Half way through driving my car today (97 lt1 383) I noticed my blm's were high. Looked at my fuel pressure gauge and my fuel pressure has dropped.

On turning the key to run, it used to jump to 48# and drop to 42# when the pump shut off.

Now it jumps to 42# and drops to 36# when the pump shuts off.

Decreased vacuum still increases the pressure. The fuel pump is a racetronix I bought new. Now has 10k miles on it.

Is there any way to tell if it is the fpr (stock), the fuel filter, or indeed the pump?

 

Quickly did a little more testing. With the fpr vacuum line off, 46psi. Also, on pressure up, like I stated earlier it jumps to 42 and then 36 when the pump turns off. However, after the pump turns off, is slowly creeps up to 42lbs which is the correct pressure for it to settle at. However, it should snap there, rather than slowly (over 30seconds) creep up to it.

Am I correct in assuming that this would mean the pump is pressuring up to the correct pressure and either the fuel filter or fpr is causing a restriction that slowly lets the pressure bleed back up to line pressure?

Thanks.

 

It's cheap and easy to change the fuel filter to eliminate that as an issue. To fully test the pump you need to see if it can maintain pressure under demand. What's your fuel pressure do when you accelerate hard?

 

The fuel pressure seems to hold under load, but I can only go about 10% throttle before it gets knock counts. When that happens, though, pressure is still about 37psi. I'll change the fuel filter and see if that fixes it. Damn fuel filter is only a year old too.