Small Engines (Lawn Mowers, etc.): Vacuum Fuel Pump, sheet metal screws, john deere 318

Question
QUESTION: Hi Eric, My dad has a John Deere 318 with what I believe is an Onan engine. I don't have the model or spec numbers but hope this is a basic enough question that you won't need them. The problem is with the fuel pump that works off of vacuum. On one end of the pump there are two hose connection, a hose from the gas tank on one and the other one goes to the carb. On the other end of the pump there is one hose fitting,  but nothing is connected to it.  Shouldn’t there be a hose going to the engine somewhere to get vacuum? If not where does it get vacuum? The engine will start after a little coaxing. The fuel filter is clear plastic and I can see there is little or no gas in it, even when the engine is running. I have a mechanical fuel pump on my Wheel Horse and the filter is at least half full all the time. Any suggestions?
Thanks, Bob.

ANSWER: Often times the vacuum source from the engine is located near the valve breather.  Did you search google pictures for Onan fuel pump vacuum or JD318 fuel pump vacuum?

Your Onan vaccum source should be behind the sheet metal engine cover. When you look at the fuel pump you see the gas line running to it then the other gas line runs to the carb. The vaccum metal nipple is 1/2" long underneath the pump going through the sheet metal cover to the vaccum rubber hose to the engine. You have to remove the sheet metal screws to remove some of the sheet metal cover to get to it.

Let me know if you can't find the vacuum source.
Eric

---------- FOLLOW-UP ----------

QUESTION: Very good Eric, the nipple for the vacuum is behind the sheet metal. So, the third hose connection on the outside of the fuel pump is not used? Should it at least have a cap of some sort on it?
Thank you so much,Bob.

Answer
Check out this Briggs link:

http://www.briggsandstratton.com/engines/support/frequently-asked-questions/Serv pump

Most vacuum fuel pumps are inter-changable and they all work the same way.  If you every need to replace your fuel pump just try to stick to the same shape as the pump/flow characteristics are just slighty different.  In a pinch, use what ever is available.   

You should use all 3 connections, one to the fuel tank, one to the carb and the other to the vacuum source.

Let me know if the link helps.

Eric