Fuel Problems possibly pump????
08-24-2008, 09:03 PM
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Fuel Problems possibly pump????
i tested fuel pressure because my truck takes awhile to start and i came up with good pressure while running (40 psi) but the weird thing was is that when i turned on the pump without the truck running the gauge moved to 45psi and then i lost all fuel pressure within 10 seconds. my question is , is there a check valve that keeps the fuel pressurized in the lines? or is the a check valve of some sort thats associated with the pumps. i have this condition with both pumps and i replaced the fuel pressure regulator and still nothing. another question, is the vacuum line on the regulator supposed to have vacuum sucking out of the line at idle or only when the engine is operating above idle rpm? i dont wanna have to replace the pumps if i dont have to ? if anyone has any suggestions i would greatly appreciate them. thanks again for puttin on such a great site .
08-24-2008, 11:02 PM
#2
Yes, the regulator will have vacuum at idle. There is a check valve to keep pressure in the lines. The check valve is part of the fuel pump, each pump has one. If either check valve is bad it will cause pressure loss with either pump no matter which pump has the bad check valve. To check for a bad check valve, pinch off the fuel supply line stopping flow from both pumps. If the leakage slows there is a bad check valve, if not an injector or injectors are stuck open. Do not pinch a plastic section of fuel line, pinch a rubber section. To find out which pump has the bad valve, pinch off the fuel supply line after the pump but before where the fuel line tees off. See if the pressure loss slows. Do this with both pumps, and don't pinch the plastic line. Pinch a rubber section. Whichever one you pinch off that slows the leakage is the bad pump. If neither slows the leakage then either both pumps are bad or the fuel injectors are sticking open. Be sure to pinch any hoses after the pump has stopped.
08-25-2008, 06:32 AM
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alright i will try that. if i pull off the vacuum line attached to the regulator while the engine running i dont feel any suction out of the line. could that be a possible problem?
08-25-2008, 07:06 AM
#4
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Good morning, not sure why no vaccuum felt at the line, might consider tracing the line back to the source. The regulator if bad, will be leaking fuel out of its port that the connects to the vaccuum line. Is there any roughness or black smoke (exhaust) on start up? As Sean commented, sounds like an injector dribbling fuel when off. Pull plugs and check for wetness to possibly verify which injector is leaking.
08-25-2008, 11:25 AM
#5
That is definitely a problem. There should be vacuum, and when it is removed the idle should pick up. So trace it back and make sure it is hooked up and all lines are in good condition. I have seen a lot of the plastic lines break from age and heat, and there are a lot of plastic vacuum lines on these trucks. I recommend inspecting all vacuum lines, if one is broken then the others are in roughly the same condition. You may find others broken and that might be the only thing wrong with the truck.