I have an 1987 IROC with stock pump (that I believe is taking a dump). With a fuel pressure gauge connected, I am getting the following readings.

Idle: 600 rpm/ reads 31 psi (needle not steady at all)
Partial throttle 2500 RPMs 32-34 psi
WOT drops to 28 psi (car doesn't downshift and feels VERY sluggish as if I am losing 30 hp)..


My fuel pressure needle kinda jumps (even on idle), not steady at all. Are these readings normal. I believe that at WOT...the fuel pressure should have shot up around 39-45 psi...not drop to 28 psi... Does this sound like the pump is suspect.

I performed the WOT drive test by connecting my fuel pressure regulator up and having it sit out from the hood's cowl so that I could read it when driving... I was surprised the needle never went past 35 psi...regardless...

 

Have you replaced the fuel filter yet?

 

The fuel filter is an easy place to start, but your problem could also be your regulator. The fuel psi should increase as you come off idle and manifold vac. decreases. If you pinch off the vac. line to the fuel pres. reg. the fuel psi should go up at idle. If it doesn't there is a problem with the vac. signal or the fuel pres. reg. If your regulator checks out the problem could be with the wiring to your fuel pump. A scan tool can tell how much voltage drop there is at the fuel pump. Changing the fuel pump is a difficult and expensive job, so it's best to rule out the easy things first.

 

87 IROC has 264,000 orig miles. FP Regulator was replaced about 2 years ago along with the injectors with AC/Delco part. The fuel pump is original. Fuel filter was replaced 2 days ago..no affect.

Pinching off the vacuum going to the FP Regulator--- no change to the reading... needle fluctuates at 30-31 psi with no increase. I do know that when I go partial throttle... needle jumps to 35 lbs... at WOT it dips to 28 lbs and idles at 31. Something sound funny here.

One thing I have noticed is after driving the car..I used to get tank pressure when I removed the gas cap you could hear the air rush in (vacuum).. now nothing...

 

Same thing happened to me when my fuel pump was bad. I would go with that. Also when my pump went bad it sounded kind of sick when it would prime. It should sound high pitch. Thats something to check for.

 

Good point. My fuel pump makes a VERY low moaning sound when it primes.... in comparison to the pump in my TTA and my wifes 95 T/A...which are high pitch and "healthy".... thanks for the advice.

 

Pump psi with no vacuum, same as key on engine off and while pump primes should be around 43.5psi. With engine on psi should drop as vacuum increases. WOT should read the same as engine off because vacuum decreases to almost zero.