weird one - stalls after filling gas tank

[shoebee2]

This one is driving me nuts.

I have been chasing a rough idle and intermittent stall
problem

The car would run fine while cold. Good power, no
hesitation, steady idle. No cel's. Once at operating temp, temp gauge 1/2 way
and stable, it would give the out of gas behavior. No codes.  Just acted like it out of gas.  Feathering the peddle a bit would bring the
rpm up but still sputtering.  pull over
put it in park and idle is fine, revs up like normal.  Put it in drive and hit gas either hard or
soft and it dies.  Let it cool down and
limp it home. Drives just fine while cold so Im thinking it’s the tcs. Replaced
tcs and cleaned maf while I was at it. That seemed to do it. I drove for about
3 miles and the sputtering started again. Same symptoms. No Codes! Let it cool
down limp home. I cleaned throttle body, IAC valve, checked everywhere for vac
leaks. Cleaned pvc valve.   Ran it
several times trying to get a code but none present or logged.  Took it for a test drive and it ran fine.
Drove 30 miles and no problems. Sweeeet.

 

Stopped at gas station filler er up and started sputtering
and died. Same behavior.  I remember when
I first noticed a rough idle the fuel tank was ¾ full and only began acting
normally AFTER I had less than ½ a tank.

Charcoal canister or purge valve seems likely but both parts
are expensive.  Anyone have this happen
can verify for me?

 

 

 

 

 

 

s​

[Fairtax4me]

Year? Model?

 

Purge valve would be my first check. Just pinch off the vacuum line that goes to the valve. If the valve is leaking that will stop fuel vapor from getting through, and should stop the problem if the valve is the cause.

Sometimes if the purge valve is leaking you'll get a code for the evap system, but it depends on what kind of driving you do. It takes some time and certain conditions for the evap system monitors to run properly, and those contitions may not be met every time you drive.

 

Other possibilities would be a bad ECT sensor, bad MAF sensor, failing fuel pump.

[wtdash]

+1

Related issue I had HERE.

 

Note that the Purge valves are not all the same, from what I've seen, even though a '97 fit my '02. The electric plug for the connector seems to vary, so if you get a USED one ensure it matches exactly...and I wouldn't buy new.

 

td

Edited September 5, 2016 by wtdash

[Theophilus]

I'm having a similar problem with my 2003 Subaru Legacy Outback.

 

Whenever I fill up the tank with gas, the car starts fine and drives away from the station, but I get about 200 yards and then the engine starts coughing and shuddering.  The car lurches and shakes that way for about half a mile, and then the problem seems to be solved.  Everything operates normally after that.  I get the same problem whether the tank is completely empty or only half empty when I fill it.  The coughing is the only symptom.  I'm not getting a check engine light or anything like that.

 

From what I read in this forum, it sounds like the purge valve is the likely culprit, but AutoZone wants $130 for a replacement.

 

Questions:

• Is this something I need to fix?  (i.e., am I damaging the car if I decide to just live with the shuddering effect?)
• Could one of the lines going to the valve be the problem?  Can I just take them off to check for leaks and obstructions or will gas start spilling everywhere?
• Can the purge valve be cleaned and restored?  (And, if so, how?)
• Is this the sort of part that would be safe to buy from an online junkyard?

Thanks for any advice!

Edited October 29, 2017 by Theophilus

[montana tom]

Just replaced the purge valve on a 04 obw. Same symptoms, poor running after fueling. It had larger size vacuum lines than the earlier years, electric plugs were the same.  On the 04 the valve was easily accessed... on the 02  & back it is on the bottom side of the manifold, slightly harder to get to. This valve is normally closed , you should not be able to blow thru it.  There are 2 vacuum lines going to it , one with direct manifold vacuum and the other is the smaller line running next to the fuel filter. Disconnect the vacuum lines and see if you can blow thru it or not.  If you can replace it! If you can't then it "may be OK "   I would buy this from a wrecking yard that I could go to...  online ....  up to you.  Look on your local craigs list for somebody parting one out.

[Fairtax4me]

I'm having a similar problem with my 2003 Subaru Legacy Outback.

 

Whenever I fill up the tank with gas, the car starts fine and drives away from the station, but I get about 200 yards and then the engine starts coughing and shuddering. The car lurches and shakes that way for about half a mile, and then the problem seems to be solved. Everything operates normally after that. I get the same problem whether the tank is completely empty or only half empty when I fill it. The coughing is the only symptom. I'm not getting a check engine light or anything like that.

 

From what I read in this forum, it sounds like the purge valve is the likely culprit, but AutoZone wants $130 for a replacement.

 

Questions:

• Is this something I need to fix? (i.e., am I damaging the car if I decide to just live with the shuddering effect?)
• Could one of the lines going to the valve be the problem? Can I just take them off to check for leaks and obstructions or will gas start spilling everywhere?
• Can the purge valve be cleaned and restored? (And, if so, how?)
• Is this the sort of part that would be safe to buy from an online junkyard?

Thanks for any advice!

I think you have a different issue. You should check for liquid fuel in the line going to the purge solenoid. Fill up with fuel, drive down the road until the problem starts and pull over and turn the engine off. Pull the vacuum line off the solenoid and see if there is liquid in the line. If there is liquid it's because the charcoal canister is flooded with fuel. The canister will need to be replaced, and possibly the vent control valve that allows vapor into the canister.

[Theophilus]

I think you have a different issue. You should check for liquid fuel in the line going to the purge solenoid. Fill up with fuel, drive down the road until the problem starts and pull over and turn the engine off. Pull the vacuum line off the solenoid and see if there is liquid in the line. If there is liquid it's because the charcoal canister is flooded with fuel. The canister will need to be replaced, and possibly the vent control valve that allows vapor into the canister.

 

For the purpose of this diagnostic, does it matter where I detach the vacuum line?  I filled up the car this morning, waited until the shuddering started, and then pulled over to check.  I disconnected the hose from the purge solenoid where it enters the throttle chamber (because that's the easiest connection to reach on a hot engine) and it was completely dry.  No liquid that I could detect.  But I see that you said to check "the line going to the purge solenoid" and I was checking the line after it left the purge solenoid.  Should I try again or should I investigate something else?

[Fairtax4me]

Doesn't really matter. If liquid is making it that far up the line it will likely be present at any point along the hose that goes to the solenoid or to the manifold.

 

So the other thing to check is if the solenoid is stuck open. Test that by trying to blow air back through the solenoid, you can use the hose that comes off the manifold. Best to do this with the engine cool.

 

Engine off you should not be able to blow any air through the solenoid.

If air does flow through the solenoid is stuck open. On the older cars it was possible to take the solenoid apart enough to clean the valve and the core. Remove it from the engine and you'll see the metal casing around it has some little fingers at one end. carefully bend the fingers back and the end plate can be removed do it over a clean surface with a clean towel laid down so you don't lose any pieces if it pops apart suddenly.

[aliscar]

have had similar issue with Mercedes 300se and Chrysler minivan if left running during fillup. I know, read the sign!   Extreme agitation of fuel in tank during fill puts major crud into suspension, clogs happily sucking pickup screen, stall or stumble or no start till crud goes away.   Cessation of fuel pump and good corn broom swat at bottom of fuel tank or 30 second vigorous shake from rear corner of car is effective.  Might sound silly but it is common symptom of crud layer in bottom of tank.    Try it.    Terry

[Theophilus]

So the other thing to check is if the solenoid is stuck open. Test that by trying to blow air back through the solenoid, you can use the hose that comes off the manifold. Best to do this with the engine cool.  Engine off you should not be able to blow any air through the solenoid.

 

Okay, I tried it with the engine cool and gave it several strong blows.  Couldn't get even a bit of air through the hose.  Any other ideas?  I appreciate all your suggestions and help with this!

[wtdash]

I've not read all the above so ignore if already done:

 

Plug  the GREEN connectors together under the dash - driver's right knee area.

 

w/the key On Engine OFF, the fans will cycle, as well as all the solenoids will click on/off, etc. See if the purge clicks on/off, too. as another test. You can feel it.

 

That's how I found mine was no good.

 

 

 Basically, w/the key off, connect the green connectors under the driver's side of the dash, key to ON >>>engine OFF, and ensure all the solenoids involved are clicking and airflow isn't continuous while clicking...the valve should open/close causing the airflow to be interrupted.

Edited October 30, 2017 by wtdash

[Theophilus]

Okay, I'm still having the same problem, but I've done a little more research.  One thing I should have mentioned before is that my fuel pump gave out about a year ago.  It developed several hairline fractures in the upper plate where the hoses attach and started spraying a mist of gasoline everywhere when the engine was running.  I just assumed that the plastic had gotten old and brittle, so I replaced it and didn't think much about it.

 

My theory now is that the pressure control solenoid valve is broken.  When pressures get high in the tank (such as after refueling) the valve should be opening to let vapors escape to the EVAP canister.  If the valve isn't working, pressurized gas is getting forced into the fuel pump, which would explain both the shuddering of the car and the eventual cracking of the fuel pump nozzles.  And if the valve isn't opening, nothing is going to the purge control valve, which would explain why it's dry.

 

Does that seem reasonable?  If I'm right about this, I need to deal with it right away before I destroy another fuel pump.

[1 Lucky Texan]

even though it could likely throw a coupla evap codes, try pulling various hoses off the carbon can. , refuel and drive. You may at least discover which system ,or, where in the system the problem is. If the canister has ever been flooded with fuel from top-offs, I'vread that carbon particles can travel to a valve and cause issues.

[montana tom]

The canister valve is available at rock auto for apx. $ 40.00    

[Theophilus]

Wow, I didn't realize how many valves were in the Subaru EVAP system!

 

 

After reading a bit more, I think I was blaming the wrong valve.  The vent valve on top of the fuel tank (#16) is the one responsible for letting vapors escape during refueling.  Seems like that's the one to look at if the problem only occurs when I buy gas.  But, lordy...  Step One in the Haynes manual is "remove the fuel tank," which seems like a massive amount of work.

 

I'm hoping Fairtax4me will weigh in here and tell me whether I'm on the right track before I start something that big.  Is there a way to test the vent valve without taking out the fuel tank?

Edited November 17, 2017 by Theophilus

[1 Lucky Texan]

see how 3 lines go to the carbon canister? remove one at a time before refueling, then see which one lets the car be 'normal'.

 

that system has multiple modes of failure. My MIL's 2010 Forester had to have the tank dropped for stuck vent valve.

 

as mentioned by wtdash , connecting the green test wire will cycle all those valves, at least put a finger or hose up to you ear on each one to make sure they cycle, if they do, then likely a clog or bad valve is the problem.

Edited November 17, 2017 by 1 Lucky Texan

[montana tom]

I suspect it will be # 7 ... fuel pump dying could be unrelated .

[rocketman]

Thank you for the diagram,I have been having problems with this for ten years,so far this is the best diagram.

[Fairtax4me]

Okay, I'm still having the same problem, but I've done a little more research. One thing I should have mentioned before is that my fuel pump gave out about a year ago. It developed several hairline fractures in the upper plate where the hoses attach and started spraying a mist of gasoline everywhere when the engine was running. I just assumed that the plastic had gotten old and brittle, so I replaced it and didn't think much about it.

 

My theory now is that the pressure control solenoid valve is broken. When pressures get high in the tank (such as after refueling) the valve should be opening to let vapors escape to the EVAP canister. If the valve isn't working, pressurized gas is getting forced into the fuel pump, which would explain both the shuddering of the car and the eventual cracking of the fuel pump nozzles. And if the valve isn't opening, nothing is going to the purge control valve, which would explain why it's dry.

 

Does that seem reasonable? If I'm right about this, I need to deal with it right away before I destroy another fuel pump.

No. Plastic fuel pumps just suck. They crack all the time.

Refueling doesn't create any real pressurization inside the tank. Less than 1psi is normal. Fuel pumps generally make around 45 psi.

Even if the vent valve is stuck closed vapor will just push out through the filler hole.

(Usually this will also result in the auto-shut off nozzles kicking off after pumping ~1 gallon of fuel. A clogged canister or drain tube/filter can result in the same problem.)

 

The combination of the vent valve and the drain valve at the canister are what allow fuel vapor out of the tank during fueling and allow it to pass through the canister. The fuel is absorbed and "clean" air passes out through the drain filter.

Later When the engine is running the vent valve is closed, the drain valve and the purge valve open the fuel vapor that is absorbed in the canister is pulled out via engine vacuum and some fresh air is allowed in through the drain filter.

 

The pressure control valve is only used when the engine is running so the ECU can check for leaks in the evap system.

 

I would disconnect the line at the purge solenoid (block off to prevent a vacuum leak) and make sure you don't still have the same problem after refueling.

[Theophilus]

Time for another update on this thread.

Thanks to everyone for all the input!  I did what FairTax suggested and took apart the solenoid.  It was perfectly clean and looked brand-new inside.  No contamination at all and everything seemed to moving easily.  But the problem continued, so I decided to just live with it and drive as gently as possible after each fill-up.  But now the check engine light has come on and the codes are for the upstream and downstream O2 sensors.  Could this be connected to the shuddering problems (which are still happening every time I fill up with gas)?  Is it normal for both sensors to suddenly have problems at the same time?

I saw some YouTube video awhile back that suggested taking off the charcoal cannister and weighing it to see if it was flooded.  Is that worth doing?  I'm not sure what I should be checking at this point.

[1 Lucky Texan]

new codes 'may' be coincidental. Live data or 'freezeframe' data with the fuel trims may be helpful here ----

 

one crazy idea, as a test (and yes, one or more codes may be thrown) fill-up the car, but leave the gas cap loose - see if you have the problem develop 200 yards w'ever later.

 

that should tell us if there is a pressure/vacuum issue in the tank's 'headspace' I guess