Tune Port Fuel Injection - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Andy4639 · 01-29-2008, 08:13 AM

Went to pick my son up at his friends house and my truck started stumbling coming home. Got it home and poped the hood. The fuel pressure showed 36PSI on the fuel runner. I pulled the vacuum hose off the regulator and the pressure jumped to 55 PSI then settled down at 45 pounds. I cut the engine off and the pressure droped to 0. Turned the key back on and it read 10 pounds.
It's suppose to go straight to 40-46 pounds correct and with the key off it should hold it for a little while before dropping back to 0 right?

Deuce · 01-29-2008, 09:25 AM

It should hold 45 for a little bit.

Sounds like the pressure reg.

hvychve · 01-29-2008, 09:36 AM

yes it should hold, called static pressure. You are correct, if its bleeding down, couple possibilites, try pumping up and at same time, right before pressure drops, pinch off supply line, if pressure holds, your check valve in pump is not holding and is cause of static fail, if it still doesnt hold after pinching off supply lines, you either have and injector leaking(pintle stuck open causine pressure to drop) or you have a regulator bad, usually you can pull vacuum line off and if any fuel runs out of regulator vacuum hose, its ruptured and needs replaced, however on another note, a regulator can stick causing fuel to not build up the proper pressure and return to tank. at any rate , you need to elimnate which is causine your drop and you may end up finding your running problem, maybe you just have a pump issue,???? keep us posted

Andy4639 · 01-29-2008, 09:48 AM

I pulled the pump and filter both off tonight. Going to replace them tomorrow after work. This pump is Life time warrinty but now it's only 1 year with the new one! Well it lasted 13 years.
It's free so. I'll post tomorrow night I hope with good news. I hope the pressure switch is good, that thing is a bugger to get to. I have to take the whole plenium off to get at it. Thanks guy's.

Andy4639 · 01-31-2008, 06:22 AM

Put the new pump,filter,strainer in last night. Truck runs a lot better than it did. Still have the 0 PSI when key is off. I guess it's time for a regulator. I hate not having the instant start anymore. Does anyone know if I can test the pressure regulator some how?

01-29-2008, 08:13 AM	#1
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Tune Port Fuel Injection Went to pick my son up at his friends house and my truck started stumbling coming home. Got it home and poped the hood. The fuel pressure showed 36PSI on the fuel runner. I pulled the vacuum hose off the regulator and the pressure jumped to 55 PSI then settled down at 45 pounds. I cut the engine off and the pressure droped to 0. Turned the key back on and it read 10 pounds. It's suppose to go straight to 40-46 pounds correct and with the key off it should hold it for a little while before dropping back to 0 right? __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

01-29-2008, 09:25 AM	#2
Deuce Registered User Join Date: Apr 2004 Location: Calgary, Alberta,Canada Posts: 1,595	Re: Tune Port Fuel Injection It should hold 45 for a little bit. Sounds like the pressure reg. __________________ I know what your thinking.......I have ESPN. Sometimes it's easier to do things the hard way. Fesler Built 1968 Chevy C10....Must resist the urge to mess with it!!

01-29-2008, 09:36 AM	#3
hvychve To The Levy Join Date: Jan 2007 Location: california Posts: 391	Re: Tune Port Fuel Injection yes it should hold, called static pressure. You are correct, if its bleeding down, couple possibilites, try pumping up and at same time, right before pressure drops, pinch off supply line, if pressure holds, your check valve in pump is not holding and is cause of static fail, if it still doesnt hold after pinching off supply lines, you either have and injector leaking(pintle stuck open causine pressure to drop) or you have a regulator bad, usually you can pull vacuum line off and if any fuel runs out of regulator vacuum hose, its ruptured and needs replaced, however on another note, a regulator can stick causing fuel to not build up the proper pressure and return to tank. at any rate , you need to elimnate which is causine your drop and you may end up finding your running problem, maybe you just have a pump issue,???? keep us posted

01-29-2008, 09:48 AM	#4
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Tune Port Fuel Injection I pulled the pump and filter both off tonight. Going to replace them tomorrow after work. This pump is Life time warrinty but now it's only 1 year with the new one! Well it lasted 13 years. It's free so. I'll post tomorrow night I hope with good news. I hope the pressure switch is good, that thing is a bugger to get to. I have to take the whole plenium off to get at it. Thanks guy's. __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

01-31-2008, 06:22 AM	#5
Andy4639 Old member Join Date: Jan 2002 Location: Liberty, & Garden City S.C. , U.S. Posts: 19,945	Re: Tune Port Fuel Injection Put the new pump,filter,strainer in last night. Truck runs a lot better than it did. Still have the 0 PSI when key is off. I guess it's time for a regulator. I hate not having the instant start anymore. Does anyone know if I can test the pressure regulator some how? __________________ 1971 LWB Custom, 6.0LS & 4L80E, Speedhut.com GPS speedometer & gauges with A/C. 20" Boss 338's Grey wheels 4 wheel disc brakes. My Driver Seeing the USA in a 71 Upstate SC GM Truck Club 2013,14 and 2016 Hot Rod Pour Tour http://upstategmtrucks.com/ Get out and drive the truck this summer and have some fun! It sucks not being able to hear! LWB trucks rule, if you don't think so measure your SWB! After talking to tech support at Air Lift I have found out that the kit I need is 60811. Per the measurements I gave them. Ride height of truck inside spring and inside diameter of springs.

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