Alright i got a fuel pressure check guage and i hooked it up and i turned my car to the run position and let the pump prime, my friend said guage shot up to 30 psi and fell quickly to 16, i guess this means the pump is bad? But once i started the car it held 39 psi and when i revved it shot to around 44-46. So is my fuel pump going bad? Shouldn't i have 40 psi when i just let the pump prime?

 

Do you have any symptoms? Hard to start?

Normally the gauge should shoot up to around 40 and HOLD there for quite some time. If it is dropping off rapidly then the check valve could be failed/failing.

 

Cycle the key several times, does the fuel pressure drop off severely each time? If it does, the check valve (inside your fuel pump), which holds your fuel pressure, is probably bad as Brent stated. This will cause hard starting. Other things to check are a bad fuel pressure regulator, a leaky fuel injector or a hole in your fuel lines.

 

Yes my car defintly has symtoms. At first my car would start stumbling around 5 grand to 6 grand, well now it stumbles through the whole rpm range and it's been doing this for weeks now. And during the last week it's starting to take longer to start. When we turned the key to run my friend said the guage shot up to around 30-35 and as soon as it hit the peak psi it fell straight back down to 15-16. When we started the car it had 39 psi and we revved it a few times and it hit about 44-46. We shut off the car and it was sitting at 39 psi, came out 15-20 minutes later and it was at 20psi. Does this mean my fuel pump is going bad? And if so is it defintly the fuel pump? I don't wanna spend 150 bucks on a pump only to find out it something else.

 

That doesn't sound like a bad check valve to me. Also the check valve won't affect performance once the car has started.

 

So are you saying there's noway my fuel pump can cause my car to stumble? A few times my rpm's have got stuck, one time they got stuck at like 4 grand and wouldnt climb anymore.

 

Tape the fuel pressure gauge to the windshield and take the car for a drive. Monitor the fuel pressure and see if it drops off at WOT. If the pressure stays steady, it's not fuel related. I'd check wires and plugs.

 

My guage doesnt have a long enough hose to reach the window

 

Should'nt the fuel pressure hit 40 psi when i turn it to "run" ? Like i said it only hits about 30-35 and then as soon as it hit that it fell to 16. Isn't this a sign that it's the fuel pump>?

 

The system is taking longer to prime than the short duration ECU controlled prime pulse allows. As mentioned before the fuel pump check valve may be allowing the fuel system to drain off a bit after shutoff causing a longer prime time. An adjustable regulator (aftermarket body) will also often allow the system pressure to bleed upon shutdown. Turn your key on and off twice before trying to start the car and see if it starts quicker. If the volume of the pump is down or restricted due to a filter that is need of service it may also take longer to build system pressure and will cause performance to fall off. It sounds as if the regulator is operating properly when the car is started. Get a longer hose for your gauge and check that filter....

 

Fuel filter is not more than 300 miles old so that shouldnt be the problem. I'll try and get a longer hose(even though i have no idea where to get one). Also i've tried turning the key to Run and back off letting the pump prime for 2-3 seconds and it seems to start faster that way. Is this an indication of anything?

 

If you have a stock regulator then your pump checkvalve is probably faulty and allowing the pressure to drop. This condition will only affect startup and does not affect pump volume unless the checkvalve has actually come apart (in pieces). You aren't going to know much unless you can read your pressure at high load. A data log might also give you some indication, but a narrow band O2 sensor just makes a guess at WOT mixture, so don't take it for gospel, unless the log shows stoich or leaner, then you know you're in trouble. If your cars got some miles its probably time for a pump upgrade.

 

I do have the stock regulator. So are saying the pump could be causing my studdering problems? Or would it only effect startup?

 

fuel, air, spark and valvesprings = rpm. If any of those are missing you will have problems.

 

Would any of this show up on a scan? I know the fuel pressure dropping is most likely causing my stuttering and shaking. So if i was to scan it would the scanner show anything about the fuel injectors or fuel pump? I've already tried to have my car scanned at two places but the people are idiots and try to hook up a ob2 scanner to my car even though i have ob1 with ob2 plug but they won't listen to me