Fuel Pump Disassembly and Reassembly (Units built before 01/01/2004

At scheduled preventative maintenance increments:

1.Check coolant hoses for deterioration. Hardened hoses may crack or be subject to rupture, particularly if thermostats hotter than 160-170 degrees F are used, or if hoses are located adjacent to an exhaust manifold. Also check all vacuum hoses. 2.The fuel vapor hose is located between the vaporizer/regulator and the carburetor. Remove the hose and check for undue deterioration.

Particularly check the vapor outlet fitting from the regulator for tightness. 3.Use a soap/water solution or leak detector solution on all fittings while engine is running. 4.If starting and idling have been consistently satisfactory, it should be unnecessary to disassemble the carburetor air valve from the bowl. If inconsistent, remove the air valve cover, spring and air valve with the diaphragm. Check the gas-metering valve and gas jet for accumulation of foreign deposits or greasy substance, and clean both with a brush and kerosene or equivalent solvent as needed.

Check the air valve diaphragm for integrity and flexibility. Hold the diaphragm up against a strong light to check for small tears or pinholes.

Normal life of the diaphragm and seat is 2,000 hours, barring excessive backfiring or similar abnormalities. When reinstalling the air-gas valve assembly in the bowl, mixer models CA100,

CA125 and CA225 require reinstallation of the gas-metering valve in position with two gas valve slots opposing the gas inlet flow. This is for ideal air-fuel distribution. 5.With the carburetor air-gas valve and cover removed, it is a simple matter to check the converter and fuel lock for leaks. The following checks should indicate each component is operating properly. • Turn fuel on at the tank and check carburetor open gas jet for leakage. If the fuel lock and the converter are operating properly, no fuel will leak through. • Press the primer button on the front of the converter to open the gas regulator valve. A small amount of gas should pass through the jet as the system is emptied back to the fuel lock. If the fuel lock is operating properly, the gas flow will soon cease as soon as the fuel downstream of the fuel lock is exhausted. • Next remove the vacuum hose to the VFF30 fuel lock from the fitting at the source of vacuum. With the primer button depressed, apply vacuum to the fuel lock vacuum hose.

Fuel should flow immediately and stop flowing when suction is relieved. 6.With consistent starting and idling, the vaporizer/ regulator need not be disassembled. If inconsistent, remove the regulator front cover and diaphragm assembly to check for oil and dirt deposits. If granules of foreign matter are embedded in the Viton rubber of the secondary valve, the valve and seat may be washed clean; however, it may be wise to replace the Viton valve for a perfect seal. These granules almost invariably enter the vaporizer in solution in the liquid propane and drop out as the fuel is vaporized, similar to salt water through a filter with deposits of salt left after evaporation of the water. It is seldom a sign of insufficient filtration.

Foreign matter and scale from the tank generally deposit in the filter when a new tank is installed.

Welding scale and rust are frequently present in new tanks, and occasionally residual water from the hydrostatic pressure testing is still in the tank.

NOTE

This manual only covers the fuel system supplied on units built before 01/01/2004. See fuel system supplements for units built after 01/01/2004.

Theory of Operations

•Impco vacuum fuel locks are normally closed. •They use air valve vacuum from the air fuel mixer to open the fuel lock. •If the engine stops or is turned off, engine vacuum dissipates and the fuel lockoff closes automatically. This is a desirable safety feature. •When the engine is cranking or running, air valve vacuum is transmitted from the mixer to the lockoff through a 3/16 in. vacuum hose. •The vacuum acts upon a diaphragm assembly.

Atmospheric pressure forces it inward against the valve operating lever. •As the valve operating lever is depressed it moves the valve operating pin. •As the valve operating pin moves it lifts the valve off of its seat. •This allows propane to flow through the lockoffs 10micron filter and on to the pressure regulator.

Vacuum Fuel Lock Service Procedures

•The Impco VFF30 vacuum fuel filter lockoff is fully field serviceable. •A repair kit is available which includes all the wear parts necessary to rebuild the unit. Each part is also available individually.

•To test a unit for external leakage, apply an approved leak test solution to the entire outer surface and watch for leaks. •To test a unit for internal leakage remove the vacuum hose from the port marked VAC. •Apply an approved leak test agent to your finger tip and lightly place finger over port marked VAC. •Position your finger so that any LPG leaking internally and escaping out of the vacuum port will create small bubbles around your fingertip. •If bubbles are found, the pin and o-ring need replacing.

Vacuum Fuel Lock Installation Tips

•Lockoffs with filter elements should be positioned so that the filter can be changed as easily as possible. •Vacuum lockoffs should be positioned so that the atmospheric vent is not restricted. •Vacuum lockoffs should be positioned so that debris will not enter the atmospheric vent. •Vacuum lockoffs should be connected to air valve vacuum, not manifold vacuum.