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Sanity Check: Evap Purge Valve Stuck Open?

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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Re: Sanity Check: Evap Purge Valve Stuck Open?

Post by RickHaleParker »

WhatAmIDoing wrote: Fri Feb 28, 2020 10:13 am Plugged off the manifold lines.
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Re: Sanity Check: Evap Purge Valve Stuck Open?

Post by Richard99 »

RickHaleParker wrote: Thu Feb 27, 2020 5:28 pm A stuck Canister purge valve would produce both of the DTCs.

During the test of the EVAP Canister shut-off valve, the Canister purge valve is pulsed. If the canister purge valve is stuck open the pressure drops too fast and the test fails.

The Canister purge valve is normally closed and opens when 12V is applied. Disconnect the wiring harness and hoses to the Canister purge valve and blow, it should be closed. If it is closed, look for a hose leak between the Canister purge valve and the Canister.
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Re: Sanity Check: Evap Purge Valve Stuck Open?

Post by jimmy57 »

The shutoff valve is there to allow tank leak detection testing. On that 98 it would only close after you drive for a qualifying period with some driving conditions met. Once you idle it can do the test and close the shutoff valve, the only reason it ever needs to close the vent line for tank. The purge valve runs a lot. If you idle for 30 seconds or so then it will do a test to see if canister has load by opening purge valve and watching response at front oxygen sensor. If it goes richer then there is something to purge an it continues at a low flow for 45 seconds and then takes a break if idling continues. If it sees lean it stops then and again does a break if idling continues. Above idle the throttle and engine load will determine a purge valve flow rate.
For that vacuum to be present in tank the shutoff is stuck closed or the vent hose with filter on end (up in quarter panel attached to filler neck). The normal functioning of purge valve would build vacuum with a block tank vent.. The leakage testing once it is started would set faults for seeing residual low tank pressure and then aborts the rest of the leakage test.
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Re: Sanity Check: Evap Purge Valve Stuck Open?

Post by abscate »

User Lexia published a tome on the purge cycle and readiness which is linked into my Elizabeth maintenance thread
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Re: Sanity Check: Evap Purge Valve Stuck Open?

Post by WhatAmIDoing »

jimmy57 wrote: Fri Feb 28, 2020 3:14 pm The shutoff valve is there to allow tank leak detection testing. On that 98 it would only close after you drive for a qualifying period with some driving conditions met. Once you idle it can do the test and close the shutoff valve, the only reason it ever needs to close the vent line for tank. The purge valve runs a lot. If you idle for 30 seconds or so then it will do a test to see if canister has load by opening purge valve and watching response at front oxygen sensor. If it goes richer then there is something to purge an it continues at a low flow for 45 seconds and then takes a break if idling continues. If it sees lean it stops then and again does a break if idling continues. Above idle the throttle and engine load will determine a purge valve flow rate.
For that vacuum to be present in tank the shutoff is stuck closed or the vent hose with filter on end (up in quarter panel attached to filler neck). The normal functioning of purge valve would build vacuum with a block tank vent.. The leakage testing once it is started would set faults for seeing residual low tank pressure and then aborts the rest of the leakage test.
Did some investigating. The purge valve was open when I removed it. Applied 12v and heard no clicking and flow of air did not change. Blew the valve out with carb cleaner, and a bunch of black gunk came out. Valve still seemed dead on the bench. Used one ordered locally from a wrecker.

Removed the shut off valve and blew through it. It is open when no power is being applied. I'm assuming that is normal?

Inspected all the vacuum lines in the engine bay. All the evap hoses were in very good shape; I think someone was here before. Only hose that was bad was the vent hose had a big slit in it. And this elbow on the manifold was torn.
IMG_20200228_125214581[1].jpg
Thinking the vent port on the charcoal canister may be blocked now. How do you remove it from the car? Haven't been able to figure that out.
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Re: Sanity Check: Evap Purge Valve Stuck Open?

Post by WhatAmIDoing »

So, I blew through the purge hose and air came out the vent hose. When I plugged the vent hose, I could hear an air leak from the left rear near the fuel tank. So I think the canister and the shut off valve are okay.

All I can think to do now is trace the vacuum leak by the tank. And maybe there's a ground short giving the shutoff valve power all the time?
'98 S70 T5M - 282,000+mi - forever a project
'99 S70 "AWD" - 220,000+mi - part out :cry:
Knows enough to be dangerous :wink:
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