KOMAI Fuel Filter & Water Separator 500FG / 900FG / 1000FG — Installation, Operation & Maintenance Guide

【KOMAI Exclusive Original Content】
If an engine is equipped with a fuel purification system, a water separation system, a fuel heating system, and a maintenance-alert system, it will operate at its best.
This is exactly what the Racor Turbine Series delivers.

The 500 / 900 / 1000FH Turbine Series Fuel Filter & Water Separator efficiently removes water from diesel fuel while filtering out harmful contaminants such as solid particles, rust, microorganisms, varnish, and asphaltenes.
By ensuring cleaner fuel, it provides reliable protection for the engine’s entire fuel injection system and helps maintain stable performance, longer component life, and reduced maintenance downtime.

The fuel purification process can be summarized into three key stages:
separation, coalescence, and filtration.

When fuel flows through the turbine section of the filter, the centrifugal force separates larger particulates and water droplets from the fuel. Since water is heavier than fuel, these droplets settle at the bottom of the collection bowl.

Smaller water droplets then coalesce on the inner wall of the bowl and on the surface of the filter element. As they merge into larger droplets and reach sufficient weight, they too fall into the bottom of the bowl.

The filter media, Aquabloc® II, is engineered with excellent water-repellent properties — water not only cannot pass through it, but also cannot adhere to the surface. Meanwhile, solid contaminants ≥2 microns are effectively captured.
Thanks to Aquabloc® II technology, the filter element delivers a longer service life and higher filtration efficiency.

The Turbine Series fuel filters should be installed on the suction (vacuum) side of the fuel pump within the fuel system for optimal performance. The mounting bracket features a single-bolt band-style clamp with adjustable mounting dimensions.
For the 900FH Series, a single tightening clamp is used, while the 1000FH Series uses two tightening clamps for enhanced stability.
The clear collection bowl allows operators to easily inspect water and sediment levels inside.

● Installation Preparation for 900 & 1000FH Turbine Series Fuel Filters

Before installation, ensure all components are properly cleaned. Prepare approximately 4 liters of clean fuel, as well as sealing materials, lubricants, fuel hoses, connection fasteners, and inlet/outlet fittings.

During installation, the filter should be mounted as vertically as possible.
If the tilt angle exceeds 10 degrees, overall system performance may be adversely affected.

The filters should be stored and installed in a well-ventilated, well-lit, and easily accessible area to facilitate safe maintenance. Installation must only be performed after the engine has been shut down. Do not install the unit in any location where smoke, sparks, or fire hazards may be present.

Ensure the fuel line is smooth and unrestricted. During installation, the filter should be positioned horizontally between the bottom level of the fuel tank and the inlet of the fuel pump.
If the filter must be mounted below the fuel tank bottom, a shut-off valve must be added on the inlet side of the filter to facilitate safer and easier filter element maintenance.

900 & 1000FH Series Fuel Filter Installation

Installation Instructions:

1. Determine a proper location for the filter between the fuel tank and the fuel pump, so that maintenance and element replacement can be carried out smoothly without removing other components or fuel lines.

2. Use fuel hoses with appropriate and larger diameters to ensure smooth fuel flow without restriction. Avoid small bending radius and hose twisting. Do not use 45-degree fittings; 90-degree elbow fittings are recommended instead.

3. During piping installation, secure the fuel lines to prevent abrasion, and keep them at a safe distance from exhaust pipes or other heat sources.
The drainage interval depends on the actual operating condition. Typically, check the water and contaminants level in the bowl, and drain before the fuel reaches the turbine section, or drain when prompted by the water sensor alarm.

Operation under negative pressure installation

Close the shut-off valve at the inlet side, loosen the drain screw on the bottom of the bowl, drain all water and contaminants, then tighten the drain screw. Excessive fuel drainage is not necessary.
Then proceed with fuel priming.

Operation under positive pressure installation

Loosen the drain screw on the bottom of the bowl to drain contaminants and water. Due to pressure, liquid may spray initially.
After drainage is complete, tighten the drain screw. Excessive fuel drainage is not necessary.

Element Replacement

The replacement interval depends on fuel contamination level. Typically replace the element every 500 working hours or 10,000 km.
When the differential pressure gauge (optional) shows more than 6–10 inHg, or during oil change, engine power drops, or first operation after long-term shutdown — the element must be replaced.
Only Racor Aquabloc® II original filter elements must be used.

Replacement Procedure

Bypass the filter.

Loosen the T-handle and remove the filter cover.

Pull the top handle of the element, twist and slowly remove the used element, and install a new one.

Replace the O-rings for the T-handle and filter cover, lubricating them with clean fuel or engine oil.

Follow the fuel priming procedure to fill the filter with clean fuel. Install the cover and hand-tighten the T-handle — do not use tools.

Different Racor installation configurations — on-panel, off-panel, and remote mounting — are compatible with water sensors.
All products are made from high-quality materials, fully tested, and 100% quality-guaranteed.

The electronic water detector analyzes resistance changes from the water sensor to determine water presence, issuing alarm or indication. It automatically resets after water is fully drained.

Installation of Optional Fuel Heater

This electrical device is only applicable to diesel filters.
In cold environments, the internal heater enables easier engine starting.
When fuel temperature is below 45°F (7°C), the thermostat activates the heater, and it automatically shuts off when the temperature reaches 85°F (29°C).

Water Sensor Installation Procedure

FH series filters can be optionally equipped with water sensors.
For non-water-sensor FH series models, water sensors must be used together with Racor electronic modules. Different modules may have different requirements:

Note: If the filter is installed above the fuel tank and fuel pump, fuel pressure can assist filling the filter with fuel.

Fuel Priming Procedure

1. Drain the bowl completely.

2. Remove the plug at the sensor port on the bottom of the bowl.

3. Lubricate the sensor O-ring and seals properly.

4. Install and tighten the water sensor into the bowl.

5. Connect the water sensor to the matching electronic module. For special requirements, refer to documentation provided.

6. Fill the filter with fuel.

7. Start the engine and check for leaks.

8. Loosen the T-handle and remove the filter cover.

9. Fill the filter with clean fuel.

10. Lubricate the O-rings on the T-handle and filter cover with clean fuel or engine oil.

11. Install the cover and hand-tighten the T-handle — do not use tools.

12. Refer to the equipment operation manual for related procedures.

13. Start the engine and check the fuel system for leaks.

14. Perform maintenance only after shutting down the engine and relieving fuel system pressure.

15. The heater prevents fuel from crystallizing or waxing inside the filter, allowing fuel to flow quickly through the element for easier starting.
    12V or 24V / 300W heaters are available. When the ignition key is turned ON, heating lasts for 1 to 5 minutes.
    If a heater needs to be installed, follow the instructions below:

16. The current for a 12V heater is 25A, and for a 24V heater is 13A. For safety, a relay must be used.
    Racor provides two relay models: Part No. RK11861 for 12V and RK11862 for 24V.
    These kits include the fuse holder and fuse. RK11862 also includes a resistor.
    The fuse rating is 25A for 12V and 15A for 24V.

17. A reliable switch must be used to control the heater relay.
    In summer, the relay power can be turned off.

18. All wiring specifications must comply with applicable standards.

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    Installation Requirements

20. The heater wiring must include both positive and negative terminals.

21. Connectors must be properly soldered and crimped to ensure reliable connection.

22. Route wiring properly to avoid damage or abrasion.

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    Diagnostic Procedure

24. Check the fuel level in the tank and ensure the valve is open.

25. Ensure the T-handle, bowl, and fuel system components are securely tightened. Check whether the outlet valve is closed.

26. If using a new Racor element, check the valve on the fuel tank and ensure the fuel strainer is not clogged.

27. Inspect each component based on the following conditions to identify abnormalities:

28. Selecting the correct FH filter model is essential.
    The maximum fuel flow rate must not exceed the filter’s rated capacity; otherwise, filtration efficiency decreases and air may be released from the fuel.

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    ● 900 & 1000FH Series Fuel Filter Troubleshooting

    A new filter must be fully primed with fuel.
    Follow the engine service manual during priming.

    Component failures are usually caused by improper initial installation, damaged parts, or fuel system issues, resulting in internal air ingress or external fuel leakage.
    Fuel leakage must be corrected immediately.
    Fuel leaks can cause engine performance problems such as hard starting, stalling, reduced power, or other related issues.

Filter elements are available in 2, 10, and 30-micron ratings. Selection should be based on operating conditions, fuel quality, maintenance schedule, and the working environment. The general principle is: the higher the filtration requirement, the finer the filter element, and the more frequently parts may need replacement; the dirtier the fuel, the more frequent the replacements.

When the system reaches a certain resistance, the filter is considered contaminated. The element will change color from brown to black or charred. In cases of microbial contamination, the element may be covered with a soft, sludge-like substance accompanied by an unpleasant odor. Such severe conditions must be addressed immediately.

The water level detected by the water sensor should be closely monitored by the operator. The quickest action is to drain the water.
Racor water detection components must work in coordination with the internal sensor. When the water reaches the sensor tip, the unit will signal an alert.
Water is detected when resistance reaches 4,700–10,000 ohms, depending on the detection unit. If this does not occur, the sensor tip may be covered with foul-smelling material. Remove the sensor and clean it with a cloth. Adjust the tip jumper, turn the ignition to ON, and check the system.
Failures often occur due to wiring connections, power supply, or other independent components.

The internal heater is intended for hot system starts, but may be used during cold starts. Maximum heating capacity is 300W and must be activated via a relay switch.
Startup current: 12V or 24V. The heater operates only when fuel temperature is below 7°C (45°F) and stops automatically when fuel reaches 29°C (85°F).

Heater testing can only be performed when fuel temperature is below 7°C and the thermostat is off. Use a voltmeter on external wiring with the engine off. Power output decreases when the heater is operating.
Note: To test, remove the heater, place it in a refrigerator until the temperature reaches 7°C, remove it, and repeat the above procedure.

All Racor FH filters are tested and 100% quality guaranteed, leak-free.
In case of malfunction or any issue affecting engine operation, immediately check for external fuel leaks. Quick checks can be performed as described above or by following previously outlined procedures.

Use the O-ring supplied by KOMAI filters (Part No. 500FG/900FG/1000FG) or an equivalent sealant. The O-ring should have a large contact surface, be intact in appearance, resilient, and capable of fitting into small gaps. Avoid using excessively soft O-rings.

Ensure the engine is shut off and all applicable valves are closed before installation.

Does fuel really need to be filtered?
Every time a vehicle is refueled, millions of tiny contaminants enter the fuel system. Even the strictest maintenance cannot completely prevent this. These particles are too small to see, yet large enough to damage injectors, fuel pumps, and reduce operational efficiency.

KOMAI has developed patented technology that removes water, dust, rust, and microorganisms from diesel fuel, establishing itself as a leading brand in fuel filtration and water separation.