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fault in diesel lawnmower electrics?

A non internet savvy acquaintance asked me to help diagnose a fault on a ageing but impressive diesel ride-on by John Deere, and it occurred to me others might know these brutes better than I, so asking the question.

When I arrived it was 'not going' and after a while he diagnosed that the fuel lift pump wasn't working. we hotwired that to te batery and it spewed diesel all over the lawn, so we thought fuses and so on.

All we could find were intact.

Then I noiced that when he hot wired the pump, the solenoid that operates the fuel cut off also worked. There was a bit of coat hanger around it 'what's that for' 'Oh that burn out ages ago: I use the wire to hold it open and remove it to stop the engine' 'well its working now' I said.

Then we decided that in fact the reason it had been working at all, was on accoiunt of the tank being full enough of diesel it didn't need the lift pump and that had in fact stopped working at the same time as the solenoid. Confirmed by filling the tank up, upon which it ran just fine.

additionally when the power was applied to the pump/solenoid a relay somqwhere also clicked.

On the mower there are the usual plethora of safety sensors - bum on seat switch, foot on brake switch, etc. etc. And two boards - one heavily weatherproofed containing discrete electronics and a lot of dodes and resistors, tow relays and an IC, which looks to me like some kind of interlock logic, and another one with two fuses on it and a few more bits and pieces. Both have masses of wires going in and out..

I am guessing either a relay has burn out on one of the boards, or that asafety sensor is OC. It would make sense would it not to put the lift pump and fuel solenoid on the same circuit so that one could reliably cut the engine in case of any safety violations..

But am at a loss to know how further to proceed..

Anyone worked on these or similar, before? Anyone gotta circuit diagram?

I have to say quite irrelevantly that the little 3 cylinder diesel is a gem. I think is 25bhp of beautifully balanced 'chug' power.

Reply to
The Natural Philosopher
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The Natural Philosopher used his keyboard to write :

You will possibly find a circuit diagram on the internet somewhere and you can only make any progress with one. Failing that, find one of the US mower web forums, and ask for a circuit diagram there.

Reply to
Harry Bloomfield

A non internet savvy acquaintance asked me to help diagnose a fault on a ageing but impressive diesel ride-on by John Deere, and it occurred to me others might know these brutes better than I, so asking the question.

When I arrived it was 'not going' and after a while he diagnosed that the fuel lift pump wasn't working. we hotwired that to te batery and it spewed diesel all over the lawn, so we thought fuses and so on.

All we could find were intact.

Then I noiced that when he hot wired the pump, the solenoid that operates the fuel cut off also worked. There was a bit of coat hanger around it 'what's that for' 'Oh that burn out ages ago: I use the wire to hold it open and remove it to stop the engine' 'well its working now' I said.

Then we decided that in fact the reason it had been working at all, was on accoiunt of the tank being full enough of diesel it didn't need the lift pump and that had in fact stopped working at the same time as the solenoid. Confirmed by filling the tank up, upon which it ran just fine.

additionally when the power was applied to the pump/solenoid a relay somqwhere also clicked.

On the mower there are the usual plethora of safety sensors - bum on seat switch, foot on brake switch, etc. etc. And two boards - one heavily weatherproofed containing discrete electronics and a lot of dodes and resistors, tow relays and an IC, which looks to me like some kind of interlock logic, and another one with two fuses on it and a few more bits and pieces. Both have masses of wires going in and out..

I am guessing either a relay has burn out on one of the boards, or that asafety sensor is OC. It would make sense would it not to put the lift pump and fuel solenoid on the same circuit so that one could reliably cut the engine in case of any safety violations..

But am at a loss to know how further to proceed..

Anyone worked on these or similar, before? Anyone gotta circuit diagram?

I have to say quite irrelevantly that the little 3 cylinder diesel is a gem. I think is 25bhp of beautifully balanced 'chug' power.

Using the model and serial number JD will (If asked nicely) furnish a manual and diagram Otherwise several pics of the machine and offending parts will usually suffice emailed to the Tech dept

Reply to
Nthkentman

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