Fuel Line Help - The 1947 - Present Chevrolet & GMC Truck Message Board Network

72ChevyCheyenne · 10-30-2002, 01:12 PM

I am putting in new lines for brakes and fuel to a rear mounted gas tank. The pre-bent line kit I ordered from Inline Tube only has one fuel line. Does this mean that I don't need a return line? The motor will be a ZZ502 with an electronic fuel pump.

JimKshortstep4x4 · 10-30-2002, 02:43 PM

If I understand correctly, the fuel pump will be in the tank and supply a fuel injected motor. If that is the case you will need a return line for all of the systems that I am aware of.

If it is a carbureted engine, with no AC and you are using an electric fuel pump, then you probably don't need a return line.

Jim

Michael A. K. G · 10-30-2002, 03:48 PM

There exist returnless EFI fuel systems, but they are rare and all the examples I've seen are relatively new. Like the Chrysler 3.2L V6.

72ChevyCheyenne · 10-30-2002, 05:06 PM

The motor is carbureted and the fuel pump will be in line and not in the tank. What does AC have to do wiith the fuel line. It will have an afternmarket Vintage Air system.

lofly'a · 10-30-2002, 07:11 PM

yea, please enlighten us. i don't understand the a/c issue either. i'd also like to know any info about return-less efi.

cableguy0 · 10-30-2002, 10:14 PM

there are a few cars that dont have a return line. one that is fresh in my head right now is actually the newer escort. i dunno how they do but it works just fine. i guess the pumps themselves are regulated to a specific pressure controlled by the computer or somethin. this is just a guess i honestly have no idea how it works

lofly'a · 10-30-2002, 10:32 PM

an aftermarket or adaptable return-less efi system sure would make rod building easier and do away with a few headaches.

*Zkast* · 10-30-2002, 11:33 PM

Chrysler is huge on this idea.. have been since early '95 on anything from the 2.0L DOHC to the 3.8L.
Your exactly right Cableguy, the pcm modulates the pressure by varying the frequency signal to the pump. Ford also uses a single line but they have a fuel pressure sensor on the rail.

As long as your staying within reason on your inline pump, you do not need to run a regulator return line. Even if you run something like a Holley "Blue" pump, it doesn't require a return line but you definatly will have to use a regulator.

The main problem I see with running this type of system on a peformance vehicle is fuel temp. The return line serves 2 purposes. 1: Allow the pump to run at the pressure it was designed for, no more no less. "Dead head" pressure is what usually takes a pump out. Plugged fuel filter would be a good example. 2: supply a constant "Cool" fuel charge to the injectors at all times. Fuel is not allowed to simply sit in the fuel rail and vaporize.

10-30-2002, 01:12 PM	#1
72ChevyCheyenne Registered User Join Date: May 2002 Location: Woodstock, GA USA Posts: 300	Fuel Line Help I am putting in new lines for brakes and fuel to a rear mounted gas tank. The pre-bent line kit I ordered from Inline Tube only has one fuel line. Does this mean that I don't need a return line? The motor will be a ZZ502 with an electronic fuel pump. __________________ Bill Durham http://home.attbi.com/~bulldurham 72 Cheyenne Restoration in progress Currently: frame sand blasted and powdercoated, Inline Tube brake and fuel lines, Blazer tank in rear, Holley Red electronic fuel pump, Eaton posi with 3.42 gears, 2 1/2" drop front spindles, 4" drop rear springs with adjustable panhard bar, KYB shocks, ZZ 502/502 GM Performance crate engine, Zoops brackets and pulleys, Vintage Air, dual electric fans, Ram Air II hood and late model sport side bed.

10-30-2002, 02:43 PM	#2
JimKshortstep4x4 Senior Member Join Date: Jul 2001 Location: Muskegon,MI,USA Posts: 6,026	If I understand correctly, the fuel pump will be in the tank and supply a fuel injected motor. If that is the case you will need a return line for all of the systems that I am aware of. If it is a carbureted engine, with no AC and you are using an electric fuel pump, then you probably don't need a return line. Jim Last edited by JimKshortstep4x4; 10-30-2002 at 02:46 PM.

10-30-2002, 05:06 PM	#4
72ChevyCheyenne Registered User Join Date: May 2002 Location: Woodstock, GA USA Posts: 300	The motor is carbureted and the fuel pump will be in line and not in the tank. What does AC have to do wiith the fuel line. It will have an afternmarket Vintage Air system. __________________ Bill Durham http://home.attbi.com/~bulldurham 72 Cheyenne Restoration in progress Currently: frame sand blasted and powdercoated, Inline Tube brake and fuel lines, Blazer tank in rear, Holley Red electronic fuel pump, Eaton posi with 3.42 gears, 2 1/2" drop front spindles, 4" drop rear springs with adjustable panhard bar, KYB shocks, ZZ 502/502 GM Performance crate engine, Zoops brackets and pulleys, Vintage Air, dual electric fans, Ram Air II hood and late model sport side bed.

10-30-2002, 07:11 PM	#5
lofly'a Registered User Join Date: May 2000 Location: Alexandria, LA 71301 Posts: 1,451	yea, please enlighten us. i don't understand the a/c issue either. i'd also like to know any info about return-less efi. __________________ -02 avalanche (daily driver) -66 gto ragtop 389/400 (garage queen, hand-me-down from dad) -72 Tribute Trans Am (6.0LS/T56 6-speed) in progress -2003 YUKON (Wife's) -71 gmc swb fleet (current project, gonna shave everything, bags, stuff w/ 20's, gen III powertrain) -48 3100 SWB - 12/31/23 LONG TERM Project

10-30-2002, 10:14 PM	#6
cableguy0 Senior Member Join Date: Apr 2000 Location: Delta,Pa Posts: 14,950	there are a few cars that dont have a return line. one that is fresh in my head right now is actually the newer escort. i dunno how they do but it works just fine. i guess the pumps themselves are regulated to a specific pressure controlled by the computer or somethin. this is just a guess i honestly have no idea how it works __________________ Owner of North Point Car Care in Dundalk Md. We specialize in custom exhaust on both modern and classic vehicles. We are a full service auto shop from classics to modern vehicles. Feel free to contact me with questions. I will give a 10% discount to any board member.

10-30-2002, 03:48 PM	#3
Michael A. K. G Registered User Join Date: Jul 2002 Location: California central coast Posts: 126	There exist returnless EFI fuel systems, but they are rare and all the examples I've seen are relatively new. Like the Chrysler 3.2L V6.

10-30-2002, 10:32 PM	#7
lofly'a Registered User Join Date: May 2000 Location: Alexandria, LA 71301 Posts: 1,451	an aftermarket or adaptable return-less efi system sure would make rod building easier and do away with a few headaches. __________________ -02 avalanche (daily driver) -66 gto ragtop 389/400 (garage queen, hand-me-down from dad) -72 Tribute Trans Am (6.0LS/T56 6-speed) in progress -2003 YUKON (Wife's) -71 gmc swb fleet (current project, gonna shave everything, bags, stuff w/ 20's, gen III powertrain) -48 3100 SWB - 12/31/23 LONG TERM Project

10-30-2002, 11:33 PM	#8
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Chrysler is huge on this idea.. have been since early '95 on anything from the 2.0L DOHC to the 3.8L. Your exactly right Cableguy, the pcm modulates the pressure by varying the frequency signal to the pump. Ford also uses a single line but they have a fuel pressure sensor on the rail. As long as your staying within reason on your inline pump, you do not need to run a regulator return line. Even if you run something like a Holley "Blue" pump, it doesn't require a return line but you definatly will have to use a regulator. The main problem I see with running this type of system on a peformance vehicle is fuel temp. The return line serves 2 purposes. 1: Allow the pump to run at the pressure it was designed for, no more no less. "Dead head" pressure is what usually takes a pump out. Plugged fuel filter would be a good example. 2: supply a constant "Cool" fuel charge to the injectors at all times. Fuel is not allowed to simply sit in the fuel rail and vaporize. Last edited by Zkast; 10-30-2002 at 11:38 PM.

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