Glad you found a problem! Might not be a bad idea to confirm your repair. Check pressure at the service port and at the filter outlet.

EDIT: The O ring must be fuel rated. Typically they are brown in color, not black.

 

The new regulator came with a black one. I'm going to pick one up in a Buna which should be fuel rated. Wouldn't happen to know what size it is would you?

 

No, sorry, I don't know the size. "Small" probably isn't close enough If the regulator is AC Delco or Delphi, it will be fuel rated. Any other brand, I would question. Chances are, if it came with the regulator, it's probably OK. Years ago, all O rings were black, but now there is green, brown and black. Green is for A/C, Brown is for fuel, and black is for oil. Trans fluid is not an oil based product and it will attack certain types of rubber. Trans gaskets are typically black, but it's gotta be something other than plain old rubber.

 

Unfortunately color has nothing to do with the type of rubber the oring is made of but there seem to be 'industry standards' as far as color.
I located both a 109 and 110 Orings. The 109 is a Viton and the 110 a Buna. Both are black and compatable with Petroleum Oils/Fuels. I believe Viton is usually brown unless otherwise noted.
Anyway, looking for a brown would be the safe way to go about it if not listed on manufacturers packaging.

I'll post which size fit best.

 

It's a 109 size o - ring. At first it didn't hold pressure very well but after a short drive it bled down slowly. It looks like it runs at 75psi so it picked up 15 with the repair.
There was a miss at idle which also went away after driving. If I can find a good deal on the CKP variance then I'll do it.
I'll consider it completed.
Thank you for the help.

 

If your key ON, engine OFF, pump running pressure at the service port is 75psi, either there's a problem with the regulator, or a restriction in the return line. 75psi will rupture the diaphragm in the regulator, guaranteed.

 

You sir are killing me.

 

Sorry. Post #11 was the "gotcha"

Fuel pressure regulator 101
Please refer to my signature line below

The image below is a "typical" drawing of a regulator. The regulators used on the 4.3 are configured differently, but they operate the same way.

Pressurized fuel from the pump goes directly to the inlet port of the pressure regulator, (arrow on left). The injector is teed off of the line just before it enters the regulator. When the pump is activated, the injector and regulator are pressurized equally. When fuel pressure on the top side of the diaphragm exceeds the spring pressure on the bottom side of the diaphragm, the valve plate is pushed down and sends the excess pressurized fuel back to the tank, (arrow on top). This causes fuel pressure to drop. When spring pressure overcomes fuel pressure, the valve plate closes, pressure rises, and the cycle continues.

If you watch fuel pressure while the engine is at idle, it's typically in the mid 50's psi range, (varies with each engine). When you quickly jab the throttle, the pressure rises, here's why. The vacuum port on the bottom is exposed to manifold absolute pressure, (manifold vacuum). That's why a vacuum hose is not necessary. When at idle or deceleration, vacuum is high, and fuel demand is low. The vacuum pulls on the diaphragm and decreases the valve plate pressure, which causes fuel pressure to decrease. This is why fuel pressure at idle is lower. When the engine is under a load, (acceleration) fuel demand is high and vacuum on the diaphragm is low. This causes pressure to rise. Fuel pressure is at its highest with the engine off, (zero vacuum). This is why fuel pressure is always checked with the engine off.



If there is a restriction in the fuel return line, the diaphragm is exposed to maximum fuel pump output pressure, (73-108psi). GM warns that when fuel pressure at the service port exceeds 75psi the diaphragm can/will rupture. Basically the fuel delivery system is constipated, and something has to give

Your 95 has CMFI, (Central Multiport Fuel Injection). Fuel pressure is slightly lower than the 96 and newer CSFI, (Central Sequential Fuel Injection). Your fuel pressure spec is 55psi to 61psi. 75psi is a problem. Either the spring pressure is too high, or the return line is restricted, those are the only things that can cause high fuel pressure.

You can narrow the problem down rather easily. Disconnect the fuel return line at the rear of the intake manifold. Connect a hose to the line where it exits the manifold. Direct the hose to a bucket etc. Activate the fuel pump. If the pressure at the service port is still high, the problem is in the regulator. If the pressure is 55-61psi, (normal regulated pressure) the problem is in the line to the fuel tank, (kinked, plugged up, etc). Good luck in your adventures

 

Well, it's the regulator. Meh, it just runs a little rich then. It'll adjust for it after a while. I'm not to worried about it.

 

Until the diaphragm pops and floods the crankcase with fuel