330GT fuel pump PUSH ROD...not the pump.

[DinoSteven]

My FISPA 150 has been rebuilt, correctly, and still doesn't pump enough fuel. Actually, it pumps great when bench-tested. I pulled it off again and measured the 'throw' of the push-rod that actuates the arm on the pump. It moves a pidly 3/16". More like 1/8" as it's difficult to measure the overall movement.

I reduced the thickness of the phenolic spacer to pre-load the arm's movement, still not much fuel is being pumped.

Ideas?

Steven
330 America 5107
Orlando, FL

[John Vardanian]

Try flipping the flat tabs.

Is there a deep dimple in the push pad, or is the tip of the push rod mushroomed?

john

[Rangeley]

I too think I have the same problem. I have greatly reduced the thickness of the spacer. My question is this: how do I measure whether enough fuel is being pumped while the auto is not running? Is there some kind of empirical test, such as some amount of time to fill some container? John

[Yale]

I always start any technical, (slightly), post from me with the caveat that -I know nothing- but my 2¢ is that this is the same thing that happened to my mechanical fuel pump. The plunger was worn out enough that it did not pump enough fuel into the carbs and the electric pump could not make up the difference at higher speeds. As the fix turned out to be an engine out situation I instead opted for a more robust modern electric fuel pump left on all the time. This has indeed made a great difference...unfortuneatley I really miss the sound of the original electric.

Yale

[DinoSteven]

Yes, turn the electric fuel pump OFF (via dash pull switch) and see if the V12 will first idle, then drive, with only the mechanical pump in operation.

Mine will not. That's what led me to first a pump rebuild (still won't sustain enough flow for the engine) then a careful determination that the actuating rod from the crankshaft (?) is not moving far enough in-an-out to move the now-working mechanical pump arm.

Steven

[Rangeley]

Yale, what make and capacity of electric pump and how is it mounted, please. John

[John Vardanian]

When I first got my car the engine would starve for fuel even with the help of the electric pump and it would stall if I turned off the electric pump.

My personal experience...

While the engine is idling and the electric pump is off, the glass jar should not have an air head; i.e., it should be completely full of gasoline. This would ensure proper volume. Then, once you got the volume right you'll need to make sure you have proper pressure. To do this, place a gauge between the jar and the fuel rail and the read should be about 3-4 psig. You can adjust the pressure with the little screw on top of the jar.

john

[John Vardanian]

The tabs, Item #2 in the diagram are sometimes flipped by the previous "rebuilder". The center hole of the tabs is off center. You'll actually get more throughput if the tabs are installed so as these center holes are on top.

You also may have a sever dimple in the pad of the push toggle (Item #1) from excessive use.

[Keith Milne]

Uh oh . . . the dreaded fuel pump issue. Do a search for my exercise with this at about this time last year. Take John's advice and make sure the in/out lines are connected correctly. (should be obvious, I know . . . )

[zac]

This is a new trick that I just learned so I will pass it along, remove the spacers temporarily mount the pump in place floating on the studs. Turn the engine over until the push rod is at its lowest point, remove the inspection cover from the pump and slide down until all the slack is taken up and the pump arms are just about to actuate the diaphragm measure the distance from the pump to the engine and set your spacer/gasket accordingly. make sure that the if you have to thin the spacer that you drill out a new hole for the pumps arms to pivot in and clear, also make sure that the hole is facing the pump and not the motor. Mount everything back up and prime the pump with the electric pump just to get the air out of the lines. I like to run the engine at idle and put a rag around the outlet side of the glass bowl filter/regulator and crack the outgoing line, you should see a nice steady pulsing of fuel coming out. than let the car idle for a bit. As long as the idle stays good and the glass bowl stays full than take the car for a nice extended test drive to get it nice and warm and if all is still well push the car good and hard to make sure you are making enough volume to keep up with maximum demand. Now all that being said there is an issue with the replacement diaphragms out there and I know it was being corrected but the last kit I got still had the problem, in that the metal cup is smaller than original so it does not displace quite as much fuel so maximum volume is less than the pump originally put out. I also know that Rudy was making up some new check valves and the rubber seals than go underneath them but I don't know where he got with that project.

These things have caused me hours of head scratching, and I do this for a living. So hang in there, and if all else fails there is nothing that says you can’t hide a good modern electric pump back by the tank and end the headache once and for all

Zac