Testing for fuel pump pressure or volume?

[Jason Mills]

I am wondering about how to test my fuel pump.

Guessing that pressure is a function of volume up to a point, and yet I am of the suspicion that the pump is not producing enough volume to create any pressure.. yet there is some fuel coming through the lines, just not enough to allow the truck to run for very long. OR maybe there is a restriction somewhere in the Pick up in the tank?

does anyone have a favorite method of testing for the volume of fuel pumped for the flathead 6?

[Gordon Maney]

I would pump it into a can and observe the flow rate; the amount accumulated after a period of cranking. My judgment would be seat of the pants. I am uncertain as to how I might communicate that to you.

Run a line into a container and crank it for five seconds. Look in the can. See if you think it is a sufficient amount to idle for a period of time longer than five seconds.

[Jason Mills]

I am lucky to be using a fuel pump with a hand primer on it.

This evening I had the idea to send a little compressed air back in the fuel line to the fuel tank.. Which resulted in a much better volume of fuel coming out of the high pressure side of the pump.. I am gonna guess there was 1-2 tablespoons per stroke of the pump.. yesterday's fuel delivery was less than a quarter of the fuel delivered per stroke.. and now that have seen what a good amount of fuel is delivered, it is kinda obvious..

So there must be a restriction in the tank.. but I am believing that such results eliminate the fuel pump as a problem.

[Charles Talbert]

I am lucky to be using a fuel pump with a hand primer on it.

This evening I had the idea to send a little compressed air back in the fuel line to the fuel tank.. Which resulted in a much better volume of fuel coming out of the high pressure side of the pump.. I am gonna guess there was 1-2 tablespoons per stroke of the pump.. yesterday's fuel delivery was less than a quarter of the fuel delivered per stroke.. and now that have seen what a good amount of fuel is delivered, it is kinda obvious..

So there must be a restriction in the tank.. but I am believing that such results eliminate the fuel pump as a problem.

What you found is very typical. Usually the best recourse is to remove and clean the tank interior and lines thoroughly. Some radiator repair shops offer gas tank service and there is always gas tank renu if your situation is more serious. Obviously debris is floating around inside and will likely clog the line again in a short time. This is especially an issue if gas has been allowed to sit in the tank for a while. Corrosion as a result of stale gas creates high $$$ repair issues in the engine valve train. If you feel old gas is an issue, get it out fast and keep it out. Gas can begin to separate and cause major issues in as little as 2-4 weeks. Like most everything else these days, it ain't what it used to be. Products like Sta-Bil will help somewhat with gas becoming stale so quickly, but even with that, don't push your luck. Sta-Bil has recently introduced new products designed to help prevent break down of ethanol enhanced gasoline, have not yet studied up on the reliability of their newer products.

[Jason Mills]

I have decided to take a look in the fuel tank through the fuel sending unit cover... and then decide what to do next, in regards to the fuel tank, assuming there is unwanted crud present...

also I am starting to believe a carb rebuild (cleaning and gaskets) will be needed, as it seems to have a misfire on occasion, which I am guessing is a lean mixture misfire.. (Hoping)

That should take care of the fuel side of this project, I hope.

Thanks to both Gordon and Charles for your insightful, as well as comprehension provoking words.