Fuel return diy

[Bextreme04]

This was my bright idea thinking it was more efficient. Pump is mounted on the frame rail down by the tank. I can see it bubbling in the clear filter when parked after running if I'm on it hard, and that fuel has not return so its just sitting there. I notice also when driving and cruising after a while, it gets a little boggy when I hit the throttle as if its flooding, and restarts are a bit delayed as well. not sure if that's due to to that issue though, just have to pump the gas a few times and BLOOOOOOM, were running, with a little ploom of smoke of course lol

That's not vapor lock. What's happening is that the pressure in the line is dropping after it goes through the regulator. Since you have the fuel sitting in the line between the pump and regulator, right next to the exhaust, the fuel is getting hot enough that when the pressure drops it flash boils. When it flash boils, the liquid turns into a vapor that then takes up significantly more volume and the pressure in that section of hose between the regulator and carb jumps up. That spike in pressure pushes the fuel in front of it past the needle and seat in the carb and floods the engine. That's why you are getting the ploom of smoke from it being pig rich.

I think you will solve all your problems by running a regulator with a return line to keep that fuel before the regulator constantly flowing so that it doesn't get as hot. The holley regulator that @Tonimus gave you the part number for above is a great option. The summit page for it shows that people are using that regulator for TBI to carb swaps and even an application using a 40psi EFI pump.

I would put that regulator as close to the carb as possible and get rid of the filter between the regulator and carb. Run a good filter directly after the pump on the frame rail. Using rubber or nylon braided line will actually help reduce the heat being transferred to the fuel in the line by insulating it a bit.

 

[SquareRoot]

That's not vapor lock. What's happening is that the pressure in the line is dropping after it goes through the regulator. Since you have the fuel sitting in the line between the pump and regulator, right next to the exhaust, the fuel is getting hot enough that when the pressure drops it flash boils. When it flash boils, the liquid turns into a vapor that then takes up significantly more volume and the pressure in that section of hose between the regulator and carb jumps up. That spike in pressure pushes the fuel in front of it past the needle and seat in the carb and floods the engine. That's why you are getting the ploom of smoke from it being pig rich.

I think you will solve all your problems by running a regulator with a return line to keep that fuel before the regulator constantly flowing so that it doesn't get as hot. The holley regulator that @Tonimus gave you the part number for above is a great option. The summit page for it shows that people are using that regulator for TBI to carb swaps and even an application using a 40psi EFI pump.

I would put that regulator as close to the carb as possible and get rid of the filter between the regulator and carb. Run a good filter directly after the pump on the frame rail. Using rubber or nylon braided line will actually help reduce the heat being transferred to the fuel in the line by insulating it a bit.

Good explanation and advice here and I learned a new word (Ploom) to boot!

 

[projectmidnight74]

That's not vapor lock. What's happening is that the pressure in the line is dropping after it goes through the regulator. Since you have the fuel sitting in the line between the pump and regulator, right next to the exhaust, the fuel is getting hot enough that when the pressure drops it flash boils. When it flash boils, the liquid turns into a vapor that then takes up significantly more volume and the pressure in that section of hose between the regulator and carb jumps up. That spike in pressure pushes the fuel in front of it past the needle and seat in the carb and floods the engine. That's why you are getting the ploom of smoke from it being pig rich.

I think you will solve all your problems by running a regulator with a return line to keep that fuel before the regulator constantly flowing so that it doesn't get as hot. The holley regulator that @Tonimus gave you the part number for above is a great option. The summit page for it shows that people are using that regulator for TBI to carb swaps and even an application using a 40psi EFI pump.

I would put that regulator as close to the carb as possible and get rid of the filter between the regulator and carb. Run a good filter directly after the pump on the frame rail. Using rubber or nylon braided line will actually help reduce the heat being transferred to the fuel in the line by insulating it a bit.

Thanks. Currently everything is as close as can be to the carb. All lines are run to the outside frame rail away from the exhaust and wrapped with heat resistant wrapping. Got this WIX filter with an extra out for fuel return and a kit to plumb it back to the fill line. Only reason I cant use the current out on the FPR is because its holding the gauge so I can get an accurate psi reading. So hopefully adding that filter will help with that issue. Let me know if I'm going about this backwards Wix filter is 33404

 

[Ricko1966]

Thanks. Currently everything is as close as can be to the carb. All lines are run to the outside frame rail away from the exhaust and wrapped with heat resistant wrapping. Got this WIX filter with an extra out for fuel return and a kit to plumb it back to the fill line. Only reason I cant use the current out on the FPR is because its holding the gauge so I can get an accurate psi reading. So hopefully adding that filter will help with that issue. Let me know if I'm going about this backwards Wix filter is 33404

All you have to do is get a tee from the hardware store mount your gauge in the tee,run the fuel return from the regulator. I would assume the regulator is all npt so it will all screw together.

 

[Bextreme04]

Thanks. Currently everything is as close as can be to the carb. All lines are run to the outside frame rail away from the exhaust and wrapped with heat resistant wrapping. Got this WIX filter with an extra out for fuel return and a kit to plumb it back to the fill line. Only reason I cant use the current out on the FPR is because its holding the gauge so I can get an accurate psi reading. So hopefully adding that filter will help with that issue. Let me know if I'm going about this backwards Wix filter is 33404

That can't be right. A WIX 33404 is a spin on fuel filter and doesn't have any return. I think you meant 33040 which is probably not going to work for you. I don't know how it does the regulation for the return or what the pressure rating is on that, but it isn't meant for that application. Can you post a pic of your current regulator setup? What regulator are you using? What pump?

 

[Ricko1966]

That can't be right. A WIX 33404 is a spin on fuel filter and doesn't have any return. I think you meant 33040 which is probably not going to work for you. I don't know how it does the regulation for the return or what the pressure rating is on that, but it isn't meant for that application. Can you post a pic of your current regulator setup? What regulator are you using? What pump?

Yep 33040 or 33041 I think 33041 is the one with 3/8ths lines. 34040 is 5/16ths lines. It'll work,but not how I'd do it,if I had a bypass regulator. There's a restrictor in the return line for pressure regulation. The way it works is 2 large lines,1 in 1 out. 1 small line with a restrictor. Fuel takes path of least resistance( in and out through the big lines) needle closes,now path of least resistance is the small line with restrictor. We used to do the same thing with a simple tee. Straight through was to carb, dog leg side was return,we'd drill a piece of brass,different orifice sizes until we had the pressure we wanted. Crude but it worked before good bypass regulators got cheap and plentiful.

 

[AuroraGirl]

Good explanation and advice here and I learned a new word (Ploom) to boot!

the spelling would be plume

You must be registered for see images attach

 

[projectmidnight74]

That can't be right. A WIX 33404 is a spin on fuel filter and doesn't have any return. I think you meant 33040 which is probably not going to work for you. I don't know how it does the regulation for the return or what the pressure rating is on that, but it isn't meant for that application. Can you post a pic of your current regulator setup? What regulator are you using? What pump?

Holley Red electric FP
Holley

Chrome Carbureted Fuel Pressure Regulator adjustable from 4.5-9psi.​

 

[Ricko1966]

Holley Red electric FP
Holley

Chrome Carbureted Fuel Pressure Regulator adjustable from 4.5-9psi.​

Show us a pic of this regulator. I want to be sure you have a bypass regulator

 

[projectmidnight74]

Please excuse the gasket seal. I am in the middle of a heater core replacement and oh how frustrating it has been lol

 

[Ricko1966]

Please excuse the gasket seal. I am in the middle of a heater core replacement and oh how frustrating it has been lol

Is that a 12-803 or 12-803 bp? What are the ports labeled?

 

[projectmidnight74]

Is that a 12-803 or 12-803 bp? What are tge ports labeled?

Bottom is in, left and right are out, I used one for the FPR.

 

[Ricko1966]

So it is not a bypass regulator. Getting and running a bypass regulator,with a return to the tank,would be a much nicer install than trying to run this regulator and and a fuel filter as a bypass.

 

[projectmidnight74]

So it is not a bypass regulator. Getting and running a bypass regulator,with a return to the tank,would be a much nicer install than trying to run this regulator and and a fuel filter as a bypass.

Drop this suggestions. Remember this is a carbbed SBC. Nothing crazy. Last regulator we tried failed miserably as it was for an EFI system.

 

[Ricko1966]

Drop this suggestions. Remember this is a carbbed SBC. Nothing crazy. Last regulator we tried failed miserably as it was for an EFI system.

Chevrolet started running 3 line bypass pumps with a return to the tank on nothing crazy,stone stock, carbureated small blocks in 1979. There is no reason that good bypass regulator would be any more liable to fail than the regulator you put on there. @Bextreme04 gave you good advice and good reason why you should run a bypass. There is one more reason and maybe even one of the problems you are having. With a 2 line pump,fuel pressure is held against the needle and seat when you park. As the fuel heats in the line in a hot soak,it expands,the extra pressure blows the needle and seat open,extra fuel spills into the bowl and floods the manifold. On a hot restart you have too much fuel,not enough air,you pump the pedal and it starts,because of the extra air,and the black poof out the tail pipe is the too rich mixture. With a bypass the extra fuel bleeds back to the tank