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Putting an ls engine in a squarebody chevy truck with dual tanks. Doing a custom rewire, so none of the factory stuff applies. I was planning to do as the diagram shows, and whichever pump I switch on is the one that supplies the engine. I'm told that Ford trucks have done this in the 90's, but have not confirmed it.
If I proceed as shown, is there any possibility of over-pressurizing the fuel rail? Such as from underhood heat after cutting the engine off? Do in-tank pumps have any sort of emergency relief valve that I would be disabling by installing those check valves?
If you have any feedback on any other ways how to do this, let me know.
Could you place the check valves upstream of the regulators and as close to the pumps as possible? That would minimize the amount of fuel line that would remain pressurized once the engine is turned off. Any under hood heat induced pressure could then relieve back to the tanks via the FPR returns. Just a thought...
I thought those trucks had a solenoid that switched between tanks and sending units. Why not use that or a similar setup from something newer with high pressure lines?
I would rethink your fuel pump choice if you are planning on running 58PSI of fuel for an LSx engine.
I thought those trucks had a solenoid that switched between tanks and sending units. Why not use that or a similar setup from something newer with high pressure lines?
I would rethink your fuel pump choice if you are planning on running 58PSI of fuel for an LSx engine.
I'm starting from scratch with the fuel system and wiring, so I don't need to go with the factory stuff. I'm also looking at what's the most dependable and simplest system available. The factory switching valves were not that.
Another expectation here is redundancy. If done correctly, the entire fuel system will be duplicated left and right; including fuses, pump relays, pumps, regulators, and filters. The only shared parts are the dash switch(which switches the ecm signal between the two relays) and the fuel rail itself.
A poster on another site(newagtalk.com) suggested using what's called a "shuttle valve" or "OR valve" in place of the two check valves. This valve has three ports, one chamber, and one ball that blocks off either of the two incoming ports. Basically, either pump can supply the fuel rail through this valve, and the valve blocks the non-pressurized pump line. Using this valve, there's always a pathway back to the tanks to accommodate bleed-back. This looks like a nearly perfect fit for my application. I'm just struggling at the moment to find one bigger than 1/4" that doesn't break the bank.
What's wrong with the ep381? I thought that was the fuel pump of choice for ls swaps. It was stock for the late 90's port injection gen one's, which expected 58 psi of fuel pressure.
I wasn't aware (having never owned a dual tank truck) the tank swap systems weren't reliable. Most times I saw someone with problems switching tanks it was because the second tank was simply empty. It was empty because they had already used the reserve and forgot to fill it. Happened enough times that certain people, myself included in the group would immediately ask "are you SURE the second tank is full" before trying to help repair the supposed problem.
I'm under the impression the 90's port injection stuff was at 3 bar or 43.5 PSI. at least I thought the stuff I worked on was but it's been a while. As far as I was aware the Gen III stuff was the first 4 bar or 58 PSI gas stuff from GM but I've been wrong before. I'm not saying your fuel pump choice won't work, my concern is a pump designed for x flow at y pressure is going to have a lower flow rate at a higher pressure. Most people I know use a 190 or 255 for stock and slightly modified LSx swaps. I believe the EP381 you listed is rated at 155 lph at 43.5 PSI.
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Fuel system question 
