I have a factory carberated 87 camaro and I'm trying to get my fuel pressure figured out to dial in carb. I got a autometer electric gauge and needle jumps all over especially at idle. It will jump from 3 to 6 psi at idle and when driving it'll go over 10 psi at times as is so erratic I don't know whats going on.

Car seems to run fine so I thought gauge was faulty. Hooked two mechanical guages to test and they are even more erratic. The one guage is for fuel injection and it jumps from about 2 to 8 psi at idle. So I bought another testing guage that does fuel and vacuum and it is really crazy. It jumps from below 0 to past 10psi at idle. Too give you a idea how erratic it is. Look at mouse pointer on your computer. Move mouse left and right as fast as you can about and inch and watch mouse pointer. That's what gauge needles are doing. What causes this and is fuel pump bad. Its a return style pump too.

 

Id have to look it up but i think your carb is an computer controlled electric Quadrajet correct? We dont know if u installed a fuel regulator somewhere in line or where your fuel pressure gauge is connected.

Since i dont know what u have i will just mention that a fuel press regulator on a mechanical fuel pump has problems controlling pressure when the needle closes on its seat inside the carb as the return line doesnt reach the carb and the carb line cannot relieve the fuel press. I tried a fuel regulator with mech pump before until i monitored the stock pump and found a stock mechanical fuel pump regulates very, very well by itself.

Next the location where to connect the fuel press gauge needs to be on the supply line to the carb and ensure there are no kinks or sharp bends in the line whether its flex or hard line.

If none of the above applies then u may have a bad spring on the needle/seat inside the carb and it cant keep the needle seated when the bowl is full or else the needle/seat are to large and fuel press drops when the neadle/seat opens. But this would cause very bad engine control and u dont have that problem. Just guesses here as i cant see much from 1,500 miles away.

Just one last advice is to use hard line where ever possible as this reduces kinks and restriction where a flex hose flattens. Oh, i have to add always, always use a bead on your hard line ends so your hose clamp has something to hang onto - to many engine/car fires from fuel hose falling off.

So what u got for carb, regulator, connection location?

 

Had a cobbled up quadrajet when I got the car many years ago. Now has a edelbrock 1405 600cfm carb.

Has no regulator.

Fuel connections from pump are 6an braided line and are in following order. pump to filter to fitting with dual 1/8 inch npt ports (for pressure gauge and nitrous solenoid) to carb.

 

Heres a link for the fitting between filter and carb I'm using for pressure gauge connection.


http://www.ebay.com/itm/PRE-62661E-6-AN-Male-To-6-AN-Female-With-Two-1-8-NPT-Ports-For-Gauge-Purge-/330749223687?hash=item4d0230a307&vxp=mtr

 

Oh BTW u need a vent on the tank to relieve press. Maybe something in the tank vent sys is plugged. Try a slow drive with the tank cap off.

That fitting looks a bit different than a regular Tee - dont know what it does inside it. U could try pulling the fitting and installing a Tee to connect a gauge.

Other than that i would suspect the pump aint regulating or the carb is not controlling inlet - but the car runs well so i look at carb very last.

Good luck.