Fuel System Procedures

This page lists 30 maintenance procedures for fuel system (engine & cooling), drawn from HIT Srl's internal procedure library extracted from manufacturer service manuals.

HIT Srl supplies engine, fuel-system and cooling-circuit spare parts for this class of machine.

General guidance only — always follow the operation and maintenance manual for your specific machine.

Fuel System

• What should be done if Diesel Exhaust Fluid (DEF) contacts the eyes, skin, or is ingested?

  1. In case of eye contact, immediately flood eyes with large amounts of water for a minimum of 15 minutes.
  2. In case of skin contact, immediately wash skin with soap and water.
  3. If DEF is ingested, contact a physician immediately.

  Note: Do not allow Diesel Exhaust Fluid to contact the eyes; avoid prolonged contact with skin; do not swallow internally.

• Why must diesel fuel never be mixed with gasoline or alcohol?

  1. Never mix diesel fuel with gasoline, gasohol and/or alcohol.

  Note: This practice creates an extreme fire hazard and may cause an explosion which could result in serious injury or death.

• Under what condition should diesel fuel refuelling be carried out?

  Periodicity: at the end of each work shift

  1. Fill up with diesel fuel at the end of each work shift.
  2. Be sure there are no sparks, flames, or other ignition sources present when refuelling.

  Notes:

  • A deadly explosion can result if proper precautions are not taken.
  • Do not do any welding or have oxyhydrogen welding flames near the fuel tank.

• What is the correct procedure to drain and clean the diesel fuel sump?

  1. Unscrew the cap on the bottom of the sump to drain off condensation and impurities.
  2. Allow the water to drain out until the diesel fuel runs clean.
  3. For cleaning, periodically unscrew the cap on the bottom of the sump to drain off condensation, impurities and washing detergent.

  Note: Draining could be easier after the machine has been at a standstill for some time, because condensation water tends to collect on the bottom of the sump.

• What is the correct sequence to replace the engine fuel filter?

  1. Remove the fuel filter using the appropriate wrench.
  2. Carefully clean the cartridge seat on the support, and remove the sealing gasket if present.
  3. Lubricate the new filter's seal with clean engine oil.
  4. Screw the new filter on by hand until the gasket contacts the sealing surface.
  5. Tighten by hand a further 1/2 to 3/4 turn, no more.

  Notes:

  • Do not fill the new filter with fuel before fitting it, as this risks impurities entering the system.
  • Over-tightening the filter can break the gaskets and strip the threads.
  • After removing the fuel filters, it may be necessary to bleed air from the fuel system.

• What is the correct sequence to bleed air from the fuel system?

  Needed after replacing the fuel filter, after refuelling from empty, or whenever air has entered the circuit.

  1. Place a collection container under the filter and pre-filter.
  2. Confirm the engine is running.
  3. Open the air bleed screw on the fuel filter support.
  4. Repeatedly operate the fuel hand pump (fitted beside the fuel filter) until fuel free of air comes out.
  5. Retighten the bleed screw while fuel is still flowing out.
  6. Give the pump another 15-20 strokes.
  7. Check there are no leaks from the system.

  Notes:

  • If the engine stops due to lack of fuel (with air entering the lines), loosen the fittings of at least two injectors, simulate starting, and retighten the fittings once bled.
  • These operations must be carried out by suitably trained and qualified personnel.

• How is the water/fuel separator drained, and how often?

  Periodicity: every 100 hours

  1. Stop the engine.
  2. Place a container under the separator.
  3. Unscrew drain valve "3" at the bottom of the separator.
  4. Let the water and impurities drain out until clear fuel appears.
  5. Screw the drain valve back in.

  Notes:

  • Do not over-tighten the drain valve, to avoid damaging the thread.
  • After switching off the engine, wait a few hours before cleaning the separator.

• What is the correct sequence to replace the water/fuel separator's filter cartridge?

  Replaced at the same time as the fuel filter.

  1. Stop the engine, or close the tap before the filter if fitted.
  2. Place a container under the separator.
  3. Unscrew the drain valve and the container, and empty it.
  4. Unscrew and change the filter.
  5. Check the new filter is perfectly clean and the gasket is undamaged and well lubricated, then screw on by hand.
  6. Refit the container and the drain valve.
  7. Confirm the drain valve is closed, and close the tap before the filter if fitted.
  8. Bleed the circuit, then start the engine and check for leaks.

  Notes:

  • Do not over-tighten the drain valve, to avoid damaging the thread.
  • After switching off the engine, wait a few hours before cleaning the separator.

• What is the correct sequence to drain sediment from the fuel tank?

  1. Place a container under the tank.
  2. Unscrew the drain plug "S" and let some fuel flow out to drain any impurities or condensation water in the tank.

  Note: If the tank is emptied completely, bleed the fuel system afterward.

• What is the correct sequence to replace the fuel level sensor?

  1. Put the machine in service position.
  2. Separate the connector and release the cable.
  3. Unscrew the sensor.
  4. Screw a new sensor into place, join the connector and fix the cable with a tie wrap.

  Note: The sensor sends a voltage signal proportional to fuel level; an alarm is shown in the display if fuel level is below 15% for more than 40 seconds.

• How is condensation drained from the fuel sump?

  Draining is easier after the machine has been at a standstill for some time, since condensation water tends to collect on the bottom of the sump.

  1. Unscrew the cap on the bottom of the sump to drain off condensation and impurities.
  2. Allow the water to drain out until the diesel fuel runs clean.

  Notes:

  • Never use open flames or smoke near the fuel system, due to explosion hazard.
  • Dispose of drained liquids in accordance with anti-pollution regulations.

• How is the fuel sump cleaned?

  1. Unscrew the cap on the bottom of the sump.
  2. Drain off the condensation, impurities and washing detergent.

• What is the correct sequence to bleed the fuel system?

  1. Clean the area around the bleeder nipples on the fuel filter's bracket and cylinder head.
  2. Place a receptacle under the fuel filter.
  3. Connect a transparent plastic hose to the bleeder nipple on the filter bracket, placing the other end in the collection container.
  4. Open the bleeder nipple on the filter bracket.
  5. Pump up fuel with the hand pump until clean fuel free of air bubbles flows out of the hose.
  6. Transfer the hose to the bleeder nipple on the cylinder head and bleed in the same way as at the fuel filter.

  Note: If only the fuel filter has been changed, no further bleeding is required.

• How is the metal filter in the fuel supply line cleaned?

  1. Use hose pliers to stop the fuel flow to the fuel filter.
  2. Disconnect the hose at its attachments (inlet and supply line).
  3. Blow the hose clean with compressed air.

• What is the correct sequence to change the fuel pre-filter?

  1. Put the machine in service position.
  2. Place a receptacle under the fuel pre-filter.
  3. Clean the area around the fuel pre-filter.
  4. Drain the fuel pre-filter of fuel and water: open the drain valve on the underside, and close it when the filter is empty.
  5. Disconnect the wiring from the sensor for water in fuel.
  6. Remove the fuel pre-filter with the filter tool.
  7. Transfer the water trap to the new fuel pre-filter.
  8. Lubricate the O-ring on the new fuel pre-filter with engine oil.
  9. Fit the new fuel pre-filter, tightening to contact and then another half to three-quarter turn.
  10. Connect the wiring to the sensor for water in fuel.
  11. Turn on the main electrical power and start the engine, checking that the filter seals tight.
  12. Turn off the engine and remove the receptacle, handling the fuel as environmentally hazardous and inflammable waste.

  Notes:

  • Avoid skin contact with fuel; use gloves, since fuel on hands may cause rashes and irritation.
  • Pay attention to fire hazard when working on the fuel system; avoid changing the fuel pre-filter when the engine is hot, since fuel may spill on hot surfaces and ignite.

• How is condensation water drained from the fuel pre-filter?

  Periodicity: The fuel pre-filter should be drained of water every 50 operating hours.

  1. Put the machine in service position.
  2. Place a receptacle under the fuel pre-filter.
  3. Open the drain valve on the underside and let the condensation water drain, closing the valve once clean fuel drains with no water bubbles.
  4. Remove the receptacle, handling the fuel as environmentally hazardous and inflammable waste.

  Notes:

  • Avoid skin contact with fuel; use gloves.
  • Wait a few hours for the engine to cool down before draining condensation water.
  • Pay attention to fire hazard when working on the fuel system.

• What is the correct sequence to change the fuel filter on one engine alternative?

  Applies to one engine alternative; a different engine alternative uses a separate fuel filter change procedure, described separately.

  1. Put the machine in service position.
  2. Place a receptacle under the fuel filter.
  3. Clean the area around the fuel filter.
  4. Remove the fuel filter with the filter tool.
  5. Lubricate the O-ring on the new fuel filter with engine oil.
  6. Fit the new fuel filter, tightening to contact and then another half to three-quarter turn.
  7. Bleed the fuel system.
  8. Turn on the main electrical power and start the engine, checking that the fuel filter seals tight.
  9. Turn off the engine and remove the receptacle, handling the fuel as environmentally hazardous and inflammable waste.

  Notes:

  • Avoid skin contact with fuel; use gloves.
  • Do not fill the new fuel filter with fuel before installing, to avoid impurities entering the fuel system.
  • Pay attention to fire hazard; avoid changing the fuel filter when the engine is hot.

  Confirmed across independent manufacturers’ manuals.

• What is the correct sequence to change the fuel filter on the other engine alternative?

  Applies to a different engine alternative than the one described separately for fuel filter changes.

  1. Put the machine in service position.
  2. Place a receptacle under the fuel filter.
  3. Clean the area around the fuel filter.
  4. Disconnect the wiring from the sensor for water in fuel.
  5. Remove the fuel filter with the filter tool.
  6. Change the seal at the filter's threaded connection on the filter holder and lubricate it with engine oil.
  7. Fill the new fuel filter with pure fuel.
  8. Lubricate the seal on the new fuel filter with engine oil.
  9. Fit the new fuel filter, tightening to contact and then another half to three-quarter turn.
  10. Turn on the main electrical power and start the engine, checking that the fuel filter seals tight.
  11. Turn off the engine and remove the receptacle, handling the fuel as environmentally hazardous and inflammable waste.

  Notes:

  • Avoid skin contact with fuel; use gloves.
  • Pay attention to fire hazard; avoid changing the fuel filter when the engine is hot.

  Confirmed across independent manufacturers’ manuals.

• What is the correct sequence to drain water from the fuel tank?

  1. Remove the drain plug to drain any water from the fuel tank.
  2. Refit the drain plug immediately once the flow of fuel is free from water and other impurities.

• What is the correct sequence to change the fuel filters?

  1. Clean the outsides of the filters.
  2. Remove the filters and discard them.
  3. Clean the filter head.
  4. Check that the new filters are perfectly clean and that the seals are in good condition.
  5. Fit the new filter canisters and tighten them by hand until the seal is in contact with the seating surface, then tighten a further half a turn.

• What is the correct sequence to bleed the fuel system on one engine alternative?

  Applies to one engine alternative; a different engine alternative uses a separate bleeding procedure, described separately. The fuel system must be bled if the fuel tank has been run dry or after long periods of operation.

  1. Put the machine in service position.
  2. Place a container under the fuel pre-filter.
  3. Open the air bleeder screw on the fuel filter.
  4. Pump with the hand pump until the flowing fuel is free from air (if only the fuel filter is changed, no further bleeding is necessary).
  5. Close the screw once clean, air-free fuel flows out.
  6. Wipe off the fuel pre-filter and remove the collection container.

  Note: The fuel system operates at very high pressure; use protective gloves and safety goggles and avoid skin contact with fuel.

• What is the correct sequence to bleed the fuel system on the other engine alternative?

  Applies to a different engine alternative than the one using the hand-pump bleeder-screw method described separately. The fuel system must be bled after fuel filter replacement, if the fuel tank has been run dry, or after long periods of operation.

  1. Put the machine in service position.
  2. Open the bleed screw.
  3. Turn the hand pump anticlockwise to open the pump.
  4. Pump until the fuel is completely free of air bubbles.
  5. Tighten the bleed screw and close the fuel hand pump.
  6. Start the engine and check sealing.

  Note: The fuel system operates at very high pressure; use protective gloves and safety goggles and avoid skin contact with fuel.

• What is the correct sequence to clean the fuel tank?

  1. Put the machine in service position.
  2. Empty the fuel tank of fuel using a pumping device.
  3. Remove the drain plug from the fuel tank.
  4. Rinse the fuel tank clean through the fuel filler hole.
  5. Reinstall the drain plug.

• What is the correct sequence to drain condensation water from the fuel pre-filter on one engine alternative?

  Applies to one engine alternative; the other engine alternative uses a separate procedure, described separately.

  Periodicity: Every 50 operating hours.

  1. Put the machine in service position.
  2. Place a container under the fuel pre-filter.
  3. Open the drain valve on the underside of the filter and let the water drain, closing the valve once clean fuel flows out.
  4. Wipe off the fuel pre-filter and remove the collection container.

• What is the correct sequence to drain condensation water from the fuel pre-filter on the other engine alternative?

  Applies to a different engine alternative than the one using the simpler drain-only procedure described separately.

  Periodicity: As necessary, or at least every 50 operating hours.

  1. Put the machine in service position.
  2. Place a container under the fuel pre-filter.
  3. Open the drain valve on the underside of the filter and let the water drain, closing the valve once clean fuel flows out.
  4. Close the drain cock by pushing the valve up and tightening it by hand.
  5. Bleed the fuel system.
  6. Wipe off the fuel pre-filter and remove the collection container.
  7. Start the engine and check sealing.

  Note: Do not over-tighten the drain cock, as the threads may be damaged.

• What is the correct sequence to change the fuel pre-filter on one engine alternative?

  Applies to one engine alternative; the other engine alternative uses a separate procedure, described separately.

  1. Put the machine in service position.
  2. Place a container under the fuel pre-filter.
  3. Drain the fuel pre-filter of fuel and water through the drain valve on the underside, closing it once the filter is empty.
  4. Disconnect the wiring from the water-in-fuel sensor.
  5. Remove the water-in-fuel sensor from the filter insert.
  6. Remove the fuel filter with the filter removal tool.
  7. Install the water-in-fuel sensor on the new fuel pre-filter.
  8. Fill the fuel pre-filter with clean fuel.
  9. Lubricate the O-ring on the new fuel filter with engine oil.
  10. Install the new fuel pre-filter, tightening to contact and then an additional one-half to three-quarter turn.
  11. Connect the line supply to the water-in-fuel sensor.
  12. Wipe off the fuel pre-filter and remove the collection container.
  13. Turn on the system voltage and start the engine, checking that the filter seals tight.

  Note: The fuel system is sensitive to impurities; only use new fuel from a clean container to reduce the risk of impurities in the fuel system.

• What is the correct sequence to change the fuel pre-filter on the other engine alternative?

  Applies to a different engine alternative than the one using the sensor-equipped fuel pre-filter described separately.

  1. Put the machine in service position.
  2. Open the drain cock and drain any water.
  3. Remove the filter cartridge.
  4. Check that the new filter cartridge is absolutely clean and that the gasket is intact, brushing a small amount of oil onto the gasket.
  5. Screw the filter cartridge onto the filter bracket.
  6. Bleed the fuel system.
  7. Start the engine and check sealing.

• What is the correct sequence to remove the fuel tank?

  It is not necessary to perform these steps in the exact order listed, but all disconnecting procedures must be completed before hoisting the fuel tank clear of the frame.

  1. Provide a suitable container to catch the fuel, and remove the drain plug to release the fuel from the fuel tank.
  2. Disconnect all fuel hoses from the tank.
  3. Remove the access panel by removing its bolts and washers.
  4. Remove the bolts and washers that release the tank from its seat.
  5. Carefully remove the fuel tank to a prepared storage area.

• What is the correct sequence to install the fuel tank?

  Install by reversing the removal procedure.

  1. If the tank is being replaced, transfer the elbow fittings to the new tank.
  2. Reverse the removal procedure to fit the tank, panel, and hoses.
  3. Apply the proper torque values from the manual's torque table.

• What fuel-system operations are checked during the 500-hour Type A preventive maintenance service?

  There are four preventive maintenance cards (A, B, C, D) covering the machine's complete maintenance plan, on a 500-hour frequency, cycling in the order B-A-B-C-B-A-B-C-B-D before repeating. Service times assume normal operating conditions and may vary with type of use, road surface, and environment.

  1. Clean the fuel pump's small filter cup.
  2. Change the fuel filter(s).
  3. Clean the fuel intake filter.

  Note: Maintenance must be carried out only by qualified, authorised personnel, working in conditions of maximum safety.

Looking for general maintenance tips and checklists? See Engine & Cooling.