C1 Fuel Pump Vacuum Draw

[Steve Westphal]

As I am having fuel delivery problems with my '56 265 4bbl, I checked the vacuum draw on the fairly new fuel pump. It is right at 3 lbs. Is this too low? Thanks

[Bernard M.]

Re: C1 Fuel Pump Vacuum Draw

You should really be measuring on the pressure side. I don't know of any reference that specifies vacuum draw. Depending on the specific model of fuel pump, you should get about 5-7 psi pressure. Less than 4 psi would be insufficient. Pressure can be affected by a leak on the supply side of the pump (check fuel lines), a weak diaphram spring in the pump itself (try another pump), or much less common, a worn fuel pump eccentric on the cam shaft (check fuel pump rod travel). I don't know what the fuel pump rod travel should be but I can measure it on a spare block if you need a reference figure. I suppose even a damaged fuel pump rod could be the cause. An original 265 rod was a hollow tube, sealed at both ends, that could be damaged, not permitting full travel, but I suspect you'd hear some noise if that were the case.

[Rob Dame]

Re: C1 Fuel Pump Vacuum Draw

Might want to check the filter on the sending unit also.