Diagnose a fuel pump

[aj_2004]

Can someone tell me if the fuel pump on a "92 Johnson 15 hp engine should create a vacuum on the input side of the pump? My motor doesn't appear to be pumping gas to the carburetor. If so, can the vacuum be seen on a vacuum gauge?

 

[aj_2004]

Can someone tell me if the fuel pump on a "92 Johnson 15 hp engine should have a vacuum on the input side of the pump? My motor doesn't appear to be pumping gas to the carburetor. If so, can the vacuum be seen on a vacuum gauge?

 

[F_R]

Well sure, it needs a vacuum or suction to lift the gas from the tank. But it is a weak suction and will not show on a vacuum gauge--at least not while the tank hose is attached to the motor. Think of it like sucking on a straw in your glass of iced tea. And the pump needs to be full of gas first, which happens when you prime the system by squeezing the primer bulb.

 

[oldboat1]

With everything set up for running (hoses attached, vent open), you should be able to hear fuel entering the carb when you squeeze the primer bulb. If in doubt, pull the hose at the carb, and look for flow (same as you can do to check fuel pump operation when engine is running).

If you can properly prime the carb with the bulb, but know you are getting no flow with the engine running (nothing coming out of the line to carb), replace or rebuild the pump. If you have one of the larger pumps supplied on electric start models, the rebuild kit is 0438618 — easy rebuild. If you have one of the little square pumps, you can get a kit and rebuild it (0393088), or just replace the pump (I recommend the latter with the little pump because of its size and complexity, but that’s a matter of preference).

 

[racerone]

The pump operates with a positive pressure pulse and a slight negative ( vacuum ) pulse.----A spring is compressed with the positive pulse and then the spring provides the suction power the pull fuel from the tank.---Fuel pumps are easy to inspect/ repair.

 

[Crosbyman]

monkeyjack pump . I got one form my 6hp you may need the large one for electric start engines et little square one is for manual start 15hp s

https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias=aps&field-keywords=monkeyjack+fuel+pump+

https://www.amazon.ca/dp/B0773C1H2Y/...518386583&sr=2

 

[Silvertip]

Disconnect the "output" side of the pump and pull the cord a few times. If no fuel is being expelled the pump may be bad. Fuel not getting to the carb may be due to a stuck float or inlet needle in the carb.