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Fuel tank pressure (or vacuum?)

4K views 17 replies 4 participants last post by  Astrofarian 
#1 ·
1997 Safari seems to be doing something new. I went to fill up and when I opened the gas cap a fairly large (it seemed) amount of air blew out from the fill opening. This has never happened before. Out of curiosity, I opened the cap again after finishing driving for the day (about 40 miles) and again pressurized air gushed out. (Note: it seems the air is coming out, but it could be rushing in. Hard to say. I feel air on my hand and hear it, but there is no fuel smell associated with it.)

MIL is on and code reads P0440, Evap System. The code has come up before, but the pressure pushing air out when opening the gas cap has not happened before today. Earlier this summer the code came up every few days, so I replaced the gas cap. We took a 5,600 mile trip this summer and the code only came up once. Now that we are back and returning to normal driving it again comes up every few days.

I did not see a topic covering this. If you know of one, please direct me to it. Or if you have thoughts on what is causing this I look forward to hearing them.

Thanks!
 
#4 ·
Thanks! Apparently GM decided it was a "good" idea to move all this from the engine compartment to under the van near the tank in '97. But if I recall from last time I was underneath it is all fairly accessible, except where the lines actually connect to the tank.

How does one go about testing the purge solenoid, by the way?
 
#6 ·
Purge solenoid is on the motor on my '99. Canister and vent valve are back near the tank.

I'm only finding replacement instructions....give me a minute.
 
#8 ·
Leeann_93 said:
Purge solenoid is on the motor on my '99. Canister and vent valve are back near the tank.

I'm only finding replacement instructions....give me a minute.
I'm OK with replacing it if it's available and reasonable. If I'm going to the trouble of taking it out anyway. I know what it looks like on our '95 and on our cars because it's right up there by the battery, but the '97 is unfamiliar. Seems everything is a little different beginning in '96!

Any advise/direction appreciated.
 
#9 ·
LeeAnn_93,

You were posting while I was typing! Thanks for the photos of pages from the manual - awesome!! The pics are quite legible.

Tomorrow is a busy day, may not get a chance to work on it but at least we won't have to drive but a few miles in the meantime. I'll keep you posted on progress.

Thanks!
 
#10 ·
Take off the doghouse, look on the passenger side for the green schrader valve cap, shown here


Follow the hard line it's on to see this


And you've found the evap purge solenoid valve.

Those pages are from the '99 manual, but it shouldn't be that different.
 
#11 ·
Thanks again!
Reading the manual pages, it does get a it complicated but I suspect it's either the purge valve, vent valve, or a pinched line. Since it is holding excess pressure (or perhaps vacuum) that rules out a leak.
Now if the hot sticky summer weather would just subside this would be more fun!
 
#13 ·
Nothing much to update. Tuesday night (nearly 5 days ago) I reset the code and it has not come back, nor has the tank demonstrated pressure / vacuum upon removing the gas cap. Leaving "well enough alone" seems to be the best course for now. Just love intermittent problems (like the Phantom Stall we're now experiencing on our Park Avenue)! (Sarcasm!)

Thanks again, Leeann_93 for the information - I have saved it all to My Documents because I suspect I will need to refer to it down the road!
 
#14 ·
Solved! Turns out the connector on the valve (evap purge) on the engine wasn't on all the way.

I had gotten used to simply resetting the check engine light about every day. Then the Safari became hard to start then wouldn't start. (Aftermarket cap and rotor was the culprit - should have listened to sage AstroSafari advice!) While in there I looked closely at the connector - it was on, but not seated. Clicked it down.

Did get the vapor system error once more after that, but not since and it's been a couple months. Feeling pretty confident that this is all it was.

Thanks for everyone's help. Great info I'll probably need again!
 
#16 ·
chevymaher said:
95AstroLT said:
Solved! Turns out the connector on the valve (evap purge) on the engine wasn't on all the way.
Congrats and only 2 years. You are a whirlwind when you get to work.
1 1/2, but who's counting! Makes the 3 years I let my Catalina sit because of leaking power steering pump seem like no time at all! :D
 
#18 ·
chevymaher said:
95AstroLT said:
1 1/2, but who's counting! Makes the 3 years I let my Catalina sit because of leaking power steering pump seem like no time at all! :D
I do it to if it isn't life and death to get it done. I got mom's pathfinder out there. I know what is wrong. I just waiting for a trans at a decent price to fall into my lap.
Older fellow working the phones last time I was at the "full service" wreckers; "I can't tell you a price until you tell me when you need it for."
Sadly, he was serious. I worked for those guys for the winter 25 years back.....typically their parts were 10-25% more than anyone else's but they were great about getting what you wanted WHEN you wanted it. No time to waste with speculators or looky-Lous; stood behind what they sold as well or better than most wreckers at the time, too. Did a HUGE business with the "LKQ" Insurance replacement market.
So yeah, sitting back and waiting sometimes pays dividends when you're looking for parts.
-Mike-
 
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