I have an MF35 with the 23C diesel, its developed a problem where air seems to be getting into the injector pump, causing it to die and I'm continually having to bleed the air out of the pump to get it going again. It started happening about a week or so ago, and has gradually got worse - today I cant do a lap of the field with the hay mower without it cutting out and needing to be bled again. I cant work out where the air is coming from, it has a full tank of fuel and I cant see any obvious leaks round any of the lines or connections. It only appears to become a problem at revs under load (I'm working a mower at 540 pto rpm). I've noticed a couple of cork gaskets on the injector pump which are badly degraded - could this cause the pump to draw in air? I would have thought everything would be under positive pressure and I'd more likely get a fuel leak - but I'm no injector pump expert! Any help would be much appreciated!
MF35 air in injector pump
- Thread starter SmallAcre
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- massey ferguson 35
namyessam
Gold Member
Although I do not have a diesel, I will try and add some other ideas to try and solve your problem. Much of what I am offering is things I have read here and by no means taking credit for them.
First I would loosen the fuel cap. It should be vented and if it is plugged the fuel may not flow out of the tank to the pump thus you may be drawing air in to the lines by a loose fitting or a bad gasket. Having a full fuel tank would make this happen quicker since there is less air in the tank so it would develop a vacumn quicker.
Next, I would check all fittings for tightness and seal. eliminating the restricted flow from the tank may reduce the necessity of this step until you have more time to check for the proper seal of all lines and components. The fuel from the tank is only under normal air pressure and may not leak but air could be drawn in if the flow from the tank is restricted. This is much the same as an intake manifold gasket leaking allowing more air into the combustion chamber rather than drawing it through a carburetor.
lastly, I see that from the parts list that the fuel bowl is screwed in to the tank, there is a screen filter connected to the fuel bowl. If this is partially plugged, the tractor may run at lower speeds but when a greater volumn of fuel is required, it may not be able to deliver enough fuel to the pump and the pump is drawing air in to the system through loose fittings and gaskets.
you should only have high pressure fuel past the injection pump to the injectors
hope this gives you some other ideas to solve the problem.
Keep us posted
namyesam
Last edited:
Ok, I've dismantled and cleaned the low pressure side of the fuel system. I haven't replaced the fuel filters yet as I'm not near anywhere at the moment that I can get them. But was told they were new when I purchased the tractor and its only done 80hrs since then, so I cant see they'd be the problem. The fuel tap/bowl did not have a screen on it - I was hoping this being clogged would have been the problem but no joy. There was a bit of crap in the fitting which screws into the tank but not enough to cause a problem. I dismantled the lift pump as well. I put it all back together and made sure everything was tight. If i remove the pipe that feeds the injector pump, I can pump the lift pump and get a small stream of fuel coming out so there didnt appear to be any major restriction.
I took it back out to the field with the mower and got about 30m before it started losing power and stalled again - bled the pump and got about another 20-30m and same thing. If anything its worse than before!
My lift pump has always been a bit weak I thought - whenever I've had to hand prime it just didnt seem to move a lot of fuel with each pump and I can never get a good spurt from the bleed screws - just a dribble, could this be a problem? It certainly sounds like a fuel starvation problem, I can drive it all day long at lower revs/load, it just seems to be at load ~1300-1500rpm that it dies.
I took it back out to the field with the mower and got about 30m before it started losing power and stalled again - bled the pump and got about another 20-30m and same thing. If anything its worse than before!
My lift pump has always been a bit weak I thought - whenever I've had to hand prime it just didnt seem to move a lot of fuel with each pump and I can never get a good spurt from the bleed screws - just a dribble, could this be a problem? It certainly sounds like a fuel starvation problem, I can drive it all day long at lower revs/load, it just seems to be at load ~1300-1500rpm that it dies.
namyessam
Gold Member
I don't remember what the symptoms were on the one thread I read recently but someone was having problems with their tractor and found that the return line back to the tank was plugged. I wonder if having the return line plugged or kinked, the injector pump was unable to pump properly due to excessive internal pressure. May be something to check.
namyessam
banjodunn
Veteran Member
G'day mate change the fuel filters, we are seeing the start to alot of algae deposits this year don't know if it is the fuel or the weather causing it.
Jon
Jon
Well I took a punt and drove to my tractor parts guy this arvo to buy a new lift pump - installed it and noticed the difference imediately when hand priming to bleed the system. Cut the rest of my hay paddock and it didnt miss a beat!
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