fuel pressure - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**dec010974** · 02-25-2013, 11:07 PM

hello to all. im having a problem with keeping fuel pressure @ 6 psi. my setup is a 1971 c10, with a carbed lq4/th400. the regulator is set @ 6 psi. my msd 6010 ignition box has pill #6. im also using the stock in cab tank, with a new 3/8 in. sending unit, while running a holly blue fuel pump and regulator. when im ready to start the engine i push the throttle/gas to squirt fuel into the carburetor. when i crank the engine, its run until the fuel runs out. eventually my fuel pressure drops to 3 psi. this happens all the time(fuel pressure drop). when the engine is cold, fuel pressure starts at 6 psi and then drops as the engine runs and shuts off. what could this be? before i sell off my kids to fund the rest of my hot rod project, i would like to trouble shoot this problem but just dont where to start. if you can, please chime in and help a c10 trucker out. im totally open for suggestions.

piecesparts · 02-25-2013, 11:17 PM

Do you a fuel pressure reading prior to the regulator? Is your fuel line pressure holding at what the pump can put out? If it is dropping off, then you have a fuel feed issue and not the regulator. Where are you tapped to the in-cab tank? If you are coming from the top of the tank, you may have to find a way to pull from the side or bottom. Elecftric fuel pumps push better than they pull liquids.

**dec010974** · 02-26-2013, 09:26 PM

hello piecesparts. thanks for your reply. my fuel pressure gauge is located on the carb feed line. the holley blue fuel pump is mounted on the frame rail, by the fuel lines coming out of the cab floor. im using the stock cab (1971) fuel tank, with a new 3/8 sending unit. also today, i adjusted the fuel pressure regulator (to 6 psi) 4 times as it had a different reading each time. if i cant fix this pressure issue soon, im gonna go fuel injected. LSx motors, to me, have been easier to fuel inject than to carburate. i have several FI swaps under my belt. this is my first Lq4, carb build and its been nothing but headaches. im so lost at this time. i may have to send it to a shop. which will drive up the cost of my build.

02-25-2013, 11:07 PM	#1
dec010974 Senior Member Join Date: Oct 2012 Location: Miami, Florida Posts: 924	fuel pressure hello to all. im having a problem with keeping fuel pressure @ 6 psi. my setup is a 1971 c10, with a carbed lq4/th400. the regulator is set @ 6 psi. my msd 6010 ignition box has pill #6. im also using the stock in cab tank, with a new 3/8 in. sending unit, while running a holly blue fuel pump and regulator. when im ready to start the engine i push the throttle/gas to squirt fuel into the carburetor. when i crank the engine, its run until the fuel runs out. eventually my fuel pressure drops to 3 psi. this happens all the time(fuel pressure drop). when the engine is cold, fuel pressure starts at 6 psi and then drops as the engine runs and shuts off. what could this be? before i sell off my kids to fund the rest of my hot rod project, i would like to trouble shoot this problem but just dont where to start. if you can, please chime in and help a c10 trucker out. im totally open for suggestions.

02-25-2013, 11:17 PM	#2
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: fuel pressure Do you a fuel pressure reading prior to the regulator? Is your fuel line pressure holding at what the pump can put out? If it is dropping off, then you have a fuel feed issue and not the regulator. Where are you tapped to the in-cab tank? If you are coming from the top of the tank, you may have to find a way to pull from the side or bottom. Elecftric fuel pumps push better than they pull liquids. __________________ Frank

02-26-2013, 09:26 PM	#3
dec010974 Senior Member Join Date: Oct 2012 Location: Miami, Florida Posts: 924	Re: fuel pressure hello piecesparts. thanks for your reply. my fuel pressure gauge is located on the carb feed line. the holley blue fuel pump is mounted on the frame rail, by the fuel lines coming out of the cab floor. im using the stock cab (1971) fuel tank, with a new 3/8 sending unit. also today, i adjusted the fuel pressure regulator (to 6 psi) 4 times as it had a different reading each time. if i cant fix this pressure issue soon, im gonna go fuel injected. LSx motors, to me, have been easier to fuel inject than to carburate. i have several FI swaps under my belt. this is my first Lq4, carb build and its been nothing but headaches. im so lost at this time. i may have to send it to a shop. which will drive up the cost of my build.



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