2012/11/14 Caterpillar

Generator Set:

C175-16 (S/N: WYB1-UP)

Engine News SEBD9706, 11 May 2011, "A Check Valve Is Released for Use with C175-16 Generator Set Fuel Systems". The original article has been revised in order to announce that a new check valve is now installed on the engine at the factory. The check valve and the O-ring seals for the valve are available for installation on engines that were built without the valve.

Description of Change: The check valve prevents fuel from draining back into the tank in order to help maintain the fuel prime for the engine. The valve is critical for installations with fuel tanks below the level of the engine.

Adaptable To: The check valve is adaptable to the above engines back to first production.

The check valve is effective with WYB01183.

Illustration 1	g03246700
(1) 398-1860 Check Valve Gp (2) 228-7105 O-Ring Seal (3) 228-7092 O-Ring Seal

The new 398-1860 Check Valve Gp is part of the 399-8681 Fuel Lines Plug Gp .

The check valve is installed in the fuel return outlet of the 326-1426 Fuel Manifold Gp .

Check valve (1) and O-ring seals (2) and (3) are serviceable parts.

If you are retrofitting the check valve, remove the 8T-7492 Connector from the 326-1426 Fuel Manifold Gp. Install the check valve in place of the connector. Refer to Illustration 2.

Illustration 2	g03250236
(4) 8T-7492 Connector

Application of the Check Valve

ReferenceSpecial Instruction, REHS4726, "Calculations for Required Inlet Pressure and Back Pressure of the Fuel on C175 Engines that are Utilizing a Day Tank or Standby Application"

In some installations with the engine fuel supply from a day tank, the excess engine fuel return drains into the main tank. If the day tank is higher than the main tank, there can be a difference in static fuel pressure. The pressure can cause fuel from the engine and from the day tank to drain into the main tank. The draining fuel could lead to a loss of prime and to hard starting.

A check valve in the return line with 35 ± 20 kPa (5 ± 3 psi) of cracking pressure will prevent leakage without creating a significant amount of restriction. For a diagram of the installation, refer to Illustration 3.

For additional information on inlet pressure and back pressure for the fuel system, refer to the publication that is referenced above.

Illustration 3	g02548176
(A) 1.524 m (5 ft) (1) Day tank (2) Ball valve (3) C175 Engine (4) Fuel return (5) Check valve (6) Fuel supply (7) Fuel pump for the day tank supply (8) Main fuel tank (B) 9.144 m (30 ft)