# P218 Onan help



## bigcountry1009 (Apr 6, 2007)

Hi, I'm new here. Just happened to be searching for some info info on Onan engines and ran across this forum. Very interesting stuff on here. 

Now, I haven't a John Deer, but this Onan is actually on a Miller welding machine. I'm having problems keeping the engine running, and when it does run it surges up and down. I'm down to it being either a vaccum problem not operating the fuel pump, or a bad fuel pump. It's not getting fuel to the carb. The fuel line is new, new filter. I've checked the fuel pump with a hand vaccum pump and can't get it to move anything, but I'm not sure if there has to be a pulse of pressure then vaccum for the pump to work. Anyway, I rebuilt the carb and I'm pretty confident it's good. It's got new intake gaskets. then I realized parts for these boogers are high. Now, I've got a fella telling me that the valves need to be re-set because I'm not getting enough vaccum. But this is just from me telling him what's going on. Motor seems to run fine using gravity feed from a tank above the motor. So, what do you guys think is happening?

Great forum again.
thanks ahead of time.
Matthew


----------



## jhngardner367 (Apr 5, 2011)

Welcome to the forum! Usually,the vacuum hose to the pump is connected to a port on the engine,or the carb,and uses vacuum/pressure pulses to operate the diaphragm.Look for a connector on the block,for the vacuum line to connect to .To test the pump, all you need to do,is connect a hose to the vacuum port,on the pump,and puff in/out,and it should pump fuel.It doesn't take a lot of vacuum/pressure to operate.


----------



## Mickey (Aug 14, 2010)

All these pump I've seen are connected to the crankcase where there is a pressure pulse. Don't see how the valves could be part of the problem. Been a while since I had one of these engines that use a mech fuel pump. The Onan engine I still have uses an electric fuel pump so that is not of any help.


----------



## bigcountry1009 (Apr 6, 2007)

I wouldn't think the valves would have an effect either, but small engines aren't my strong point. I'm even thinking of putting a generic auto electric pump on it.


----------



## P218G (Jun 10, 2016)

I have a p218g onan with time delay mod. It just shuts off after 5 min. 
New coil


----------

