Re: Fuel Pump Pressure??

Posted by Owen_Dyneto On 2009/3/20 13:48:28

Thanks for the added info, it helps. 3 psi of pressure is still adequate but the big clue to my way of thinking is that the pump won't prime itself. 99+% of the time, if not the pump diaphram or valves, that means an air leak on the suction side somewhere between the pump and the tank, probably not one big enough to let much (or any) gas leak out. (You could try this, fill the tank, park on a slope with the nose of car down hill, and look for seepage or a leak). I'd suggest removing the rubber flex line and either replacing it with the right one (PAC and others sell the right one) or temporarily rigging some nice fresh rubber tubing, taking care to insure that it fits TIGHT. Then remove the fuel line from the carb, and try cranking the engine again. If that works, your flex line was bad.

If that fails, fit a longer rubber hose onto the pump inlet, put the other end in a gasoline car or temporary gas storage container at about a foot or so off the ground, and try again. If it then primes, you've got an air leak in the steel line between the pump and the tank. Remember, the pump would much rather pull air that fuel.

As to the pressure, it's controlled in part by the spring beneath the diaphram so was the spring gets hot, it wouldn't suprise me if the pressure dropped a bit, but can't say I've ever actually done that test and made that observation. It doesn't rise with increased engine rpm, just the volume of delivery increases, not the pressure. Still, 3 psi should be adequate except perhaps for blasting down the highway with the highway patrol in pursuit but if you get down to 2-1/2, I begin to think the pump is suspect (but it may not be your only problem). Why not just bite the bullet and send the pump to Gould or Terrill for a rebuild?