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Autopapyrus · JMC 1052 (2007)
https://autopapyrus.com/guides/jmc/1052/fuel-system-layout-and-wiring-with-pump/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

JMC 1052 (2007): Fuel System Layout and Wiring with Pump

The JMC 1052 is powered by the JX493ZLQ3 diesel, a 2.8 L turbodiesel based on the Isuzu engine with a mechanical injection pump. A classic electric in-tank gasoline-style pump is usually not fitted on this engine. Fuel is delivered by a vane-type transfer pump built into the injection pump, while the electrical system handles the fuel cutoff solenoid, the power supply circuit and the level sender. An exact wiring diagram for the specific 2007 trim level is not documented in publicly available service materials, so what follows is the general principle and the order of checks. Check wire colors and pin numbers against the manufacturer's service manual.

DifficultyMedium Time1-2 hoursinspection and circuit testing Steps9

Key figures

  • Voltage at the stop solenoid or pump relaywith the ignition on; check with a multimeter in steps 4 and 5 to confirm that power is present.
    about 12 V

Check these values against the manufacturer’s specification for your vehicle before you start.

Diagram: fittings, stop valve and lever on the injection pump

Injection pump seen from the side, from the injector-line side1Pump housing2Fittings to injectors3Stop valve4Lever with rodRow of 4 fittings on the headValve power wireTap to enlarge
  1. 1Pump: cast housing that feeds fuel to the injectors. Without fuel-system experience, go to a workshop.
  2. 2Fittings: four nuts in a row on the pump head, high-pressure lines run from them to the injectors. Tighten and check for leaks.
  3. 3Stop valve: electromagnet on top of the housing with one power wire. With ignition on it has about 12 V and clicks.
  4. 4Lever with rod on the pump housing: a landmark so you do not confuse the unit.

Parts

5
№Part
01 Diesel fuel filter/water separator with manual priming pump
02 Electric engine stop solenoid on injection pump (fuel cutoff)if faulty
03 Power circuit relayif faulty
04 Power circuit fuseif faulty
05 Fuel level sender in tankif faulty

Tools

6
  • multimeter
  • test light
  • wrench and socket set
  • screwdrivers
  • shop rags
  • fuel catch container

Step by step

9 steps
  1. Determine which pump you have. If the engine has a mechanical injection pump, the injection pump itself creates fuel delivery, and the filter has a manual priming pump. If there is an electric module with a connector in the tank, your vehicle has a modified fuel system.
  2. The fuel line runs as follows: tank, pickup tube, filter/water separator with water-in-fuel sensor, manual priming pump, injection pump, high-pressure lines, injectors, return line to the tank. The arrows on the filter and fittings show the flow direction, so do not mix up the supply and return lines.
  3. Injection pump electrics. The engine stop solenoid is mounted on the injection pump body and usually has a single power wire. It receives +12 V from the ignition switch through a fuse and possibly a relay. The solenoid body is grounded through the injection pump.
  4. Testing the stop solenoid: turn the ignition on without starting the engine. You should hear a light click, and the solenoid wire should show about 12 V. If there is no voltage, check the fuse in the panel under the dash or in the engine compartment, the ignition switch contacts and the relay. If 12 V is present but there is no click, the solenoid is faulty and should be replaced.
  5. If the vehicle has an electric lift pump: power runs through a fuse and a relay. Positive is supplied to the pump terminal from the relay, and ground goes to the body through a separate wire. Check the connector at the tank: the power terminal should show about 12 V with the ignition on, and the ground terminal should have a solid ground. Connect the pump only through a fuse.
  6. The fuel level sender in the tank is connected to the instrument cluster gauge by a separate pair of wires. It is a variable resistor with a float and has nothing to do with fuel delivery.
  7. Ground points. The battery negative terminal, the ground strap on the engine block and body, and the contacts on the rear frame rail for the tank circuit. A corroded ground causes the same symptoms as a failed pump. Clean and tighten the terminals.
  8. If the engine does not start: prime the system with the manual pump on the filter until you feel firm resistance. Then check the stop solenoid, the fuse and the tightness of the supply lines. Air in the fuel supply system is the most common cause of a no-start.
  9. After working on the fuel line, tighten and check the clamps and fittings, then prime the system and make sure there are no fuel leaks. Check the tightening torques for banjo bolts and fittings against the manufacturer's service manual; a typical reference for small fittings is 15-30 N·m (11-22 lb-ft).

Common mistakes and warnings

  • Disconnect the battery negative terminal when disassembling electrical connectors
  • Fuel is highly flammable, so do not smoke and keep sparks away
  • Diesel fuel degrades rubber parts, so use a catch container and wipe up any spills
  • If you have no experience with fuel injection equipment and injection pumps, it is better to take the vehicle to a repair shop