specie

After shutting off the car, my fuel pressure drops down to zero in less than a minute. When the motor is running, I'm getting consistent 42psi. The only thing I could think of right now is the fuel cap...I've checked it and the seal is still good and a good bit of pressure is released when I opened it. However, I still trying to find someone's just to make sure that the fuel cap isn't the problem.

Anyone knows of any other reason for such a quick drop in pressure?

JimBlake

The gas cap can't have anything to do with it. It's either leaking down forward through the FPR, back through the pump, or out through an injector.

The FPR is supposed to leak more slowly than that, I think.(?) Maybe the Helm book has a spec for how fast it's allowed to bleed off?

The pump is supposed to have a check valve or something to prevent backflow.

But it's NOT supposed to stay pressurized forever. There has to be some bleed-off, otherwise everyone would have burst fuel lines the first time they parked in the sun...

EE_Chris

Are you using a stock fuel pump?

Stock fuel pumps feature the check valve Jim Blake was referring to....I'm unsure whether aftermarket pumps, such as the Walbro 255lph, feature one.

kpt4321

It should fall off, but possibly slower than that.

As long as you are getting proper fuel pressure, and you're not leaking, then I wouldn't worry.


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How do you figure?

Liquids barely expand when exposed to heat.

The fuel lines can take more than 100 psi.

Heat is created when the motor is on, and that doesn't burst the lines.

JimBlake

Now that I think about it, the FPR would handle that anyway. If the pressure wants to climb, the FPR would open & let a little gas back to the tank. The FPR is a passive device - it doesn't need electricity to work.

When the car is running, gas is continuously recirculating, so it's not bottled up. I'm accustomed to thinking about water in steel tubing. Liquids expand enough to do some damage if you close valves at both ends...

specie

I have a walbro fuel pump. I think the fuel pressure problem might have to do with the Code 43 that I've been battling with. Changed the injectors, 02 sensors, fuel filter, fpr, fuel pump. Not sure what else is there to check.

Fuel pressure does bleed off, but not this quickly....anyone have a problem like this before?

JimBlake

Your code 43 is something happening while the engine's running. As long as the pump & FPR maintain the proper pressure while it's running, the ECU doesn't know or care how long it takes for pressure to bleed down.