Yet another EVAP thread

[project_x]

My solenoid works... but there is a break somewhere in the harness.

When I check my scanner... I never seem to see the point where the vent is commanded to be closed... it always says commanded open.

Does anyone know when it is supposed to be closed?

Can I keep it open all the time? or replace it with a hose?.... filling this thing up is painful (and it is too cold to find the break).

 

[Fless]

Tell us a bit more about which "solenoid" you're talking about. Sounds like you're having trouble adding fuel to the tank??

The canister vent valve ("solenoid") at the rear of the truck should be open when the ignition is off (like when you're fueling up).

The purge solenoid on the engine should be closed when the ignition is off (like when you're fueling up). Normal status without voltage applied is closed.

When the engine is running, either one can be commanded open or closed, depending on what particular evap command is being run by the ECU. If you have a bidirectional scanner you should be able to turn either one on or off as a test.

If the pump is clicking off too quickly and you can't pump fuel at a good rate, it's likely that one or more of these is true:
- the vent valve is not actually opening (open should be normal status with no power applied; e.g., not commanded closed)
- the vent valve is plugged, or the vent filter is plugged
- the canister and/or the evap lines are plugged

 

[project_x]

I was speaking of the vent solenoid. It is not opening. It works, but the wire controlling it is broken somewhere in the harness.

The pump is clicking off every 1/2 gallon.

 

[Fless]

With no voltage applied it should be open (and unrestricted) at all times, so if it's not physically opening it's defective. A new one won't close unless or until you apply voltage to it.

 

[rockola1971]

I was speaking of the vent solenoid. It is not opening. It works, but the wire controlling it is broken somewhere in the harness.

The pump is clicking off every 1/2 gallon.

What makes you think there is a broken wire? As @Fless said, the solenoid should be normally open (Voltage applied to the solenoid CLOSES it) when ignition is off and you are filing up with fuel. Have you blown throught the solenoid to verify it is mechanically open?

 

[Scottydoggs]

when filling up and the pump keeps clicking off like the tank is full, is 99% of the time a clogged up canister and lines to and from the canister. inside the canister is charcoal pellets, the canister breaks and the pellets clog the lines up and the tank dont vent, then the pump clicks off.

 

[OR VietVet]

Are you saying wite is broken to vent solenoid, because you never have 12 volts at solenoid? Check the ground?

 

[houstontaylor]

Here is something that may add to the conversation. I thought may be having vent valve problems also and my ground was showing open circuit but voltage was good at the vent valve connector. So I looked on the Alldata wiring diagram and it shows that the computer controls the vent valve by opening or closing the ground and not turning voltage on or off. The voltage seems to always be on when the engine is running so an open ground isn't necessarily a problem.

 

[6speedblazer]

Here is something that may add to the conversation. I thought may be having vent valve problems also and my ground was showing open circuit but voltage was good at the vent valve connector. So I looked on the Alldata wiring diagram and it shows that the computer controls the vent valve by opening or closing the ground and not turning voltage on or off. The voltage seems to always be on when the engine is running so an open ground isn't necessarily a problem.

This is correct, the PCM controls the ground side of the circuit.

another tid bit if information. Without a load the circuit has a hard time switching off after its been turned on. When using a standard multimeter you will see bleed by voltage even after the circuit is commanded off with bi-directional controls. A non-led test light seems to work the best for testing this circuit.

 

[Fless]

Here is something that may add to the conversation. I thought may be having vent valve problems also and my ground was showing open circuit but voltage was good at the vent valve connector. So I looked on the Alldata wiring diagram and it shows that the computer controls the vent valve by opening or closing the ground and not turning voltage on or off. The voltage seems to always be on when the engine is running so an open ground isn't necessarily a problem.

An always-open ground at the vent valve isn't a problem until the evap test is attempted, and it will fail since the evap system can't seal.