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Old 05-15-2009, 10:29 AM   #1
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Fuel Pressure Problem?

I have an '87 YJ that seems to have fuel pressure problems. Jeep has a new mechanical fuel pump, and new fuel filter with two outlets.......one leading to a return line back to tank. Why is this return line even needed? A local mechanic installed a homemade check valve in this return line and said that was the only way to keep enough fuel pressure in the carb to run. I've currently got that return line out of the fuel filter plugged, and I've installed an adjustable fuel pressure regulator in the line set to it's max pressure of 5.5 lbs.......and the carb still seems to be starving for fuel.

Anybody know how many lbs of pressure a mech fuel pump produces? Is it enough for the carb under normal circumstances? Any reason to have the return line hooked up?

Appreciate any advice.

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Old 05-16-2009, 01:06 AM   #2
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i googled fuel pumps and fuel systems. i found a blog by a guy who took off the pressure regulator and the two outlet filter and all his problems were solved. wish i could lead you to it but i can't............it was a long trip.

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Old 05-16-2009, 05:46 AM   #3
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There is a difference between pressure and flow and i think you should measure both. without a pressure gauge you are guessing your at 5.5 lbs but you may be less still. And yes, the pump should provide enough fuel at all times.
I dont understand why the regulator in the system, not needed unless you are running a aftermarket high pressure/volume pump and even then most carb pumps are internally regulated at 6psi.
so ide get a gauge and hook up to fuel line and crank motor, then disconnect and put line into a bottle and crank. you should have answer to pressure and flow right there.
hope this helps
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Old 05-16-2009, 10:21 AM   #4
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what size bottle and how long should it take to fill it?
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TREAT EVERY STRESSFUL SITUATION AS A DOG WOULD.
IF YOU CAN'T EAT IT OR PLAY WITH IT,
JUST PEE ON IT AND WALK AWAY.
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Old 05-16-2009, 05:11 PM   #5
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just a soda bottle. crank it for like 5-10 seconds. should have at least a few ounces.
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Old 05-16-2009, 07:55 PM   #6
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good to know, tanks
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TREAT EVERY STRESSFUL SITUATION AS A DOG WOULD.
IF YOU CAN'T EAT IT OR PLAY WITH IT,
JUST PEE ON IT AND WALK AWAY.
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Old 05-17-2009, 08:04 AM   #7
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Old 05-18-2009, 09:02 AM   #8
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Thanks to all that replied. I took off the regulator and plugged up the return line and still had problems. Ended up taking the Carter carb apart to see how she worked. Found out there is a little check valve in the fuel inlet fitting that the fuel line screws into. This valve gets closed when the bowls are full and the floats rise. But guess what.......if the rubber washer that seals the inlet fitting is too small or mashed flat, the inlet screws too far into the carb and stops the check valve from working correctly! Basically it stays shut. The whole dang fuel system brought to it's knees by a rubber washer on the inlet...

Long story short, 29 cents later she's running like a champ........at least for the time being...

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