[Chuck]

Fuel Pumps Revisited

Ron McCall’s post prompted us to check the operation of the Holly 125 fuel pumps and the Aeroquip check valves; something we should have done while we still had the purchase receipts. It is a good thing we did.

The pumps worked great. They really sucked. With the bottom of the intake hose 19 inches below the intake on the pump (as low as we could get it without removing the pump from the car) it put out a stream that would make a Flowmax commercial proud.

Then we inserted the Aeroquip check valve in the intake line. Nothing. Then the output line. Nothing. Ron was right.

The Aeroquip check valve has a ball held in place with a spring. A red insert holds the spring in place. It seemed that if the insert could be backed out it would reduce the tension on the spring and thus reduce the resistance. Lacking a proper tool, we ground the edges off a ½” butterfly bit to make it fit. With a lot of effort we finally were able get the red insert out. Sure enough, the distance the insert is screwed in has a direct affect on the tension on the ball. In our application, the easiest solution was to just leave out the red insert and then stretch the spring until it just kept the ball in place with the fitting we were using; just enough tension so one could not hear the ball rattle. Now we could easily blow through it one way, but not the other.

We reconnected the check valve and tried it again. It worked perfectly. Same strong stream, same 19 inches of lift, and same result on both sides. Problem solved.

Special thanks to Ron for alerting me to the potential problem and the helpful comments of everyone. I cannot imagine undertaking a project like this without the internet..