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Old 07-17-2019, 07:43 AM
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Fuel pump and return line

I'm back again, i have truck, i use to drag never had any problems with it until i started driving on the street. It was built in 2012. Ok here we go.

I have mallory 140 fuel pump, regulator 4207, And aeromotive fuel filter.
This setup as a dead head no return line. I have 2 fuel gauges install 1 near the carb and install in the truck.

I was driving the truck about 35 miles in the ride speed was around 55 miles in hour. fuel pressure drops to 3 to 2 psi. It was set at 6 psi. Motor temp went up to 205 to 210 hot out side about temp about 92. This happen a maybe 3 other times I was out.

Could this be vapor lock or my fuel pump going bad.

Should I run a return. If so could I run the return line of this regulator blue blug down to this line 5/16 line going back to the gas tank this is cap off near the tank. Can it be run to the vent line 3/8 going up to the filler neck.

"O" the 5/16 line is below the headers next the frame you can kinda see it nothing connect to it. Put a tee in the vent line near the filler neck.
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Old 07-17-2019, 08:41 AM
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Quote:
Originally Posted by jagco View Post
I'm back again, i have truck, i use to drag never had any problems with it until i started driving on the street. It was built in 2012. Ok here we go.

I have mallory 140 fuel pump, regulator 4207, And aeromotive fuel filter.
This setup as a dead head no return line. I have 2 fuel gauges install 1 near the carb and install in the truck.

I was driving the truck about 35 miles in the ride speed was around 55 miles in hour. fuel pressure drops to 3 to 2 psi. It was set at 6 psi. Motor temp went up to 205 to 210 hot out side about temp about 92. This happen a maybe 3 other times I was out.

Could this be vapor lock or my fuel pump going bad.

Should I run a return. If so could I run the return line of this regulator blue blug down to this line 5/16 line going back to the gas tank this is cap off near the tank. Can it be run to the vent line 3/8 going up to the filler neck.

"O" the 5/16 line is below the headers next the frame you can kinda see it nothing connect to it. Put a tee in the vent line near the filler neck.

Not to be sarcastic, but, GOOD LUCK!! I've been chasing this demon for over 5 years now. I have made a little progress with extreme insulating of the carb, but still gets to the point of rough idle and balky cruise. I cannot find the problem after relieving underhood temps, replacing fuel pump and all lines, carbs, you name it. I've been thru EVERYTHING thrice. Still go from 6.5 psi to 3 or less in 45 minutes. What I ask is, if you do find a resolution, could you please post it? I'm ready to sell my truck.
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Old 07-17-2019, 08:47 AM
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I ran a holley electric pump last year and earlier this year and I had issues of my fuel boiling in my bowl after I shut it off during hot summer months and it took a while before I found the problem. I thought my carb was leaking internally as I have sight glass windows and after two days they bowls were low. I checked everything and the gaskets were good and no warpage on the blocks and main body. My pump was setup as dead head and after that issue I put on a fuel pressure gauge and it would start up at 6 psi then after it would get real hot it would go down to 4 to 3 psi then 2.5 psi.

I then relocated my heater hoses and some other things and I then thought of running a return line so I got a holley billet regulator that has a 5/16 return line and I also went to a phenolic spacer and the fuel boiling problem pretty much went away but the return line helps with fuel to keep moving as underneath my s10 there is a lot of heat and recently I put on a 4 inch cowl hood to help with pressure release of heat and more venting.

I then had to remove my electric pump as before I even installed my return line it was on its last leg and kept loosing pressure till one day it just died out and had crank and crank and luckly got it home ok. I then changed back to a mechanical fuel pump and now I have steady pressure but the bad part the pump is only putting out 3 psi which is too little so I have to change it out one I go to do my cam swap. But I never loose pressure like I did before.

Electric pumps on dead head systems get hot and over worked when they are just holding fuel in the line while the carb bowls are full and don't need anything. I know many run them like that with no issues but for me it was a problem since day one as once I got hot it would loose pressure. The pump died shortly after less then a year.

A return line can't hurt anything and can get rid of any vaporlock most of the time. I had my return line port on my fuel sending unit capped off and I just made a whole line of my own to go from my sending unit along side my fuel line that is my main line and have it going all the way down the side of the frame like my main line and then up to my fender well hooked up to my holley fuel regulator. Mine is one that has a return line. The one port is the main line from the fuel pump and the other line goes to my carb and the down line is my return that goes to my tank.
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Old 07-17-2019, 08:56 AM
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You can't run that regulator as a bypass type, it is a dead-head only regulator. You could set up a "return" line from that pressure port, but it would have to be a jet restricted return and not a full volume return.

All you can do with the current regulator is bleed some back to the tank and hope that cures any heat/vapor lock problem if that is the actual problem.

You could use that existing 5/16" line for the bleed return set-up, but it isn't big enough for a full return fuel system fed by 3/8" line.

For a full bypass system you'd need Mallory regulator #4209.
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Old 07-17-2019, 12:10 PM
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At 55 mph the carb is not using near as much fuel as that pump delivers. The result with a dead head regulator is the fuel is being thrashed to death in the pump. So the output is super hot fuel.a bypass regulator putting the bypass into the tank would by of great help.


Bogie
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Old 07-18-2019, 05:10 AM
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think for the info I order mallory 4209 / 29387 I will keep every 1 posted thanks.

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Old 07-18-2019, 05:12 AM
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Quote:
Originally Posted by jagco View Post
I'm back again, i have truck, i use to drag never had any problems with it until i started driving on the street. It was built in 2012. Ok here we go.

I have mallory 140 fuel pump, regulator 4207, And aeromotive fuel filter.
This setup as a dead head no return line. I have 2 fuel gauges install 1 near the carb and install in the truck.

I was driving the truck about 35 miles in the ride speed was around 55 miles in hour. fuel pressure drops to 3 to 2 psi. It was set at 6 psi. Motor temp went up to 205 to 210 hot out side about temp about 92. This happen a maybe 3 other times I was out.

Could this be vapor lock or my fuel pump going bad.

Should I run a return. If so could I run the return line of this regulator blue blug down to this line 5/16 line going back to the gas tank this is cap off near the tank. Can it be run to the vent line 3/8 going up to the filler neck.

"O" the 5/16 line is below the headers next the frame you can kinda see it nothing connect to it. Put a tee in the vent line near the filler neck.
Quote:
Originally Posted by BogiesAnnex1 View Post
At 55 mph the carb is not using near as much fuel as that pump delivers. The result with a dead head regulator is the fuel is being thrashed to death in the pump. So the output is super hot fuel.a bypass regulator putting the bypass into the tank would by of great help.


Bogie
Quote:
Originally Posted by ericnova72 View Post
You can't run that regulator as a bypass type, it is a dead-head only regulator. You could set up a "return" line from that pressure port, but it would have to be a jet restricted return and not a full volume return.

All you can do with the current regulator is bleed some back to the tank and hope that cures any heat/vapor lock problem if that is the actual problem.

You could use that existing 5/16" line for the bleed return set-up, but it isn't big enough for a full return fuel system fed by 3/8" line.

For a full bypass system you'd need Mallory regulator #4209.
Quote:
Originally Posted by eric32 View Post
I ran a holley electric pump last year and earlier this year and I had issues of my fuel boiling in my bowl after I shut it off during hot summer months and it took a while before I found the problem. I thought my carb was leaking internally as I have sight glass windows and after two days they bowls were low. I checked everything and the gaskets were good and no warpage on the blocks and main body. My pump was setup as dead head and after that issue I put on a fuel pressure gauge and it would start up at 6 psi then after it would get real hot it would go down to 4 to 3 psi then 2.5 psi.

I then relocated my heater hoses and some other things and I then thought of running a return line so I got a holley billet regulator that has a 5/16 return line and I also went to a phenolic spacer and the fuel boiling problem pretty much went away but the return line helps with fuel to keep moving as underneath my s10 there is a lot of heat and recently I put on a 4 inch cowl hood to help with pressure release of heat and more venting.

I then had to remove my electric pump as before I even installed my return line it was on its last leg and kept loosing pressure till one day it just died out and had crank and crank and luckly got it home ok. I then changed back to a mechanical fuel pump and now I have steady pressure but the bad part the pump is only putting out 3 psi which is too little so I have to change it out one I go to do my cam swap. But I never loose pressure like I did before.

Electric pumps on dead head systems get hot and over worked when they are just holding fuel in the line while the carb bowls are full and don't need anything. I know many run them like that with no issues but for me it was a problem since day one as once I got hot it would loose pressure. The pump died shortly after less then a year.

A return line can't hurt anything and can get rid of any vaporlock most of the time. I had my return line port on my fuel sending unit capped off and I just made a whole line of my own to go from my sending unit along side my fuel line that is my main line and have it going all the way down the side of the frame like my main line and then up to my fender well hooked up to my holley fuel regulator. Mine is one that has a return line. The one port is the main line from the fuel pump and the other line goes to my carb and the down line is my return that goes to my tank.
Quote:
Originally Posted by Greg T View Post
Not to be sarcastic, but, GOOD LUCK!! I've been chasing this demon for over 5 years now. I have made a little progress with extreme insulating of the carb, but still gets to the point of rough idle and balky cruise. I cannot find the problem after relieving underhood temps, replacing fuel pump and all lines, carbs, you name it. I've been thru EVERYTHING thrice. Still go from 6.5 psi to 3 or less in 45 minutes. What I ask is, if you do find a resolution, could you please post it? I'm ready to sell my truck.

All good thinks, I wiil keep you posted on this.
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Old 07-18-2019, 12:06 PM
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When all else fails, make this test. Drive around with the hood on the safety latch. My guess is your problem will be gone. Ive got a thread with, I think, way more than 100 posts attempting to fix this exact problem. After 3 carbs, two or more regulators and two or more pumps, all new -8 line, etc. I still have the problem. The only thing that helps is driving with the hood on the safety latch. I even put 1.5" spacers in the back of the hood, which should simulate a cowl hood. Doesn't work. Apparently, it's not the heat you take out that matters,. It's the fresh air you take in. I've already made my inner fenders into swiss cheese and punched 4" holes in my core support. STILL losing pressure. Hope you have better luck than I.
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Old 07-20-2019, 03:13 PM
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regulator is in

Go it in, can I run in to vent line on the gas tank going up to the filler neck.
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Old 07-20-2019, 03:41 PM
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Regulatior w return
https://www.summitracing.com/parts/q...hoCeiUQAvD_BwE

Above the header for feed/return lines

https://www.amazon.com/DEI-010487-He...31764228&psc=1


Your tank lines look good.
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Old 07-21-2019, 01:54 PM
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Quote:
Originally Posted by cerial View Post
Regulatior w return
https://www.summitracing.com/parts/q...hoCeiUQAvD_BwE

Above the header for feed/return lines

https://www.amazon.com/DEI-010487-He...31764228&psc=1


Your tank lines look good.

thanks the info
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Old 07-23-2019, 11:24 AM
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I have this kit came in but.

Be for I cut me full hose neck. Just making sure on this can I use the vent line hose 3/8 for the re-turn line in the picture. When press the full hose air is coming out of my gas cap. it must be a vented cap.
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Old 07-23-2019, 01:25 PM
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You can use that hose neck fitting for the return line.
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Old 07-23-2019, 02:25 PM
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Quote:
Originally Posted by ericnova72 View Post
You can use that hose neck fitting for the return line.

thanks will let you no how everything works out.
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Old 07-27-2019, 05:56 AM
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return line install

Hi guy's thanks so much for the help, I have 8an gas line with 3/8 return line so pressure won't go lower than 10 to 11 psi but i did notice in the float bowls levels stand the same. Gas did not blow pass the needle's seats. With the return line install. I did not no, I need the same 8an to 10an size return line. So I order a 8an 20 feet line set. For now re-install me old mallory regulator 4207 in front of the new mallory regulator 29387 so was able to get the pressure to 7.5 psi. Road test full throttle pressure is 6.5 to 7 I like this. Out for about 35min's on the road cut the water pump off motor temp 225 no problems with gas pressure dropping. Everything seem to be working ok.


I have never use a return line, Man the pump runs smoother and the it's a little quieter. Man I'm a be-leaver "O" the fuller neck adapter is where you see the black 3/8" gas line in the pic.
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