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Cat 420 E backhoe won’t start. When I turn the Key to on I…

Cat 420 E backhoe...

Cat 420 E backhoe won’t start. When I turn the Key to on I get a flashing ! And a repetitive Beep. Will not crank when turned to start.

Mechanic's Assistant: How long has the vehicle failed to start after cranking? Has the security system been triggered recently?

No security system that I know of. It is a 2007

Mechanic's Assistant: What's the make, model, and year of your car?

2007 Catapilar 420E Backhoe

Mechanic's Assistant: Anything else you want the Mechanic to know before I connect you?

No voltage at pin 85 on start relay (K1). There is voltage when key turned to start at the back of ignition (orange) and on pin 8 (orange) of shifter

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Answered in 1 minute by:
1/24/2021
Mechanic: catmastertech, Technician replied 1 year ago
catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,965
Experience: Field service technician for CAT 19 years.
Verified

Hello,

What is the complete machine serial number of your 420E?

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Customer reply replied 1 year ago
CAT0420EKPRA00231
Mechanic: catmastertech, Technician replied 1 year ago

Thanks, ***** ***** pull up a schematic to help you.

K1 is shown as the backup relay.

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Customer reply replied 1 year ago
If I climb under I can jump the starter solnoid and get it to turn over but I still will not start
Mechanic: catmastertech, Technician replied 1 year ago

K1 is shown as the backup alarm relay.

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Customer reply replied 1 year ago
Okay on K1. I was reading off another post that said to check K1
Mechanic: catmastertech, Technician replied 1 year ago

The E model is different.

Look for a separate relay a little further back and by the power distribution blocks.

It will had 4 wires. Red to terminal 30. Green to terminal 86. Black to terminal 85. And white to terminal 87.

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Customer reply replied 1 year ago
Will that be in the fuse block area?
Mechanic: catmastertech, Technician replied 1 year ago

The power flow is from the key switch on the orange 307 wire to the shift controller on the column. The neutral safety in the shifter closes the circuit to the 306 green wire which goes to the start relay. This triggers the relay to close and send power from the battery to the 304 white wire which goes to the start motor solenoid.

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Customer reply replied 1 year ago
Okay I jumpered orange 307 to green 306 on the terminal at the shifter and still no luck. Would that mean it might be the start relay?
Mechanic: catmastertech, Technician replied 1 year ago

That would be the next thing to check.

It is very rare for these relays to fail.

I would suspect a broken wire first. Did you check for voltage to the shifter?

Did you check for a short to ground on the 306 green wire?

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Customer reply replied 1 year ago
voltage is on pin 8 orange 307 when key turned to start. No short to ground on green pin 7 (306)
Mechanic: catmastertech, Technician replied 1 year ago

The relay is where I would test next.

You can check for a short on the White 304 wire and then see if it has continuity to the solenoid. Or, try a jumper from terminal 30 to 87 and the solenoid should engage and crank the engine.

It is strange the engine didn't start tough when you jumped at the starter.

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Customer reply replied 1 year ago
Pulling the panel to get to the relay. I thought maybe a bad relay would cut off fuel too causing it not to start when jumpered.The white wire is groundedThe whit wire also has continuity to the solenoid
Mechanic: catmastertech, Technician replied 1 year ago

Starter solenoids have low resistance. You might see 3 to 4 ohms. If it is less than 2 ohms, that might be a shorted wire.

I would look for a stick or other debris that got pushed up under the machine and hit the wiring harness.

If it did short, it should have blown the 60-amp fuse on the middle distribution block.

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Customer reply replied 1 year ago
White wire to ground is 0.2 ohms. Whit wire from solenoid to starter is also 0.2 ohms. Harness underneath looks good.
Any reason for the flashing explanation mark on the gauge cluster?Blown 30 amp fuse fourth position from leftThe 60 amp fuses were good along with all others on that row
Mechanic: catmastertech, Technician replied 1 year ago

The light only calls out a machine system fault.

You will need CAT ET to find the actual codes, if it is an ECM monitored fault. I would think the other indicators would also be on if it has an active code.

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Customer reply replied 1 year ago
Not one of those. There is a row of Jtype fuses to the right of this panel under the start relay in the first drawing you sent
Mechanic: catmastertech, Technician replied 1 year ago

Normally, the fourth position is for the HVAC

The schematic show both fuses as 40 amp

The third one is for the engine. It has a 30 amp on top and a 50 amp below.

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Customer reply replied 1 year ago
HVAC has been working fine. It was the only 30 in that row.Back to the white wire from relay to solenoid. It showed .02 ohms to ground. That means it is shorted right?
Mechanic: catmastertech, Technician replied 1 year ago

Yes, if you disconnected it from the starter solenoid and the relay, then the wire is shorted to ground. Fabricate a jumper wire for a quick bypass test.

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Customer reply replied 1 year ago
Okay I will make up a temp jumper for the white wire and get back to you.The fuse that is blown is two position to the Right from #38 in the first drawing. Hope that makes sense
Mechanic: catmastertech, Technician replied 1 year ago

The schematic and the parts images do not match (as usual).

The first block should have two 60 amp fuses.

The second block should have a 60 amp and 40 amp.

(this is the 60 amp for start solenoid and 40 for a main key switch power relay[to all other fuses])

The third block has a 30 amp and a 50 amp fuse.

(this is the engine ECM power [30amp] and [50amp glow plug])

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Customer reply replied 1 year ago
We replaced the 30 amp I am guessing it was ecm. We did not Run the jumper bypassing the white wire.It started right up after replacing the 30 ampThank you very much for your help. You are awesome!!!
Mechanic: catmastertech, Technician replied 1 year ago

Great! Glad to hear you have it fixed.

Thank you for using JustAnswer, if you do need further help please let me know.

If you are satisfied with my service, please take a moment to provide a rating.

Thanks again, Don

CATMASTERTECH

catmastertech
catmastertech, Technician
Category: Construction and Road Equipment
Satisfied Customers: 3,965
Experience: Field service technician for CAT 19 years.
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