1970 Mercury 500 fuel pump issue

[ata]

Hi this is my first post. What will keep the fuel pump from pumping? I know it used crankcase pressure to pulse the diaphragm. I have replaced the pump diaphragm and the check valves. This old engine will run on muffs with an alternate method of fuel supply to the carbs. Thanks for reading ... any insight is appreciated.

 

[GA_Boater]

Welcome aboard.

Did you put the check valves in the right way? The check valve on the input side has the top hat down and the output side is up.



If you take the output hose that goes to the carbs and pump the bulb, fuel should squirt out with each squeeze after fuel reaches the pump. If the fuel doesn't squirt, a good chance the check valves need to pointed in the right direction.

What is the alternate fuel supply?

 

[ata]

The alternate fuel supply is a garden sprayer with a gauge on it. Pumped up to 5 psi she runs good in the driveway.. I put the alternate fuel supply on the intake for the fuel pump,pumped it up to almost 15 psi. while cranking on it and i finally got some fuel out of the pump outlet.. STRANGE.. I will take them back off and check.. Easy to do.. but I think there is a Boss in the casting that one of them will only go in one way.. Thanks for the reply..

 

[GA_Boater]

Oops - I think I got this backwards - The check valve on the input side has the top hat down and the output side is up.

If it took 15PSI to get fuel through the pump, something isn't right. Is that with the pump output hose disconnected or not? The bulb should move fuel through the pump sand that's no where 15 PSI.

 

[ata]

so I should be getting gas outta this check valve...

 

[ata]

Well I didn't get this project finished before I had elbow surgery....so it will have to wait a little bit. I've ordered new check valves from another vendor to see if the valves are the problem. I am thinking it is but we will have to wait and see. Thanks for your help!

 

[ata]

No Title

OK well I found the problem...