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Evap problem 850 1997

posted by David Samuels on Thu Apr 7 10:49 CST 2016
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last visit: Mon Oct 20 12:23 CST 2014

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Thought I would tap the FWD brain trust. We own a 97 855 NA, had it since new. About six months after installing a new engine I started having CEL/EVAP problems. I get the 0455 "small leak" code. I have been through the evap system front to back several times. Have fixed several minor leaks in hoses, changed others that don't seem bad, changed the little purge valve on the fan shroud, changed vacuum elbows, changed fuel caps back and forth (currently has a new one), replaced the J hose atop the tank at the beginning, pulled the fender liner and checked the solenoid valve and all that plumbing. The fuel pump was out at one point and I found a small crack in the top as well as a top tank seal that may have been bad--no go. I have vacuum and pressure checked the system from a half dozen points without finding a thing. Fill tube has a slight bit of dinging from the fill nozzle, but nothing even close to serious. At my wits end after a year of diddling. The only thing that I can point to is the fact that the CEL may light in a few days, or a few weeks. However, if I clear it, and leave the car idling, it will set after a few minutes. I am tempted to check the tank sensor and a friend recommends doing that at the ECU plug, but haven't pulled out the schematics to find which pins yet. Anyone have a similar experience? My daughter's S70 has a similar problem, but will take 3-6 months to set the code! Same work has been done. Both have new PCV plumbing. Thanks, Dave

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Evap problem 850 1997

posted by someone claiming to be dg on Mon Apr 11 05:45 CST 2016 [RELATED]

Did you ever replace the charcoal canister?

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Evap problem 850 1997

posted by David Samuels on Mon Apr 11 05:59 CST 2016
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last visit: Mon Oct 20 12:23 CST 2014

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At one point I found a crack in the hose from the canister to the solenoid...but no, I never considered that the canister itself might be cracked someplace. Worth investigating. Certainly a pain to get out, but not as much so as the gas tank!!

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Evap problem 850 1997

posted by KlausC on Thu Apr 7 18:17 CST 2016
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last visit: Fri Oct 24 10:15 CST 2014

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Have you checked the vacuum hose back by the fuel filter? It is about 6 inches long and tends to rot and split. Every 850 I have ever seen has had this problem. The hose has a slightly larger diameter on the tank end Vs the forward end. I used some 1/4" injector fuel line to replace it - a very tight fit at the tank end and clamped on the front end.

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Keeping it running is better than buying new

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Evap problem 850 1997

posted by David Samuels on Sat Apr 9 22:21 CST 2016
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last visit: Mon Oct 20 12:23 CST 2014

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Klaus, have you had any experience with the tank pressure sensor? DS

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Evap problem 850 1997

posted by KlausC on Sun Apr 10 10:02 CST 2016
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last visit: Fri Oct 24 10:15 CST 2014

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I have never had a pressure sensor fail. But, you may want to investigate this thread, I love his write ups!

https://volvo850wagon.wordpress.com/2012/07/02/57-evap-leak-fuel-tank/

BTW, the P0455 is a 'large' leak. You might be able to smoke test it. There are youtube demos for making your own smoke machine.
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Keeping it running is better than buying new

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Evap problem 850 1997

posted by David Samuels on Sun Apr 10 13:11 CST 2016
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last visit: Mon Oct 20 12:23 CST 2014

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Have a smoker and have done it from end to end, can't get a whisp. J-hose already done. As noted, I've pressurized the tank, cannot hear a thing anyplace. 0455 in OBD-speak is minor, but in Vol-FCR speak is major tank leak. Soooo frustrating. Hoping someone will post with something I've missed, some obscure tidbit. The only thing I can offer is this strange penchant to set the light if it idles for a long time. Guess I need to drop the tank and go over every inch.

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Evap problem 850 1997

posted by KlausC on Sun Apr 10 18:31 CST 2016
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last visit: Fri Oct 24 10:15 CST 2014

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I know you said that you got a new purge valve, but does it work? Read this about the valve repair:

http://www.matthewsvolvosite.com/forums/viewtopic.php?t=31691

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Keeping it running is better than buying new

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Evap problem 850 1997

posted by David Samuels on Sun Apr 10 19:04 CST 2016
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last visit: Mon Oct 20 12:23 CST 2014

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Yikes! Neat writeup. Guess I'd better check the valve, make sure it's holding.

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Evap problem 850 1997

posted by B.B. on Mon Apr 11 06:48 CST 2016
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last visit: Mon Oct 6 13:15 CST 2014

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The hose from the evap valve to the charcoal canister might be leaking badly,
but it only would show when the evap valve is seeing 12V, making it tricky to find, and I suppose the canister could leak too.

You could power the evap valve with jumpers to the battery and see if that
forces a quick code. I found that you need really tiny female spade lugs
and shrink wrap, and it's a tight fit, another way would be to pull the evap
valve and join the two hoses with a suitable union, so that you can test drive the car and look for the car to throw an instant code. That would be easy to do
and check for a rude evap system leak.

Good luck, Bill

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Evap problem 850 1997

posted by David Samuels on Mon Apr 11 09:26 CST 2016
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last visit: Mon Oct 20 12:23 CST 2014

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Thanks....but i'm confused about replacing the evap valve with a connector as a test. That would certainly throw a code. Maybe I'm missing something, but what am I checking by doing that? DS

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Evap problem 850 1997

posted by B.B. on Mon Apr 11 15:27 CST 2016
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last visit: Mon Oct 6 13:15 CST 2014

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You might jump the evap valve open to expose a rude vacuum leak in the Evap system. I'd be surprised that an open evap valve would throw codes.
More likely that there might be a vacuum leak exposed when it's opened.

Do a test as explained and see if that what might be throwing codes for your car that passes all the other tests. It's a test to diagnose the mysterious problem.
See if the Evap system might be the culprit without having to throw parts and much labor at it.

Bill

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Evap problem 850 1997

posted by David Samuels on Thu Apr 7 18:30 CST 2016
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last visit: Mon Oct 20 12:23 CST 2014

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Yes, thanks Klaus, changed both of them. Saved them as they were not bad, but did 'em as a matter of course. What a pain with the two different diameters. Cali car, with secondary air pump. My regulator is back there, Motronic...4.4 I believe.

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