This repair document explains JCB equipment fault code K4718 indicating Intake manifold pressure drop too high at start-up. For other JCB repair examples see JCB Fault Repairs .

Related Content:
- JCB Diagnostic Tools

Problem description

The measured intake manifold pressure (signal from the boost pressure sensor) is below the warning limit when the engine is started.

Possible causes

1. The air supply to the engine is cut off.
2. The boost pressure sensor is wired incorrectly.
3. The boost pressure sensor is defective.

EEM response

- The error code (FC) is stored.
– Warning light is illuminated.
– CAN message indicates an active error.

NOTE: The engine may not start, be slow to start, or run poorly.

SOLUTION

STEP 1: Check the engine air supply system.

1. Check the air filter:
- Make sure the air filter is clean and not clogged.

2. Check the lines from the air filter to the turbocharger:
- Check all connections and bends for blockages or damage.

3. Check the turbocharger:
- Make sure the turbocharger is functioning properly.

4. Check the piping from the turbocharger to the intercooler:
- Check for clogged or bent connections.

5. Check the intercooler:
- Make sure the intercooler is working properly and not clogged.

6. Check piping from intercooler to intake manifold**:
- Check for clogged or bent connections.

Step 2: Check for electrical faults

1. Check boost pressure sensor:
- Check sensor, wiring, and regulator input.

2. Error Log Management:
- Save and delete error logs and reboot the ECU. If the error occurs again on the next drive cycle, perform the following checks:

3. Check the boost pressure sensor wiring:
- Check the wiring, connector and pin contacts for oxidation or damage.

4. Test using a different boost pressure sensor:
- Swap the boost pressure sensor with a known good sensor to check if the sensor is defective.

These procedures will help to diagnose and fix the problem of excessive pressure drop in the intake manifold when starting a JCB machine. If the problem persists, contact a professional technician or refer to your JCB service manual for detailed instructions.