Fuel System Questions

[5150]

I'm almost done (or at least I thought I was) with my LS swap when I ran into a complete cluster..... with my fuel system. It's been at the guy that did my wiring and computer flashing's house all week. He's doing the final tune on it and ran into some problems with the fuel system.

Here's what I have now:

Return style system
87 G10 Chevy Van tank
EP381 pump
New steel lines on frame rail
Fuel Injection hose going from frame to engine(double clamped)
Fuel Injection hose going from frame to sending unit (double clamped)
Inline Fuel Filter on frame rail.

Here is his estimate on what I need:

Is there a more cost effective way? What are some of you guys using?

[66LSx]

If your doing an LS swap...

Hose clamps shouldn't be anywhere near your fuel system plumbing.


Your EP381 has been used on a variety of swaps both in gen III and IV apps..

Fuel pressure issues could be a variety of things... (voltage to the pump? are you running a vette regulator setup? etc etc etc)

without pictures of what you have at the fuel rails for connections.... we have no idea how to judge if they are truly 'sufficient'

Cost seems reasonable to be paying someone else to do your fuel system {labor} and then ontop of plumbing it correctly...the cost of new pressure rated fittings, new line, new connections and a new tank.

[BR3W CITY]

You can uplug the vacuum line from the rail and see if FP stays normal or fluctuates immediately.

That pump should be fine, so if its not getting full pressure, then there is a restriction somewhere in the suction or feed line, or the pump isn't getting full power.

you can hotwire the pump to see if it changes the pressure output. If not, then the problem is probably a restriction (or a DOA pump). Make sure that fuel filter you have is rated for Fuel Injection pressures, and that it isn't too small, or causing any restriction (you can bypass it to test).

If the sending unit was modded for an aftermarket FI pump, its possible the line and hose used on the sending unit was not FI rated, and has leaked or burst and is leaking pressure back into the tank.

Afaik, truck return systems usually don't stay pressurized after shutdown...but start fine everytime. I know for one, that my current one doesn't stay pressurized.

What is not correct about the fuel filter or rail connections?

FI hose and FI clamps work just fine for setting up a stock swap, as long as heat and vibration areas are avoided. Are they ideal? No, but can they work, sure. Before I went all-braided, mine was fired up on a system with a few FI rubber sections.

[5150]

I'm just using regular hose clamps, I just doubled them up just in case. I did however use FI hose.

It runs and will drive, but bogs down at half throttle.

If I buy a new factory tank, is there a parts list for a return style system on the board somewhere?

My show is in 12 days and I really want it there.

[Jon01]

Sounds like it's having delivery issues. Has he put a gauge on it to verify it's dropping pressure?

I ran mine all last summer with doubled up regular clamps on the suction side (between pump and tank). No issues.
I would not clamp on the pressure side of the regulator.

If you hurry up and order what you need it could be done in a week easily. I wouldn't skimp, a) you're playing with gas and b) this will easily strand you if something gives up.

[5150]

I just talked to him, he says it's not getting over 48 psi and then it's loosing pressure within 10 seconds of the engine being cutoff. Normally it should hold pressure for an hour. He isn't keen on having the pump in the tank, but I told him that several guys are using the EP381 with no problems. I bought a new sending unit for the tank, but i cut off the ends of the lines coming out and put FI hose and clamped them. I'm just an idiot about the pressure that is going through these lines.

It's a brand new pump so I'm not sure if it got something in it or what. The tank was clean when I put the new sending unit back in it. He also said that he pressurized the tank at 3psi and it leaks. It's not leaking on the floor, but it's not sealed good somewhere.

Sounds like I need a new tank, another new sending unit(leave the threaded lines on this time), and possibly a new pump if I can't tell that something is blocking it. Along with braided lines coming off the sending unit to the steel line. Then braided lines coming off the steel line going up to the fuel rail. Of course fittings all around and also for the inline fuel filter(which I'm not sure which one I need).

[Hart_Rod]

Return style fuel systems will lose pressure as soon as the pump shuts off. I thought the Gen IIIs only required 42 psi? If you are going to change everything, why not buy a Boyds tank that will bolt into stock location and have all of the features you need. I'm sure it will be a little more, but at least you know it will work.

Boyds tank with internal pump/sending unit
Corvette FPR
Braided line and some AN fittings

Wish I were closer and I would fix it for you....

[BR3W CITY]

Where was the pump when he did these tests? If its a stock tank, there isn't a good pickup point externally to hook up a pump. I just want to make sure his tests aren't false-positive.

Hart, we want 58psi like everyone else, I think its only the Flex Fuel trucks that had the lower requirement. They had a different FPR on that metal rail.

[Hart_Rod]

Originally Posted by BR3W CITY

Where was the pump when he did these tests? If its a stock tank, there isn't a good pickup point externally to hook up a pump. I just want to make sure his tests aren't false-positive.

Hart, we want 58psi like everyone else, I think its only the Flex Fuel trucks that had the lower requirement. They had a different FPR on that metal rail.

Roger that. So many different versions, I get them mixed up, . Couldn't Brian convert his fuel rail to a non return style and just run the Corvette FPR back by the tank? This would simplify things greatly. I think I have a fuel rail from an 07 Denali I would give him, if anyone knows if it will fit.

[BR3W CITY]

Originally Posted by Hart_Rod

Roger that. So many different versions, I get them mixed up, . Couldn't Brian convert his fuel rail to a non return style and just run the Corvette FPR back by the tank? This would simplify things greatly. I think I have a fuel rail from an 07 Denali I would give him, if anyone knows if it will fit.

Did GenIV keep the same injector clips?

[Jon01]

I think they did but I don't know if the lengths are the same.