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Possible fuel pump problem?

Old Jun 4, 2006 | 08:49 PM
  #1  
BADNBLK's Avatar
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From: WINDSOR, CO
Car: 91 Z28, 87 SC, 90 IROC, 92 RS
Engine: LS1, 305 TPI, L98, NADA
Transmission: T56, 700r4's, and NADA
Axle/Gears: 3.89, 3.42, 3.23, NADA
Possible fuel pump problem?

I was driving my car on saturday adn it was very hot out (97) degrees. Had been running the car in town trraffic so, it was running just a hair over 220. Suddenly while sitting at a light the engine stalled. Died so smoooth that i did not realize it. It restarted fine, but bucked and surged anytime the throttle was applied. The problem was worse the more I put my foot into it. I pulled over and vented the fuel tank (lots of pressure). Restarted - problem still there. Checked pressure on fuel cap still lots of pressure - vented again - still not help. When keying up the car and listening to pump pressurize it sounds normal. After letting the car sit for about 20 minutes, while trying to get a tow truck set up it started fine, and was smooth. I drove the car home with no other problems, but felt like maybe laking a little power. I had about 1/3 tank of 91 octane, the fuel filter only has about 8k on it. The engine has not thrown any codes. 110k miles.

Does this sound like the beginings of a fuel pump failure? Maybe something else I did not think of?
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Old Jun 4, 2006 | 09:04 PM
  #2  
badCHEVELLEman's Avatar
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From: sanger, Cali
Car: chevelle + camaro
Engine: 520hp 350 350
Transmission: th 350 700r4
Axle/Gears: 4:56 3:23
im in the same boat dude cant find a fuel pressure gauge in town to test it. but it does prime like it should, it has trouble starting now so i wouldnt veture to far from home if you dont fix it
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Old Jun 5, 2006 | 09:18 AM
  #3  
Trickster's Avatar
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From: conway, s.c.
Car: 1989 Iroc-Z
Engine: 5.7L TPI
Transmission: 700R4
Look at getting a vented gas cap, there is also a fuel tank vent located near the left rear tire that might be clogged. It is a white or clear plastic unit.
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Old Jun 5, 2006 | 11:42 PM
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wulff's Avatar
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Car: 1987 Monte Carlo SS
Engine: 406 TPI
Transmission: T56 6-speed
The factory fuel tank vent goes to the vacuum canister and is supposed to purge through the solenoid mounted on the top of the canister. The factory hasn't vented the tank into the atmosphere since the 70's... when the smog police test your tank they put a vacuum on the opening and pinch off the vent tube at the canister to make sure there are no venting to the atmosphere so if your state does smog checks you can't use a vented cap. (the "vent" on the rear only allows air to flow into the tank and it is then sucked into the charcoal canister).
By the way, you said 'pressure' are you sure it wasn't vacuum you were hearing when you cracked the cap open?

Last edited by wulff; Jun 5, 2006 at 11:50 PM.
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Old Jun 5, 2006 | 11:59 PM
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From: WINDSOR, CO
Car: 91 Z28, 87 SC, 90 IROC, 92 RS
Engine: LS1, 305 TPI, L98, NADA
Transmission: T56, 700r4's, and NADA
Axle/Gears: 3.89, 3.42, 3.23, NADA
Originally Posted by wulff
The factory fuel tank vent goes to the vacuum canister and is supposed to purge through the solenoid mounted on the top of the canister. The factory hasn't vented the tank into the atmosphere since the 70's... when the smog police test your tank they put a vacuum on the opening and pinch off the vent tube at the canister to make sure there are no venting to the atmosphere so if your state does smog checks you can't use a vented cap. (the "vent" on the rear only allows air to flow into the tank and it is then sucked into the charcoal canister).
By the way, you said 'pressure' are you sure it wasn't vacuum you were hearing when you cracked the cap open?
Yeah I understand the evap. system the car has and that is why it was so strange that it would continuosly have soo much pressure. It was pressure you could put you hand over the filler and feeling it pressing on your hand. You could also see the vapors rising out of the filler very quickly. I have heard of pressure differences in the fuel tank when the tank was filled at a cooler temp, then when the temp goes up can create pressure. But I onyl drive the vehicle on nice days, so when last filled it was like 80 degrees. I am going to install fuel pressure gauge this weekend and drive around (if hot) and see what happens there.
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Old Jul 19, 2006 | 06:30 PM
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82tarecaro's Avatar
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From: NYC
Car: 1982 Recaro TA, 1989 TTA#948
Did you figure this out?
I am having the same problem with my 1982 CFI
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Old Jul 20, 2006 | 09:37 AM
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it will build some pressure that feels like a lot but really is very low because the fuel coming back in the return line is hot from it's travels and has to expand somewhere. The canister isn't vented constantly so it's not unusual to see a few psi of pressure. Like I said, it will feel like a bunch but it's more volume than pressure though. As far as a pump failure, when mine decided to take a crap the last time it did it in traffic much like yours did. I shut it off and it would drive a few more miles. It died as I pulled in the drive and never ran again until I replaced the pump. Man, I hate those frikken pumps!!
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