Electric Fuel Pump
2026 Loser of the Year
Joined: Sep 2013
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From: New Or-leens Loo-z-anna
No....but I used a 50 PSI OEM fuel pump which I had on-hand from another vehicle.
BUT....
I installed a bypass-valve (WHICH IS AN ABSOLUTE NECESSITY WHEN USING A HIGH PRESSURE FUEL PUMP on a carbed engine) into the OEM return line between the bypass valve and the carb inlet.....which dropped the pressure at the carb to 6 PSI....which I confirmed by temporarily installing a fuel pressure gauge at the carb inlet.
It has worked perfectly for 6 years.
HOWEVER....it would be better for most people to buy the correct-pressure electric pump to start with.
BUT....
I installed a bypass-valve (WHICH IS AN ABSOLUTE NECESSITY WHEN USING A HIGH PRESSURE FUEL PUMP on a carbed engine) into the OEM return line between the bypass valve and the carb inlet.....which dropped the pressure at the carb to 6 PSI....which I confirmed by temporarily installing a fuel pressure gauge at the carb inlet.
It has worked perfectly for 6 years.
HOWEVER....it would be better for most people to buy the correct-pressure electric pump to start with.
Thread Starter
Racer
Joined: Aug 2008
Posts: 326
Likes: 5
From: central Florida Florida
Well this pump is only 14psi and comes with a regulator to knock the psi to 6psi, but it recommends using the same or bigger line going back to the tank as a return. I really don't want to run another line back to the tank. I could have bought another inline pump at the local auto store, but they looked so cheap and suggested using a regulator with the pump. The regulators they had at Autozone did not have a return fitting on them. I have read that the setup is better with the return so the pump runs cooler.
Safety Car
Joined: May 2004
Posts: 4,347
Likes: 1,576
From: los altos hills california
The limited understanding I have is that the reduced size of the return line creates a back pressure that affects the regulator function. The regulator instructions all say to have at least an equivalent size return line. My practical experience is that I couldn't get a Mallory fuel log, which has an integrated regulator, to function correctly with the stock return. However this was complicated by the fact that my electronic fuel pressure sensor was also malfunctioning and I didn't know it. Essentially ???? at the time!
Right now I am running a dead headed system set at 6 psi. I would like to put in a higher pressure pump and hook up the return line. Would appreciate your posting your results.
One more thing - with 14 psi you might be OK without a regulator. The cross sectional area of the return line is very roughly 1/2 and my 6 psi pump was 3 psi with the return line hooked up. If that relationship holds true you would be about 7 psi with no throttle input. At least you would have reduced the danger of flooding.
Right now I am running a dead headed system set at 6 psi. I would like to put in a higher pressure pump and hook up the return line. Would appreciate your posting your results.
One more thing - with 14 psi you might be OK without a regulator. The cross sectional area of the return line is very roughly 1/2 and my 6 psi pump was 3 psi with the return line hooked up. If that relationship holds true you would be about 7 psi with no throttle input. At least you would have reduced the danger of flooding.
Last edited by ignatz; Nov 2, 2013 at 02:36 PM. Reason: second thoughts
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,559
Likes: 7,006
From: New Or-leens Loo-z-anna
You could always install a $15 inline fuel pressure gauge directly before the carb inlet in any case....then you'll be sure of the pressure that the carb is getting....
Better safe than on fire.
Which reminds me......always have a good fire extinguisher in your car.
Better safe than on fire.
Which reminds me......always have a good fire extinguisher in your car.
Thread Starter
Racer
Joined: Aug 2008
Posts: 326
Likes: 5
From: central Florida Florida
Well, just got back from picking up the pump fittings to put this system together. I will see what happens and hope that the lines can handle the flow. I hope to fit a fuel gauge in the line also.
Melting Slicks
Joined: Oct 2007
Posts: 2,310
Likes: 9
From: KB7TIF Ville NV
The limited understanding I have is that the reduced size of the return line creates a back pressure that affects the regulator function. The regulator instructions all say to have at least an equivalent size return line. My practical experience is that I couldn't get a Mallory fuel log, which has an integrated regulator, to function correctly with the stock return. However this was complicated by the fact that my electronic fuel pressure sensor was also malfunctioning and I didn't know it. Essentially ???? at the time!
Right now I am running a dead headed system set at 6 psi. I would like to put in a higher pressure pump and hook up the return line. Would appreciate your posting your results.
One more thing - with 14 psi you might be OK without a regulator. The cross sectional area of the return line is very roughly 1/2 and my 6 psi pump was 3 psi with the return line hooked up. If that relationship holds true you would be about 7 psi with no throttle input. At least you would have reduced the danger of flooding.
Right now I am running a dead headed system set at 6 psi. I would like to put in a higher pressure pump and hook up the return line. Would appreciate your posting your results.
One more thing - with 14 psi you might be OK without a regulator. The cross sectional area of the return line is very roughly 1/2 and my 6 psi pump was 3 psi with the return line hooked up. If that relationship holds true you would be about 7 psi with no throttle input. At least you would have reduced the danger of flooding.
Yep On a high pressure fuel pump with bypass regulator, one would need to install 3/8" return line, or the pump will back up. The nipple on the tank is still 1/4" but the loss of restriction in the line will make it a go.
I installed mine due to gas boiling in the original non-return stock pump. Also For a roots blower install.
But untill the return line is increased you may not be able lower the pressure low enough . I can run 3psi if needed.
I used high quality Braided teflon return line.
My pump is a Holley 440 GPH Im pretty sure
Last edited by illenema; Nov 2, 2013 at 04:13 PM.
Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
I have a carbed 1984 C4 and the intank pump has 15 psi. I used a Mallory 4309 fpr to drop my pressure and used the factory 5/16 return line and it works fine. If you only have 15 psi your stock 1/4 or 5/16 return line should work with no problems.
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Thread Starter
Racer
Joined: Aug 2008
Posts: 326
Likes: 5
From: central Florida Florida
Thanks, that's what I wanted to hear. I really didn't want to run a line all the way back to the tank. I have enough other projects to do on this car. I recently wired the entire car with aftermarket harness. It had the wire for the fuel pump built in , which made it convenient for the pump power.
Le Mans Master
Joined: Aug 2010
Posts: 5,339
Likes: 546
From: Central Texas
I just installed a Holley electric HP-125 pump on my '81. I ran a new 6an line from the tank to the carb. The fuel pump is low pressure (7 psi) and supposedly didn't need a regulator. After flooding out at two intersections I decided to install a Holley bypass regulator.
I used the factory 3/8" fuel supply line as a fuel return line back to the tank. The system works great but there are two things that you may want to consider installing. A direct power switch to prime your pump or actually run it. Also a Hobbs switch which shuts off power to the fuel pump when oil pressure drops below a predetermined pressure point.
Also power the pump with a relay and use fuses in all of the power circuits.
I used the factory 3/8" fuel supply line as a fuel return line back to the tank. The system works great but there are two things that you may want to consider installing. A direct power switch to prime your pump or actually run it. Also a Hobbs switch which shuts off power to the fuel pump when oil pressure drops below a predetermined pressure point.
Also power the pump with a relay and use fuses in all of the power circuits.
Thread Starter
Racer
Joined: Aug 2008
Posts: 326
Likes: 5
From: central Florida Florida
Ok, I got the fuel system all plumbed from factory hard lines. I used the 1/4" line for the return. What I am experiencing with this unit is the lack of adjustment with fuel pressure. I have a small gauge hooked up before the carb and I cant get the pressure bellow 9 psi. On the regulator I had the screw almost all the way out and the gauge still reads 9psi.
I am in the prosses of rebuilding this 74 vert, so this was the first time I did a start up on the motor since I tore the car apart. It took me a few days to even get the thing fired up because the balancer had slipped and the timing mark was way off. Talk about frustrating.... especially after replacing intake, carb, all new aftermaket harness and so on. The car does idle sweet though, but I am sure the pressure is too high.
I am in the prosses of rebuilding this 74 vert, so this was the first time I did a start up on the motor since I tore the car apart. It took me a few days to even get the thing fired up because the balancer had slipped and the timing mark was way off. Talk about frustrating.... especially after replacing intake, carb, all new aftermaket harness and so on. The car does idle sweet though, but I am sure the pressure is too high.
Le Mans Master
Joined: Aug 2010
Posts: 5,339
Likes: 546
From: Central Texas
The 1/4" line may be too restrictive for the return line. That may be making your pressure too high. It should be 7 psi or below. If you no longer have a vapor canister hooked up you could use the 3/8" vapor return line as a return line.
Thread Starter
Racer
Joined: Aug 2008
Posts: 326
Likes: 5
From: central Florida Florida
Thanks Street Rat, I didnt even think of that line. The only thing is the line is on the oposite side of the car, but I will give it a look. I am running hooker headers with side pipes and are they scarey hot. I will have to be carefull if I decide to run that line over to the drivers side.
Safety Car
Joined: May 2004
Posts: 4,347
Likes: 1,576
From: los altos hills california
My plan is to pulse width modulate the supply current to the motor with some custom electronics. Got most of the way there when the wife explained that I was spending a little too much time in the garage. Will report on this sometime in the future.
I did not investigate commercial solutions too much. Found something online but it was hugely expensive. Still if you are flush with $, try
http://www.professional-products.com...ller-p391.html
I did not investigate commercial solutions too much. Found something online but it was hugely expensive. Still if you are flush with $, try
http://www.professional-products.com...ller-p391.html
Drifting
Joined: Mar 2006
Posts: 1,263
Likes: 188
From: Wabasha Mn
Before you go too far I would check that you are turning your fpr the right way as some regulators lower pressure when turning the screw clockwise. Next I would question the accuracy of your fuel pressure gauge as many of them are way off. If the fuel pump is rated at 7 psi and your engine runs fine the gauge may be at fault. The 1/4" (maybe 5/16) should be fine with the low 7 psi pressure.
Thread Starter
Racer
Joined: Aug 2008
Posts: 326
Likes: 5
From: central Florida Florida
Before you go too far I would check that you are turning your fpr the right way as some regulators lower pressure when turning the screw clockwise. Next I would question the accuracy of your fuel pressure gauge as many of them are way off. If the fuel pump is rated at 7 psi and your engine runs fine the gauge may be at fault. The 1/4" (maybe 5/16) should be fine with the low 7 psi pressure.
The car is idling and running sweet right now with this set up, so I am hoping this set up is ok.