Lift pump problems???? MF 1080

Was changing the oil filter on my MF 1080 and I figured i'd do the fuel filters too (has the dual filter system) and changed them, primed with the manual lift pump, bled it to the injector and then fired her up. Ran for about 2 minutes then shut itself off. Re-primed, took 300+ pumps with the lift pump to get fuel to flow from the bleed screw above the filters. Tried to start, no dice, went back to lift pump, opened bleed screw and it was air logged again, took another 300+ pumps to get fuel flowing, air logged seconds later again. Tried using the ignition to prime, would get fuel flowing from bleed screw but only got enough to the motor to fire it up once and it immediately shut down.
Sounds like a bad lift pump right?

Look in the fuel tank for anything sitting on the bottom of the tank that could restrict fuel flow, or one of the new fuel filters could not be sealing properly allowing air to get into the system. Was it running fine before you changed fuel filters?

After you bled the system did you loosen the injector lines at the injectors at the top of the head, and crank it over until fuel came out of them, then tighten them back up?

Hi Steve and PT,
It is not uncommon to have to tow (if you can do it if MP is not fitted) a tractor to start it after the fuel system has been disturbed. When you were operating the lift pump did it feel like you were pumping the full amount of fuel? If the engine camshaft happens to stop with the lift pump on the lift the hand lever will have limited or no effect. If this happens turn the engine slightly by hand or a short burst on the key. Slacken the filters and turn them back and forth to ensure that they are seated correctly.
Open the bleed screws and either turn the engine over on the key or operate the lift pump. Ideally you should have a jet of fuel from each screw. Slacken two injector pipe nuts and turn the engine over until a spurt of fuel appears at each one. Tighten and you should be able to start. Ensure that your battery is charged enough to get good cranking speed. A slower speed may prevent it starting. When the engine is running slacken each injector nut in turn and note the drop in engine speed. This should be even across all cylinders. If there is a noticeable difference you may have a problem brewing with that cylinder.
Let us know how you get on.
DavidP, South Wales

Thanks for the replies PT and David.
What is confusing us is the amount of air getting into the system repeatedly.
Hundreds of pumps with the hand pump to get fuel to the bleed screw and then another fifty pumps or so to get a steadier stream of fuel out of the bleed screw above the filters.

Once we get the steady stream of fuel, moments later it loses prime again....

when we operate the lift pump with the bleed screw cracked it makes a sound like it is breathing in and out...is that correct or is it incorrectly sucking air into the system...

I don't know, i remember last time we did the fuel filter on this tractor it was a bear to prime and bleed.

perhaps we will go back to the beginning and re-seat the filters...as you said, it seems like we are sucking air somewhere...

If the lift pump is quite old it may not hurt to replace it anyways (it shouldn't cost too much). Also like David said you can pull the tractor around a while rather than cranking on the starter too much (we had to pull a Ford 2000 diesel around quite a while to get it bled).

A cracked diaphragm in the lift pump might cause that problem.