General diesel engine fuel problem

08 bobcat 335 mini ex with kubota v2203 engine.
machine is starving for fuel. I replaced the fuel filter, filled fuel filter with diesel 911, replaced lift pump. replaced fuel shut off solenoid, replaced suction fuel lines from tank to lift pump. tried removing primer bulb. still fuel starved...or so it seams. if I squeeze the fuel primer bulb while it is running it clears up. if I remove the fuel line at the injector pump and squeeze the primer bulb ,fuel flows freely.

machine runs great for 5 minutes or so then fuel starvation slowly comes back. My brother has a 341 and had to put a new engine in because of nearly identical situation. dealer said compression was low ( i think 320 when it was suppose to be 375...im not 100% convinced my brothers machines issue was because of compression, he hasn't gotten it back yet) My machine fires up barely touching the key, I would think if it was low compression it would take more turns to fire???

not sure if the engine temp is a factor.
maybe cam that runs lift pump is worn?


any ideas?

I'd be highly suspect of the suction line in the tank. Go to the skid steer forum and look at one of the stickies about bobcat fuel problems. Their excavators probably used the same setup as their skid steers. They used to use a rigid plastic line that was prone to breaking off and then suck air. When it starts starving for fuel, is the suction bulb collapsed on its own?

Have you checked for crud moving around in the bottom of the tank?Sawdust,bits of rust? Fuel bacteria is bad in our area,it get worse when it dies off in the tank.

Try running it with the fuel cap off or loose

I had the tank suction line off today, it looks good. The primer bulb is not collapsed. With fuel line pulled off the injector pump and a squeez of the primer bulb it shoots a full stream of fuel.

I tried running with fuel cap off

If it runs clean when you squeeze the bulb then the system is nt moving enough fuel and building pressure. Are you sure you have the right fuel pump? Those dam parts guys aren't very bright sometimes lol

i might try to put a fuel can on top the rops and see what that does.

Is there a small valve near the where the return line comes out of the pump?
The air vent valve.
You open it to fill the filter then close it to run the engine. If it has one is it closed?

Do you have a spin on fuel filter? Is that filter even with or below the fuel tank? Does the filter get sucked dry? If you remove the filter does fuel continue to slobber from filter head? Some filter heads have a little flapper valve that catches the holes in the filter, tightening a filter is supposed to open the valve and removing is supposed to close it. Its supposed to prevent siphoning the tank dry in a filter change. If the little doo-dad gets damaged, it might be hanging half closed. Worth looking into.

funwithfuel said:

Do you have a spin on fuel filter? Is that filter even with or below the fuel tank? Does the filter get sucked dry? If you remove the filter does fuel continue to slobber from filter head? Some filter heads have a little flapper valve that catches the holes in the filter, tightening a filter is supposed to open the valve and removing is supposed to close it. Its supposed to prevent siphoning the tank dry in a filter change. If the little doo-dad gets damaged, it might be hanging half closed. Worth looking into.

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I'll look into that, make sense...spin on is below fuel tank. Thanks for the input!

mekanik said:

Is there a small valve near the where the return line comes out of the pump?
The air vent valve.
You open it to fill the filter then close it to run the engine. If it has one is it closed?

Click to expand...

There is, but its closed. Thanks for the idea.

Ended up being gasoline in the diesel. Fuel supplier mistake

tnc110 said:

Ended up being gasoline in the diesel. Fuel supplier mistake

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Can you get the fuel supplier to pay for cleaning out the tank on your machine including a new set of filters?

Had the opposite problem at work many years ago. The Chevy service truck I drove started running real bad and pinging like crazy with even light throttle like timing was way advanced. Truck was pretty new so I was told to take it to local Chevy dealer. They checked a few things like timing and such. Then one of the mechanics thought to siphoned out some fuel. Guy noticed pretty quick that when gas evaporated it left an oily film. Turns out the fuel company had a new driver who mixed up the two tanks and filled the gas storage tank with diesel!