Tractor engine fuel system – Test and inspect


Fuel System - Inspect

A problem with the components that transport fuel to the tractor engine can cause low fuel pressure. This can decrease engine performance. Check the fuel level in the fuel tank. Ensure that the vent in the fuel cap is not filled with dirt. Check all fuel lines for fuel leakage. The fuel lines must be free from restrictions and faulty bends. Verify that the fuel return line is not collapsed.
Install new fuel filters. Cut the old filter open with a suitable filter cutter. Inspect the filter for excess contamination. Determine the source of the contamination. Make the necessary repairs. Operate the hand priming pump (if equipped). If excessive resistance is felt, check that there is fuel in the fuel return line to the tank.

Air in Fuel - Test

This procedure checks for air in the tractor engine fuel system. This procedure also assists in finding the source of the air. Examine the fuel system for leaks. Check the fuel level in the fuel tank. Air can enter the fuel system on the suction side between the fuel transfer pump and the fuel tank.
Install a suitable fuel flow tube with a visual sight gauge in the fuel return to tank line. When possible, install the fuel flow tube in a straight section of the fuel line that is at least 304.8 mm (12 inches) long. Do not install the fuel flow tube near the following devices that create turbulence:
• Elbows
• Relief valves
• Check valves
Observe the fuel flow during engine cranking. Look for air bubbles in the fuel. If there is no fuel that is present in the fuel flow tube, prime the fuel system.  If the tractor engine starts, check for air in the fuel at varying engine speeds. When possible, operate the engine under the conditions which have been suspect.


(1) A steady stream of small bubbles with a diameter of approximately 1.60 mm (0.063 inch) is an acceptable amount of air in the fuel.
(2) Bubbles with a diameter of approximately 6.35 mm (0.250 inch) are also acceptable if there is two seconds to three seconds intervals between bubbles.
(3) Excessive air bubbles in the fuel are not acceptable.

If excessive air is seen in the fuel flow tube in the fuel return line, install a second fuel flow tube at the inlet to the fuel transfer pump. If a second fuel flow tube is not available, move the fuel flow tube from the fuel return line and install the fuel flow tube at the inlet to the fuel transfer pump. Observe the fuel flow during engine cranking. Look for air bubbles in the fuel. If the diesel engine starts, check for air in the fuel at varying engine speeds.
If excessive air is not seen at the inlet to the fuel transfer pump, the air is entering the system after the fuel transfer pump. If excessive air is seen at the inlet to the fuel transfer pump, air is entering through the suction
side of the fuel system. To avoid damage, do not use more than 55 kPa (8 psi) to pressurize the fuel tank.
Pressurize the fuel tank to 35 kPa (5 psi). Do not use more than 55 kPa (8 psi) in order to avoid damage to the fuel tank. Check for leaks in the fuel lines between the fuel tank and the fuel transfer pump. Repair any leaks that are found.
If the source of the air is not found, disconnect the supply line from the fuel tank and connect an external fuel supply to the inlet of the fuel transfer pump. If this corrects the problem, repair the fuel tank or the stand pipe in the fuel tank.

Finding Top Center Position for No.1 Piston

Remove the front cover. Use Tooling in order to rotate the crankshaft until the hole (X) in the camshaft gear (1) aligns with the hole in the front housing.


Install Tooling through the hole (X) in the camshaft gear (1) into the front housing. Use Tooling in order to lock the camshaft in the correct position.


Remove the plug (4) from the cylinder block. Install Tooling into the hole (Y) in the cylinder block. Use Tooling in order to lock the crankshaft in the correct position.

Fuel Injection Timing - Check

• Removal of the fuel injection pump
• The bolts that hold the fuel injection pump to the front housing are loosened.
Set the number one piston at the top center piston on the compression stroke.
Carefully remove the fuel injection pump from the front housing..

To check the fuel injection pump timing

Position Tooling onto the shaft (8) of the fuel injection pump. Align the lever of Tooling with the key slot (7). Engage the lever into the key slot.
Insert the locking pin of Tooling into the hole (6) in fuel injection pump. If the locking pin can be inserted into the hole, the fuel injection pump timing is correct. If the locking pin cannot be inserted into the hole, the fuel injection pump timing is not correct. If the fuel injection pump timing has been lost follow Steps in order to reset the fuel injection pump timing.
If necessary, loosen the locking screw (4) on the fuel injection pump. Slide the spacer (5) into position (X). Tighten the locking screw (4) to a torque of 9 N·m (80 lb in). This will prevent the locking screw from tightening against the shaft (8). The fuel injection pump is now unlocked. Position Tooling onto the shaft (8) of the fuel injection pump. Align the lever of Tooling with the key slot (7) in the fuel injection pump. Engage the lever into the key slot.
Use the lever of Tooling to rotate the shaft (8) until the pin of Tooling can be engaged into the hole (6). Engage the pin of Tooling into the hole.
Loosen the locking screw (4) in the fuel injection pump. Slide the spacer (5) into position (Y). Tighten the locking screw (4) against the shaft of the fuel injection pump to a torque of 9 N·m (80 lb in). The fuel injection pump is now locked. Remove Tooling. Reinstall the fuel injection pump to the front housing.  

Diesel Engine Fuel System - Prime

Do not crank the tractor engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again. If air enters the fuel system, the air must be purged from the fuel system before the tractor engine can be started. Air can enter the fuel system when the following events occur:
• The fuel tank is empty or the fuel tank has been partially drained.
• The low pressure fuel lines are disconnected.
• A leak exists in the low pressure fuel system.
• The fuel filter has been replaced.

Hand Fuel Priming Pump

Use the following procedures in order to remove air from the fuel system:
Ensure that the fuel system is in working order. Restore the fuel supply.


Operate the fuel priming pump (1). Count the number of operations of the fuel priming pump. After 100 depressions of the fuel priming pump stop.
The tractor engine fuel system should now be primed and the engine should now be able to start. Do not loosen the high pressure fuel line in order to purge air from the fuel system. This procedure is not required. Operate the diesel engine starter and crank the engine. After the engine has started, operate the engine at low idle for a minimum of five minutes, immediately after air has been removed from the fuel system.  Operating the engine for this period of time will help ensure that the fuel system is free of air. After the engine has stopped, you must wait for 60 seconds in order to allow the fuel pressure to be purged from the high pressure fuel lines before any service or repair is performed on the engine fuel lines. If necessary, perform minor adjustments.
Repair any leaks from the low pressure fuel system and from the cooling, lubrication or air systems. Replace any high pressure fuel line that has leaked. If you inspect the engine in operation, always use the proper inspection procedure in order to avoid a fluid penetration hazard.

Electric Fuel Priming Pump

Ensure that the fuel system is in working order. Restore the fuel supply.
The electric fuel priming pump will operate for 90 seconds. If necessary the electric fuel priming pump can be stopped during the 90 seconds of operation, by operation of the switch.
Turn the keyswitch to the “RUN” position. Operate the switch for the electric priming pump. After 90 seconds of the electric fuel priming pump operation the fuel system will be primed and the electric fuel priming pump will turn off.
The diesel engine should now be able to start. Do not loosen the high pressure fuel line in order to purge air from the fuel system. This procedure is not required.
Operate the engine starter and crank the engine. After the engine has started, operate the engine at low idle for a minimum of five minutes, immediately after air has been removed from the fuel system.
Operating the tractor engine for this period of time will help ensure that the fuel system is free of air. After the engine has stopped, you must wait for 60 seconds in order to allow the fuel pressure to be purged from the high pressure fuel lines before any service or repair is performed on the engine fuel lines. If necessary, perform minor adjustments. Repair any leaks from the low pressure fuel system and from the cooling, lubrication or air systems. Replace any high pressure fuel line that has leaked. If you inspect the engine in operation, always use the proper inspection procedure in order to avoid a fluid penetration hazard.