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LTX and LSXPutting LT1s, LS1s, and their variants into Third Gens is becoming more popular. This board is for those who are doing and have done the swaps so they can discuss all of their technical aspects including repairs, swap info, and performance upgrades.
I’m trying to finish up my ls-1 swap and although I can get the engine running I put a fuel pressure gauge on the fuel rail just to see what it’s at. Oddly, the 100psi gauge is pegged at 100 which is confusing to me.
Here is a little background on the fuel system I am running:
4th gen tank
corvette filter/regulator in the same location the stock filter is normally.
stock ls1 fuel rail up at the intake with regulator .
it should run around 58 psi but the gauge as stated above is pegged at 100
Any thoughts ?
Lol exactly, Im thinking that’s my issue but at the same time I would think the redundancy would make the pressure lower not higher.?
If that is my issue, which regulator(s) do I get rid of, because the stock 4th gen ls1 has the in tank regulator and the fuel rail regulator. I really don’t want to remove the corvette filter or the in tank one. I don’t have an access hole and won’t be making nor do I want to drop the tank. I also don’t want remove the corvette filter regulator because I made a custom hard line and braided lines for that filter. Could I get away with removing the intake rail filter?
Last edited by camarorsssss; Aug 15, 2021 at 01:49 PM.
Pick one or the other. If your combo is mild, the inline filter/regulator combo is enough. If you bypass that, keep the one on the rail. Also, how is the one on your rail routed? Before or after the fuel rails?
I'm not sure the pump can get to 100 psi without being dead headed (no flow) and unregulated (no return flow to tank). I think somehow you've created a situation where there is no return flow to tank through any of your many pressure regulators....
First let's get a baseline of what we're really dealing with. Sketch every fuel line on paper and show us what goes where.
Fuel rail: What engine did your fuel rail come from? Did you add your own pressure regulator? Do you have just one line in, or did you plumb a return line too? The reason I ask is because a real LS1 fuel rail does not have an integral pressure regulator. It has a pressure pulse damper inside the tube which is not interfering with anything in your setup. I believe trucks do have a pressure regulator at the fuel rail. Or if you did aftermarket pressure regulator then we need to know exactly what you've got, where is it, and how it's plumbed.
Corvette filter: Show us how your lines are routed at all 3 ports. On the side with 2 ports, the port in the center is the return line back to fuel tank, and the port on the outside edge is the inlet from fuel pump. On the side with 1 port, this is the feed to engine.
Fuel tank filter: You actually have a 4th gen plastic fuel tank? And it's 100% stock, or did you swap out the pump or fuel module? If swapped, then EXACTLY what did you install? And do you have a picture of which nipple you attached the return and feed?
Our replies crossed in cyberspace. Thanks for the pictures, that's helpful.
No pressure regulator in engine bay to worry about as far as I can see. I think that canister is just the fuel pulse damper. That leaves you with just the C5 filter/regulator and the 4th gen in-tank regulator. You're going to have to remove one or the other.
Looks like the general orientation of the C5 filter/regulator is correct. But I don't know which of your soft lines is the return vs. feed. Seems you marked one with a piece of tape to know which is which. You can easily verify again by pulling the lines and seeing which one flows fuel with a short key-on.
Hmmm. It is a racetronix wiring kit with a new stock fuel pump setup. I would think the lines could only be run one way for it to function, as in when the return line and inlet line are reversed, you would get no pressure to the engine.
oh I am running 42lb injectors to accommodate for the modifications to the engine, but I don’t see how that would change the pressure.
Last edited by camarorsssss; Aug 15, 2021 at 04:30 PM.
Hmmm. It is a racetronix wiring kit with a new stock fuel pump setup. I would think the lines could only be run one way for it to function, as in when the return line and inlet line are reversed, you would get no pressure to the engine.
Maybe the input/output is correct and each pressure regulator is regulating to 58 psi locally, resulting in 116 psi total. I don't know if it can really work that way though.
The 4th gen Camaro fuel system doesn't actually have a "return line", that's a misnomer. It's actually just one big feed line to the engine with a Y at the filter. The whole thing is in front of the pressure regulator and is sitting at 58 psi. The actual return line is post-regulator and is the little spill spout inside the fuel tank.
The Corvette regulator has a real return line post-regulator that goes back to the fuel tank. Now plop a Camaro regulator in that return line and it tries to hold the line at 58 psi.... Basically you put a huge restriction in the return line of the Corvette regulator that won't flow even an ounce until pressure in the return line exceeds 58 psi (where the valve in the Camaro regulator finally opens). Pump is pushing a lot of fuel and very little is going back to tank so the pressure at engine goes sky high.
So, removing the “regulator” that is in the tank should correct this high pressure problem ie allow the corvette filter/regulator so it’s job properly.?
I'm not sure the pump can get to 100 psi without being dead headed (no flow) and unregulated (no return flow to tank). I think somehow you've created a situation where there is no return flow to tank through any of your many pressure regulators....
I have gotten stock Fuel-Pumps to make that kind of pressure with an aftermarket Regulator...
The Pressure will only go that high, when there is a very low demand for Fuel (Volume).
As soon as the demand for Fuel (Volume) increases... the Fuel Pressure will plummet.
So it is worthless to try.
Last edited by vorteciroc; Aug 18, 2021 at 06:50 PM.
Lol exactly, Im thinking that’s my issue but at the same time I would think the redundancy would make the pressure lower not higher.?
Have you educated yourself on how this type of Fuel Pressure Regulator operates?
Do you know how a Fuel Pressure Regulator increases Fuel Pressure above a Fuel-Pumps "Free Flow" Pressure output?
Ok cool, you are welcome to come out here anytime and tinker around . Maybe when I finally get this thing squared away and driving I’ll bring it out there.
off topic a little but do you know any good tuners in this area?
Ok cool, you are welcome to come out here anytime and tinker around . Maybe when I finally get this thing squared away and driving I’ll bring it out there.
off topic a little but do you know any good tuners in this area?
I do not (personally) know of anyone, sorry.
No one that I could say that I actually trust... but there are people in the area.
I was the only big tuner around for Holley EFI (I retired).
Fuel pressure problem resolved. I removed the in tank regulator (I hate dropping the tank fyi) and checked everything over and pressure sits right around 58-60. Car fires right up as well, phew.
The 4th gen Camaro fuel system doesn't actually have a "return line", that's a misnomer. It's actually just one big feed line to the engine with a Y at the filter. The whole thing is in front of the pressure regulator and is sitting at 58 psi. The actual return line is post-regulator and is the little spill spout inside the fuel tank.
The Corvette regulator has a real return line post-regulator that goes back to the fuel tank. Now plop a Camaro regulator in that return line and it tries to hold the line at 58 psi.... Basically you put a huge restriction in the return line of the Corvette regulator that won't flow even an ounce until pressure in the return line exceeds 58 psi (where the valve in the Camaro regulator finally opens). Pump is pushing a lot of fuel and very little is going back to tank so the pressure at engine goes sky high.
Even though this explanation is 4 years old, I thank you Qwktrip. I'm going to remove the in tank regulator this weekend.
Last edited by johnw999; Oct 29, 2025 at 09:53 AM.
. Maybe when I finally get this thing squared away and driving I’ll bring it out there. 
