There are a lot of threads on very similar issues and I have scoured them... so I'm going to tell the whole story

Truck died, 15a efi fuse blown. Replaced it, ran for a few seconds and blew again. Towed it home and looked around, blew a few more efi fuses, put a 20a DC breaker in (only size I had), but then when I cranked it the 30a AMT2 fuse blew. So I guess the breaker rating was not accurate. Hoping I did not roast anything in that moment. Replaced the fuses and removed the breaker.

~230k miles so I replaced the fuel pump. I dismantled the old one and found a broken brush, snapped right in half. Feeling comfortable that poor contact -> high resistance -> blown fuse I took the truck for a test drive and then sold it (as I had been planning). Buyer didn't make it out of the driveway before the efi fuse blew again. Traced every wire I could see, o2 sensor wires are fine and not touching exhaust and unplugging it made no difference. Took apart MAF sensor, no signs of shorting. Unplugged distributor resonator cap. Tested the EFI and circuit opening relays. The next day I replaced the fuse, started right up and drove, I warmed it up and rattled every wire I could find back to the fuel pump, all good. Decided to go to town, half way down the driveway it popped again.

I got frustrated and let it sit for a month. Started it yesterday to try again, warmed it up and zoomed around the property for quite a while, hitting bumps and everything, can't make it blow. But I know it will as soon as I try to go somewhere. I live on a long bumpy road and my instinct is a worn wire hitting a ground. But I'm coming up empty. Thanks in advance for any advice.

 

when you changed the fuse it happened all over again?

 

Yes once the fuse blows it will continue to blow. If I then let it sit overnight it will start and run the next day, for a while. This at first made me think it was engine temp related but no, I can let it idle forever. It has only ever blown while driving. I guess my next approach is pack a tool kit and a handful of fuses and try to go somewhere...

 

Well I finally found it in case anyone finds this thread it was below the fuse box one of the wires to the OBD port

 

Nice find!!! glad you got it fixed