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dieseldan55
dieseldan55, Mechanic
Category: Construction and Road Equipment
Satisfied Customers: 756
Experience:  Road Mechanic for Volvo Construction Equipment.
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I have a Komatsu WB140-2 backhoe. It has been working fine,

Customer Question

I have a Komatsu WB140-2 backhoe. It has been working fine, but now when I turn the key to start, it does not turn over the motor. The battery tests perfect, shifter is in neutral, drive lever is in neutral. It did this once before but fixed itself. In the last week I changed the oil and started it without problem. Next I removed the seat and put on a new cover and fixed the steering wheel adjustment. After those two items, it won't turn over the motor. Blinkers, lights and other electrical seem fine. Turning the key to ACC causes alarm sound (normal), but when I turn key to START motor does not turn over. I can see fuel shutoff solenoid working fine.
Submitted: 2 years ago.
Category: Construction and Road Equipment
Expert:  dieseldan55 replied 2 years ago.

Hello, did you check for power at the starter when trying to turn over? Possible bad brushes in the starter causing no current flow. I will look at schematic tonight. Is this the same machine with the short on the reverse solenoid?

Customer: replied 2 years ago.
No I cannot access the starter because it is a sealed plastic case. Can I test power to starter from somewhere else? When I put steering wheel lever into reverse position, it makes the normal back up beep alarm. This shuts off when I put lever back to neutral position.
Expert:  dieseldan55 replied 2 years ago.

ok, let me look at the schematic for the start and i will give you another option for checking. I'm on the road so a few hours from now

Expert:  dieseldan55 replied 2 years ago.

okay took a look at schematic, there is a starter relay K01 or connector X10 do you know where these are?

Customer: replied 2 years ago.
I saw the K01 on schematic, is it under dash with the fuses? There appear to be 6 relays with fuse box. I do not know where connector X10 is.
Expert:  dieseldan55 replied 2 years ago.

it should be a yellow wire off terminal 87 on the relay and it also ties into the preheater timer. That wire will engage the solenoid on starter to turn over so if you supplied battery voltage to that point the starter should spin. if it does then there is issue in other circuit components but it will be a quick test to verify starter is functioning.

Expert:  dieseldan55 replied 2 years ago.

i will try to find a page with that info, not easy

Customer: replied 2 years ago.
I've uploaded picture of main circuit board. I see the botton left green connector is labeled X2 and the purple one next to it is X3. Can you determine from this picture which is terminal 87, X10, or K01?
Expert:  dieseldan55 replied 2 years ago.

okay great pic, i found the location and id of board. There is a black plastic box under the hood near the latcht. I will send the info when i return home but i think it will be helpful. thanks for the patients.

Expert:  dieseldan55 replied 2 years ago.

here is that panel you showed

Customer: replied 2 years ago.
Thank you for the pictures.I was messing around with the F-N-R lever ("directional control lever") and got it started. Here's what worked: (1) Turned the key to start, (2) At same time slowly moved the F-N-R lever from Forward to Neutral position. It then started. So the problem is not the starter but something related to the directional control lever. I'm glad I got it started, but the problem still exists.What do you suggest next to pinpoint the issue so I can replace the part so this doesn't happen in the future?
Expert:  dieseldan55 replied 2 years ago.

well I would look at the output form the f/r switch to the relay to verify that the switch is sending the signal. I'm away fro the weekend but will look and try to advise further on Monday. thanks for the update.