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Checking for fuel check valve drain


I’m trying to determine if the check valve is faulty on my new Delphi fuel pump (for 1995 Chev Camaro), before moving on to checking other reasons for low initial fuel pressure. On this video (Fuel Pressure testing, they use a bunch of adapters and fittings to put a gauge inline with the pressure line before it gets to the fuel rail. Then they clamp off the line after the gauge and determine that pressure is good, before dropping in the fuel rail/injectors.

I’ve rented/borrowed fuel pressure gauges, but they don’t really come with the parts needed to do something like this. What’s the easiest way to get a gauge on the pressure line? Or is there another way I can determine if the fuel is draining back into the tank?

If you pinch off the return line and pressure jumps to 90+psi and then release the return line and it quickly drops to 48psi the check valve is working, don’t you think.

Can’t speak to your configuration directly, but I had an older VW Rabbit that needed some specialized fuel pressure test fixtures. I removed the 2-3 hoses that connected to where I wanted to insert my pressure gauge, took them to my local auto parts store, and w/the store’s help was able to configure what I needed by trial and error at the parts counter. Took about 15 minutes to assemble all the parts, and it worked fine. That’s a lot easier than trying to figure out what type and size connectors you are dealing with.

I expect what they were doing by clamping off lines is isolating the pump, which allows you to test what pressures the pump is capable of, independent of the rest of the car’s fuel pressure regulating system.

Use the proper tool.


Nothing much is simple anymore. The car is a quarter century old and if that’s the original pump in it then it has served well.
I seem to remember that the exhaust is configured where it has to be cut at the back and removed to gain access. The rear axle also has to be dropped a bit.

With some careful figuring one might be able to remove the rear seat and cut an access hole in the floor pan. A guy did this on a Lincoln site some years ago and provided a pattern for public use. Even though the pump in my car was fine I went ahead and did the modification.
Now instead of dropping the exhaust and driveshaft changing the pump is a 15 minute job if necessary.

Oh, I’ve been through this whole thing. I’m not interested in cutting up the car, so I’ve removed the exhaust (and everything else in the way back there) and dropped the tank out twice now.

Basically the key on pressure is low, and drops back to zero after a few seconds. Car does start with a longer crank and runs at the correct pressure once started. I think it’s the pump itself, which is a new Delphi… I found a 3 way fitting in the gauge kit to go on the pressure line at the fuel filter. I tested the new fuel pressure regulator first (clamped the return line, still lost pressure fairly quickly after cycling the pump).

Then I tested to see if the check valve is allowing fuel to drain back into the tank. Clamped the pressure line before the fuel rail, cycled the pump, and got the same result. Methodology is correct here right? If the fuel is just in the pressure line, isn’t able to go anywhere else, and it’s losing pressure then it has to be draining backwards after the pump shuts off?

That sounds correct.

I’ve had that test set many years @Tester and still had to cobble up a few connections to tap into pressure. Luckily a real hardware store was near my shop.