Another fuel pump issue

[wewsel]

I've searched and thought I seen something about this before, but can't find it now. The previous owner changed the fuel pump and said he had to do some re-wiring to make it work. I can see the wiring work near the fuel tank. The truck runs fine. Although I have a cel for p0300, p0446, and p1404. She has a mis one one cylinder, but is still drivable. I know the p0300 is a random mis fire. I've also notices that the fuel gauge vibrates the entire time the key is on, weather the truck is running or not. I want to check this re-wiring job and make sure everything is right. I just have no clue what the issue was that warranted the re-wire to begin with.

 

[SAATR]

I've searched and thought I seen something about this before, but can't find it now. The previous owner changed the fuel pump and said he had to do some re-wiring to make it work. I can see the wiring work near the fuel tank. The truck runs fine. Although I have a cel for p0300, p0446, and p1404. She has a mis one one cylinder, but is still drivable. I know the p0300 is a random mis fire. I've also notices that the fuel gauge vibrates the entire time the key is on, weather the truck is running or not. I want to check this re-wiring job and make sure everything is right. I just have no clue what the issue was that warranted the re-wire to begin with.

Could have been a burnt harness, or that the replacement pump required the wiring harness be updated to the new, improved design. The vibrating needle will be an issue in the cluster itself, and is common to GMT400's. The p0446 is either a vent solenoid issue or a leak somewhere in the evaporative emissions system. Check the lines and the vapor canister for holes, leaks, cracks, and rotted rubber. The p0300 could be several things, but I would check your ignition system first if you've never replaced anything. The cap and rotor on the Vortec motors are horrible for causing misfires with minor corrosion. I have not personally encountered the p1404, but it appears to be something to do with EGR valve closed performance. I'll do more research and see what I come up with.

 

[wewsel]

Thanks for the quick reply. As far as the p0300, I did a complete tune up the day I bought the truck and it still had this mis. New plugs, wires, cap and rotor. Replaced the intake gaskets. The p1404 is a new one that i just pulled tonight. Never seen it before. Again, Thanks for the quick reply.

 

[SAATR]

Thanks for the quick reply. As far as the p0300, I did a complete tune up the day I bought the truck and it still had this mis. New plugs, wires, cap and rotor. Replaced the intake gaskets. The p1404 is a new one that i just pulled tonight. Never seen it before. Again, Thanks for the quick reply.

A scanner that can read live data would be a great help here. I recently had a misfire issue with my Burb that caused it to throw a P0300. Ran horribly and smelled of fuel. Tied a scanner into it and found the P0300 was actually a cylinder 2 and cylinder 8 misfire, which I traced back to an internal short in the cap. Moral of the story is the P0300 can be very misleading, and could actually be an issue on as few as 2 cylinders. Is the miss noticeable, and consistent? It's possible that it could be the coil, but I would definitely check the live data and spark first. I would also check fuel pressure, though you should get a rich or lean code if there is an issue in the injection system. That would also help you narrow down a plugged fuel filter, if that were the case.

 

[sewlow]

First thing I would do to try to eliminate the po446 is replace the gas cap with a new one. May or may not be the cure, but a new cap on both my trucks cured the po446 code.