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Sticking Evap Purge Valves

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I've had 2 vehicles in the last month with gross evap leak codes stored in the pcm that have been caused by the purge valve not opening enough to draw the tank down enough when running the test. The first one was a 12 or 13 F150 with the 3.7. The second one is on an 11 Fusion that just had the recall done by another shop.

 

Anyone else running across this?

 

The F150 took me to school trying to find the leak. I almost put a filler neck in it, even though I couldn't find any smoke coming out.

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Lots of purge valves. Also, if they leak vacuum with the engine running they can set a code for small leak while testing for vapor generation with the engine off.

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Have done a couple on the 1.6 Escapes. Not sure if it is the purge valve itself or the check valve as it comes as a complete assy, but either way the result is that the system cannot pull a vacuum.

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Yes.  I see it a lot on Ford and Chevy trucks.  No vacuum generates during the pulldown phase of the EVAP monitor, as you noted, and the PCM interprets it as a Gross Leak.  It trips up a lot of techs that diagnose it with a smoke machine and find no leak.  

Joe

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  • 1 month later...

We see tons of these. A purge valve is actually one of the three parts we stock.

 

I diaged one on a 13 explorer today.  Set a DTC P0456 for a small leak.  The bleed up rate was out of spec until I pulled the purge valve out and stuck my finger over the end that fits in the intake.  Then suddenly my leak stopped.

 

Most of ours fail like yours where they won't draw a sufficient vacuum but they also will not seal completely and cause an excessive leakdown.

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