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Fuel tank pressure issues 86 Iroc-Z

 
jester_587
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Posts: 4
Joined: 06/08
Posted: 06/10/08 04:53 PM

I am having some issues guys, I am at a loss for what to do.  I have an 86 Iroc-Z 305 Fuel injected.  The Tank is being way over pressurized.  The fuel pump will begin to whine in the tank and I will have to pull over and open the Gas Cap and let it vent.  I have experimented with the gas cap and also the vent tube on the bottom of the tank.  I replaced the cap and took off and cleaned the vent on the bottom of the tank. Did not fix my problem.  The problem is worse on HOT days.  I have called chevy, and all the parts stores around to get advice and nobody can give me an answer on what to do that I havent already tried.  The fuel pump burned out and I had to replace it, and I put a Bosch pump in there.  I had no problems with whining until the Bosch pump went in there.  But I also burned out the old pump for some reason, probably over pressurization. Please list all ideas on what I may be able to do.  

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waynep712
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Posts: 11
Joined: 06/08
Posted: 06/13/08 11:17 PM

how many miles doe the fuel filter have on it??????/    the fuel systems on new cars  except for the newest  circulate the gas through the filter, lines , rails and past the injectors time and time again..     the regulator controls the pressure releasing just enough to maintain the correct pressure..

if the filter is clogged,,,  the pump will pump agenst the dead head...  not what it was designed for...    

if the lines are crimped or crushed..  there will also be a restriction...

also... try not to run the tank below 1/4 full..   the intank pump is cooled by the  gasoline splash on it...  it is also cooled by the gas flowing through it...  but with the level low.. it starts pumping air through it...   this reduces the lube to the ceramic or brass bearings..  

oh... and please use new o rings for the filter..  they are the same as the large ones for the fuel injector rails...  (not the injectors them selfs..)   some well meaning parts clerks sell plumbing grade black o rings for them..  can you say fuel leak..     the o rings wear flat on the outside.. so they need to be changed...
viton is what you want.. i don't know what gm uses.. it is reddish brown..


also... is there a chance that when you had the tank out...   not an easy thing on that car..  that the vent hose got smashed or misrouted..   or maybe the carbon canister is plugged.. it is up in front.. as i recall...  

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jester_587
I love my Chevy Chevette!
Posts: 4
Joined: 06/08
Posted: 07/16/08 12:53 PM

The fuel pump is only about 3 months old, so mabye it has 2k miles on it.  The vent line that comes off the top of the tank is not crushed or pinched.  There is a valve on the vent line and when I take the valve off pressure is released like that valve is plugged or something but i have replaced it with 2 used ones and they both dont seem to make a difference.  The pump whines in the tank at all fuel levels now.  I looked at the carbon canister up front left and did not see any way to change the filter in it out.  The fuel filter is also brand new and was checked and rechecked to make sure that it was not plugged.  I am wondering if i should replace the carbon canister in its entirety or something.  

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jester_587
I love my Chevy Chevette!
Posts: 4
Joined: 06/08
Posted: 07/16/08 12:53 PM

The fuel pump is only about 3 months old, so it has 2k miles on it.  The vent line that comes off the top of the tank is not crushed or pinched.  There is a valve on the vent line and when I take the valve off pressure is released like that valve is plugged or something but i have replaced it with 2 used ones and they both dont seem to make a difference.  The pump whines in the tank at all fuel levels now.  I looked at the carbon canister up front left and did not see any way to change the filter in it out.  The fuel filter is also brand new and was checked and rechecked to make sure that it was not plugged.  I am wondering if i should replace the carbon canister in its entirety or something.  

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jester_587
I love my Chevy Chevette!
Posts: 4
Joined: 06/08
Posted: 07/16/08 12:54 PM

The fuel pump is only about 3 months old, so it has 2k miles on it.  The vent line that comes off the top of the tank is not crushed or pinched.  There is a valve on the vent line and when I take the valve off pressure is released like that valve is plugged or something but i have replaced it with 2 used ones and they both don't seem to make a difference.  The pump whines in the tank at all fuel levels now.  I looked at the carbon canister up front left and did not see any way to change the filter in it out.  The fuel filter is also brand new and was checked and rechecked to make sure that it was not plugged.  I am wondering if i should replace the carbon canister in its entirety or something.  

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waynep712
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Posted: 07/16/08 04:16 PM

by the way... in the lower grey line that says post reply... on the left end when you are logged in... there is an edit button.. to remove the extra posts...

check out this link to the vapor control vacuum circuits./..
http://econtent.autozone.com:24991/znetrgs/repair_guide_content/en_us/images//0900c152/80/09/8f/3f//large/0900c15280098f3f.gif

there is a restrictor and the line and a the tank pressure control valve... probably the item that you were changing..   did you check the filter on the bottom of the charcoal canister.. sometimes when those get clogged they cause crazy problems...  

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smitty73
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Joined: 08/08
Posted: 08/13/08 07:58 PM

I HAVE A 1991 CAMARO WITH THE SAME PROBLEM! I REPLACED THE GAS CAP, THEN THE FUEL PUMP QUIT AND WAS REPLACED, THEN I WAS LOOKING AT THE NEW 3" EXHAUST THAT CAME WITH THE CAR, I THOUGHT MAYBE THE MUFFLER WAS TOO CLOSE, BUT USED AN INFRARED THERMOMETER WHEN THE FUMES WERE VENTING AND THE MUFFLER WAS 300 DEG. F. AND THE TANK WAS ONLY 130 DEG. F. THEN I CHECKED THE FUEL PRESSURE AND MADE SURE THE REGULATOR WAS WORKING, ALL WAS GOOD. DOES THE VENT LINE TO THE CHARCOAL CANISTER WORK AS A PRESSURE RELIEF VALVE? FOUND AN ARTICLE ON AUTOZONE SITE THAT EXPLAINS ABOUT THE 1993-1998 EVAPORATIVE EMISSION CONTROLS, I HAVE ALSO CHANGED THE FUEL FILTER AND RIGHT NOW TAKING A GUY'S ADVICE AND DRILLED A HOLE INTO MY GAS CAP AND WAITING FOR A WARM DAY AND A DAY OFF FROM WORK TO SEE IF THIS SOLVES MY PRESSURE/HEATING GAS PROBLEM, ANY ADVICE WOULD BE APPRECIATED!!  

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mpayne
I have an SS396 tatoo
Posts: 258
Joined: 10/07
Posted: 08/20/08 10:40 AM

wow, to many caps. WHY SMITTY WHY, please no more caps.  

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jjkgdms
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Posted: 08/23/08 07:04 AM

had same problem with a gm rear end i ended up taking the valve off and reroute the vent tube also bosch has a high voulme pump maby the gave u the wrong one  

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smitty73
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Posted: 08/25/08 07:42 PM

I just took the camaro out for a drive with a hole drilled in the gas cap, and within the hour of driving on a warm day the fuel pump was whining meaning the gas is getting warm. I siphoned some gas out and the temp of the gas was 100+ deg. F. Then started the car and then lot's of vapors start venting out of the fill tube probably due to the pump stiring up the hot gas, the temp of the vapors was 120+ deg F. and started melting the plastic holder for the termometer. The fuel pump that was installed was from the local G.M dealership. With the gas cap having a hole drilled in it would eliminate the pressure issues so I am leaning towards a problem with the engine. I had one guy mention that I might have a weak fuel injector, meaning that when the piston is on the upward motion it is pushing hot air into my gas, does this make sense?? should I check into this? any advice would be appreciated as I am running out of options!  

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waynep712
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Posted: 08/25/08 09:22 PM

100F gasoline is almost at its boiling point...   that is why it is building up so much pressure...

figure out a heat shield between the exhaust and the gas tank...  maybe even a dual layer one...    

there is no chance that the compression is blowing back into the fuel rail... that only happens on diesel motors when the pintle tip breaks or burns off the tip of the diesel injectior... but this only goes as far as the individual diesel injector line into the injection pump...   this does not happen in normal fuel injected cars...  



how close is the rest of the fuel system to the exhaust system...    

your fuel temps are getting to dangerous levels...  

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smitty73
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Posted: 08/26/08 07:32 PM

One of my next experiments is to remove the muffler and run a straight pipe out the back to see if the fuel heats up, the car came with 3" exhaust installed 3 years ago but only has 2000km on it, have had it to a muffler shop 2 times as the muffler was on a angle and actually touching the bottom of the gas tank. Now we have at least 1 1/2- 2 inches of room between the muffler and heat shield which is pretty well standard on these cars but the muffler is huge and could be working like a hot plate. My previous testing with muffler was a temp of 300 deg. F. which should be about normal. Just to clarify, the exhaust system was only added on from the rear of the catylitic convertor, so nothing else was touched like sensors, etc. The rest of the fuel lines are away from the exhaust so I guess I will try removing the muffler and see if it works.  

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Jen1
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Posted: 08/10/09 06:42 PM

Smitty and Jester,

I have a completely different type of car, but am experiencing the same kind of problems..
Overpressurization, and fuel coming out of the filler cap.
I have replaced many of the same things you have listed in your post but nothing has fixed it.

The exhaust that came on the car is nonstock.. larger diameter and possibly closer to the gas tank.

I was wondering if you found what was causing your problem and if it was the exhaust location and size or what?

Thank you,
Jen  

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mikeblanco
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Joined: 04/10
Posted: 04/07/10 09:38 PM

I have the same thing going on over here with an 89 GTA TPI 350. I have an aftermarket (flowmaster) exhaust that I have to take a look at because there is a heat issue around the filler door and the fumes are melting the paint away. I think the fuel is heating up and with all the vapor, there's air there no, and that has to be going through the pump with that hotter fuel making my "new" pump whine as well on the warm up, thus  creating the stalling issue or not starting after stalling issue. I had a fuel pressure regulator and distributor put in and now I'm saying for what. The problem is still there. Did anyone out there tackle the heat issue yet?  

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waynep7122
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Posts: 109
Joined: 11/09
Posted: 04/08/10 06:20 AM

i have run across some more information since the last time this thread came up....

this might help...

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/e5/c1/large/0900c1528008e5c1.gif

look at items

4 canister purge solenoid
6  vapor restrictor
8 tank pressure control valve...

Tank Pressure Control Valve
Using a hand-held vacuum pump, apply a vacuum of 15 in. Hg. (51 kPa) through the control vacuum signal tube to the purge valve diaphragm. If the diaphragm does not hold 5 in. Hg. at least for 10 seconds, the diaphragm is leaking. Replace the control valve.

With the vacuum still applied to the control vacuum tube, attach a short piece of hose to the valve's tank tube side and blow into the hose. Air should pass through the valve. If it does not, replace the control valve.

this image shows were it is.... its a vacuum control valve inline near the carbon canister... in the fuel tank vent line...

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/08/e6/71/large/0900c1528008e671.gif



i did some digging for part numbers and came up with 2 possible...

special order through  AZ,  other companies also
Wells / Canister Purge Valve
Price:$19.99
Part Number: PV106
OEM Brand: Delco_GM
OEM Number: 17087244



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~




According to Tomco, this is a replacement for the OE Evap Canister Vent Valve.



For future reference: Tomco part number 19015, OE#17087294


snipped from another forum... on a google search...

http://www.thirdgen.org/techboard/tech-general-engine/378880-fuel-tank-pressure-control.html
My car has been giving me extreme amounts of pressure, I mean, the pump has been squealing from the pressure until I open the cap, let it out, and close it up again. I'm gonna try undoing the clamp at this valve, and see if pressure vents through there. If it does, there's something wrong with that valve.

Oh, and as a sidenote, my parts manual lists part number 17087244 as the correct part for a L98. Which corresponds to Tomco's 19014. *Shrug*


i went looking through the az parts book..   wells pv105, pv106, pv107, pv108  are similar.. but have different fitting sizes..

so if they don't have one.. they might have another..


since EVERY GM car and truck in the 80s and 90s  came with them.. there should be quite a few in the junk yards...   test them there...   there is some reference to different opening pressures..

i hope this helps...  

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