Hi think I have a problem with my fuel pressure. This is on a 91 pickup 22re/5spd. I jumper the fuel test in the diagnostic box and listen to the fuel pump. I can hear it spin but there is also a bubbling type leak noise. I can't see any gas leaking on the top of the tank but have had some symptoms, minor surges and cel code 25 is present. Any suggestions? Should I drop the tank? Check the fuel pressure somehow?

thanks
bw1

 

The leak type noise is coming from inside the gas tank. Sounds like maybe the pump is sucking up some air possibly? There's almost 1/4 tank full.

Also I recently noticed the last 2 times I bought gas there was no hiss when I removed the cap, which makes me think I'm losing pressure somewhere?

 

the fuel leaves the tank, goes up to the fuel rail and some of it is held back by the fuel pressure regulator causing the pressure the injectors need to squirt the fuel into the engine. since the pump is capable of making more pressure than the engine needs the regulator allows some of the fuel to go back into the tank. you're probably hearing the returning fuel entering the tank.

 

Can anyone else confirm that the fuel pump makes a sucking/leaking type noise from when in operation?

Should I have pressure when I remove the fuel cap? It should hiss right? The o-ring on the cap looks ok.

 

When I run mine via the test jumper, it sounds like an air leak up under the hood. Sort of a hissing sound that comes from the fuel pressure regulator.
You will often get a slight pressure (or vacuum) release from the gas tank upon opening the cap. It is basically a sealed system, so if you filled up with cold gas and then open the cap when it is hot outside, some vapor pressure is built up.

 

I can totally hear the leak type noise from inside the tank. Stuck my head up in there, definitely where the sound is coming from. I can also hear some hiss from the pressure regulator/fuel rail area too.

 

At the tank, you are probably hearing the return line dumping excess fuel back into the tank, may vary with how much fuel is in the tank. I hear a whirring sound back at the tank.

 

Could be just a bad valve in the gas cap. Time to buy a new one if it's the original cap.

Loss of tank pressure could be a leaky fuel tank hose(s), pinhole in one of the metal fuel lines, bad fuel pressure regulator, malfunctioning charcoal canister.