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Onan P218 Carburetor

Onan P218 Carburetor Adjustment

Onan P218 carburetors have a fixed main jet. An optional fixed main jet is available for altitude compensation above 5000 feet. The carburetor idle mixture was set for maximum efficiency at the factory and should normally not be disturbed. If adjustments seem necessary, first be sure the ignition system is working properly and governor sensitivity is properly adjusted.

The carburetor has a limited adjustment range between stops of ±1/8 turn. The screw should only be adjusted within these limits; in to lean the mixture, out to richen. Overtightening the mixture adjustment screw will cause carburetor damage. Turn mixture adjustment screw in only until light tension can be felt. If replacing idle mixture screw, turn in until lightly seated, then turn screw back out 1-1/4 turns. Replace limiter cap with the plastic stop approximately centered.

Carburetor Speed Settings

Start the engine and allow it to warm up thoroughly (at least 10 minutes). Some equipment manufacturers may require higher throttle stop speed and governor low speed rpm settings. Refer to equipment manufacturer’s Operator’s Manual for the correct rpm settings. When rpm settings are not specified by the equipment manufacturer, use the rpm settings listed in Steps 2 and 3.

Move the engine speed control to the slow position. Bend or turn the low speed stop on the governor so the throttle stop screw on the carburetor controls engine speed. Adjust the throttle stop screw for 1000 rpm idle. Adjust the governor low speed stop for 1100 rpm idle. Move the engine speed control to the fast position. Bend the high speed stop on the governor so the engine runs at the equipment manufacturer’s recommended speed.

Onan P218 Carburetor Overhaul

Carburetion problems that are not corrected by mixture adjustments are usually a result of gummed-up fuel passages or worn internal parts. The most effective solution is a carburetor overhaul. In general, overhauling a carburetor consists of disassembly, a thorough cleaning, and replacement of worn parts. Carburetor overhaul kits are available.

Removal

Remove air cleaner assembly. Disconnect governor and throttle linkage, choke control, and fuel line from carburetor. Remove the four intake manifold cap screws and lift complete manifold assembly from engine. Remove carburetor from intake manifold.

Disassembly

Remove main jet and idle adjustment needle. Remove attaching screws and separate upper and lower carburetor sections. Carefully note position of float assembly parts, then pull out retaining pin and float assembly. Remove needle valve.

Cleaning and Repair

Soak all metal components not replaced in carburetor cleaner. Do not soak non-metal floats or other non-metal parts. Follow the cleaning manufacturer’s recommendations. Clean all carbon from the carburetor bore, especially where the throttle and choke plates seat. Be careful not to plug the idle or main fuel ports. Dry out all passages with low pressure air (35 psi). Avoid using wire or other objects for cleaning which may increase the size of critical passages. Check the condition of the adjustment needle; replace if damaged. Replace float if loaded with fuel or damaged. Check the choke and throttle shafts for excessive play in their bore. This condition may necessitate replacement of the carburetor. Replace old components with new parts.

Onan P218 Carburetor - Reassembly and Installation

Install needle valve, main jet, and float assembly. Make sure float pivot pin is properly placed and float moves freely without binding. Turn carburetor on its side and measure float level. Adjust float level only if necessary. Measure float drop (the distance from the top of carburetor body to top of float). Adjust only if necessary. Position gasket on lower carburetor section and install upper carburetor section. Install idle adjustment screw, throttle stop screw, and fixed main jet plug.

Mount carburetor on intake manifold and install assembly on engine. Connect governor and throttle linkage, choke control, and fuel line. Mount air cleaner assembly. Adjust carburetor and governor according to directions given in this section.

Onan P218G Carburetor Adjustment

High-Altitude Jet

If the engine is operated at an altitude above 5,000 feet (1,524 metres), it is recommended that the carburetor main fuel jet be replaced with the optional high-altitude jet (which has a slightly smaller orifice). To avoid slipping and gouging the main fuel jet, use a screwdriver with a 5/16 inch (8 mm) wide blade.

Onan P218G Carburetor Replacement

Other than replacing the carburetor main fuel jet (fixed-type) with the optional high-altitude jet, fuel mixture adjustments should not be attempted. Not should the carburetor be overhauled. Instead, a malfunctioning carburetor should be replaced. Before replacing a carburetor, however, make certain: That all other necessary engine and generator adjustments and repairs have been performed; That the carburetor is actually malfunctioning.

To remove the carburetor, remove the air cleaner, disconnect the fuel line and choke and throttle linkages and unbolt the carburetor from the intake manifold. When mounting the carburetor always use a new gasket. Readjust the choke and throttle cables and engine speed as instructed in the engine or equipment Operator’s Manual.