hesitation/missing under load?

[kyle]

I have a 313 poly in my 59 fury. It was giving me hesitation under load. I changed my plugs,wires,carburator,set timing, installed new points, condensor, rotor/cap, coil. Then I went to the fuel pump, installed a new one, put a pressure tester in line. It read about 7 psi and the plastic fuel filter on top of the pump was full of fuel. Then it became close to empty with less than 2 psi. Should that fuel filter always be close to full? Can it be possible that the front of the eccentric (lobe of cam is worn out)? Would it be ok if I change the arm and install one with a higher pitch? Can I get a fuel pump with a adjustible pitch? Have any of you guys had this problem and just installed a low presser electric fuel pump?

Thanks for any input;

Kyle

[Denver 59 Fin Convert]

I will defer to Mopar Ricky on this one since he is a mechanic by trade. Others might have had this issue too...

I had this happen on a 74 Cuda of mine and it was partially functioning mechanical fuel pump. I would be guessing, So I will let others comment if they have had this issue before.

John Q.

[rogerh]

"not a mecahnic" replying here:
I believe the fuel filter should always show "full".
My car had a hesitatiion...turned out to be the butterfly valves were hitting the carb gasket.

[big m]

Generally, the fuel pressure should be 4-7 PSI from the mechanical pump. Many times, there will be air visible in an inline clear filter even with normal fuel pump pressure.

Another way to check is to attach a rubber hose to the fuel pump outlet, with the other end going into a clear bottle. Disable the ignition to prevent a chance for fire, and crank the engine. The pump should produce roughly a pint of liquid after cranking the engine over 6 or 7 times. This will show that you are getting a volume of fuel.

---John

[rogerh]

With that new fuel pump installed, and variable pressure, maybe the screen on the pick-up tube in the fuel tank is partially clogged after all these years! Just a thought-

[big m]

With that new fuel pump installed, and variable pressure, maybe the screen on the pick-up tube in the fuel tank is partially clogged after all these years! Just a thought-

Another possibility is that the small rubber hose that attaches the tank to the main fuel line has a small crack and is drawing in some air along with the fuel.
---John

[RICKYMOPAR]

Kyle, All the ideas are good to check, eccentrics do wear out as well as the pump arm, limiting volume of fuel delivery. clogged filters and socks do cause delivery problems. Here in Colorado our fuel reed vapor pressure is not what it was in the 50'sand 60's, i have added the low pressuer booster pumps at the rear as near the fuel tank as possible with great success. Our 1984 W350 only has an aftermarket carter style electric fuel pump. Note; I did retain the vapor separator fuel filter. The truck seldom has any fuel related problems now, some times if the ambient temp exceeds 100F. Towing a heavy load. but very minor.