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Car Randomly Dies and Fuel Pressure doesn't hold steady

I have a 1993 buick Park Avenue and it has been randomly dieing on me. It happens when I am stopped, acceleration, turning, but only once every 15-20 miles. After about 15-30 minuets I can start the car back up, and while it doesn’t start it will turn over and I have full electrical systems like radio and lights.

I checked the fuel pressure and it is about 44 but drops off to about 32 in 3 min. If I pinch off the fuel line from the fuel pump after pressurizing I drop off more slowly but still drop off. 44-35 in about 5 min. If I clamp on the fuel return line after pressurizing I get the same drop off of 44 to 32 in around 3 minuets. I changed my fuel filter and put some injector cleaner in my gas but that hasn’t helped. Does anyone have some suggestible on what to do next to either fix or further diagnosis?

I have seen that my symptoms could be indicative of a faulty crank shaft position sensor, but the fuel pressure problems would leave me to think it was a fuel pump or injector problems.

Sounds like a failing fuel pump to me and if it has never been changed in the past then it’s had a good long life.

Running for long periods of time with even a partially clogged fuel filter can also wear a pump out by making it work harder and fuel filters should be changed about every 15-20k miles; even more often if any contamination is suspected.

Not too long ago I pulled the fuel filter off of my Mark VIII (not that easy to do on these cars) and it was partially clogged. I had changed that filter approx. 6k miles before this. It’s also quite common for a car to run well even in this condition.

Thanks! It sounds like even if it isn’t the fuel pump for certain than it is a good idea to change it anyways.

Before you replace the fuel pump find the fuel pressure regulator and remove the vacuum hose from it. Check to see if there is fuel in the vacuum line, if fuel is present then the pressure regulator is leaking.

If you are pinching off the fuel return line and the pressure still drops that indicates either a injector is leaking or the pressure regulator.

The pump may still be the problem but check the regulator before you replace the pump.

I pulled off the vacuum line and there was no fuel in it. Also the pressure rose about 7 psi. I think that means the pressure regulator is ok.

I don’t believe you have a fuel problem. Have seen a lot of wiring harness problems on these cars. Crank sensor pigtail from being oil soaked, ignition module pigtails from vibration, the harness from engine movement. Start the engine and shake some wires.

Not that anyone is still looking at this but it was my fuel pump! Thanks for the help.

I came back to see your results…most others will, too. Thanks!