Ok, I hooked up the fuel pressure guage tonight, when I prime the rail it will go up to about 45psi and then drop to 0 very slowly. I tried pinching the return line with a pair of vice grips and it still does the same thing. However the car does start after a fair bit of cranking. Once it does start it maintains about 48 psi with the vacume line plugged in. With it unplugged and running it maintains 42 psi. I have replaced the fuel pressure regulator diaphram about 2 months ago. Im starting to wonder if its a leaking injector. If so how would I go about determining which one it may be?

 

First set the fuel pressure to 43.5 psi line off.

running at idle should be 38-39psi.

Block off bothe the feed and return lines. See if the pressure still drops, if it does, either the regulator or the injectors are leaking down.

If the vacuum line for reg is clean, its the injectors.

Also deadhead the fuel pump(be careful you will get severe pressure if everything is working)

Clamp the return line off and prime the pump and then do it again as soon as it allows u too turn the key and prime again. This should spike it too 60psi or so and make it real easy to find bad injectors on a cold motor. If it leaks down, pulll all the plugs immediately thereafter. U wil find wet ones if thats the case.

later
Jeremy

 

Ok so I set the fuel pressure to 43.5 psi with the motor running and the vacume line unhooked. With it plugged in it should idle at 38-39psi ?

With the motor running i clamp BOTH the feed and return line?

 

It's the fuel pump leaking down, meaning it's going. It should hold that pressure for a LONG time, unless you vent it.

 

great..... The pump thats on there probably only has 10,000 miles on it. Is it that common for them to go out so frequently? Maybe some other issue causing them to go south?

 

Maybe it's the tank inlet screen, and there was crud in the tank. As fas as locating which injector, run it on the road a while, shut it down, and when it cools down, check each plug. If one or more injectors are leaking, they'll be wet with gas. That would also explain the extra cranking needed to start it too, just like 3.8 said.

 

do you have a holley regulator

If so this is normal

 

the regulator is a adjustable one from TPiS. The pump is just an oem replacement I assume. I had a shop do the work last time but I think if it does end up going out ill do it myself this time. Cant justify $600 if its only going to last a few months. Does anyone have any suggestions on weather to go with walbro, holley, bbk, edlebrock....etc Im going try as you guys suggested and run it for a little bit and check the plugs this afternoon. Im almost hoping its an injector but I doubt that the pressure would drop off that quickly after being primed if that was the case.

 

well I did as mentioned above and didnt find any fuel on the plugs. then i hooked the guage back up primed the rail again with the vacume line disconnected on the regulator and noticed fuel spooging out of it. I think it would be safe to say its time for a new diaphram.

 

I have one, is that why my fuel pressure dropes so quick? Is that normal?

 

all i know is that flexible rubber like stuff doesnt hold up very well. Took the old one out today n it was ripped right around the metal part in the middle. I think ill have to hold onto the receipt this time and hopefully when it goes again it will be within the year warantee.