mechanical fuel pump question

[mentalQtip]

Ok, new probem. I have an AK engine, 1600 in a 74 thing, with one of those fuel pumps that has the four screws on the top. For some reason I'm not getting fuel into the carburetor anymore and I can't figure why. When I lower the fuel line from the tank gas streams out and when I manually work the lever in the pump I get some suction at the intake hose, but when I put them together no gas flow. How long do I need to turn the engine over before I should see gas coming out the hose?
Do I need to prime the pump or something?
I have opened the pump and can see nothing wrong. When I work the lever in the base everything seems to work fine.
What gives with this thing?
I felt really good about how nicely I had it running.
As soon as one thing gets taken care of something else breaks.

[Amskeptic]

As soon as one thing gets taken care of something else breaks.

Quit whining. Wait until it is your body pulling that crap on a daily basis.

Have you measured the pushrod extension as you rotate the engine? If the pump itself does all the correct moves, you have to go to the thing that activates the pump. Sometimes, the removal of a gasket "shim" can restore your pumping efficiency. If the pushrod has worn down, replace it. If the stroke is insufficient, you have the very first distributor driveshaft eccentric wear I have heard of. The Bentley provides decent information to help you give us informed symptoms.
Colin

[mentalQtip]

Ok, after careful measuring, I come up with right about 13 mm. on the pushrod. I replaced the hose to the pump and I think that I saw a slight response when the engine was cranked, maybe.
If I have a good stream of gas with gravity feed from the tank, the pushrod is right length, I feel a slight vacuum when I manually pump the lever in the base, there isn't much left. So, what is left?

Actually, since it was running so well before it stopped running, what could have changed so suddenly?

Frustrated in Oregon

[BellePlaine]

Does it idle at least? Have you checked for a clogged main jet in the carb? Perhaps the carb accelerator pump diaphragm is bad?

[mentalQtip]

No. The fuel pump doesn't send any fuel to the carb at all. My son has cranked the engine while I hold the hose from the pump to the carb and it is dry.

[hambone]

Try another pump, it may need a rebuild. They are cheap.

[Amskeptic]

Ok, after careful measuring, I come up with right about 13 mm. on the pushrod. I replaced the hose to the pump and I think that I saw a slight response when the engine was cranked, maybe.
If I have a good stream of gas with gravity feed from the tank, the pushrod is right length, I feel a slight vacuum when I manually pump the lever in the base, there isn't much left. So, what is left?

Exactly. A good pump needs a good eccentric on the distributor drive shaft. You need a good lift and drop back down. What is the specified lift? Compare yours to specification.
Colin

[mentalQtip]

Well, as best I have been able to measure with what I could find, (a tinkerbell mm ruler), it peaks at 13 mm and sinks to about 5 mm. I see where 13 mm is to spec. but where does it say how low it should go?

[mentalQtip]

Taking Hambone's advice, I tried another fuel pump. The sucker fired right up. Not runnning all that good compared to before the pump went bad but still the pump is pumping and the engine is running. Yippee!