thats your problem, but something to look at also. Maf wires.

 

[mymustang44]

Well it's not the noise isolators and ,if it helps any, if I turn the key fast enough, I can start the car and it'll run great for a couple of seconsd then the fuse will pop and the car dies.

 

[mymustang44]

My friend had this problem, but only under hard acceleration.

Only thing he changed was removing his STB, so after replacing fuel pump, tracing wires, etc, etc, I checked the maf and noticed the wire had shorted against the firewall. Since he removed his STB the car flexed enough to rub that wire and short it. There is all of 1/8" of space there to begin with. Taped it up, checked it and worked perfect. Not sure if thats your problem, but something to look at also. Maf wires.

I've got a vortech so my maf is in the fenderwell, but I'll definitely look at the wires.

 

[mymustang44]

Well I finally got it running. I honestly have no clue what we done that fixed it so I'm kinda weary of driving too much right now. The only thing at all we found that was causing the wires to pull a ground was the maf, but I plugged it up this morning and now the car starts and runs without blowing a fuse. I'm at a loss really.

 

[99cobra09]

U must have short somewhere, it may be in contact with the ecm power source.