'01 Monte Carlo; vent valve location

[Sharky]

Hi. I've got a 2001 Monte Carlo LS with the Check Engine lit, spitting out
a code of P0440 (I've got my own OBDII scanner). It has been lit since I
bought the car and everytime I clear the code, it comes back at least two
days later, or the first highway trip the car takes. Even when the code is
erased, the emissions status on the scanner is still showing yellow, which
is mid-range. I've determined that the purge solenoid and the fuel pressure
sensor on the sending unit are not the cause of the code by switching them
out with known working good parts. My next step is to check the vent valve
and lines running to the canister and vent valve. Where exactly is the vent
valve located on the fuel tank? Is it accessible by removing the access
panel in the front part of the trunk (this lets you access the sending unit
on top of the tank without lowering it). I dont't remember seeing anything
similar to a valve when I replaced the pressure sensor. Or would I need to
lower the fuel tank to get at it? I thought I read in an internet forum
that access was gained by removing one of the rear wheel inner fenders, but
I don't recall which side of the car. A clear answer to this would be very
helpful, and possibly save me a lot of extra work.

Any help to locate this part would be greatly appreciated. Also, I'm
looking for a part number for the vent valve, I'm having trouble finding one
on any internet parts store.

Thanks,
Sharky

[80Knight]

Post by Sharky
Hi. I've got a 2001 Monte Carlo LS with the Check Engine lit, spitting
out a code of P0440 (I've got my own OBDII scanner). It has been lit
since I bought the car and everytime I clear the code, it comes back at
least two days later, or the first highway trip the car takes. Even when
the code is erased, the emissions status on the scanner is still showing
yellow, which is mid-range. I've determined that the purge solenoid and
the fuel pressure sensor on the sending unit are not the cause of the code
by switching them out with known working good parts. My next step is to
check the vent valve and lines running to the canister and vent valve.
Where exactly is the vent valve located on the fuel tank? Is it
accessible by removing the access panel in the front part of the trunk
(this lets you access the sending unit on top of the tank without lowering
it). I dont't remember seeing anything similar to a valve when I
replaced the pressure sensor. Or would I need to lower the fuel tank to
get at it? I thought I read in an internet forum that access was gained
by removing one of the rear wheel inner fenders, but I don't recall which
side of the car. A clear answer to this would be very helpful, and
possibly save me a lot of extra work.
Any help to locate this part would be greatly appreciated. Also, I'm
looking for a part number for the vent valve, I'm having trouble finding
one on any internet parts store.
Thanks,
Sharky

This may sound silly, but every vehicle I have scanned, that came up with
that P0440 code, only needed a new gas cap. I would give it a try, it's
only a few dollars and could solve your problem.

[Sharky]

Hi. Forgot to mention that I have already switched out the fuel cap and it
made no difference. But thanks anyway,

Sharky

[80Knight]

Post by Sharky
Hi. Forgot to mention that I have already switched out the fuel cap and
it made no difference. But thanks anyway,
Sharky

I'll throw something else in too, not that it matters to your car's
condition. You said that when you clear the codes, the OBDII scanner still
shows yellow. That is normal. It shows yellow until the computer runs
enough cycles to either register as green, or go back to red, and illuminate
the Check Engine light, showing you the P0440 code. One last thing. Did
you check the fuse box to make sure the fuse for the vent solenoid hasn't
blown? From research, that is a common problem as well. If you are still
having trouble, I would take the car to a shop and have a smoke test done.
You likley have a leak somewhere, and replacing parts randomly isn't going
to fix it. It could just be a small o-ring.

[Sharky]

No, I don't think I ever have checked any fuses for the solenoid. I didn't
realize there was a fuse for it. Don't suppose you know which fuse panel it
is on, right off hand? There's one on either end of the dash, and a
distribution block under the hood. I'll have a look in the manual as well,
should be listed in there. If it isn't the fuse, I'm still going to look
for the vent valve and at least check it visually, and the lines going to
it.

As far as the yellow light on the scanner, it always goes back to red once
the CEL comes back. But the fact is, 3 of the tests never complete until
the p0440 comes back, and then, of course, it obviously fails ands sets the
CEL. When I switched out the pressure sensor, the fuel cap and the
solenoid, all 3 times the tests never completed when I erased the old code,
which told me there was still something wrong. BTW, my brother-in-law has a
junked Lumina with the same engine that I am switching the parts from. The
car runs and there is no CEL on in his car.

Thanks for the help thus far.
Sharky

Post by 80Knight

Post by Sharky
Hi. Forgot to mention that I have already switched out the fuel cap and
it made no difference. But thanks anyway,
Sharky

I'll throw something else in too, not that it matters to your car's
condition. You said that when you clear the codes, the OBDII scanner
still shows yellow. That is normal. It shows yellow until the computer
runs enough cycles to either register as green, or go back to red, and
illuminate the Check Engine light, showing you the P0440 code. One last
thing. Did you check the fuse box to make sure the fuse for the vent
solenoid hasn't blown? From research, that is a common problem as well.
If you are still having trouble, I would take the car to a shop and have a
smoke test done. You likley have a leak somewhere, and replacing parts
randomly isn't going to fix it. It could just be a small o-ring.

[Sharky]

Just checked the fuses and they are fine. There are two, one on the drivers
side panel (ABS, PCM) and one on the lower engine fuse panel (Engine
Devices). Just to make sure, I switched each one of them out with a spare
and it didn't make any difference.

Oh well, looks like I'll be searching for the vent valve.

Sharky

[Rocky]

replying to Sharky, Rocky wrote:
Located on the driver's side by the fuel fill kneck you can access it from
underneath the car

[Paul in Houston TX]

Post by Rocky
Located on the driver's side by the fuel fill kneck you can access it from
underneath the car

Finally, 6 1/2 years later, Sharky gets an answer.