Extreme pressure in fuel system, looking for a cause - JeepForum.com

 
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post #1 of 7 Old 03-07-2010, 05:31 PM Thread Starter
ElvisV04290
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1990 YJ Wrangler 
 
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Location: Macomb, Illinois
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Extreme pressure in fuel system, looking for a cause

Alright guys, got an odd issue with a buddies Jeep and its got me stumped. Over the weekend we replaced his YJ's Carter with a Weber. We drove it to the auto parts store to get a fuel filter and a regulator. When we go back and disconnected the fuel return line from the filter gasoline sprayed out of the hose with a good deal of force. We clamped it and removed the fuel in line to the filter and once again, spraying fuel. I removed the gas cap from the tank and a large release of air pressure came out, and fuel no longer came out of the lines under the hood.

What on earth could have caused such a huge pressure?! I don't think it is because we put the Weber on or an issue with the installation, because my friend says that several times when he has filled up at the gas station there has been this pressure release when he removes the cap.

The Jeep is running, but I can't see how this kind of pressure in the system is a good thing, or how rich it is making the carb run. Any insight would be great!

Specs: 1990 4.2L Weber carb, TF999, mostly stock.


1990 YJ, Colorado Red with 'Laredo' markings, 4.2L, TF999, NP231, Valvoline Syn fluids, Weber 32/36, Nutter Bypass, Dana 30/35, 16" Electric Fan, Optima Yellow Top, 140amp alt., K&N Air Filter, Cherry Bomb muffler, SRC Front Bumper, CH&F Shackles, KC 100w Daylighters, Homemade Lightbar, Rear Aux lights, Cobra CB/PA/WX, 102" Whip Ant., 400 watt power inverter, 2 fire extinguishers, Mobile Internet & WiFi equipped.
Daily Driver since April 23rd, 2003

Northern Illinois Extreme Jeep Club Member www.extremejeepclub.com
Weber 32/36 Install -> http://www.jeepforum.com/forum/f12/weber-32-36-install-write-up-382309/
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post #2 of 7 Old 03-07-2010, 05:51 PM
skeeterbeater
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1995 YJ Wrangler 
 
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mine is doing almost the exact same thing, without the pressure in the tank. it idles at 80 pounds of pressure which is over double speck. i replaced the regulator ($75 i'll never see again) it has vacuum. i'm going to wrestle the return line off and see if there is any comming out of the regulator, then drop the tank and see if there is any fuel making it to the back of the line. will comment back.

its not the biggest baddest rig on the trail, but i beat the hell out of it and have a good time.
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post #3 of 7 Old 03-08-2010, 01:47 PM
skeeterbeater
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update, can't get the lines off the fuel rail (stupid quick connects stuck)

anywhoo there seems to be a problem with the return line getting pinched at the tank. will check this out when i get an extra pair of hands to help with the tank

its not the biggest baddest rig on the trail, but i beat the hell out of it and have a good time.
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post #4 of 7 Old 03-08-2010, 08:49 PM
TSEJEEPERS
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Check where the fuel lines go through the crossmember just before the tank.
Mine was pinched closed there.

93 YJ SOA 2" springs front, XJ springs rear w/main leaf added, High pinon 9 inch rear detroit locker front Dana 44 ARB 4.56 Gears, 36 inch Irok tires too much to list. www.mijc.org
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post #5 of 7 Old 03-08-2010, 09:02 PM
Burnerman
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Besides a pinched return line the only other thing I can thing of is the tank vent line to the charcoal can is non exsistant and an exhaust that may be heating the fuel tank. That'll cause a pressure buildup in the tank that'll push fuel thru the lines.

96 ZJ.
05' Grand Cherokee Limited, 2"OME lift
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post #6 of 7 Old 03-08-2010, 10:05 PM
for-play
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My vent lines were plugged. i had to drive with a loose gas cap to vent the tank till I had the time to pull the tank. I replaced the lines from the tank to the charcoal can and didn't have any more problems.
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post #7 of 7 Old 03-09-2010, 02:24 PM
skeeterbeater
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1995 YJ Wrangler 
 
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dropped the tank and beat my skid back to flat. seems to be fine now

its not the biggest baddest rig on the trail, but i beat the hell out of it and have a good time.
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