SteveG75

Looking for some advice on my fuel system for my EFI system.

Engine is a 496 big block with custom tripower EFI manifold. Port injection using FAST XFI 2.0. Injectors are rated at 65lb/hr at 58 psi. Fuel pump is an Aeromotive Stealth 340 in tank setup.

Original fuel system was a returnless setup. Used a LS Corvette filter/regulator back at the tank. -6 feed line using the stock 3/8 hard line with -6 line to one rail, crossover to the second rail and dead head at the end of the second rail. System ran well but fuel pressure would drop to ~56/57 psi under wot and spike to 61/62 when I let off the throttle.

On the advice of the shop that is supposed to be tuning my car, I went to a return style setup with -8 feed line, split to both rails, regulator after the rails set to 42 psi and used the original 3/8 feed line as a return. Car runs really well with this setup and idles very nice. Problem is heat in the gas. After about 45 minutes of driving, the gas tank is hot to the touch and I have vapor locked the pump a couple of times. The gas is getting heated and returned to the fast tank.

I have insulated all the lines in the engine compartment and added a fuel pump speed controller to try and slow down the fuel and reduce heating. This helped a little but not much. Never had a problem with fuel heating with the returnless setup.

My choices are:

1. Add a fuel cooler to the return line. Not sure of this will help much or is just a bandaid fix.

2. Move the Aeromotive regulator to the tank and set the system up as returnless at 42 psi using the -8 feed line. Wonder if I will have stable fuel pressure though.

3. Reinstall Corvette filter/regulator. Just a pain to recreate all the line.

Thoughts? Ideas?

427Hotrod

I dunno...I've got -10 feeding EFI with -8 returns and an external Aeromotive A-1000 pump. It does return a lot of fuel to the tank...but I've taken 2000+ mile road trips in the summer with no issues. Deadheading it would be tough on things so I think you're better setup now. Does it act up with lower fuel levels only?

JIM

Richard454

Vent the tank and add a cooler...at idle over 95% of you fuel is returned to your tank.


I have a non-vented cap- and from what I have read just changing over to a vented cap (designed for a carbs) will shorten the life of the pump (heat) and cause venting issues- not to mention that gas smell.

I looked at the vent on the Aeromotive Phantom Pump and the manual said the vent should be 6" above the tank and use a roll over valve. In a Vette to do this the vent would have to be a couple of inches above the rear deck!!!



I added a roll over valve- connected it to a charcoal canister ( used in GM cars for the brake vacuum line) and then a vent used in marine applications. I put the vent in the rubber neck at the gas filler. I also ended up going w/ Russel Synthetic rubber hoses to hopefully stop the permeation of the ethanol in the gas - and gas smells,


roll over valve




Vent for boat hulls-



How it's plumbed


I moved the vent to the antenna hole-


DSCN4419

DSCN4420

The other thought I am contemplating is putting a fuel cooler on the return -a few OEM new cars have it- can't imagine it would hurt -

Here's the one I am looking at-

SteveG75

Vent from the Aeromotive pump is tied into the stock vent system so that should be good. Never had any heating issues when using the returnless system. Return fuel line gets hot so I thinking I am just picking up heat from the engine bay.

tektrans

It has to be poor venting or poor fuel line routing (meaning next to headers, exhaust etc)
I'd be surprised if its anything else-considering all parts are working properly.

That vent in the antenna hole is a trick idea. Very nice dude!!

tektrans

Or the tank is pressurized from poor venting and the returning fuel and the pump is fighting that pressure-letting fuel hang around in the lines longer that it should and heating excessively.

74modified

Well if you are tuning for 42psi the Corvette filter/regulator is for a LS that runs ~58psi -- So that by itself will not work.

I like the regulator at the fuel rail, to get the most stable pressure.

Here is a stupid idea, (and I would never run like this), put the Corvette filter at the pump. Send 58psi to the rail, control with your rail regulator @42psi. Only a small amount would return from the rail. Yea, two regulators and two returns in the system.... I said it was stupid.

7t2vette

Have you tried to switch to a vented gas cap, assuming you have a sealed one now?

FWIW, I have an in-tank EFI pump, and the feed and return lines are the same size. I am using the factory vent system through the charcoal canister, and I am also using a GM factory vented gas cap. With this setup, I have had no problems with vapor lock, heat, or gas smell.

Also, usually it is preferred to have the return line the same size as the feed line. Here is a diagram produced by Aeromotive with some sample fuel system setups at different horsepower levels:

zwede

I've also not had any problems the 15 years I've had EFI on it. I've driven my car in 110F temps, stop-n-go traffic. No vapor lock, gas smell or anything.

I have an in-tank LS1 pump, 3/8" feed and return line. Vented cap. I run it at 43 PSI.

74modified

I don't have any problem with mine - in tank LS pump running 58psi to a vacuum modulated regulator on the rail. Late model style nylon feed and return lines. Vent is in the pump module to a brake booster carbon canister.