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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 1234
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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I have a 432e backhoe that keeps blowing fuse in fuel pump /

Customer Question

I have a 432e backhoe that keeps blowing fuse in fuel pump / solenoid circuit , I have disconnected everything ( in steps) to try and locate problem , however I can not find it.
Submitted: 1 year ago.
Category: Construction and Road Equipment
Expert:  catmastertech replied 1 year ago.


Please post the machine's full serial number (PIN) so I can find the correct schematic to help you.

Customer: replied 1 year ago.
Cat432ecbxe03242.... I have had a bit of a look over schematic but still no luck , hopefully you can help.
Expert:  catmastertech replied 1 year ago.

Thanks for the serial number.
I will list all the circuits I have found for this machine including all options.
I am guessing this machine has all of them as it is shown with the Premier arrangement. (Not common here.)

Connect your ohm meter and read from fuse load terminal to chassis ground. Less than 5 ohm is short to ground. More than 5 ohms but less than 5000 ohms is a connected circuit. O/L is open circuit.

The ride control pressure switch is located on the ride control manifold mounted near the battery box but, on the inner side of the frame. Disconnect the pressure switch or the harness.

This is the torque limiter relay power. It is shown a relay K7 but, it may not be in the relay/fuse panel. The schematic is conflicting with the Operators manual. It should be in the same console area but, you may need to remove the panel to verify the wire number. Disconnec the relay from the panel.

This connects to the roof harness and runs to the keyswitch connection for the radio. Remove the radio and disconnect it or disconnect the roof harness. The connector is in the side console and the harness runs up the side post.

This is part of the ride control system that is seen more in your area. It is not clear that your machine has this function. It is called Load Control but, it is a dead engine lowering attachment to allow the loader to place on the ground when the engine stops. It may replace part of the ride control harness and is connected in the same area. If equipped, you may see to relays tied to the harenss near its harness connector to the platfrom harness. It may be easier to access this through the floor plate than from under the machine. (I'm not certainas this is not used in the US.)
Disconnect the harness as it the 123 white wire is conencted to everything in this harness.

This is to the engine harness and connects to several items. (I assume you have already checked these but, I just want to list everything for you.)
123-EF23 is to the cold start advance solenoid. It is connected to a temperature switch on the left front of the cylinder head and then to the solenoid under the fuel injection pump. Dsconnecct the temperature switch is the easiest
123-EF28 is to the shutoff solenoid located on the top of the fuel injection pump. Disconnect the solenoid.
123-EF10 is to the start aid relay. This is located with the relay group in the engine compartment on the right side frame support of the upper loader pin. Disconnect the relay.
123-EF18 is to the fuel pump relay and is located with the other three in the engine compartment. Disconnect this relay too.
123-EF52 is to the fuel water seperator sensor. Unplug the connector, not just the sensor.
123-EF53 is to the alternator excitation resistor. This is tied to the harness near the alternator. It may look like a block or just a capped connector but, closer inspection will show it has pins inside or is green in color.

These wires are all White and marked 123. Keep testing with your meter and note changes. If you have disconnected all of these components and still have a short to ground (<5 ohms), the plateform harness is damaged. Look for pinched or rubbed areas where harness may have worn. Since it connects to so many items it cannot be easily bypassed.

If you need more help on any of this, please let me know. I will be glad to help.
Keep me posted on what you find. I hope this is helpful and would like to know if you find the problem. No service letters are shown for this issue.

Customer: replied 1 year ago.
Thanks for all that , am still plugging away with not much luck , about all I have left is plateform harness. Will keep you posted.
Expert:  catmastertech replied 1 year ago.

Thanks for the update.

I will be looking for your reply.