I have gotten a lot of information by reading the posts on this forum but I'm still a bit unclear about the possible causes of low fuel pressure. I have a 1991 RS 3.1v6 about 197K miles. I have owned this car since new. I have checked the fuel pressure and found it to be about 20 psi before and after starting. Removing the vacuum line from the regulator does not seem to change the pressure. It leaks down but takes a few hours to do so. I'm thinking that it is time for a new pump. Changing pumps is a pain in the butt and things could get expensive it something else is the problem. Could a faulty regulator cause low pressure?

 

There is a certain sequence of tests you can do to narrow down the cause. Since the vacuum line disconnect doesn't affect the pressure, and it takes hours for the pressure to leak down, I would bet it's a bad fuel pump.

Replacing it isn't that bad, just a bit time consuming.

Where are you at?

 

I'm in SW Indiana. I just want to identify the real problem before I start instead of starting a endless cycle of parts changing.

 

That's the exact reason you need a shop manual.

 

How old is the fuel filter? Has the car been sitting for any length of time, which would cause the fuel to turn to gum in the fuel lines, or has anything happened that may have caused the fuel lines to become partially plugged?

 

The filter is recent and the car has not been sitting. I want to make the pump run for more than 2 seconds with the engine off. Running the pump could tell me that the filter is OK if the pressure does not climb or tell me that the filter is bad if the pressure continues to climb slowly. It is probably a worn out pump. Could the regulator be bypassing back to the tank before 37-47 psi is achieved?

 

Yes it could; pinch off the return line with a clamp and then check the pressure.

 

Is there a good spot to do this on the Camaro? It is all steel lines on top of the engine. Do I use plain old vise grips?

 

Use the 2 rubber hoses next to the windshield washer bottle... The big one is the pressure line and the small one the return. Use 2 pairs of clamps of some sort with PADDED jaws (you don't want to damage those hoses).

Pressurize the system and pinch off the return line. If pressure goes up, the regulator is leaking and needs to be replaced.

There is also a flow test for the fuel pump, which is done by disconnecting a line or hose and putting the end into a measuring device...

You may also want to test the voltage available at the fuel pump. Cover all of your bases before you decide to go ahead and tear apart the rear of the car to get the fuel tank out. You don't want to spend a weekend replacing the pump to have the exact same problem with the new one.

 

Thanks for the info Maverick. I hate to blindly change parts and hope for the best. Your info will help me to narrow down the possible problems so that I can fix it right the first time. Is there a good way to make the pump run without the engine running? Haynes said to run a hot wire to terminal G in the assembly line link but when I check "G" I see that there is no wire coming from it so that will not work.

 

There MAY be a big red wire coming out of the fuel pump relay socket. There is no test terminal on the 90-92 cars (another reason why Haynes sucks). This wire is given 12V to turn the pump on. Otherwise, if the wire isn't there, you unplug the relay and jump the orange wire to the gray one.

 

pinched off the return line and no change in pressure. I even disconnected the return line and noting comes out with engine running. Looks like I have a weak pump. Thanks for all of the help. Like you guys, I don't like the Haynes manuals very much. I will admit that the wiring diagrams in the back have helped me out on a few different vehicles.

 

And now.... the rest of the story. I should have followed up sooner on this one. I replaced the fuel pump which was a terribly sucky project. After I got everything back together the fuel pressure was back to where it should be. I took the car for a ride. It ran better but not great and I smelled gas. I stopped and found lots of gas leaking under the engine. I decided to try driving 2 miles back home hoping the car didn't catch fire. I made it to within a 1/4 mile and coasted into the driveway. The car ran out of gas. A bit of investigation showed that I left a fitting on the fuel rail that connects to the gauge. Gas was squirting out of the fitting the entire time of the test drive. Remove fitting, add gas, & go for another ride. Car runs better than it has in years. Thanks to all of the help from the folks here at Thirdgen.