Fuel filter static electricity jokes


Picked up Case 646 which someone had installed a electric fuel pump. As I ran the tractor for a while fuel and oil started to sputter out the breather tube. Lots of gas in oil bringing up the level in crankcase and then the pressure. Looking at manual I see that the Onan originally had a vacuum type pump. I suspect this elec. pump was to strong psi and kept the float open in carb. Perhaps? It really esculated when I increased the throttle. With the original vacuum pump there is suppose to be a line from the dipstick tube to operate the pump. With the electric pump they had rerouted the line off the dipstick to the drain on the vent assembly diaphragm up by the carb. Where is this drain hose off the vent assembly diaphragm suppose to go? Its #34 in the parts manual? Where was the original vacuum pump location on the 646? Maybe new a carb rebuilt. When the key was on without the engine running the fuel pump would run and fill the carb until it was leaking out around carb. This is why I think the psi was too much kept float open.

Can you post the serial number of your 646, so if anyone references something for you from a parts manual,, they’ll be on the same page as you. (For example, part #34, I can’t find that on the fuel pump assembly in the parts manual, or on the carb assembly of the same manual) I may have looked at the wrong manual.

I would think before adding more, the above information is sort of needed, but I will post my thoughts on a vacuum fuel pump versus an electric fuel pump, (Numerous post can be read on this). Both styles work quite well, but what is not that great on the vacuum style pump, is when your tractor sits for a period of time,, it will requite more turning over of the starter,, to start the motor up, where as the electric style,, just starts after 1 or 2 turns of the motor, each and every time. Now, it is important to have the correct electric pump though, and most prior owners, typically just run down to the nearest auto parts store, pick up one and off they go. It should have a very low PSI output of 1-3 PSI,, which most auto parts stores don’t have, so they end up with a higher rated pump, so that may be your problem, (but I’m not fully convinced of this yet, as I’ve removed several from my tractors that I’ve redone, that were high rated pumps, and evidently, had seemed to be operating effectively) Regardless, if that’s what it is, we’ll be able to steer you to the correct style anyways.

Based off your original post, I guess it could be a couple of problems, 1- you’ve already mentioned the fuel pump, 2- The carb itself. The original float, (assuming this is original motor) has a fiber type float which has failed over time. So, poor float, doesn’t close off incoming fuel, with the same results. (In my way of thinking) Perhaps, (my bush league side of me) would try just a gravity type of fuel metering to the carb, and see if it still over flows? Say a couple liters of fuel in a plastic bottle, with a small hose to the carb inlet and the bottle, sitting higher then the carb? Should work long enough to, run the motor, see if you like what you hear, and more importantly,, if it doesn’t overflow the carb,, well fuel pump time, if it does, well, points to carb kit time.

For sure, the guys on here will be able to get you up and running nicely,, but, one guy that you should get to know fairly well is a gentleman that goes by the name of Boomer. (Robert). For any Onan related parts; carb, starter, motor, kits ect, IE, it goes on the motor, or knowledge wise, talk to Boomer, (he’s on the south side of the border but does deal with us guys on the north side as well)