Just converted my 89 to carb and in the process of getting it dialed in, I set the fuel pressure to 7 psi. When I started it up cold it was 12 psi. After driving for a while I checked again it was at 4 psi. I have a brand new Holley blue and pressure regulator with steel braided line from tank to carb. It is 3/8 line. I was told that this is ok but it worries me. Why is my fuel pressure fluctuating so much? Thanks

 

reason number one to run a return fuel system.

 

I will be running a return system in the future, but I am trying to get this dialed in as much as I can for right now.

 

When pressure is bypassing the needle and seats it will cause also eratic pressure. should be using Viton (spelling?) needle and seats. 100's of race cars use the blue holley without a return with no problems. on a street car though I would rec it to keep the pump cooler and keeping the pressure from spiking. Also check your regulator make sure its working by adjusting the pressure up and down. By the way thanks for the xpipe worked out great.

 

What kind of gauge are you using and where is it mounted?

 

Regulator is definately working. I believe its an autometer (it is liquid filled) and is mounted on the line going from the regulator to the carb.

 

my aeromotive system stays right at 5-6PSI (cant remember what it is set at). Im running 1/2" aluminum line and -8 braided hose before the regulator, from the reg. to the carb is 2 -6 braided lines.

 

I would check the gauge. If it really had 12psi going to the carb when you started it up cold, fuel would be pooring out the bowl vents.

I have seen liquid filled gauges do funny things when they are mounted in the engine compartment and are subjected to the heat. Barry Grant has a notice in the box when you buy one of their carbs stating "not" to mount liquid filled gauges near the engine or close to a heat source.

I have a Barry Grant 280 fuel pump on my car with #8 line to the regulator and #6 lines to the carb. No return line and the fuel pressure stays steady at 6 3/4 pounds. I will however have a return on the fuel side of the nitrous whenever I get around to installing it on the car.

It's just a guess, but it's worth a try.

 

You were dead on!! I put a new gauge in/ set it and it has not budged since. Thanks. Also owe a thanks to NA306Stang

 

Hey man glad all worked out. good to hear it was a simple fix you got my # give me a ring if you need anything else