Thread: Small Engine Mechanic

Built in tank or remote with bulb? I would start checking line from carb back for pinch,air leak or internal blockage.

I have an external 6 gal tank with bulb. Before I broke into the carb I changed all fuel fitting to straight in-line brass barb fittings. Still used same hose I originally had, maybe I can replace the hose and bulb. I don't have anyway of measuring vacuum pressure on motor.

Have you tried pumping bulb while it's surging like that? Not familiar with the onan motor but assuming it has a fuel pump. Find it and check the pulse line from pump to the block, it could be plugged,cracked or loose. If that appears to be ok, pull line and check it and the port at block for carbon build up or anything that might be obstructing it.

Ethenal gas can cause all of the above probs, plus it can cause the probs if it is not fresh especially with the weather we have been having. Good luck!
Alfred

Yes, I have primed the bulb while engine is surging but when I do I don't see any gas filling up fuel filter. It just gets real tight. Yes it has a fuel pump, the vacuum diaphragm type.

You have a restriction some where between bulb and filter housing then. Hose could be coming apart inside. Take hose loose from fitting and pump bulb. If fuel comes out ok pull any fittings and line from filter back to connection and make sure they are clear also remove filter and check for flow through housing. could have a peice of trash in filter housing.

I do notice that when the motor is running looking at the fuel filter, very little fuel is being sucked into the filter from pump. Could this be a fuel pump issue? Also the hose that runs to the crank case, what does that do, create a vacuum pressure?

I had a similar problem a while back, motor would bog down then pick up and run fine for a minute then bog again, it turned out to be the pick up line inside the fuel tank, ethanol had ate it up, new tank fixed the problem