MF 390 fuel problems.

[Dry Rot]

My 390 just stopped while turning hay. I bled the fuel system and started off again. Then it stopped again. The fuel lift pump was totally choked with crud. It was amazing that it was working at all. I replaced it with a new one, also replaced the fuel filter. But I haven't been able to get any life out of it since. I haven't had the fuel tank off to clean it as I can't get the large bolts to the nose undone so I have repeatedly drained and refilled the tank, filtering the fuel in between. Everything is now sparkling clean. But no improvement. I can get clean fuel to the lift pump but working the external leaver doesn't move fuel through the pump. The lift leaver doesn't feel right. I'd expect to feel some resistance and for the lever to return by itself -- but I have to lift it with my finger. No fuel comes out the other side going to the fuel filters. I've worked that leaver over 200 times without moving any fuel beyond the pump. There's a blockage somewhere, but where? I got the old pump working and have tried that, but the symptoms are exactly the same. I've been advised that the internal leaver of the pump isn't resting on the cam free area of the crank shaft and to turn the engine. I've done that (several times) but there is still no change. Is there a filter in the injection pump? But that can't be it either or fuel would be getting past the lift pump.

 

[Mur Huwcun]

Whip the outlet pipe off the lift pump and crank the engine over a few times to see if it will pump any through, the lift pump arm as you mention can be against the cam and sometimes will need the engine turned over a bit to release back.

 

[Wisconsonian]

if you loosen the fuel line going to the filter, will it leak fuel there when you pump?

A diaphragm transfer pump will feel different when it's pumped up and holding pressure vs when it's pumping fuel. Either the cam, or the pressurized fuel will hold the diaphragm and the manual priming lever won't have anything to move until the fuel pressure drops, or the cam is moved. The cam or lever don't pump fuel, they pull the diaphragm back and the spring pressure is what pumps the fuel, but only to a very low pressure.

 

[Dry Rot]

Whip the outlet pipe off the lift pump and crank the engine over a few times to see if it will pump any through, the lift pump arm as you mention can be against the cam and sometimes will need the engine turned over a bit to release back.

I'll try that. Also without the tap connected. I am pretty sure I've tried that which is what makes it all so frustrating! To get fuel to flow from tank to pre-lift pump. I have to attached a rubber tube and suck.

 

[Dry Rot]

if you loosen the fuel line going to the filter, will it leak fuel there when you pump?

No. Fuel is not getting beyond the lift pump. I can hold the lift pump in my hand (detached from the engine of course), work the external lever and the pump behaves as it should. When it is bolted to the engine, it doesn't seem to be working.

A diaphragm transfer pump will feel different when it's pumped up and holding pressure vs when it's pumping fuel. Either the cam, or the pressurized fuel will hold the diaphragm and the manual priming lever won't have anything to move until the fuel pressure drops, or the cam is moved. The cam or lever don't pump fuel, they pull the diaphragm back and the spring pressure is what pumps the fuel, but only to a very low pressure.

There doesn't appear to be any fuel pressure (or spring) when the pump is bolted to the engine.

This is from the manual. Logically, the stop (4) would seem to be on the wrong side as when it's closed it stops fuel draining from the fuel filter but not from the fuel tank when the lift pump is removed. The blockage has got to be at the lift pu,p but I can't see how.

 

[David1968]

No. Fuel is not getting beyond the lift pump. I can hold the lift pump in my hand (detached from the engine of course), work the external lever and the pump behaves as it should. When it is bolted to the engine, it doesn't seem to be working.

There doesn't appear to be any fuel pressure (or spring) when the pump is bolted to the engine.

On my combine it's easier just to slacken the lift pump bolts to allow it to move away from the cam, than trying to turn the engine. Should be able to bleed it by hand then.

Don't forget to tighten the bolts up again before trying to start it...

 

[tomlad]

Inside Some of those lift pumps are two one way valves, like a little button.
Same valve but fitted other way around, if that makes sense .to get the not return effect, they can pop out , then obviously it will only suck and blow but not pump.
When off the pump should sound like a duck quacking eh .
Be sure ur tank outlet is clear mate , had symular on my 65 due to gravel shite in tank , would block inside the tank tap .

 

[milkloss]

See if you can rig up a pipe and bottle to the outlet of the pump….. much the same as bleeding brakes. Sometimes lift pumps prefer to be in the wet to do any work. Still doesn’t solve your problem but might shed some light if you use clear pipe so you can see bubbles or rubbish in the fuel.

 

[shumungus]

No. Fuel is not getting beyond the lift pump. I can hold the lift pump in my hand (detached from the engine of course), work the external lever and the pump behaves as it should. When it is bolted to the engine, it doesn't seem to be working.

If its working when in your hand but not when its attached to the engine it must be against the cam when on the engine. You will have to turn the engine over slightly to free the pump movement.
Also does fuel flow freely from the pipe connecting the fuel pump and the diesel tank when you unscrew it at the pump end?

 

[Neil MP]

No. Fuel is not getting beyond the lift pump. I can hold the lift pump in my hand (detached from the engine of course), work the external lever and the pump behaves as it should. When it is bolted to the engine, it doesn't seem to be working.

There doesn't appear to be any fuel pressure (or spring) when the pump is bolted to the engine.

This is from the manual. Logically, the stop (4) would seem to be on the wrong side as when it's closed it stops fuel draining from the fuel filter but not from the fuel tank when the lift pump is removed. The blockage has got to be at the lift pu,p but I can't see how.

Blow back down the line from lift pump (5) to tank(10) first, in case excess crud has gotten stuck at inlet, then make sure you have shut off tap open (4) try blowing through to filter head, if you can’t, try turning tap whilst blowing, open bleed screw on filter head (6) if none disconnect the pipe going to fuel pump the one with the arrow pointing down beside the (7).
Try bleeding to fuel filter with lift pump unbolted from engine, if or when successful tighten pipe beside (7) and open bleed screw on fuel pump, bleed to fuel pump, retighten fuel pump bleed screw, then slacken/crack open the nearest injector to the cab that you have access to, bolt back on lift pump to engine and try starting, if/when successful tighten injector and make sure you don’t get caught up in any moving parts, if tightening the injector with the engine running!

 

[tomlad]

The system doesn't have a check ball in does it
Mates combine used to give trouble, crap would block it .
Think it was on lines on filter head , were lines screwed in Looked like a wide hex fitting. Like a very wide nut ?
Presumably it stopped fuel running back to tank ?

 

[Highland Mule]

How is the filter/ tap at the tank outlet? That has been blocked on my 290 recently.

What about the gauze/ filter inside the lift pump?

if you disconnect the feed line to the lift pump, does fuel pee through at speed?

 

[Dry Rot]

On my combine it's easier just to slacken the lift pump bolts to allow it to move away from the cam, than trying to turn the engine. Should be able to bleed it by hand then.

Don't forget to tighten the bolts up again before trying to start it...

I like that and will try it today. This is the first year I've been glad it is raining during hay making! Sorry for everyone else, of course, but it doesn't make me feel so bad!

 

[Dry Rot]

Inside Some of those lift pumps are two one way valves, like a little button.
Same valve but fitted other way around, if that makes sense .to get the not return effect, they can pop out , then obviously it will only suck and blow but not pump.
When off the pump should sound like a duck quacking eh .
Be sure ur tank outlet is clear mate , had symular on my 65 due to gravel shite in tank , would block inside the tank tap .

See above. I replaced the lift pump with brand new and have since got the 'old' one working (it's only 12 months old). Both now work off the tractor but not on. Pipes are all clear and have been blown through. Got to be that cam, I think.

 

[Dry Rot]

Blow back down the line from lift pump (5) to tank(10) first, in case excess crud has gotten stuck at inlet, then make sure you have shut off tap open (4) try blowing through to filter head, if you can’t, try turning tap whilst blowing, open bleed screw on filter head (6) if none disconnect the pipe going to fuel pump the one with the arrow pointing down beside the (7).
Try bleeding to fuel filter with lift pump unbolted from engine, if or when successful tighten pipe beside (7) and open bleed screw on fuel pump, bleed to fuel pump, retighten fuel pump bleed screw, then slacken/crack open the nearest injector to the cab that you have access to, bolt back on lift pump to engine and try starting, if/when successful tighten injector and make sure you don’t get caught up in any moving parts, if tightening the injector with the engine running!
View attachment 1047334

There is no fuel coming out of the exit side of the lift pump (between 4 and 5). So any fuel situation in the system beyond 4 has got to be due to lift pump (5). Yes? I'll check the tap (4) but pretty sure that is OK. I will also check fuel comes out of the lift pump with tap (4) removed. Got to be that contact with the cam? Rained again over night.

 

[pycoed]

I have no experience of this Ford engine, but on some you can refit the fuel lift pump with the lever on the "wrong" side of the cam with the result that no pumping will occur. Again, on some engines this will result in the pump lever deforming or breaking off as well, so check the old pump lever looks the same as the new.
Ah - I see that the new pump won't work either, so double check the fitment & try priming the pump as well (just had to do that after chasing air leaks on my Zetor, but that has a piston pump so you can feel directly if it's pumping or not)

 

[Dry Rot]

Tractor now working. Thanks to TFF panel of expert mechanics! I turned it over until the battery went flat, then recharged it and had another go. Finally, it burst into life after a long drawn out puffing of white smoke. I think the problem was probably a variety of things, the most vital being the filthy fuel tank which clogged up the fuel system. Not entirely my fault as it is s/h and has clearly been neglected.

Anyway, the diesel polishing seems to have been a success. I transferred fuel from one 5 gallon can to the next through a fine filter, then through the diesel washing gizmo. It came out pretty much as if straight out of the pump. Glad I didn't cut my hay now as it is still showers, on and off, for weeks now.