Maintenance at quarter million?

[about20ninj45]

I detached the vent line at the canister side...no improvement at all.

It is frustrating that I can't find diagrams that represent the reality of what I have. The pictures at ALLDATADIY, generally the best I have access to, do not bear any relationship to the reality of what I have under this vehicle. NONE. They tell me that what they have they were given by GM/Chevrolet.

I've got other stuff that is more pressing, so I'll be leaving this one for a while. Next step is probably to check the actual vent hose from the quick-release at the back end of the tank (on none of the diagrams) to the filler. After that, the check valves where they connect to the tank itself (If I can get to them, as they may be where the fuel pump is).

If any of you GM tech types can shed some light on this, perhaps with actual pictures of what it really looks like under there, that would be great.

Replace the purge valve that sits on top of the gas tank

 

[NMPastor]

You mean the canister purge solenoid that is on top of the intake manifold? That's already been replaced.

 

[about20ninj45]

You mean the canister purge solenoid that is on top of the intake manifold? That's already been replaced.

NO!!! I mean the solenoid directly on the gas tank, right above it!!!!

 

[about20ninj45]

Looks like this

 

[NMPastor]

I am aware of the purge solenoid, on the intake manifold. I am aware of the solenoid canister vent valve. I have not so far heard of a solenoid on top of the tank, or seen it in any diagrams. What is it called and what does it do?

 

[NMPastor]

That's not a solenoid. That's the fuel tank pressure sensor, part and parcel of the new fuel pump assembly I had installed in September.

 

[about20ninj45]

That's not a solenoid. That's the fuel tank pressure sensor, part and parcel of the new fuel pump assembly I had installed in September.

And it could still be suspect as its part of your emissions system, and its part of the fuel pump assembly, but doesn't necessarily mean that it's functioning correctly because its new. If you measure voltage on him and its sitting at full zero volts or full five volts then its bad. It talks to the PCM, which reports an emissions fault. If the fuel pressure sensor isn't working correctly, then neither will the evap canister nor the purge solenoid.

 

[about20ninj45]

PCM or powertrain management computer relies on a fuel tank pressure sensor to detect fluctuations in the tanks internal pressure.


The PCM has determined that the system pressure is unusually low indicating a problem in the system, not necessarily just at the sensor. This sensor is used primarily for emission control strategy only. Your fuel tank will have a tendency to build fuel vapor pressure when the temperatures are high and a vacuum when under a load.


The sensor sends a voltage to the computer for analysis, the value of the current is dependent on the pressure or vacuum


Potential causes for this DTC include: Failed fuel tank pressure sensor Harness to the sensor has an open or short circuit Faulty electrical connection to the FTP sensor Cracked or broken vapor line to the vacuum canister Cracked or broken positive vapor line to the tank Plugged line Leaky gasket at the fuel pump module Gas cap left loose resulting in a loss of vacuum Pinched vapor line.

 

[NMPastor]

This is a Delphi fuel pump assembly for a 2005 Suburban. On top from the right: Fuel lines, fuel sender power connector, Fuel pressure sensor. Now it is possible that it has failed, wires were damaged in repair, etc. in which case I have a warranty issue. I'll put the electronics on it tomorrow, to see if I'm getting a reading.

This issue has progressively worsened over a couple of years, which makes me less inclined to think it is an electrical part failure, and more inclined to think that it is a progessive blockage or sticking of a check valve.

 

[NMPastor]

If I get no reading from the sensor, then I'll talk to the repairing dealer. But I'll do everything I can to try to track the problem first, because I don't want to have to drop the tank on this thing again.

And thanks for the recommendation. Dealing with this issue has been a hassle.