EVAP system 2008 Chevy Avalanche

[campbeba]

Hello,

 

I have recently replaced Purge Solenoid, Vent Solenoid, and charcoal canister.

 

after that I discovered that there was a broken wire going to the vent canister. I fixed the wire and heard the click of the solenoid engaging closing the vent solenoid.

 

The next time I drove I noticed that the gas gage was going up while I was driving till a half empty tank read full. When I got out I looked under the avalanche and noticed that the fuel tank was imploded, it looked like a squished pop can.

I unplugged the wire that had been repaired. I heard the click of the solenoid disengaging and the fuel tank immediately began expanding back to its normal shape.

 

This tells me that the vent lines, purge lines, and the lines going to the tank are all clear and hold a vacuum. The solenoids are all new so I believe that they work. I tested the signal wire coming from the fuel tank pressure sensor and it read 1.5V with the fuel cap off and 5 volts when the tank is compressed like a pop can, and I verified that the signal wire voltage is reaching the PCM.

 

I believe that it must be a wiring fault issue.

Connecting the broken wire definitely causes the vent solenoid to function so I believe that wiring is ok.

The purge solenoid voltage is 0 with the ignition turned to run. I do not have a code reader so I cannot trigger the purge solenoid to close to see if the voltage going to it works.

 

Any ideas, suggestions, or help you can offer sure would be appreciated.

 

 

Thank you.

[tbarn]

You could have a bad vent solenoid or a short to ground. The vent valve is almost always open. It is only closed for testing purposes, The circuit is always powered with the key in run. The PCM grounds the other circuit to close the valve. You shouldn't normally here a click just plugging it in. I think I would take a good look at the ground side of that vent solenoid. Seems it may be shorted to ground before it gets to the PCM . Or the driver in the PCM for that circuit could be bad. Never seen that one though.

[campbeba]

Thank you Tbarn, now have tracked problem to a ground short either in the pcm or between the pcm and where the wire broke.

 

Would like to disconnect pcm so I can isolate the wire.

Can't figure out how to disconnect the connectors though and do not want to damage them