Bleeding fuel Lines

[Don Highfill]

I have a 1970 MF 150 with the 152 Perkins diesel engine. I recently replaced the fuel lift pump. I pumped the manuel pump but never got any air out of the top of the fuel filter or either bleed screws on the injector pump. The tractor starts easily and idles OK but it seems to have a "lag" when trying to accelerate going up hill. The rpms drop and stay there until I get to a level spot and then the rpms take off like crazy.Is there air trapped in my system somewhere that would cause this? Thanks for any help.

 

[Anonymous-0]

Sounds like you got water, and or ice in a filter. park in a warm garage, try drains, if the filter has them, replace filter, re-bleed, and also add some anti-gell to the tank.

 

[Don Highfill]

Thanks for the reply. The temp was in the mid 50's here today, and I drove the tractor for about an hour and a half putting out hay. The glass bowl on the bottom of the fuel filter is clear and clean and I removed tank and cleaned it last summer. The tractor runs fine at 1500 rpms but just lugs down at 1000-1200 rpms. Will it run with air in the system? I don't know why I was never able to get any bubbles out after replacing the lift pump.

 

[Don Highfill]

Another thought. Do the thick rubber washers in the lift pump go between the ends of the inlet and outlet lines and the lift pump or around the steel lines between the nut and the flange on the lines? Thanks again.

 

[Anonymous-0]

Not sure about the washers, but it still sounds like something is obstructing flow. My experience is general, not specific to your model tractor. I would start with a filter change, if not already done recently, then follow the feed line over to the pump. Some injector pumps have another filter or screen, where the line goes into the pump. Some rotary pumps also have a lift pump, as part of the injector pump, that takes the gravity flow, from the filter, and boosts pressure slightly, as it goes into the injector pump. This type of pump is prone to wear on the carbon vanes that move the fuel. This type of pump wear will show up as less power, as the tractor and fuel heats up, with use. After about 20-30 minutes, a slow loss of power. Not sure if this helps, perhaps someone with more specific info, on your model tractor will chime in. Good luck, Dave

 

[Anonymous-0]

When you bled your fuel line you said you never got bubbles or air out. Was it a steady stream of fuel?
If it was then you probably have it bled of O.K.
My tractor does not accelerate while under load or going up hill until you level off or remove the load (push in the clutch) then the rpm come up. I think this is normal on most tractors.

 

[Tommy D6-8U]

The grommets go between the nut and the flare on the fuel lines. That very likely could be causing your problem.

 

[Don Highfill]

Thanks Tommy. I had one each way. I moved the other one as you said today and it didn't make any difference. Thanks. Do you know anything about injector pumps? I have another question.

 

[Don-Wi]

Sounds like it needs new filters. It can't keep up with the demand when under a load, but when the load eases up it'll run fine. Had that happen before on our Oliver 1855.

Donovan from Wisconsin