I have an L69 with a holley mechanical secondaries 600cfm carb and stock fuel pump. I just installed a fuel psi gauge on the fuel system and the psi varies rapidly between 3.5 to 4 all the way to 5 5.5 and the psi increases in fluctuation with rpms. Is this normal? Or is the pump on the way out. The car goes good, but does stumble a little off of idle to which I attributed to the slightly warn accel pump cam. Also do these cars have an in tank pump as well? And how are they triggered, just by ignition alone?

 

do you have the vacuum line connected to it?

 

your car should have a mech. fuel pmp.Sounds like your gauge is craping out. How is the guage hooked up ?

 

What vacuum line???? This is an inline mechanical gauge that was used that I pulled off of something else so it could be bad. The engine has a mechanical fuel pump, but I was wondering if it also has an electric booster pump in tank since I doubt that it would work if it still does. Does anyone have a gauge hooked up to a stock fuel pump??? How much psi does it read and how steady doe it stay??

 

I bought my 1984 Z28 new and there wasn't an elect fuel pump in the tank but I had one installed at the Dealers under warrenty because of vapor locking. There is a bullitin on that problem. I have an elect fuel pressure gauge hooked up to the fuel line with a "T" and the sending unit is installed just before the fuel enters the carb. I hope you don't have a the fuel pressure gauge installed inside the car with a hard fuel line? I have around 4 to 5# ideling and between 1 1/2 to 2# at WOT. The 1984 Z28 L69 had a Hi perf fuel pump and sells for around $27 at NAPA. The fuel pressure will flucuate when the carb needle opens and closes.

Auggie

 

I definately am not dumb enough to plumb fuel inside of the passenger compartment. This mechanical mr. gasket gauge is tee'd into the fuel line just before the carb and seems to fluctuate quite a bit. I've never done a psi test on it so I have no idea what it should look like but it does whip back and forth quite wildly. Does yours stay fairly consistent at a certain rpm? I didn't expect it to remain dead steady, just not to fluctuate 3 times a second like it does. I'm tempted to buy a Carter fuel pump "w/ high performance," as they describe for $18 from Rock auto.

 

Sorry about that. My fuel pressure is fairly steady. I tryed the Carter fuel pump and it's a long story but it was nothing but a big headach. Like I said I went to NAPA and asked for a pump for a L69 and unlike the Carter all the fuel lines hooked up in the stock locations and had great steady fuel pressure. Your gauge is mounted under the hood right at the carb so that fluction may be normal where as my set up uses a sending unit that may be dampened some what.

Auggie

 

So you just went to napa and got a pump that was for an l69 and it worked well? I assume they must have more then one choice of pump depending on the vin g or h?

 

The pump that I bought was part# NFP M6626 $23.88 vin G. Uses 3/8" fuel line and has a 1/4" return line. GPH = 23. Fuel pressure = 7.5 to 9.0 You can go to the NAPA web site and look it up.

Auggie