2000 JCB 3CX Electrics

[KIJCB]

Hello,

I have a 2000 JCB 3CX backhoe that won’t start. I have it all torn apart right now. I don’t know the machines history.
I’m able to start it by applying 12v straight to the starter when the ignition is at pos 1.

I set up a relay to send 12 v from the battery to the starter while the ignition module is in pos 3 (turned all the way clockwise)
I would like to find out why it won’t start at pos 3 (starter engaged).

The fuel solenoid is not on at pos 3, but I think that’s how it’s supposed to operate?

Any help is greatly appreciated!
CK

[agrimax]

I'd have thought that position one is only for auxiliary power for say the radio.The fuel solenoid should be activated at position 2(ie ignition on and dashboard warning lights on). It should also be on at position 3 otherwise the engine can't start. If the engine isn't(or wasn't cranking at pos 3,perhaps the neutral safety start circuit is at fault. F/R shuttle lever needs to be in neutral to make the circuit.There isn't an actual separate safety switch like older models so it's likely your shuttle lever that's faulty.

[kaos]

Does it crank but not fire on the key? If it doesn't crank, then as Agrimax said, the neutral safety start would be a likely culprit. If it cranks but doesn't fire, and particularly if you can start it with external power with the key in the accessory position, I would wonder if somebody has been working on the electrical system and made a mistake.
I've come across a case like that myself. A tractor that had suffered heat damage to the wiring loom, but somebody had found what they thought was suitable power for the fuel solenoid, but still it would never fire up without the use of ether, even with a warm engine. Turned out that they had connected the fuel solenoid to the accessory line, which got turned off during starting. The only reason the ether helped was that it was the ether that it fired up on, key was released, engine still rotating, and only then did it start working as a diesel.

--
Best regards, Kári.

[KIJCB]

With the original starter wire on it does not crank at all. When I bypass it and send 12v to starter it starts at pos 1 but when I wire it to send 12v at pos 3 it will crank but not fire.

I do think someone has messed with it before. Perhaps to bypass the neutral safety start. And idea how to troubleshoot neutral safety start? Is there a good source I could wire to fuel solenoid to stay on at positions 1 through 3 but shut off at 0?

[gecko.cx]

Could be the ignition switch it's self

Is there a good source I could wire to fuel solenoid to stay on at positions 1 through 3 but shut off at 0?

Probably easiest to run a new wire

[kaos]

What is the machine serial number? With that we might be able to find the proper service manual and circuit diagram.
I've been digging a little into the downloads available here, and for those machines it seems the keyswitch has positions 0, Ign, H and HS, with spring return to Ign from both H and HS. Does that match what you have? If so, there is no accessory/aux position, so it could not be that which is used for the fuel solenoid. But then, the Ign line should be active in all positions except 0. Gecko.cx's suggestion of a faulty ignition switch is then sounding likely.

--
Best regards, Kári.

[gecko.cx]

Must admit I just took a guess this machine is 460xxx.
If so, the switch is common with earlier models and will be: 701/80184.

At this stage of it's life, the original switch may have been replaced with another (perhaps NQR)

[KIJCB]

Serial # is 494043
I'm going to figure out what this ignition module is doing and I'll be back with more info.

[gecko.cx]

Later serial than I guessed, but still the same switch - should look like this

[KIJCB]

Thanks Gecko, that is the same ignition switch I have. I've made a scabby little drawing of what it is doing. I hope it makes sense. If anyone has the relevant wiring diagrams that would be great.
-- I think its not starting because the fuel solenoid is not powered during ignition (pos 2 and 3).
-- I believe its been modified in the past, possibly bypassing the "neutral safety switch".
--the starter wire does not provide power, I think it is broken somewhere, but I can apply 12v to starter and start when ignition in pos 1.
--Note-this ignition switch does not stay in Position 2, there is still spring return pressure and when released returns to pos 1.

My goal is to run a new wire to the starter, and possibly one to the fuel solenoid from a source that will power the solenoid only at pos 1,2,3 and then still allow the ignition switch to remove power from the solenoid and shut off the machine at pos "0".