Onan P220G fuel pump

[flyboy1015 0]

I have a 1986-ish 520-h with an Onan P220G. Recently, it started running like it was leaning out while mowing. It only happened once the last time I mowed, but it has done it a couple of times this mowing. Choke and it perks up, but it still takes a minute to run without the choke. A short time later, it does it again. I pulled the fuel line off the outlet side of the fuel pump and it was just trickling out. Shouldn't it spurt just a little? Seems to me that this is the problem. Anyone else had this happen?

Update: I topped up the tank, which was at about 1/4 when I started. It is running much better. This tends to confirm my suspicion that the fuel pump is weak.

[TT-(Moderator) 1,129]

Here's my thoughts on this:

There's dirt (sediment) in the bottom of the carburetor float chamber that intermittently restricts the main jet. This happens occasionally on my 416 and the cure for it is to remove the air cleaner assembly, the top of the carburetor and the float, and remove all of the gas from the chamber. (I use a Mighty-Vac vacuum pump, but you can also soak most of it up with a rag) Use compressed air to blow all of the crud out of the chamber, hit all of the passages with carb cleaner, and blow everything out again.

If that doesn't work..........

Have you ever checked/cleaned the strainer on the fuel shut-off valve at the tank?

The shut-off valve could also be plugging, and you might want to check the vent on the fuel tank cap while you're there. The pump only has to pump enough to keep the float chamber "full", so don't expect to see a lot of volume at the pump outlet.

[flyboy1015 0]

TT, you seem to be the winner. I pulled the fuel line and checked flow. It just barely came out. After getting the tank nearly drained, I could see some grass and other stuff in the bottom around the screen. I pulled the tank, screen and valve. When I put everything back together, the flow was much better and the mower runs great now. I never considered a screen being in the tank. Thanks.