3H6-00021-0 Tohatsu PISTON PIN

Fuel System Inspection
A problem with the components that send fuel to the engine can cause low fuel pressure. This can decrease engine performance.
Illustration 1 g00435718
Fuel System (1) Fuel inlet port (fuel transfer pump). (2) Tube assembly (fuel filter to fuel gallery). (3) Tube assembly. (4) Pressure regulator. (5) Tube assembly (fuel transfer pump to fuel filter). (6) Fuel filter. (7) Tube assembly.
Check the fuel level in the fuel tank. Inspect the cap for the fuel tank. Make sure that the vent is not filled with dirt.
Check the fuel lines for fuel leakage. Make sure that none of the fuel lines have a restriction or a defective bend.
Clean the screen inside the inlet fitting of the fuel transfer pump.
Make sure that the pressure regulator (4) is installed correctly, and make sure that the regulator functions properly.Checking Engine Cylinders Separately
Low temperature at an exhaust manifold port is an indication of no fuel to the cylinder. This can possibly be an indication of an injector with a defect. An extra high temperature at an exhaust manifold port can be an indication of too much fuel to the cylinder. High temperatures may also be caused by an injector with a defect.Refer to Testing And Adjusting, "Measurement of Exhaust Temperature" for the procedure for checking the temperatures in the exhaust manifold port.Start Up Procedure
Note: Refer to Operation and Maintenance Manual, "Engine Starting" in the Operation Section .Consider the following precautions before starting the engine after work has been done on the fuel system. Make sure that you use this starting procedure to start the engine only after the fuel system has been worked on:
Disconnect the air inlet system from the turbocharger.
Be careful when placing the steel plate against the opening on the turbocharger air inlet. To avoid crushed fingers, do not position fingers between the steel plate and the opening on the turbocharger air inlet. Due to excessive suction, the plate can be forcefully pulled against the opening on the turbocharger air inlet.
Another person will need to help as a precautionary step. This person should be ready to use the steel plate to cover the turbocharger air inlet if a problem occurs.Note: Make sure that the steel plate is large enough to cover the entire turbocharger air inlet.
Start the engine.Immediately place the steel plate against the opening on the turbocharger air inlet, if the engine operates in one of the following ways:
The engine runs too fast.
The engine runs out of control.Covering the opening will stop the air supply to the engine, so the engine will stop.Fuel Pressure
Table 1
Tools Needed    
Part Number     Part Name     Quantity    
1U-5470     Engine Pressure Group     1    
3Y-2888     Connector     1    
3J-1907     O-Ring Seal     1    Note: Both the 5P-2720 Probe Adapter Group and the 5P-2718 Pressure Probe can be used with these tools. Use these additional tools to allow the future installation of pressure probes.The 1U-5470 Engine Pressure Group can be used in order to check the engine's fuel pressures.
Illustration 2 g00284796
1U-5470 Engine Pressure Group (1) Pressure indicators. (2) Zero adjustment screw. (3) Pressure indicator. (4) Pressure tap. (5) Pressure indicator.This group has a gauge that is used to register the pressure in the fuel manifolds. Instructions for using this group appear in Special Instruction, SEHS8907.
Illustration 3 g00435719
(1) Tube assembly (fuel transfer pump to fuel filter). (2) Tube assembly (fuel filter to fuel gallery). (3) Fitting (fuel return to tank). (4) Regulating orifice and check valve. (5) Cylinder head. (6) Fuel gallery. (7) Fuel outlet port.
Illustration 4 g00435720
(8) Fuel pressure tap (unfiltered tap). (9) Fuel filter base. (10) Fuel pressure tap (filtered tap).During both normal operating conditions and load conditions, the fuel pressure should register the following range:
400 to 525 kPa (58 to 76 psi)At low idle, the fuel pressure at the fuel filter's inlet should be at the following amount:
400 to 435 kPa (58 to 63 psi)The fuel pressure to fuel gallery (6) should be the same amount, if you subtract the change in pressure (delta P ) across the filter. With a new filter, the pressure drop across the fuel filter typically registers the following amount:
35 kPa (5 psi)As deposits collect on a fuel filter, the pressure differential will increase. If the fuel pressure in fuel gallery (6) decreases to approximately 69 kPa (10 psi), misfiring may occur.Fuel pressure regulating orifice (4) is mounted at the fuel return port at the rear of the fuel gallery in the cylinder head. The fuel pressure regulating orifice maintains fuel pressure at low engine rpm. The regulating orifice also contains a spring loaded check valve. The spring loaded check valve prevents the fuel from draining from the fuel gallery back to the fuel tank after engine shutdown.To check the unfiltered fuel pressure, follow this procedure:
Remove th