840898A 3 Mercruiser GEAR SET, (16/19)

High Fuel Pressure
Excessive fuel pressure can cause fuel filter gaskets to rupture. The following conditions can cause high fuel pressure:
Plugged orifices in the fuel pressure regulating valve
Stuck fuel metering valve in the fuel transfer pump
Pinched fuel return lineChecking Fuel Pressure
Table 1
Required Tools
Part Number Part Name Quantity
1U-5470
or
198-4240 Engine Pressure Group
or
Digital Pressure Indicator 1
Illustration 1 g00293196
1U-5470 Engine Pressure Group
Refer to Special Instruction, SEHS8907, "Using The 1U-5470 Engine Pressure Group" for more information. Refer to Operating Manual, NEHS0818, "Using the 198-4240 Pressure Indicator Tool Group" for more information.
Fuel leaked or spilled onto hot surfaces or electrical components can cause a fire. Clean up fuel spills immediately.
Keep all parts clean from contaminants.Contaminants may cause rapid wear and shortened component life.
Care must be taken to ensure that fluids are contained during performance of inspection, maintenance, testing, adjusting, and repair of the product. Be prepared to collect the fluid with suitable containers before opening any compartment or disassembling any component containing fluids.Refer to Special Publication, NENG2500, "Dealer Service Tool Catalog" for tools and supplies suitable to collect and contain fluids on Cat® products.Dispose of all fluids according to local regulations and mandates.
Use the following procedure in order to measure the fuel pressure that is after the secondary filter:Note: Fuel pressure readings near the fuel supply manifold have pressure spikes. The pressure spikes are caused by excess fuel that is returning to the fuel system from the injectors. Excessive needle movement at the gauge may be present. Connect the gauge with a section of suitable hose. The air in the hose absorbs the spikes, achieving an average reading and a steady needle. Keep the gauge above the measuring point.
Illustration 2 g03117257
C9.3B fuel filter base
(1) Input fuel
(2) Output fuel
(3) Fuel pressure sensor/ Test port
Install the 1U-5470 Engine Pressure Group into port (3). This port is the proper test port.
Adjust the engine speed to 1800 rpm with no load.
The fuel pressure should be 586 kPa (85 psi) nominal. Record the pressure.
If excessive pressure is found, check the conditions that are listed previously under the "High Fuel Pressure" heading.
Illustration 3 g06258438
C9.3B fuel transfer pump mounted on the high-pressure fuel pump
Illustration 4 g06258445
C9.3B fuel transfer pump
(4) Low-pressure fuel inlet
(5) Low-pressure fuel outlet
(6) Pressure regulating valve
Use the following procedure to check the output of the fuel transfer pump:
Remove the fuel line (4).
Tee the 1U-5470 Engine Pressure Group into the port that contained the fitting for the fuel line (5) .
Adjust the engine speed to 600 rpm with no load.
The fuel pressure should be 690 kPa (100 psi) to 724 kPa (105 psi).
If the fuel pressure is within the specified range, proceed to Step 3.
If the pressure is less than 655 kPa (95 psi), the fuel transfer pump is weak. The fuel metering valve (6) in the pump may be stuck or worn. Remove the fuel metering valve, the spring, and the pin. Inspect the fuel metering valve. If contamination is not found, and the fuel metering valve is worn out, replace the fuel transfer pump. If dirt is found, clean the valve assembly and reinstall the valve assembly.
Check the fuel pressure again. Replace the fuel transfer pump if the fuel pressure still measures less than 655 kPa (95 psi). The fuel transfer pump is operating properly if the fuel pressure measures at least 690 kPa (100 psi) to 724 kPa (105 psi).
Once the fuel transfer pump has been confirmed as properly operating, check the fuel pressure again after the secondary fuel filter base. Refer to Step 1. If the fuel pressure is not at the nominal specification, continue to Step 3.
Illustration 5 g06258450
C9.3 fuel manifold
(7) Fuel pressure regulating manifold
(8) Return line from the cylinder head (Input)
(9) Return to tank (output)
(10) Fuel rail pres