So....I think some of you remember that I have had a problem with my car losing power at certain RPMs. Hooking up a fuel pressure gauge shows a 3 PSI drop when this happens. I haven't tested vacuum yet.

Recently, the car has also started taking a super long time to start every once in a while. I'll turn it over for a good 5 seconds and it will start to run, but will just barely hang on by a thread at <300rpms.

A real, on the road WOT test shows a fuel pressure drop all the way down to 15psi at 5400 RPMs. :P

What do you guys think? Replace the regulator first and then see if it runs better, or is there any other tests you would recommend? And what brand regulator? ACDELCO ($90), or Delphi ($40)?

 

It is almost never the regulator.....
Probably the pump. Start by measuring the voltages at the relay and at the fuel pump feed connector near the tank...

 

The engine could not run on 15 pounds of fuel pressure. You need to figure out why you were getting that reading. (From an equipment standpoint).

Suppose for a moment you could get it to run on that low a pressure. You would then get all kinds of diagnostic codes from running lean.

Not to mention the pistons would be toast. I don't mean to indicate you don't have a fuel pressure problem. Merely that it can't be that low.

 

Sure it could. The engine won't die if it's spinning that fast and runs our of fuel. it'll just sputter down and catch itself when fuel demand also drops and the pressure goes back up. It'll kinda automatically regulate itself at some happy medium. Saying it can't run isn't really accurate because it also won't die.

Try another gauge to rule out the possibility. I'ts probably a clogged filter/pickup strainer or a dying pump.

 

Start with a new filter.

 

I know what he means. My car did run on like 8 psi and 10psi just idling and chugging. I just went through this and my problem was very similar. Sounds to me like a pump. I would change the filter first as this is an easy cheap way that might help you get some of that pressure back. Can you hear the pump prime when you flick on the key? Pop your trunk and have someone stand back there and listen for it. If it does not make a whine for a few seconds or sounds strange it could be like mine and have a dieing pump. At WOT i would drove from 44 to 15 from 38 to 8. Sometimes it would take a long time to start or just not start or prime. My bet is on the pump as I just did all the testing in my car. I would change the filter, maybe the relay if the pump isnt turning on at all and then check to make sure you are getting power to the pump.

 

Already changed filter, so I'll measure voltage. I'll recheck the reading one more time, but I already did twice.

I can hear the pump prime. I can drive the car fine, too, it's just getting harder and harder to start it, and it cuts off at certain RPMs, correlating with a 3 PSI drop in fuel pressure (which I suppose could also be related to vacuum).

 

idling at 8 lbs and running at 5K RPM at 15 PSI is another. 5K at 15 lbs is impossible. Anyone want to prove me wrong. Post the results.