Fuel pressure/delivery

[v-mad]

I am having fuel starvation problem on a stock 260 with original carb. After a short spell at full throttle, the engine starts to hesitate until I have waited a minute or so. Also when stationary I noticed the pump ticks constantly at about 1 to 2 ticks a second with engine off. The pump is a non-original electric type of unknown brand (not facet, looks like the German ones for sale on ebay).

I might try a replacement pump. Can anyone tell me what pressure and delivery rate I need? Thanks.

[barry-knight]

Chris,

Assuming that you have the original Ford / Holley carburetor, you don’t want the pressure to be more than about 5 PSI or the float and needle valve may not be able to shut off the flow of fuel when the bowl is full. Something like 25 GPH ought to be plenty for a stock 260 (164 HP).

Before you replace the fuel pump, have you checked for the dreaded “black flakes” clogging the fuel line?

[v-mad]

The carb is the original Ford type. Most pumps seem to be around 4 psi so they should be OK, but their delivery rate varies from 8 to about 14, sometimes 18 gals/hr depending on the model. I have not seen any with as much as 25. Surely its not necessary to go that high for a stock 260?

[barry-knight]

Chris,

A good rule of thumb is a minimum of one-half pound of gasoline per hour for each horsepower, so you should have at least 82 pounds per hour and that is equal to about 13+ gallons per hour. You should always include a fudge factor, so I would want at least 20 gph.

Try this link: http://www.fuelsystem.co.uk/web-facet.pdf

The smallest unit listed is 25 gph, so…..

A friends Mk-II did fine on the U.S. equivalent of the SS500 until he replaced it with a SU for originality.

[v-mad]

I wonder if the pumps we get here are quoted in imperial gallons or US gallons? That might account for the lower figures. The other reason may be that our cars generally had much smaller engines, so most pumps were not designed for supplying a 260 V8 engine!

Today I took off the hose after the filter, to check the delivery rate. Switched on, and watched the fuel piddle out pathetically, no wonder the engine was dying. But after half a minute, I noticed there were quite a few bubbles coming through, and then the pump started a different rhythm, slower and more purposeful, followed by good spurts of fuel. The can then filled up quite rapidly. So it seems like there was an air lock, which has now cleared. Fortunately there was no sign of black flakes or other detritus. So I will run the car again, and hopefully, that’s cured it. Thanks for you replies Barry.

[Author]

Posts