Fuel Problem Diagnosis???

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patrickm
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Fuel Problem Diagnosis???

Post by patrickm »

I have a fuel problem with my Dexta as follows. After adequate priming and bleeding of all lines, the tractor runs fine...for about 15 minutes, then it dies from lack of fuel. I have observed that the fuel filter "canister" is low of fuel when the tractor stalls out from lack of fuel. (This can be seen by removing and looking into either of the 2 bleed screws on the top of the fuel canister). The primary fuel pump can be worked manually to pump fuel into the canister, but the flow of fuel seems slow, (though I am unsure of what a "normal" flow should be.

I believe the problem may be a bad or weakened diaphragm in the primary fuel pump, which is not able to keep up with the fuel requirements of the tractor, hence, when fully primed and bled, the tractor will only run for 10-15 minutes.

Do any of you Dexta experts think this novice, (ie. that'd be ME), has diagnosed this problem correctly? There is adequate fuel from the tank to the primary pump and I have observed no fuel leaks elsewhere in the system. The injection pump / injectors work fine when there is fuel available. Thanks for any advice you may share.

Patrick Mainville, Mineral Bluff, GA, USA, pjmainville@tds.net

Brian
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Re: Fuel Problem Diagnosis???

Post by Brian »

Patrick, your problem is most likely the pencil filter in the fuel tap which will require you to remove the whole tap to clean it. Nice job if you have a tank full of diesel. :cry:

When you say there is adequate fuel to the lift pump do you mean that the flow is full bore out of the pipe not just trickling out?

When the diaphragm fails in the lift pump it usually fills the injection pump with diesel. I have just had to replace the lift pump on my Nuffy but that was due to the fuel draining back and causing an air lock that had to be bled every time I started in the morning but, once running it was OK.
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Brian

patrickm
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Re: Fuel Problem Diagnosis???

Post by patrickm »

Hey Brian, nice to hear from you again. (If you recall, you saved me a few years back with injection pump problems….yeah SeaFoam!!!). Anyway, the previous owner had installed an “inline” fuel filter between the gas/diesel tank and the primary/lift pump. (Inline filter is a cheap-o, removable glass housing style filter held in place with conventional rubber fuel line and clamps). I have removed and cleaned this a number of times, the little filter inside was always clean and fuel just poured out as fast as gravity allowed. Please tell me this means the “pencil filter in the fuel tap” is OK. (The fuel tap itself is stuck in the open position…I have never messed with it…it looks like a potential nightmare).
Not sure I understood what you meant by “When the diaphragm fails in the lift pump it usually fills the injection pump with diesel” If the diaphragm fails….how can it fill the injection pump…??? (or the original equipment fuel filter canister, which is next in line prior to the injection pump. I think I’m missing something here, which does not come as a surprise).
As previously mentioned, after the tractor has “died”, removal of the outermost bleed screw on the original equipment fuel filter canister shows that the fuel is about 1 cm or so low from the very top of the bleed screw opening. Manually pumping the little handle on the lift/primary pump does push fuel into the canister, but it is slow, at least 50 – 100 pumps to fill the 1 cm void. Is this normal?
To get the tractor running, I have used my truck to jump/ “crank it over”, ie. get fuel to all the lines / bleed them. The tractor will then run fine…for 10-15 minutes…then just die.
Thanks again for all your help. Am going on vaca for the next 2-3 weeks, but will check the website.

Brian
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Re: Fuel Problem Diagnosis???

Post by Brian »

The add in filter with rubber fuel lines may be your trouble. They were probably made for a petrol system and diesel will affect the plastic (as you can see with your fuel tap) and will dissolve the rubber hose internally causeing a blockage. You need to replace any rubber hose with plastic or metal fuel line and get rid of the inline filter. If you have fuel flowing freely to the in line filter but not to the main filter your problem is in the line to the lift pump.

On a Dexta the fuel lift pump with the little handle on, is driven by a cam from the fuel pump. When the diaphragm leaks fuel goes through the hole and into the cam box on the injection pump. It has been known to find its way past the seal on the pump drive from the timing cover and down into the sump
Fordson Tractor Pages, now officially linked to: Fordson Tractor Club of Australia, Ford and Fordson Association and Blue Force.
Brian

patrickm
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Re: Fuel Problem Diagnosis???

Post by patrickm »

OK, I think I understand all that, will give it a go when I get back from vaca. (and hopefully advise of a success story). Thanks again.

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