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If it ain't broke don't fix it (EVAP System Monitor) Topic is solved

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
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

800artfreed
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800artfreed

If it ain't broke don't fix it (EVAP System Monitor)

Post by 800artfreed » Thu Sep 26, 2019 7:01 pm

Since fixing a large split hose providing vacuum for the purge valve I got rid of my P0455 code. Checking the STFT and LTFT my 1999 S70-GLT is sitting at 10% LTFT. No check engine lights. I began a quest to try to get the LTFT lower.

I smoke tested the engine twice and found 2 small leaks. One was on the air plenum going into the turbo. This was where the PTC "valve" meets the plenum. I used "liquid electrical tape" to seal the seam. The second test showed another small leak at the 3-way adapter (plastic) on the vacuum lines on the left side (drivers side) of the engine. I replaced that with a spare I had.
During this search and repair I could reset the OBD2 monitors with my scan tool and ALL of them would go to ready condition fairly quickly. My 1998 S70-T5 took forever but the 1999 appeared to have an easier drive cycle.

Now the 1999 has a Not Ready EVAP monitor that won't set. The PURGE VALVE is cycling at idle. I have changed the valve. The replacement is behaving the same way. So I went from fixing a problem to creating another. Any thoughts?



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abscate
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abscate

Re: If it ain't broke don't fix it (EVAP System Monitor)

Post by abscate » Thu Sep 26, 2019 8:38 pm

Getting Evap to set is tricky, it’s easy to end the drive cycle early by simple things like using AC,going over 60 mph, or full throttle operation.


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Re: If it ain't broke don't fix it (EVAP System Monitor)

Post by Eddystone » Fri Sep 27, 2019 7:29 am

"Now the 1999 has a Not Ready EVAP monitor that won't set. The PURGE VALVE is cycling at idle. I have changed the valve. The replacement is behaving the same way. So I went from fixing a problem to creating another. Any thoughts?"

I have an EVAP light on in my 1998 non-turbo V70. I've yet to do a smoke test for leaks. I did find and replace the little two-diameter hose behind the fuel filter which was bad, as well as the long hose that is inside the left front fender on my car which looked questionable.

Part of my problem is really understanding the sequence and function of the EVAP system so that I can troubleshoot it.

So, MY question to you (a selfish one that doesn't help you, I'm afraid) is do you have any sort of flow chart or logic diagram describing the function of this system AND are you detecting the things you detect by interfacing with the car's computer beyond simple OBDII codes?

I gather that the purge valve only opens at certain times to clear the vapors via the intake manifold. I guess Step One is to get out there with my homemade smoke machine, but I am also aware that the smoke will be blocked at certain points in the system when it is functioning properly by things like the purge valve being properly closed when it should be closed.

If someone wants to chime in an SPLAINE this system operation to me or point me to some service document describing it, I would be very grateful.

I hope I am not hijacking your thread, here. Thanks.


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abscate

Re: If it ain't broke don't fix it (EVAP System Monitor)

Post by abscate » Fri Sep 27, 2019 9:26 am

Ill find the link to the

"Good Evap system discussion by user lexis' which I think I bookedmarked in my T5 maintenance thread

that is a complete tech vomit on the EVAP system


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Re: If it ain't broke don't fix it (EVAP System Monitor)

Post by abscate » Fri Sep 27, 2019 9:31 am

Link to a good one

viewtopic.php?f=1&t=84507


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Re: If it ain't broke don't fix it (EVAP System Monitor)

Post by 800artfreed » Fri Sep 27, 2019 6:33 pm

Latest update. On the cycling of the purge valve I swapped valves with no difference. I then decided to check the previously replace 2 size vacuum line that comes from the center of the manifold to a T fitting. This contained the line that split along the length of the larger of the two lines. In the middle was an "adapter". Actually it is a CHECK VALVE. It only is supposed to allow vacuum to be applied from the engine to the purge valve. However it is a line that goes to a T fitting and I suspect under boost the valve prevents any pressure from affecting the dynamics of the manifold. When I compared my check valve to another from the PnP, mine would not seal in the "closed" direction. I replaced this and the purge valve has stopped cycling. Maybe just a coincidence. Still have not made EVAP monitor go to ready.



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Re: If it ain't broke don't fix it (EVAP System Monitor)

Post by Eddystone » Fri Sep 27, 2019 9:35 pm

800artfreed wrote:
Fri Sep 27, 2019 6:33 pm
Latest update. On the cycling of the purge valve I swapped valves with no difference. I then decided to check the previously replace 2 size vacuum line that comes from the center of the manifold to a T fitting. This contained the line that split along the length of the larger of the two lines. In the middle was an "adapter". Actually it is a CHECK VALVE. It only is supposed to allow vacuum to be applied from the engine to the purge valve. However it is a line that goes to a T fitting and I suspect under boost the valve prevents any pressure from affecting the dynamics of the manifold. When I compared my check valve to another from the PnP, mine would not seal in the "closed" direction. I replaced this and the purge valve has stopped cycling. Maybe just a coincidence. Still have not made EVAP monitor go to ready.
Worst thing can sometimes be putting the system back together and forgetting which way the check valves face. I had my 1999 T5 apart and replaced most of these evap hoses, and I had to scratch my head a few times putting it back together. I now take photos of some of these things as I disassemble them.


1998 V70 Non-Turbo/Auto
1993 945 Turbo/Auto
1999 S70 T5 Turbo/Auto
All U.S. market models.
All on the road and running.
PM me if you are near Philadelphia.
;-)

800artfreed
Posts: 41
Joined: Tue Apr 03, 2018 3:49 pm
Year and Model: 98 S70T5; 99 S70GLt
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800artfreed

Re: If it ain't broke don't fix it (EVAP System Monitor)  Topic is solved

Post by 800artfreed » Wed Oct 02, 2019 4:44 pm

Some success. I have replaced all the vacuum lines for the EVAP/Purge valve system and another Purge Valve with OEM parts from a PnP. This is the line that originates at the (1999/2000 year) intake manifold's center nipple (approx: 1/4 " or 6mm diameter). I also reused the original 3-way adapter (sealed with "liquid electrical tape" ) that comes from the cylinder #5 exit port (approx: 1/2" or 12mm diameter). I most recently replaced the vacuum line from the T fitting that goes to the nipple on the intake tube near the PTC valve. ALL of the adapters used on the vacuum lines are ONE WAY CHECK VALVES.

If you check out the photo of the spit hose and check valve you will notice the adapter/check valve on the line that caused a P0455 code. I have no idea how long this split existed. What I realized is that this created an unfiltered source of air being sucked into the check valve by manifold vacuum. I suspect that dirt OR disintegrating rubber from the hose was introduced into the valve and contaminated the check valve and prevented it from functioning properly.

In the picture you will notice there is an arrow. This indicates the flow direction of the vacuum. A quick test of sucking and blowing into the valve will show whether it is closing and actually functioning as a one way valve. Mine did not seal.

The 3-way adapter on the larger line is also a one way valve and there is an additional small grey one way check valve that goes toward the brake booster.

In one sense these valves allow for vacuum to be applied where and when they are needed. As an example if your engine stalls you still have vacuum in the brake booster for at least one application of the brakes. If you pump the brakes you eventually lose the "boost" on you brakes. This is one reason that the check valves are important. Another is when we are running under turbo boost pressure. Others can contribute about how that effects the vacuum circuits but I am guessing the check valves play a role in keeping the engine performing under all conditions.

As for the EVAP readiness monitor it as finally reset into a READY STATUS! What is puzzling is that prior to going after my high LTFT issue ALL OBD2 monitors appeared to reset easily. After sealing and correcting the vacuum issues the EVAP monitor didn't reset quickly (more like my 1998 S/V-70s). All these cars are TURBO engines. That means the vacuum system is slightly different than that of N/A vehicles. After a couple of short distance drives(10 miles of stop and go driving) the EVAP monitor is READY! I still have a higher than average LTFT (approx: +10% indicating compensation for a LEAN exhaust situation as seen by the O2 sensor). That is a challenge for another day.
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