Blows Injector Fuse

[cedave]

I have a 2002 Liberty Sport 2wd 3.7L v6 auto-trans. While passing a car on the highway all the gauges on the dash, including tack and speedo, started swinging from max and then back to zero. Also, the stereo quit working as well. The vehicle never lost power but afterwards only one of the gauges was working, either the temp or fuel (can't remember), the stereo also no longer worked. Then after driving for approximately 3 miles the engine died and wouldn't start. At this point the stereo started working again and the dash started working again but the tack & speedo are all the way around up against the little stop pin. The engine will turn over but not start. After checking the fuses I found the 15 amp injector fuse was blown. I replaced it and the engine started and seem to run fine for a minute or two and then I revved the engine and it blew the fuse again.
Please help, what should I check first and how do I get the tack and speedo needles spun back around where they need to be?

 

[ltd02]

Sounds like it could be your BCM.

 

[van462]

Fuse #26 provides power to the Powertrain Control Module and to the fuel injectors. It sends power to pin 1 of each injector (pink/grey wire color). I would ohm check pin 1 of each injector to ground and look for one that reads low ohm to ground. Possible turn the key to on with them disconnected see if the gauges come back to position. If these check out then the PCM looks highly suspect.

I haven't troubleshot this problem before, but its where I would start.

 

[cedave]

Ok, I'll try that. As far as the tach, & speedo go, I was able to reset them by holding down the trip odometer reset button then turning the ignition to run waited for the gauges to start moving then released the reset button. The needles then went through an interesting choreographed maneuver and after a couple seconds they were all reset :gr_grin:
So, now I just have to figure out what's popping the injector fuse.
Going out of town this weekend but next week I plan on starting my diagnosis with the multi-meter.
Thanks for the advice!

 

[cedave]

Ok, here's what I've got so far. Checked all the injector wires throughout the engine harness, checked the white/drkblu wire from pin 25 to the alternator and all is good, no shorts. I've tried a good used PCM and even had the alternator tested; I had changed the alternator just one week before this problem started.
As of now it will not start, just cranks and cranks. Before I changed the PCM it would take a few attempts to get it started and then, like before, it would blow the fuse once I revved the engine. Now it doesn't want to start no matter which PCM I have installed.
Any ideas?

 

[ltd02]

Is the ASD relay fried now?

 

[cedave]

Finally figured it out!!!!
Aparently the alternator field circuit shorts out at a higher rpm. Even though It tested good at Autozone, they exchanged it for another remanufactured alternator and it no longer blows the injector fuse. If this alternator starts doing it later down the road I'm going to Napa for a replacement!