1 DwnCam

How does the stock TPI fuel system setup? I want to know how the system keeps it's pressure on the return side? Does the FPR act as a check valve to hold pressure? or is there somthing else along the way to the tank? I have an SX inline for a few years and I never had a check valve on the inlet side, so after it sat for awhile the fuel would drain back to the tank, then I would have to prime it a few seconds to gain pressure.

I talked to the SX tech and he said to purchase a check valve that is made for my particular pump that screws directly infront of the pump, this should help on the inlet side. But what about the return side? I don't know what the parameters are.

Any info is greatly appreciated.

IROCZZ3

You don't need a check valve on the return side. The FPR just bleeds off excess pressure back to tank...the return line doesn't need to maintain pressure.

In a way it's sorta like a check valve in that a bad FPR can cause fuel pressure to drop quick after you shut off the motor (assuming the check valve isn't bad and the fuel injectors aren't stuck open or leaking). It's normal for pressure to drop off after a few hours though.

The stock pump has an internal check valve to keep the pressure line primed all the way to the regulator. By installing the check valve SX recommends you'll accomplish the same thing as the stock pump.

Are just having a problem keeping the pressure line primed?

72LT1VETTE

The pump should have a very small needle valve type check valve built into it. The FPR is a pressure relief type assembly. The fuel is delivered by the pump through the fuel rails then into the FPR. The FPR whether factory or aftermarket has a diaphram and spring assembly inside. The incoming pressure pushes against the diaphram to overcome the spring tension (thus fuel pressure). The excess fuel flows back into the tank with very little pressure. You can check the FPR by connecting a pressure guage to the fuel rail and turning on the key to let pump pressurize. Start engine. IF PRESSURE IS LOW, carefully with a pair of pliars, squeeze the rubber line connected to the FPR (return line) while watching the pressure guage. Pressure should increase. If not, pump is bad.

1 DwnCam

I was just making sure about the FPR and no check valve on the return system, it was a question asked to me and I wasn't sure. Though the built in check valve in the OE fuel pump is somthing I just learned. I am having a problem with pressure drop off on the inlet side and it was just explained to me, I replaced a pump with a check valve for a pump with no check valve.


Thanks for the answers..