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 gaugebin the tee,run the fuel return from the regulator. I would assume the regulator is all npt so it will all screw together.