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1985 fuel pressure regulator problem



In November I got a bargin on stock '85 Vette. It was hard starting and running very rich. The owner said it was a bad fuel pump.

I replaced the fuel pump and fuel filter with new NAPA brand, but the problem persisted. Testing revealed a bad regulator. After removal and inspection, the rubber diaphragm was found to be torn around the center. Also, the return passage in the aluminum base was completely blocked with some type of corrosion.

The base was cleaned out via a pick and carb cleaner. The diaphragm was replaced. The lines were checked for corrosion blockage, and etc. As a precaution, I also put a bottle of Redline in the tank. This fixed the problem and the car ran great.

However, upon start-up the other day the problem returned. Again, testing revealed a regulator problem. I just tore it out and found the diaphragm tearing around the base...AGAIN.

Any ideas? I suppose the replacement diaphragm was bad, but what are the odds of that?


Do yourself a favor and get the adjustable fuel regulator. Also, fuel injectors tend to go bad (leak) in the older vets. Some of the symptoms of bad injectors are hard starts after a couple of hours. You might also want to check the fuel pump/sender unit for crap in the tank, before you touch it make sure you have a gasket.


Well-known member
Jul 3, 2001
Auburndale, Florida
1969 Killer Shark
I see them get torn from over tightening the crazy little screws that hold the lid of the diaphram on.

They don't requir much torque, but it is a scary thought having all that raw fuel on top of the motor.

I suggest getting either a high quality adjustable unit, or going straight to G.M. and getting a quality A/C delco replacement. Make sure the torque is very light and even, and you should be fine.

Good luck, and welcome to CAC.


Thanks for the feedback guys.

It's easy to believe I over-torqued those tiny screws. I'll give TPIS's adjustable regulator a shot.

Thanks again.

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