Biggun
Newbie
Some trucks have a pressure sensor on the fuel pump, that looks a lot like a MAP sensor.
So, would that sensor be on the pump inside the tank or on on top? If there is one, then the harness I do have must contain the wire that talks to the PCM.
When buying a fuel pump you have to get one with the right code.
Good Lord. Well, I have no idea...the original pump had been replaced already when I got the truck...could Chevy find out by VIN?
Still haven't done anything with the EVAP system???
Yes. I replaced the purge solenoid and the gas cap. My truck doesn't have another solenoid on the charcoal canister, it just vents to atmosphere. I'd say all of the lines and connections are good, since it pulls (and holds) enough vacuum to suck your face off.
Although the tank pressure sensor being disconnected is a pretty big red flag
I can vouch for the tank pressure sensor not being used on the 3500's as well. No harness there for it, just for the pump/sender connection.
someotherguy's picture looks exactly like what I see on my truck; there is no other harness that plugs into the fuel pump. That said, it would make sense that if it has a purge solenoid (which it does), then it must have some sensor to trigger the PCM to open the solenoid.
Doesn't EVAP require a tank pressure sensor? How is the ECU supposed to know when to vent to atmosphere or open purge solenoid for gas vapors from tank to be sent to intake for combustion?
I had an F-150 where the purge solenoid was sort of opened randomly by the computer and did not have a tank pressure sensor. I mean to say, it used some sort of computation to figure out when to open the solenoid, but it wasn't based on information from a tank pressure sensor.
I guess I could just leave the gas cap cracked open a little...I've driven 300 miles this week like that, and no CEL. It just bugs me because it's not right, and now I'm really curious as to what I've got going on here. I guess I'll try to find some diagrams of the different permutations of fuel/EVAP wiring/plumbing for these trucks.
As always, thanks for the input!