low fuel pressure when trying to start
 

It's a 1991 trans am 305 tpi

when I try to start my car after it has set for a few days with a fuel pressure guage connected to the runner port it takes for ever for it to finally start.I watch the guage and it will go up to 20psi then go down to 0psi as I'm cranking it.after a while it'll go back up round 20-30psi and will run but stays around 30psi.I know it can really be a few things so I'm planning on trying the easiest first and putting a new filter on it.But my worry is that it'll be the pump..after it initally starts it'll start and run fine as I turn it off and restart it.after I drive for a while and it will do the same thing but the pressure will not be quite as low,just take a while for it to start up and run....any insight guys?Thanks

Re: low fuel pressure when trying to start
 

43 psi is the recommended pressure so it is not " running fine"

You need to do the fuel system tests to determine if it is a supply ( pump ) or a return ( regulator ) problem.
If the reg is faulty and bleeding pressure off, you will have dropped the tank to replace the pump for nothing

Re: low fuel pressure when trying to start
 

I'm trying to find a good source to buy an adj fpr to install along with a new fuel filter
I've done the test the shop manual suggest to try and find the culprit by squeezing the return line with the pump running and Im assuming I'm squeezing the right line..when I squeeze the smaller line there is no change but as I squeeze the larger line the pressure rises..any suggestions?

Re: low fuel pressure when trying to start
 

Won't help any if your pump is failing

I think you are confused but anyhow ,with the pump running
Obviously if you squeeze the supply line , pressure will drop because you cut off the line
(You are supposed to build up pressure with pump , clamp the line , then turn off the pump and see if pressure holds )

If the pressure rises when you squeeze a line then most likely that is the RETURN line that is now holding the pressure that was leaking past a faulty regulator.
(once again are supposed to raise pressure with pump , clamp the line , turn off pump and see if pressure holds )

As it stands from what you say, the pump is fine ( how much pressure with line blocked ???? ) and you have pressure leaking past the reg

Re: low fuel pressure when trying to start
 

well the test I'm conducting is illustrated in the shop manual as checking the pressure regulator and states to
"have ignition off,apply 12 volts to fuel pump test connector,slowly pinch fuel return hose,pressure should rise above 47psi not to exceed 60psi as damage will occur in regulator....if pressure is above 47psi=faulty regulator and pressure but less than 40.5psi=faulty in tank pump,coupling hose or pulsator,inlet filter,wrong fuel pump"

now that I may not not be "confused" anymore,when I slowly pinch the return line nothing happens,when I pinch the feed line the pressure will rise(now to avoid further confusion I'll state that the feed line is the larger of the two fuel lines going to the fuel rail).....but yes when I do the test you describes the pressure goes up to about 20psi then slowly bleeds off

Re: low fuel pressure when trying to start
 

:huh:
Where is your gauge located ?

Playing with the supply line ( regardless what your manual says ) should cut off the pressure to the rails

Re: low fuel pressure when trying to start
 

Yep my thoughts exactly....I thought I was going crazy and messing with the wrong line even though I knew I wasn't...The gauge is connected to the schrader valve under the map sensor on the fuel rail.

Re: low fuel pressure when trying to start
 

I have a similar problem. Just began, when the car sits for a long time takes a few sec of cranking before it starts (normally starts instantly) strong smell of gas but no leaks anywhere? Where is the filter & regulator located?

Thanx for the help.