Fuel Pressure Fluttering

[Brutus]

After installing a new fuel pressure regulator my fuel pressure needle flutters around 4-5 psi, so its next to impossible to set it to exactly 37psi with it bouncing up and down. I searched and thought that a liquid filled gauge might help and it did, but its still fluttering too much.

Could this be a issue with my pump not sealing properly? Also, the car doesnt hold pressure after shutting the car off. Before it would hold pressure and slowly bleed off, now its instant as soon as I shut off the car there is zero pressure in the lines.

 

[Brutus]

A little update, I went back and checked all my AN fittings from the rail to the regulator and they are all tight and I cant find any leaks. The car is hard to start now. I have to hold the key over for several seconds and the regulator makes a strange whirring noise, almost like its having prime itself. It only does this when sitting for several hours.

Im thinking the fluttering and priming could be the same issue, but one just started and the fluttering was around before the regulator swap.

 

[63tuner]

try using carb cleaner and spray it on the injectors seals, if the idle change, than you have a leak there. And use the injector cleaner to clean clogged injectors. any problem while driving the car? did u install the regulator correctly? and don't forget to check your fuel pump O-ring. check the injectors resistance first.

You can check the AFPR by
1) take out the return line , point the hose into a bottle and try to start the car, if there is any fuel going out, than it is alright
2) pull the vacuum hose, you can hear the idle going up
3) pinch the fuel line, the pressure should raise
10) take the AFPR out and check the diaphragm
100) buy a new regulator

 

[No_Skillz]

Could this be a issue with my pump not sealing properly?

This is the best possibility. If you have the Walboro 255, The O-ring that sits on the sending nipple of the pump has a tendency to not seal well. Symptoms are as you described them. Immediate fall-off of pressure after shutdown, FPR fluttering and "priming." The pump is basically having a hard time keeping the pressure up since you basically have a large fuel leak (albeit back into your fuel tank; it's not dangerous). The "priming" sound is due to all of the fuel in the lines dropping back through that bad O-ring and having to push out the air and fill the FPR again.

You can try to find a couple of O-rings that fit better and stack them,

or

I have found that using a short length of appropriately sized vacuum hose does a great job (basically a fat o-ring in this application).

 

[weldtuner]

What rpm are you siting at when your trying to get the base fuel pressure? if your engine isnt idling properly that can throw off your adjustment.