I'm getting a different fuel pressure almost every time I start the car up. I've replaced the fuel pump, pump relay, filter, and made the regulator adjustable. My only guess is maybe a get a new spring for the regulator from TDS.

I'm thinking about switching to a vafpr also with the new spring from TDS.

 

What gauge are you using? If it's the cheap-o do NOT take it's reading to be accurate. We figured this out a while back. With the cheap ones from Summit and Jegs, you can hold a cold gauge and watch the needle go down. It's only good for triming, setting and forgetting. Only check it when it's the same temp.

 

It has more to do with thermal properties than the cost of the gauge. The gauge reads the pressure difference between the fluid inside the gauge and the fluid exposed to the gauge. Since the fluid inside the gauge is trapped, its pressure will rise when heated. Remember that PV=nRT stuff from high school physics? The fuel pressure exposed to the gauge won't rise because the fuel system is not closed. The regulator maintains a constant pressure maintained by the spring(neglecting the slight pressure rise caused by the spring expanding). Any pressure rise in the fuel line due to thermal expansion is "bled" off by the regulator.

This can be overcome by getting the gauge away from the heat. One option is to install the gauge further upline under the car or by use of a fuel pressure isolator. It's not convenient to read the gauge under the car but the pressure will remain constant. The isolator allows the gauge to be mounted in the passenger compartment. Autometer sells one. Not cheap, but if you want the gauge to function all the time it's what needs to be done. The isolator can be mounted away from engine heat and a line(filled with anti-freeze) is run from the isolator to the gauge(cheap Summit or Jeg's will work fine). This way the line that runs to the gauge and the gauge itself remain at a constant temp and will not fluctuate. The gauge will still reflect ambient temp changes. If it's 50° when you start and the day warms up to 90°, you will still see the gauge pressure drop. No way around that.