SECTION I
Contents
1. ECONOMIZER SETTING MA 4 5 FLOAT LEVEL TOO LOW BLOCKAGE IN MAIN NOZZLE BLOCKAGE IN BOWL VENT 7 NO RISE AT IDLE CUT OFF LEAN BLOCKAGE IN IDLE CIRCUIT INTAKE MANIFOLD LEAK CRACKED PRIMER LINES IDLE MIXTURE ADJUSTMENT 8 HIGH EGT AND CHT READINGS LEAN CONDITION LOW FUEL CONSUMPTION Page 2 1 CARBURETOR TROUBLESHOOTING CHART MSA MARVEL SCHEBLER FACET FLOAT CARBURETOR NOTE THE FOLLOWING SUGGESTIONS ARE TO AID IN TROUBLESHOOTING MARVEL SCHEBLER FLOAT CARBURETORS PROBLEM ROUGH ENGINE RICH ROUGH ENGINE LEAN PROBABLE CAUSE LEAKY PRIMER REMEDY DISCONNECT AND CAP OFF TO ELIMINATE WRONG VENTURI OR INSTALLED INCORRECTLY USE FULL SERVICE MANUAL FOR PROPER PART NUMBERS AND M 83 TOOL FOR PROPER INSTALLATION BAD ACCELERATOR PUMP CHECK VALVE REMOVE AND TEST BY BLOWING AIR BY MOUTH INTO VALVE IF ANY AIR LEAKS REPLACE VALVE ACCELERATOR PUMP STEM PACKING WET AROUND SHAFT REMOVE PUMP PLUNGER AND REPLACE STICKY FLOAT REMOVE AND INSPECT FOR MARKS AND SCRATCHES RE PLACE FLOAT IF ANY FOUND FLOAT VALVE NOT SEATING LEAKING FUEL PRECISION RECOMMENDS REPLACING NEEDLE AND SEAT EVERY TIME CARBURETOR IS DISASSEMBLED THROTTLE SHAFT O RING LEAKAGE MA 4 5 MA 5 OUTBOARD O RINGS CHECK FOR LEAKAGE WITH COMPRESSED AIR REPLACE AS NECESSARY WORN OUT JUST NEEDS AN OVERHAUL RECOMMENDED OVERHAUL AT 10 YEARS OR TBO WHICHEVER OCC2. For Brass floats be sure to check both floats to proper dimensions making sure that the floats are parallel to the bowl gasket NOTE For new style Floats Delrin white refer to SIL MS 4 introduction of advanced polymer floats for MA series updraft Carburetors For the Delrin Floats the pontoons may not be bent to adjust Float pontoons might not be the same height above the gasket The allowable height difference between pontoons is 090 inch If the heights are not the same set the float height such that the average of the two pontoon heights is the called out float level for that particular Carburetor CAUTION Do not apply pressure to the valve and seat during adjustment bending ACCELERATOR PUMP ADJUSTMENT The accelerator pump lever has three holes into which the upper end of accelerator pump link may be fastened The outer hole no 3 which is approx midway between upper and lower holes gives largest stroke or maximum accelerating fuel The lower hole no 1 gives the shortest stroke or minimum accelerating fuel and the upper Page 1 5 hole 2 provides a medium supply of accelerating fuel The normal position of accelerator pump is in the no 3 hole the maximum setting however for extremely hot weather or for high test fuels no 2 hole may be necessary to prevent heaviness or slowness on acceleration Rarely if ever should no 1 hole be required 4 LUBRICATION No lubrication is required on MA 3s MA 4
3. gaskets or loose and damaged gas line fittings This condition constitutes a dangerous fire hazard and must be corrected at once Safety locking wires and washers should be checked monthly to ensure the tightness of all screws Linkage should be inspected monthly for evidence of wear MAINTENANCE NOTE Always refer to appropriate engine airframe manual for proper adjustment procedures a ADJUSTMENT OF If after checking all other points on engine it is found necessary to readjust the carburetor proceed as follows With engine thoroughly warmed up set throttle stop screw so that the engine idles at approx 600 650 rpm Adjust the idle mixture to obtain a 25 50 rpm rise at idle cut off optimum A change in idle mixture will change the idle speed and it may be necessary to readjust the idle speed to 600 650 rpm with throttle stop screw CAUTION Care should be taken not to damage the idle needle seat by turning the idle adjustment needle too tightly against seat as damage to this seat will make a satisfactory idle adjustment very difficult FLOAT HEIGHT The float height is set at the factory and can be checked by removing the throttle bowl bowl cover and float assembly and turning upside down Proper setting of the two floats from bowl gasket to closest surface of each float should measure MA 3 and MA 4 Carburetors 7 32 inch 4 5 MA 5 and MA 6 Carburetors 13 64 inch HA 6 Carburetors 187 inch
4. mixture to the engine as the throttle is opened coming into play progressively and blending with the primary idle delivery to prevent the mixture from beginning too lean as the throttle is opened and before the main nozzle starts to feed These Carburetors are provided with a third and possibly a fourth idle delivery in addition to the secondary idle delivery depending on the application to cover the broader idle range in these Carburetors b METERING Ref appropriate figure for a particular model fuel delivery on idle and also as steady propeller speeds up to approx 1 000 rpm is from the idle system At approx 1 000 rpm the suction from the increasing amount of air now passing through primary and secondary venturi causes the main nozzle to start delivering and the idle system delivery diminishes due to lowered suction on the idle delivery openings as the throttle fly is opened for increasing propeller speeds until at approx 1 400 rpm the idle delivery is practically nil and most of the fuel delivery from that point onto the highest speed is from the main nozzle However the fuel feed of any full throttle operation is entirely from the main nozzle The idle system and main nozzle are connected with each other by the idle supply opening The amount of fuel delivered from either the idle system or main nozzle is dependent on the whether the suction is greater on the idle system or main nozzle the suction being governed by throttle v
5. ASS Y FUEL AIR MIXTURE EL AIR MODEL 45 IDLE EMULSION CHANNEL THROTTLE FLY PRIMARY IDLE DELIVERY SECONDARY IDLE DELIVERY THIRD IDLE DELIVERY IDLE ADJUSTING NEEDLE IDLE AIR VENT FLOAT VALVE amp SEAT VENTURI NOZZLE AIR VENT IDLE AIR VENT NOZZLE NOZZLE WELL 3i NOZZLE BLEED HOLES FUEL BOWL ASSY 4 PUMP MIXTURE METERING x DISCHARGE TUBE VALVE ASS Y IDLE SUPPLY OPENING RS IDLE FUEL ORIFICE P IDLE TUBE BOWL DRAIN PLUG POWER JET FUEL CHANNEL MIXTURE METER SLEEVE FIG 3 FUEL AIR MIXTURE EN Fue AIR MODEL 45 ACCELERATOR PUMP LEVER ACCELERATOR PUMP LINK ACCELERATOR PUMP CHAMBER PUMP FOLLOW UP SPRING ACCELERATOR PUMP PLUNGER HOLE 2 MEDIUM i 2 lt y 22 NS HOLE 1 MINIMUM LL WU 6 HOLE 3 MAX NORMAL gt m 27 ES PUMP INLET SCREEN ROS PUMP INLET CHECK VALVE CARBURETOR PUMP DISCHARGE CHECK VALVE FUEL AIR mixture EEUU FUEL AIR 4 5 5 CARBURETOR FIGURES MODEL 4 5 PUMP IDLER LEVER RETAINING SCREW FLOAT LEVER SHAFT BOWL VENT CHANNELS FUEL BOWL FIG 3 PUMP IDLER LEVER AND BUSHING ASSEMBLY FLOAT ASSEMBLY FUEL AIR mixture Fue AIR 58 s 32 5 El 25 gt 3 E N N 52 5 AS 2 a Mer XO i lt AN gt O 32 SS a 5
6. chamber when the accelerator pump 15 inoperative any constant throttle position accelerator pump discharge check valve assembly mounted in the Carburetor is provided with an accelerator pump discharge check valve loaded by an accelerator pump discharge check valve spring POWER ENRICHMENT ECONOMIZER SYSTEM Ref appropriate figure for a particular model Aircraft engines are designed to produce a maximum amount of power consistent with their weight But since they are not designed to dissipate all of the heat the fuel is capable of releasing provisions must be made to remove some of this heat This is done by enriching the fuel air mixture at full throttle The additional fuel absorbs this heat as it changes into a vapor Power enrichment systems are often called economizer systems because they allow the engine to operate with a relatively lean and economical mixture for all conditions other than full power MECHANICAL AIRBLEED ENRICHMENT SYSTEM Large MA 4 5 HA 6 Carburetors Ref appropriate figure for a particular model When we increase air velocity through the main venturi we get an increased pressure drop that enriches the mixture and to prevent this enrichment an air bleed of a very precise size is used between the float bowl and the discharge nozzle If we increase the size of this air bleed we lean the mixture and 1f we decrease it more fuel is pulled from the discharge nozzle and the mixture becomes richer The air f
7. LUNGER ASSY BOWL COVER GASKET gt S LU O RING RETAINER PUMP ROD RING PACKING PUMP ROD RING PACKING V RING RETAINER FUEL FROM BOWL 777 5 PUMP INLET CHECK VALVE ASSY PUMP DISCHARGE CHECK VALVE ASSY PUMP DISCHARGE CHECK VALVE PLUG PUMP SYSTEM FUELAIR mixture EN Fue AIR MODEL 6 FLOAT SETTING 187 FUEL INLET GASKET ASSY FLOAT VALVE CLIP PITOT TUBE FLOAT INLET amp BOWL VENT SYSTEM FUELAIR mixture Fue AIR
8. PRECISION AIRMOTIVE S MSA FLOAT CARBURETOR HANDBOOK Formally Marvel Schebler Facet amp TROUBLESHOOTING TECHNIQUES 9 10 2002 Form MSAHBK 1 Revision 1 CONTENTS NOMENCLATURE PAGE Section I Introduction 1 1 Section II Description 1 1 Section III Operation 1 2 Operating Instructions 1 4 Section Service 1 5 Troubleshooting Charts 2 1 Figures MA 3 amp 4 SPA Figures MA 4 5 MA 5 Figures HA 6 SECTION I INTRODUCTION This Handbook covers description installation operation maintenance and troubleshooting of Float Carburetor models MA 3 and MA 4 MA 4 5 MA 5 and HA 6 as manufactured by Precision Airmotive Corporation Marysville Washington All material contained in this Handbook applies to all Carburetor Models unless otherwise specified by a particular model Fora listing of Factory Authorized Repair Centers please see SIL PAC 1 or visit us on the Internet at Www precisionairmotive com Precision Airmotive Product Support may be reached at 360 651 8282 SECTION II DESCRIPTION GENERAL Models MA 3 and MA 4 MA 4 5 and MA 5 are updraft Carburetors used on Continental Franklin and Lycoming Engines They are of the plain tube fixed jet type Models HA 6 are side draft Carburetors and are used only on Lycoming engines They are of the plain tube fixed jet type DETAILED NOTE The definitions below are of all models of Carburetors in general a ACCELERATOR PUMP This pump is provi
9. PRIMER RE ADJUST IDLE SPEED PER ENGINE MANUAL DISCONNECT AND CAP OFF TO ELIMINATE CRACKED PRIMER LINES INSPECT ALL JOINTS AND CONNECTIONS REPAIR AS NECESSARY INTAKE MANIFOLD LEAKS PRESSURIZE AND TEST MIS ADJUSTED IDLE MIXTURE LEAKY PRIMER RE ADJUST MIXTURE PER ENGINE MANUAL DISCONNECT AND CAP OFF TO ELIMINATE IDLE MIXTURE ADJUSTED TOO RICH RE ADJUST PER ENGINE MANUAL OPTIMAL TO HAVE 25 50 RPM RISE AT ICO IDLE TUBE AIR BLEED BLOCKAGE NOTE TORQUE IDLE TUBE 3 5 IN LB REMOVE IDLE TUBE FROM BOWL AND CLEAN AIR BLEED CLEAN WHOLE IDLE CIRCUIT WITH COMPRESSED AIR AND SOLVENT PUMP PLUNGER LINKAGE MIS ADJUSTED TOO MUCH FUEL ON ACCELERATION BAD ACCELERATOR PUMP LEATHER BOOT FUEL GETTING TO OTHER SIDE FORCED OUT VENT WHEN THROTTLED BACK Page 2 3 ADJUST TO LESSER THROW ON ACCELERATOR PUMP LINKAGE REPLACE PUMP PLUNGER CARBURETOR TROUBLESHOOTING CHART MSA MARVEL SCHEBLER FACET FLOAT CARBURETOR Page 2 4 MA 3 4SPA CARBURETOR FIGURES CARBURETER PUMP DISCHARGE CHECK VALVE ASS Y FUEL INLET SCREEN ASS Y THROTTLE SHAFT THROTTLE STOP SCREW THROTTLE BODY amp BOWL COVER amp FLOAT ASS Y FUELAIR mixture Fue AIR MODEL 45 MIXTURE CONTROL LEVER THROTTLE STOP ECONOMIZER CHANNEL ECONOMIZER HOLE ATMOSPHERIC BOWL VENT BACK SUCTION ECONOMIZER BOWL COVER GASKET FLOAT FLOAT
10. URS FIRST ECONOMIZER SETTING MISADJUSTED 4 5 MA 5 CRACKED PRIMER LINES RESET PER PRECISION OVERHAUL MANUAL P N FSM OH2 INSPECT AND REPAIR AS NECESSARY INTAKE MANIFOLD LEAKS PRESSURIZE AND TEST BLOCKAGE IN MAIN DISCHARGE NOZZLE OR IN BOWL VENT CLEAN AND ENSURE ALL PASSAGES ARE FREE FROM CONTAMINATION FIND SOURCE OF CONTAMINATION THROTTLE SHAFT O RING LEAKAGE MA 4 5 MA 5 INBOARD O RINGS CHECK FOR LEAKAGE WITH COMPRESSED AIR REPLACE AS NECESSARY ECONOMIZER SETTING MIS ADJUSTED MA 4 5 MA 5 Page 2 2 RESET PER PRECISION OVERHAUL MANUAL P N FSM OH2 CARBURETOR TROUBLESHOOTING CHART MSA MARVEL SCHEBLER FACET FLOAT CARBURETOR PROBLEM ROUGH IDLE POOR IDLE CUT OFF CAN T ADJUST IDLE HESITATION ON ACCELERATION HESITATION OR QUIT ON DECCELERATION PROBABLE CAUSE MIS ADJUSTED IDLE MIXTURE REMEDY RE ADJUST IDLE PER ENGINE MANUAL BAD OR LEAKY PRIMER DISCONNECT AND CAP OFF TO ELIMINATE CRACKED PRIMER LINES REPAIR AS NECESSARY INTAKE MANIFOLD LEAKS MIXTURE LINKAGE NOT FULL TRAVEL PRESSURIZE AND TEST RE ADJUST MIXTURE LINKAGE MIXTURE VALVE BEING PULLED UP BY MIS ALIGNED MIXTURE CABLE RE ALIGN MIXTURE CABLE STRAIGHT WITH MIXTURE LEVER MIXTURE VALVE WORN OUT REPLACE MIXTURE VALVE LEAKY PRIMER DISCONNECT AND CAP OFF TO ELIMINATE IDLE SPEED ADJUSTED TO HIGH LEAKY
11. WL IDLE DRILLINGS BOWL COVER COVER IDLE ADJUSTING NEEDLE SCREW Ss Ta JIN IDLE ADJUSTING NEEDLE WASHER peace IDLE ADJUSTING BOWL CHAMBER nk Xd ub FN NEEDLE O RING THROTTLE FLY BOWL CHAMBER THROTTLE SHAFT AND STOP ASSY lt lt pes I Nx POWER JET 7 LATI A E 2 ART THROTTLE amp VENTURI ADJUSTING SCREW FUELAIR mixture IDLE SYSTEM AIR MODEL 6 FLOATVALVE FUEL INLET SEAT amp GASKET STRAINER ASSY ASSY FUEL INLET FITTING je m RNE 2 22224 N SECONDARY NOZZLE xa BOWL CHAMBER AIR N VENTURI MIXTURE N CONTROL VALVE N 72222227 III MIXTURE CONTROL JET VALVE ASSEMBLY POWER SYSTEM FUEL AIR mixture EM FUEL AIR MODEL 6 BOWL COVER SECONDARY J NOZZLE 2222 CS AIR METERING PIN ROD RING BOWL COVER GASKET AIR METERING PIN ROD AIR METERING PIN 2221422272222227222222222222211 PACKING AIR METERING PIN RETURN SPRING AIR METERING PIN JET MAIN NOZZLE AIR METERING PIN JET PLUG ECONOMIZER SYSTEM FUELAIR MIXTURE AIR MODEL 6 PUMP PLUNGER RETAINER WASHER BOWL COVER PUMP PLUNGER ROD PUMP PLUNGER GUIDE e 7 PUMP P
12. alve position and engine load The main nozzle feeds at any speed if the throttle 15 open sufficiently to place the engine under load which drops the manifold suction Under such conditions of low manifold suction at the throttle fly the main nozzle feeds in preference to the idle system because the suction is multiplied on the main nozzle by the restriction of the venturi c ACCELERATOR PUMP Ref appropriate figure for a particular model The accelerator pump discharges fuel only when the throttle fly is moved towards the open position and provides additional fuel to keep in step with the sudden inrush of air into the manifold when the throttle is opened By means of an accelerator pump lever connected to the throttle shaft the accelerator Page 1 2 pump plunger is moved downward when the throttle is opened thus forcing fuel past carburetor pump discharge check valve into the accelerator pump discharge tube which delivers accelerating fuel through the primary venturi into the mixing chamber of the carburetor Upon closing the throttle the accelerator pump plunger moves upward thus refilling the accelerator pump chamber by drawing fuel from the fuel bowl through pump inlet screen and pump inlet check valve On any quick opening of the throttle the pump follow up spring yields and thus prolongs the pump discharge sufficiently to prevent slugging the engine with fuel Asa precaution to prevent fuel from being drawn into the mixing
13. ded with a discharge jet which discharges fuel into the mixing chamber to provide smooth acceleration under all operating conditions b MANUAL MIXTURE CONTROL The Carburetor has a manual mixture control which adjusts the Carburetor for all throttle positions and loads It is not normally employed under 5 000 feet msl IDLE SYSTEM Both primary and secondary idle air vents ensure proper air and fuel emulsion for starting and idling 9 FUEL PASSAGES Simplified design resists vapor locking of high test aviation fuel e SAFETY THROTTLE LEVER SPRING This spring holds the throttle in OPEN position for take off in the event of throttle control failure NOTE Continental no longer incorporates this spring and has a Service Bulletin A2 66 referring to this f FUEL INLET STRAINER AND SCREEN This screen prevents the entry of dirt or foreign matter apt to cause failure 2 VENTS All air vents open into the main air entrance which ensures against the entry of dirt into the Carburetor passages or fuel bowl when an efficient air cleaner is used h BOWL DRAIN PLUG The bowl drain plug is located at the lowest point in the fuel bowl and is used to drain water Page 1 1 SECTION III OPERATION 1 PRINCIPLES OF OPERATION a IDLE SYSTEM Ref appropriate figure for a particular model With the throttle fly slightly open to permit idling the suction or vacuum above the throttle on the manifold side 15 very
14. etering valve and the metering edge of the mixture metering sleeve in the FULL RICH position is narrower than the total angular travel of the mixture metering valve 2 OPERATING INSTRUCTIONS a STARTING COLD ENGINE With mixture control in FULL RICH position prime the engine as directed by the engine manufacturers instructions and set the throttle approx 1 10 open throttle stop 3 32 inch from throttle stop screw With the throttle in this position engage the starter This will draw a finely emulsified mixture of air and fuel through the manifold into the combustion chamber The engine should start within 3 5 revolutions and there should be sufficient throttle opening to keep the engine running The Carburetor is calibrated to give the richest mixture at this throttle opening and therefore a cold engine will run the smoothest with the throttle in this position For this reason the engine should be allowed to warm up until firing evenly before operating the throttle further STARTING HOT ENGINE To start a warm or hot engine put mixture control in FULL RICH position and pull the throttle stop back against the throttle stop screw If the ignition has just been shut off for several minutes it may be necessary to turn the engine over once or twice before turning on the ignition A warm or hot engine should start and continue with the throttle in the idling position CAUTION Do not open and close throttle in start
15. high Very little air passes through the venturi at this time and hence with very low suction on the main nozzle it does not discharge fuel This high suction beyond the throttle however causes the idle system to function as the primary idle delivers into the high suction zone above the throttle Fuel from the fuel bowl passes through the mixture metering sleeve fuel channel power jet and into the main nozzle bore where it passes through the idle supply opening in main nozzle through the idle fuel orifice in idle tube where it is mixed with air which is allowed to enter idle tube through the primary idle air vent and secondary idle air vent The resultant rich emulsion of fuel and air passes upward through the emulsion channel where it is finally drawn into the throttle body through the primary idle delivery opening subject to regulation of the idle adjusting needle where a small amount of air passing the throttle fly mixes with it forming a combustible mixture for idling the engine The idle adjustment needle controls the quantity of rich emulsion supplied to the throttle barrel and therefore controls the quality of the idle mixture Turning the needle counter clockwise away from its seat richens the idle mixture to the engine and turning the needle clockwise towards its seat leans the idle mixture On idle some air is drawn from the throttle barrel below the throttle fly through the secondary idle delivery opening and blends with the idling
16. ing as this is likely to deposit raw gasoline in the Carburetor air box and constitute a definite fire hazard Do not prime a hot engine USE OF MIXTURE CONTROL The mixture adjustment should not be used under 5 000 feet When adjusting mixture control for altitudes higher than 5 000 feet move control in and out slowly with the throttle at CRUISING or FULL OPEN position until the highest rpm is attained The Carburetor mixture will then be correctly adjusted for all throttle positions and loads at that particular altitude If an EGT gauge is installed lean to peak temperature and then richen to 50 100 degrees rich of peak CAUTION Always have the mixture control in the FULL RICH position when coming in for a landing so that if full power is required in an emergency near the ground the engine will operate satisfactorily and will not overheat because of too lean a mixture STOPPING Set throttle for idle speed of 800 rpm and pull the mixture control lever to the full lean position allowing the engine to stop from lack of fuel before shutting off ignition thus Page 1 4 3 assuring that the cylinders are dry of fuel The idle cut off feature now operates to ensure against accidental starting of engine SECTION IV SERVICE INSPECTION MAINTENANCE AND LUBRICATION SERVICE TOOLS REQUIRED No special service tools are required SERVICE INSPECTION The Carburetor should be inspected daily for leakage due to worn
17. onsists of mixture control lever which is attached the mixture metering valve assembly The mixture metering valve assembly is provided at its lower end with mixture metering valve which rotates in stationary mixture sleeve Mixture metering sleeve is provided with a transverse slot through which the fuel enters and fuel metering is accomplished by the relative position between one edge of the longitudinal flat on the mixture metering valve and one edge of the slot in the Page 1 3 mixture metering sleeve When mixture control lever is in toward carburetor throttle flange a full rich mixture is provided for takeoff With the mixture control lever in the FULL RICH position metering is controlled by the power jet but in other than FULL RICH position metering is accomplished by the relative position of the respective edges of the mixture metering sleeve and mixture metering valve as described above To make the mixture leaner for altitude compensation move the mixture control lever away from the carburetor throttle flange With the mixture control lever in the full lean position with mixture control lever in a position farthest from the carburetor throttle flange no fuel is allowed to enter the nozzle and idle system thus providing what is known as IDLE CUT OFF to prevent accidents when working around a hot engine This cut off is accomplished by the fact that the angular opening between the metering edge of the mixture m
18. or the air bleed comes from the float chamber and passes through the air bleed metering valve The needle for this valve is held off of its seat by a spring and is closed by an operating lever attached to the throttle shaft When the throttle 15 wide open the lever closes the air bleed valve and enriches the fuel air mixture BACK SUCTION TYPE ENRICHMENT SYSTEM Small MA 3 MA 4 Carburetors Ref appropriate figure for a particular model The back suction mixture control varies the pressure in the float chamber between atmospheric pressure and a pressure slightly below atmospheric This pressure variation is accomplished by using a control valve located in the float chamber vent line The float chamber is vented to the low pressure area near the venturi through a back suction channel This lowers the pressure in the float bowl When then mixture control is in the rich position the vent valve is open and the pressure in the float bowl is raised to essentially the atmospheric pressure and a differential pressure exists across the main metering jet This causes fuel to flow out of the discharge nozzle When the mixture control is moved to lean it closes the vent valve and pressure in the float chamber is decreased to a pressure that 15 essentially the same as that of the discharge nozzle This decreased pressure differential decreases the flow of fuel MIXTURE CONTROL Ref appropriate figure for a particular model The mixture control c
19. s and MA4 5 Carburetors Lubrication is required on HA 6 Carburetor pump linkage rods Refer to Precision SIL MS 1 5 SERVICE TROUBLES AND REMEDIES The following attached troubleshooting chart is to aide the pilot mechanic in isolating a carburetion problem effectively The process of elimination is vital to isolating a Carburetor problem Page 1 6 CARBURETOR TROUBLESHOOTING CHART MSA MARVEL SCHEBLER FACET FLOAT CARBURETOR THE FOLLOWING TROUBLESHOOTING CHART IS TO AID IN EFFECTIVE TROUBLESHOOTING OF THE MSA FLOAT CARBURETORS TO DETERMINE IF THE CARBURETOR HAS A RICH OR A LEAN CONDITION THE FOLLOWING STEPS ARE RECOMMENDED SYMPTOM TROUBLESHOOT FOR 1 EXCESSIVE OR AGGRESSIVE LEANING AT RICH ACCELERATOR PUMP CHECK VALVE ANY THROTTLE POSITION IN CRUISE OR FULL POWER ACCELERATOR PUMP STEM PACKING FLOAT LEVEL TO HIGH NEEDLE amp SEAT NOT OPERATING PROPERLY 2 EXCESSIVE RISE IN RPM AT IDLE CUT OFF RICH IDLE MIXTURE 3 EXCESSIVE FUEL CONSUMPTION SOME RICH CONDITION TIMES ASSOCIATED WITH ROUGH ENGINE 4 HESITATION ON ACCELERATION FROM RICH AIR BLEED BLOCKAGE IN IDLE TUBE IDLE CIRCUIT TO MAIN JET AND VENTURD RICH ACCELERATOR PUMP LINKAGE MISADJUSTED MUCH FUEL FROM PUMP DURING ACCELERATION 5 POOR IDLE CUT OFF RICH LEAKY PRIMER OR WORN MIXTURE VALVE IDLE MIXTURE ADJUSTMENT 6 NO RISE WHEN LEANING AT CRUISE OR LEAN THROTTLE SHAFT O RINGS FULL POWER INNER O RINGS 4 5
20. u BOWL VENT STRAINER SCREEN HOUSING D s 744 S ett ISTE Ar 5 L Y lt Els e u 5 z m O eal El El 88 5 FI THROTTLE LEVER MODEL MA4 5 THROTTLE STOP THROTTLE STOP SCREW FUEL PRESSURE TAKE OFF HOLES AIR METERING PIN PLUG MIXTURE CONTROL LEVER FUEL AIR mixture BOWL DRAIN PLUG diss AIR AIR ENTRANCE OPENINGS MODEL 4 5 BOWL VENT SYSTEM BOWL VENT STRAINER SCREEN AIR METERING PIN JET NOZZLE AIR VENT CHANNELS BOWL VENT CHANNELS PRIMARY IDLE DELIVERY SECONDARY IDLE DELIVERY AIR METERING PIN AIR METERED MECHANICAL THROTTLE FLY ECONOMIZER ACCELERATOR PUMP PUMP LEVER AND AIR METERING CAM ASS Y THIRD IDLE DELIVERY IDLE ADJUSTING NEEDLE IDLE EMULSION CHANNEL Ni FLOAT VALVE AND SEAT SN MIXTURE METERING VALVE ASSEMBLY IDLE TUBE 222 lig IDLE FUEL ORIFICE IDLE SUPPLY OPENING ERRORS MIXTURE METERING SLEEVE NOZZLE MAIN PUMP INLET CHANNEL MIXTURE METERING VALVE PUMP INLET CHECK VALVE FUEL CHANNEL NOZZLE OUTLET POWER JET NOZZLE BLEED HOLES POWER JET GASKET NOZZLE WELL PUMP PLUNGER VENTURI PUMP IDLER LEVER AND BUSHING ASSEMBLY FUEL AIR MIXTURE LI AIR 6 CARBURETOR FIGURES MODEL 6 IDLETUBE BO
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