Blowing MFI Fuse

[belize1334]

So, having put my new transmission in, the car is now blowing MFI (MPI / EFI) fuses non-stop. So, one fuse could have been a fluke but 3 is a problem.

I'm actually leaving town tomorrow for 10 days so I'll be hit-and-miss checking this and I won't be able to do anything hands-on until after I get back but I thought I'd go ahead and throw this up to get peoples' creative juices flowing.

Clearly there's something shorted in the MPI circuit but I don't really know what's on that circuit or how it all ties together. I'm hoping we can generate a list of what pulls power from that fuse and any dependencies between those components. I know that the ECU, MFI relay, ISC, and possibly something alternator related are all pulling power through the MFI fuse. What I don't know is what talks to what and who gets power from where... If you have any insight please post up.

Thanks,

-Roger

 

[BoostedAWD91]

Check you o2 sensor harness for bare wires

 

Make sure all your grounds are connected, clean, and intact.

 

[belize1334]

Found it. I apparently pinched the o2 wiring harness between the block and transmission which crushed the PWR and GRND wires and shorted the MPI circuit to ground. Yay for soldering.

 

[broxma]

Let it be known when this happens to the next guy this is the second instance of the MFI Fuse blowing due to a pinched wire on the motor itself. Mine did it with a COP wire on the valve cover.

Glad you found it.

/brox

 

[belize1334]

^^ Oh yeah I did that a couple of months ago too. Pinched the power wire between the VC and the mounting plate. Fuse blew at 7K on a 20psi pull while "ironing out the kinks" before autocross the next day. I thought I'd killed her for sure.

Be careful of your wiring whenever you move parts around!