SECTION 6

Fuel System

DESCRIPTION

The complete fuel system consists of the fuel tank and lines, fuel filter, fuel pump, carburetor, and leaf valves (see Figure 6-1). This section gives complete service procedures on all komponenter of the fuel system, carburetor adjustments, and synchronization of the carburetor and magneto. Principles of carburetion, operation of leaf valves, and description of fuel pumps, lines, and tanks, are included in Section 2. Detailed instructions for removal of carburetors for all models are included with eftersyn Procedures (Section 5).

Fig. 6–1.

SERVICING SINGLE BARREL SIDEDRAFT CARBURETORS

Removal

Remove choke control and low speed needle valve knobs. Remove manual starter. Disconnect cam follower spring. Disconnect fuel hose at fuel pump, keeping free end of hose above carburetor to prevent fuel from spilling into lower motor cover. Remove two nuts and carburetor from intake manifold studs.

adskillelse

1. Drain carburetor by removing screw plug (see Figure 6-7) from bottom of float chamber.
2. Remove fixed high speed jet (orifice plug) (see Figure 6-8). To prevent damage to threads in float chamber assembly, use fixed jet screwdriver (see Section 15).
3. Remove low speed needle valve packing nut, (see Figure 6-9) then remove the needle valve. Remove the needle valve packing from the carburetor body, using care to avoid damaging threads in carburetor body.
4. Remove screws attaching float chamber to carburetor body and remove float chamber and gasket (see Figure 6-9).
5. Remove hinge pin and float and arm assembly. Remove float valve, float valve seat and washer.
6. Remove high speed nozzle and boss gasket.
7. Clean carburetor as described under "rensning, inspektion, and reparation."

samling

Reassemble the carburetor, paying particular attention to the following procedure. Keep all dust, dirt, and lint out of the carburetor during samling. Be sure that parts are clean and free from gum, varnish, and corrosion when reassembling them. Replace all gaskets and sealing washers. DO NOT attempt to use original gaskets and washers as leaks may develop after the engine is back in use.

1. Install high speed nozzle and a new boss gasket in float chamber. Replace float valve seat and gasket, float valve, and float and arm assembly, and hinge pin.
2. Check for correct positioning of float (see Figure 6-12). Turn carburetor body upside down so weight of float closes needle. Top of float should be even and parallel with rim of casting.
3. Reassemble float chamber to carburetor body.
4. Install new needle valve packing in carburetor body. Install packing nut but do not tighten nut against the packing.
5. Install low speed needle, then back it out approximately one turn. DO NOT turn needle valve down tight as taper on needle may be damaged. Adjust the low speed needle as described under "Installation and Adjustment" after installing carburetor on power head. Tighten packing nut until needle can just be turned under finger pressure.
6. Install fixed high speed jet (orifice plug). Use fixed jet screwdriver (see Section 15) to prevent damage to threads in float chamber. Install drain screw ping.

Installation and Adjustment

1. Using a new gasket, place carburetor in position on manifold studs and attach with nuts and lockwashers. Reinstall gear drive starter.
2. Reconnect fuel hose between fuel pump and carburetor. Install cam follower spring.

1. Advance throttle control from STOP position until mark on throttle cam is in line with center of cam follower roller (see Figure 6-15). Throttle valve should just begin to open at this point. If not, loosen hex head screws attaching cam to armature base. Push cam forward until it contacts cam follower and just begins to open throttle valve.
2. Tighten screws and recheck position of throttle valve. Throttle valve should just begin to open when mark on cam aligns with center of cam follower roller.

1. Gently seat low speed needle by turning clockwise. DO NOT force. Turn low speed needle counter clockwise 3/4 turn. NOTE: Allow motor to reach normal operating temperature by running in a tank with test propeller at 1/2 throttle or slightly more for at least live minutes before proceeding to next step.
2. With motor at operating temperature run at a fast idle speed (800 rpm) with test propeller in tank or on boat. Adjust low speed knob until motor runs fastest and smoothest performance is obtained. Allow 15 seconds for motor to respond to each adjustment.
3. Replace low speed needle valve knob in normal running position. DO NOT disturb the position of needle while installing knob. Adjust idle adjustment screw so motor will idle at 550 rpm in gear.

Rensning, Inspektion og Reparation

1. Clean all except the following carburetor komponenter in carburetor rensning solvent:
   
   • choke solenoid
   • choke assembly
   • choke shaft bushings
   • gaskets
   • "O" rings
   • floats
   • float valve needle
   • needle valve knobs and linkage
   • cam follower roller
2. Be sure all particles of gaskets are removed from gasket surfaces. Flush out passages in the carburetor body and float chamber with solvent and remove any gummy deposits with OMC Accessory Engine Cleaner.
3. Blow out all drilled passages with compressed air and check to make sure they are clean. NOTE: DO NOT under any circumstances, use wire or other pointed instruments to clean drilled passages or calibrated holes in carburetor. Holes and passages are carefully calibrated and use of wire or other rensning instruments will destroy calibration of carburetor.
4. After rensning in solvent, rinse all parts clean of solvent in kerosene and blow dry with compressed air. Inspect each part for wear and replace if necessary. NOTE: DO NOT dry parts with a cloth as lint may cause trouble in the reassembled carburetor.

Inspect float and arm assembly. If float has become oil soaked, discard it and install a new one. Check float arm wear in the hinge pin and needle valve contact areas and replace if necessary.

1. Inspect hinge pin for wear which may result from excessive vibration. Replace if necessary.
2. Inspect the float needle valve and seat, and replace if nicked, scratched, or worn (see Figure 6-44). The valve seat and needle are a matched set; if either is worn both parts must be replaced. Use a new sealing gasket when installing the needle seat.
3. Inspect the tapered ends of the low speed or high speed needles for grooves, nicks, or scratches (see Figure 6-45). If any are found, replace the needle valve. DO NOT attempt to alter the shape of the needle valve.
4. Check operation of choke and throttle shafts; if excessive wear exists, the complete carburetor body should be replaced.
5. Check all gasket sealing surfaces for nicks, scratches, or distortion. Slight irregularities can be corrected with the use of a surface plate and abrasive material such as 180 grit emery cloth.
6. Choke solenoids require very little attention. For efficient operation, the plunger should be free from corrosion so that it can move freely in the solenoid housing. DO NOT lubricate the solenoid plunger since the oil film will only attract dust and cause sluggish plunger movement.

1. If leakage occurs at a core ping area, a smart tap with a hammer and flat end punch in the center of the core ping will normally correct this condition.
2. If leakage persists, drill a hole through the center of the ping to a depth of not more than 1/16 inch below the surface. With a punch, carefully pry out core ping (see Figure 6-46)
.
3. Inspect and clean casting contact area; if Dicks, scratches, or an out-of-round condition exists, the casting will have to be replaced. If the casting opening is normal, apply a bead of Sealer 1000 to the outer edge of a new core plug and place the new core plug in the casting opening, convex side up. Flatten to a tight fit with a flat end punch and hammer. Check for leakage.
4. If leakage occurs at a leadshot area, a smart tap with a hammer in the center of the leadshot will normally correct this condition.
5. If leakage still exists, remove the leadshot with an appropriate sharp tool. Clean and inspect casting opening.
6. If the casting opening is normal, install new leadshot in casting opening and flatten out with a punch. Check for leakage.

LEAF VALVES

1. Remove carburetor as described above.
2. Disconnect starter lock-out lever, if used.
3. Remove intake manifold.
4. Remove leaf plate assembly.

1. Inspect the leaf plate assembly and disassemble if necessary (see Figure 6-49). Special caution is necessary in disassembling the leaf block assemblies. DO NOT damage or interchange the leaves.
2. The leaves must be flat to maintain a seal with the plate. 00 NOT under any circumstances bend or flex the leaves by band. It is advisable to clean, inspect, and immediately reassemble the leaf valve assemblies rather than leave them apart for samling later.

1. The only requirements for leaf valves are that they be cleaned of all dirt, gum, and varnish, and that the leaves be flat and without distortion to form a seal with the plate.
2. Check condition of leaf stop for bent elements and replace if damaged.
3. Rinse leaf valves, leaf stops and leaf plates in rensning solvent and blow dry with light air pressure to prevent leaf damage. NOTE: DO NOT disassemble leaf block assemblies on V -4 engines. If a defective leaf housing, leaf valve, or stop is found, the entire leaf housing assembly must be replaced. Visually inspect each leaf for the presence of foreign particles by gently lifting each leaf off its seat. Each leaf must seat properly (flat and undistorted) to prevent compression loss from within the crankcase cavity during the piston's downward stroke.
4. Check tightness of leaf valve retaining screws and tighten any that appear loose. Remove any traces of gasket particles that are found adhering to the leaf plate. NOTE: The mere udskiftning of a broken leaf valve is not always a lasting reparation since in some cases a bent leaf stop may have been the actual cause of valve breakage. Often a broken leaf valve will also damage leaf plate after several hours of operation in such a way as to result in failure of the udskiftning valve after a short period of time.

1. The importance of keeping the leaves in these valves free from distortion cannot be overemphasized. Replace any leaf or leaf stop which shows any indication of distortion.
2. The leaf is designed to maintain constant contact with the leaf block and to spring away from the block when predetermined pressure is exerted against it. Leaf travel away from the block is limited by the leaf stop. When pressure is removed, the inherent spring action of the segments returns and holds them against the block. Attach the leaf segments and leaf stop to the leaf block or leaf plate, then examine leaves carefully. Each leaf must lie flat against the block with no edges turned up or away from the block.
3. Make certain that leaves are centered over alignment recesses in leaf plate (see Figure 6-50).

1. The oil drain valve ordinarily requires little or no attention; however, when the motor is being serviced, remove and clean the drain valve and screens (see Figure 6-52).
2. If gum or varnish is found in the crankcase during servicing, clean the leaf valve assembly in OMC Accessory Engine Cleaner, as it is likely that gum and varnish have also been deposited there. Blow out the bleeder channels or drains with compressed air to insure against possible clogging later.
3. Make sure that the leaf valve seats squarely against the leaf plate and that the screens are not clogged. Reassemble and install. Make sure that the leaf stop is properly installed to permit functioning of the bleeder valve segments.

FUEL PUMP AND FILTER -

1. If an engine that dies frequently can be made to continue running by squeezing the primer bulb, in most cases the fuel pump will require servicing. Before starting fuel pump servicing, check all fuel hoses, the fuel filter, and the gasoline tank vent.
2. Remove the fuel hose from the fuel tank and blow through all lines with compressed air to be sure they are clean. Tighten any loose fuel line connections and look for bands or kinks in lines which would reduce fuel flow.
3. An inoperative tank vent can be detected by loosening filler cap. If the engine runs only after the cap has been loosened, the tank vent is clogged.
4. Check for a clogged fuel filter element. The fuel filter element on an engine that has been in storage may be clogged without appearing to be. During storage, volatile agents, as well as anti-gum and anti-varnish agents, evaporate from the gasoline that remains in the fuel filter. The result is contamination of the filter element with a clear form of varnish. This varnish is not readily soluble in gasoline or rensning solvent; therefore, the filter should be replaced at the start of each season. NOTE: Since the purpose of the filter is not only to trap dirt but also to prevent moisture from entering carburetor and engine, do not attempt to run the engine with the filter element removed.

1. Disconnect hoses from pump and filter assembly.
2. Remove two screws attaching pump and filter assembly to power head (see Figure 6-53), and remove pump and filter assembly.
3. The fuel pump komponenter are not serviced separately. If a malfunction occurs, replace the complete pump.
4. Inspect the filter for accumulation of sediment by removing the filter cap screw and the filter cap (see Figure 6-53). Clean the filter cover and fuel connectors in solvent and blow dry.
5. Reassemble the fuel filter. Attach fuel pump and filter assembly to power head with screws. Reconnect fuel hoses.

FUEL TANKS

1. For correct fuel and oil mixtures and break-in instructions, see Section 3.
2. The importance of using a fresh fuel mixture should not be underestimated. An aging fuel mixture precipitates petroleum gum which will clog screens, fuel passages, carburetor orifices, valves, etc. The use of last year's fuel is false economy. The tank should be emptied of old fuel and filled with a fresh supply at the start of each season.
3. Fuel tank pumps are available commercially for completely draining the tank. Complete draining and flushing of the tank should be done at the start of each season and as a part of each tune-up. This applies also to portable and permanently installed tanks.
4. It is advisable to leave tanks filled with fuel during storage to avoid moisture precipitation. Atmospheric changes will cause moisture condensation in a partially filled tank. The resulting water accumulation can cause hard starting, possible stalling, and rough operation.

MILE-MASTER TANKS

DESCRIPTION

The tank is of simple but rugged construction, having a capacity of 6 gallons of fuel mixture. It includes the bulb primer (for priming the fuel pump), fuel level gage, fuel hose and connectors, a bracket arrangement to hold fuel line when not in use, and a carry grip (see Figure 6-59). The fuel tank upper housing, which provides the connection to the fuel hose, contains two release valves and a disc valve which prevent any escape of gasoline or fumes, minimizing the danger of explosion or fire.

Rensning, Inspektion og Reparation

The fuel level indicator is mounted to the upper housing and fuel line assembly (see Figure 6-60). Lift the assembly from the tank carefully to avoid damaging the indicator float or the screen at the end of the fuel hose.

Check for free movement of the indicator on the indicator pin. Remove the pin from the indicator to make sure that the float arm is not bent and that the float is not damaged or oil soaked.

Remove the two screws attaching the lens support to the upper housing, and clean it with solvent to remove any deposits which may be clouding the lens. Inspect the lens seat for cracks or shrinkage which may allow leakage. The release valves must seat tightly to prevent gasoline or fumes from leaking out, but must open a clear passage for air to enter the tank and for fuel to be drawn out when the fuel hose is connected. Dirt may clog the passage s and may also prevent the valves from operating properly. The release valves are hest cleaned by removing the core plugs and disassembling. To remove core plugs, carefully drill a small hole through the center of the plug (avoid damaging spring), and pry out the plug with a punch. Replace valve seats (O-rings) to assure a tight seal.

The air inlet disc valve must seat tightly to prevent fumes from escaping the tank when the .fuel hose is connected, but must allow air to enter the tank. The disc valve spring retainer is staked to the upper housing and may be removed by filing off the burrs if udskiftning is necessary. Restake with a small punch.

HOSE AND PRIMER BULB ASSEMBLY

1. To disassemble hose clamps, grip clamp firmly with pliers (see Figure 6-61). Bend overlapping hook backward to release clamp.
2. To assemble hose clamps, grip clamp firmly with pliers (see Figure 6-62). Apply slight pressure to hook on underside of clamp with screwdriver. Squeeze clamp with pliers until hooks interlock.

CONNECTOR HOUSINGS

Installation of the O-ring and the fuel hose connectors requires the use of two instruments, one to hold the plunger down and one to remove the O-ring (see Figure 6-63). Both instruments can be made of 16 gage (1/16" diameter) steel wire. A piece of discarded remote control wire may be used. Form a small hook on the bottom of the longer tool of about 1/16" radius. After cutting the wires to length, be sure the ends are rounded off to prevent scratching or damaging the O-ring seats or the plungers. To remove the O-ring from the connector, proceed as follows:

1. Place the connector in a vise between two wood blocks.
2. Push the plunger down with the straight edged instrument.
3. Insert the hook instrument between the O-ring and its seat with the hook in a flat or horizontal position.
4. Twist the hook around to grasp the O-ring, then pull up (see Figure 6-64).

1. Place a drop or two of oil on the O-ring.
2. Twist the O-ring on face of connector.
3. Push the plunger down with a straight instrument.
4. Pinch the O-ring together and gently push into position with fingers.

When reassembling fuel hose, check for cracks in the primer bulb or in the hose. The primer bulb must be attached so that fuel flow is from the shorter to the longer hose length. Fuel flow through the primer bulb is indicated by an arrow (see Figure 6-65).