Ok, disconnected fuel pump harness, oil sending unit harness, fuel relay harness, and ECM, along with pulling the fuse and unplugging both batteries. Did Ohms/continuity check on all the harnesses. Everything showed open loop/infinite except the gauge wires from the fuel pump and the oil pressure sending unit (pink and then tan wire respectively). Those wires showed resistance at like 108 Ohms. Im guessing they should since the gauge cluster is a different circuit. So, from this I do not have a short standing still. Does this mean I need to recreate the reverse motion??? Cause thats gonna suck....

Next thing, I did an Ohms check on the fuel pump starting at the harness on the fuel pump. The pink fuel gage sending wire indicated open loop/infinite. The tan/white wire showed a DEAD SHORT, all Zeros for complete circuit. The ground wire outside the tank was disconnected. My question is there a ground inside the tank, is the fuel pump unit grounded to the tank since it is locked into place by metal??? If it is not grounded, did I just find my ECMB short?????? PLEASE HELP!!!

 

The pump assembly is grounded. The Tan/Wht wire is the main power feed to the pump and will show continuity to ground as it passes through the pump motor.

 

So considering that and the fact that the entire circuit showed open circuit and no short am I screwed or what??? Dude, I have been messing with this damn problem for a month now and I am seriously considering trading this POS into the dealership today and buying a brand new truck..in fact, I bet the dealership wont even take the piece of crap....I quit

 

Have you inspected, fully inspected, the wiring involved?

 

Not fully inspected it...been tryin to keep it easy....but yes, my last and final step is to tear apart the plastic and tape and go inch by inch....I am really starting to get concerned though with the engine as a whole....I filled the coolant overflow to proper level three weeks ago. Just looked at it today and it is no longer bright green, but instead dark green with a hint of oil color. When I filled it up i did clean the tank with a pressure washer. What does this have to do with ECMB, who knows...What I do know is when I was just working on it now, and was going in reverse at idle, with gas and just parked in reverse, and the fuse popped with any type of load. When I changed fuse and started back up, the engine barely would start and smoked black (fuel) bad! Turned it off, let it sit 5 mins, started back up and it smoked white bad! The white smoke is getting worse every day and the engine is trying to stall at most of the time. When I drive forward, it works like a champ! Little bit of white smoke here and there once in drive. I think I need to buy a new engine, take old out, inspect and redo all wires, then put new engine in. Lot of money though.

 

Wires are in working condition. Pulled all the tape and flex tubing and cant find anything wrong. I even ran continuity tests again and everything indicates NO SHORT. I turned the truck to run, and put a lighted fuse in the ECMB circuit, pulled on every harness, wire and ecm connection and nothing.....the fuse would not pop.

I called the mechanic that changed the fuel pump for the P/O. He remembers the truck very clearly and the same problem. He changed the fuel pump and also said there was an aftermarket stereo wire spliced into the ecmb fuse panel. The wire was the signal wire for the amplifier. The mechanic said I need to test the fuel pump by disconnecting the tan wire, reconnect a jumper wire from the fuel pump to another 12volt source such as the ign. fuse panel, run an inline 10 amp fuse into it and see if the fuel pump pops that separate line and fuse when the truck is on and going in reverse. Is this safe???????? fire hazard???????? He even said at the shop, they will 'smoke test' for a short by replacing fuse with paper clip and try to find where smoke is coming from to find the short????? If so, fuel pump is bad, and if it is bad, he said he is going to warranty the fuel pump for me since he changed it last. Better yet, dude says he will work for beer and probably come to my house and help me rebuild this poop bucket But, I am running out of options.......

 

Pulled the entire harness apart, traced down orange power wire where it branches into four wires, one to sending unit, one to relay and two to the ECM. I then placed in line 10 amp fuses in each wire, secured harness and started it up. The truck did not blow any fuses in all different speeds in reverse. So maybe by undoing the harness I un grounded something somewhere. I plan on re-taping harness and taping/securing the orange wires in their own wire loom and leaving in line fuses in for a bit. BUt, now a new problem came up. I have noticed that over the past couple of weeks the battery gage has been dipping and not comin back up. Now its dead and I have to jump the two batterries off of each other. I have not been driving the truck at all other than leaving it running for a few minutes in the driveway. Running volt check shows 12.20 volts on primary battery which I am guessing bad alternator???? maybe bad battery? With engine off, primary battery shows 11.60 volts. Alternator was changed in October 2005. Well see what happens with new alternator.

 

I would remove the suspect battery and the alternator, taking them to your nearest autoparts store that is capable of testing them both.

 

Truck will not pop in line fuses or ECMB now. Going to wrap up the harness tonight and wrap the ECMB circuit separate with the inline fuses for a bit. Took the one battery and alternator to Autozone. Battery was dead. Alternator passed bench test, but they said it was on its last leg. Bearing was very loud or something and brushes were dead. Alternator was a Reman that was five years old. The great thing is I got a 800 cold cranking amp battery - gold line - for $20 since the dead one was under warranty with the previous owner. The battery was $119. And then, with that purchase I hit my free $20 with my autozone card and got a brand new, not reman, 105 amp alternator for $100!!! Saved about $100 all together.

Got home, put new battery/alternator in and still ran at 12 volts and way low with dim lights and all. Truck has a multi-battery isolator which I found the yellow or "excitation" wire going to the fuse box to be unplugged. Plugged it back in and BAM!!! 14 volts and she started up with a huge roar!!! The yellow wire is what provides 12 volt startup power to the isolator, which then in turn sends power to the alternator. Thank God that was a simple fix! Thank you all for your help

 

Sounds good! Glad to help!!