I am assuming my fuel pump is bad but wanted to see if anyone agrees. Gravity flow from the tank (I found out when I disconnected the line from the pump and accidentally dropped it) but it does not draw. There is a clear inline filter before the pump that is dry. Pulled the pump and it does not appear to make a sucking sound when pushing the cap that attaches to the rod. It moves very freely but seems to have almost no resistance. Bad pump?

EDIT - the glass bowl was full.

 

A pump that is good should have resistance when working the arm. Place your finger over the inlet and work the pump arm, you should feel suction. Does sound like a bad pump but verify. A leak anywhere in the inlet line, hose, fuel bowl gasket, will appear to be a bad pump.

 

With the pump is on the engine and line from tank disconnected, put finger over inlet fitting on pump and crank engine briefly. If pump is good you should feel definite suction on your finger. Or disconnect line at carb and put in container or plug into fuel pump pressure/vacuum gauge (a combo test gauge that is inexpensive and useful enough to be in everyone's tool collection) and crank engine a couple times. See if gas comes out or pressure develops. From your decription tho it sounds like the pump diaphram may be torn, but sometimes the check ***** stick when it sits for a while. If your pumphas bolts holding the two parts together, open it up and check the diaphram condition. If the diaphram is good, you can check for a stuck check valve by alternating putting pressure and suction on the inlet fitting. Pressure should pass but suction should be blocked as soon as applied. If your budget allows, and/or it's your daily driver just put a new pump on it and not mess with it.

 

Saw this recently... The springs in the pump can pop out, so there is nothing to force the diaphragm back down. The pushrod only lifts the linkage. Take the pump apart, there's nothing sinister inside. See if they are missing and what shape the linkage and diaphragm are in.

 

Any dry rot or leaks in the rubber line from the tank to the pump will keep it from pulling a vacuum, make sure everything looks good from the tank to the pump.

 

As Ross said take it apart . It's always fun to see what makes things tick .

 

Took the advice and took it apart. Looks clean and no visible problems, springs in place, diaphragm looks solid, etc. I didn't find a check ball, there was a separate rubber valve at the top - maybe taking the place of a check ball?

Metal line from the tank to the firewall is relatively new, and there is only about 8" of rubber fuel line. The rubber line is old but no visible problems there and no apparent fuel leak. I'm going to replace the rubber fuel lines and clamps and see what happens.

The fuel pump is only $40 from NAPA, I'll probably go ahead and do that too to eliminate any problems with the pump reassembly

I'll post results tomorrow.

 

Can you operate it by hand? It should be quite hard to compress the springs.

 

Yes, with one finger and very little effort.

 

I suspect your pump is broken. I tested one recently and to get it to cycle, had to put a spare pushrod in a vice, and put at least 30 - 40 pounds force down on the pump. And it was a bad pump!

 

The only thing I would add is: No, that wasn't a dumb question.

 

If it is a dual action (fuel and vacuum) pump, they will be a booger bear to work by hand. It sounds like your diaphragm rod may have become unhooked from the actuating lever.

 

I guess that we'll never know for sure. I replaced the pump with a NAPA part ($43.25) and replaced the rubber lines and in line filter at the same time. Total $60 and it fired up once fuel was back in the system.

Thanks for all the advice and help. I learned a lot for next time!