Transcription

WORKSHOP MANUALPorscheK-JetronicROBERT BOSCH

CONTENTSTest EquipmentComponent LocationVacuum DiagramTrouble-Shooting ChartVacuum LeaksComponent TestsAir Flow Sensor459101112Fuel PumpCold Start SystemWarm-Up RegulatorSystem PressureLeakage TestTesting InjectorsComparative TestIdle Speed and CO AdjustmentMounting Pressure TesterComponent RepairFuel Distributor Repair (911, 914)Fuel Distributor Repair (928)Fuel Pump RepairPressure Regulator RepairWarm-up Regulator Repair (911)Injector Removal (928)Throttle Activated ValveElectric Wiring DiagramParts ListTest Sheet2ROBERT K-Jetronic

INTRODUCTIONTesting Procedures . The construction and operation of the K-Jetronic (CIS) fuel injection system isdifferent from other fuel injection systems . Thetechnical instruction booklet Fuel Injection - Continuous Injection System (CIS) at the back of themanual describes the components and operation ofthe K-Jetronic fuel injection system in detail . Athorough understanding of the various components is required before working on K-Jetronic fuelsystems .Before trouble-shooting, testing or adjusting theK-Jetronic fuel injection system, the ignition system and the mechanical system of the engine(compression, valve timing, etc .) must be withinspecification and operating properly . Verify thatthese systems are in proper working order beforeproceeding further.K-Jetronic fuel systems have an electric safetycircuit which prevents the electric fuel pump andother electrical devices from operating unless theengine is running or being started . The electricsafety circuit can be bridged to apply voltage to anyelectrical component without running or startingthe engine . This procedure can be found in theElectric Wiring Diagram section of the manual .In addition, 911 SC models use a thermo-valve,which enriches the fuel mixture during starting byblocking the warm-up regulator vacuum which decreases control pressure . After starting, the valveopens by means of an electric heating element .Always use new gaskets, seals and 0-rings wheninstalling components or fuel lines .When installing the mixture control unit, tighten thefastening screws uniformly.Whenever work is performed on the fuel injectionsystem, the idle and CO must be adjusted .How to use this manual . Use the trouble-shootingchart to find the cause(s) for a given symptom . Thecause column will indicate what component(s)should be tested . Each component test instruction isa complete instruction . One component may bechecked by following the test instructions for thespecific component, or the entire system can bechecked by following all the component instructionsin order.The Tool List and Component Location sections willhelp identify the necessary tools and help locatevehicle components to be tested . Specific component removal and installation information can befound in Mounting the Pressure Tester and Component Repair The Electric Wiring Diagram sectionshows how to bridge the electric safety circuit toapply voltage to electrical components without running the engine . Replacement parts lists and complete test specifications can be found at the end ofthe workshop manual .Several component tests (Auxiliary Air Valve andWarm-up Regulator) require that the engine is cold .For cold tests, the engine must not have been runfor several hours, preferably overnight .Most vehicles since 1978 have fuel distributorswhich use push valvesin the system pressureregulator to maintain pressure . Several componenttests require special testing procedures for fueldistributors with push valves . The Fuel Pump section describes in detail how to identify a fuel distributor with a push valve in the system pressureregulator.Thoroughly clean the fuel fittings before removingany fuel lines . Dirt must not enter the fuel systemunder any circumstances . Do NOT bend the steelfuel lines . When removing fuel lines, always holdthe hex fitting on the component with one wrenchwhile loosening the fuel line with another wrench .Do not bend the steel type fuel lines .K-JetronicPorscheROBERT BOSCH3

TEST EQUIPMENTTOOLPART NUMBERAPPLICATIONPressure TesterKDEP 1034tests all working pressuresConnecting PartsKDEP 1034/10KDEP 103411013KDEP 1034/11pressure tester fuel line adaptersfor various enginesWrenchKDEP 1035manufacturer tooladjusts idle mixture (CO) all except928adjusts idle mixture (CO) for 928Guide RingsKDEP 1040/10KDEP 1040114for 80 mm diameter sensor platesfor 110 mm diameter sensor platesComparative TesterKDJE 7451tests injectors and fuel distributorfor equal deliveryAccessory SetKDJE 7451/25for use with KDJE 7451 when engineis fitted with steel fuel linesValve TesterKDJE 7452tests injectors1500 cc Graduatecommercially availablemeasures fuel pump deliveryTachometercommercially availablemeasures engine speed for idle andCO adjustmentCO metercommercially availablemeasures CO for fuel mixture adjustmentVacuum Pumpcommercially availablefor testing full load enriched warmup regulators4 ROBERT BOSCHPorscheK-Jetronic

COMPONENT LOCATION911T, 911,911Sthrough model 1975Mixture Control Unit (1), Injectors (2) . The Start Valve is located on backof intake manifold below the venturi assembly . The Thermo-timeSwitch is located on engine block below the secondary air pump .Warm-up Regulator (1)Fuel Pump Test Point (arrow)Electric Fuel PumpSecondary Air Pump Pressure Hose (arrow)K-JetronicPorscheBridging Electric Safety CircuitROBERT BOSCH 5

COMPONENT LOCATION911,911s, 911SCbeginning model 1976Mixture Control Unit with Air Filter Removed (1), Throttle Valve Assembly (2), Intake Housing (3), Secondary Air Pump (4)Fuel Pump Protective Cover (above), Fuel Pump(below)6ROBERT BOSCHFuel Pump Test Point (arrow)PorscheInjectors (5), Auxiliary Air Valve (6)CO Test Point for Vehicles with Catalytic ConverterK-Jetronic

924COMPONENT LOCATION.4yl123456Nv Start Valve (hidden) Warm-up Regulator Auxiliary Air Valve Injectors Fuel Filter Mixture Control Unitp17,Thermo-time Switch (aiiunderneath engine. viewed fromFuelcumulatoisDampers (3),NoiseExhaust Gas Ac ii(arrow)il,itiun ba-11Fuel Pump and Fuel Accumulator - 1976 modelK-JetronicFuel Pump Test Point (arrow)PorscheSecondary Air Pump Pressure Hose (arrow)ROBERT BOSCH7

COMPONENT LOCATIONStart Valve (1), Auxiliary Air Valve(4),Warm-up Regulator (5)(2), Thermo-time Switch (3), Injector928Mixture Control UnitFuel Pump Protective Cover (above), FuelPump No . 1 (below)Fuel Accumulator and Fuel Filter - located inright rear wheel welltlFuel Pump No . 2 - located under right rearfenderFuel Pump Test Point (arrow)Bridging Electric Safety Circuit, relay No . XVII(arrow)PorscheK-Jetronic8ROBERT BOSCH

VACUUMDIAGRAMit11IllF-18b-Lzz:z"[74610tI911 since 19761 Throttle Valve Assembly2 Electro Air Valve3 Auxiliary Air Valve4 Thermo-valve (only 911 SC)5 Warm-up Regulator6 Ignition Distributor7 Exhaust Gas Recirculation Valve (only California)8 Changeover Dump Valve9 Vacuum Limiter10 Vacuum Takeoff for Auxiliary Air Valve and Auxiliary Air Device11 Vacuum Takeoff Power-assisted Brake SystemK-JetronicPorscheROBERT BOSCH9

TROUBLE-SHOOTING CHARTFCD c0 a aqy roh- cy0,c \aa a'&Pco awayhyo\ayasc a.,y cs'. ,clb ,o moo J0 cyy Q ac0,a0,c. L cby0 \ '\a\aCauses)10-0-tt0-Vacuum system leaking (see Vacuum Leaks)0 Air flow sensor plate and/or control plunger not movingsmoothly (see Air Flow Sensor Movement)Air flow sensor plate stop incorrectly set (see Air FlowSensor Position)Auxiliary air valve does not open (see Auxiliary Air Valve)Auxiliary air valve does not close (seeAuxiliaryAir Valve)mo.Electric fuel pump not operating (see Fuel Pump)Defective cold start system (see Cold Start System)IN.Leaking cold start valve (see Cold Start System)0-Incorrect cold control pressure (see Warm-up Regulator)Warm control pressure too high (see Warm-upRegulator)10.11-Do-0-IIN-No.Warm control pressure too low (see Warm-up Regulator)Incorrect system pressure (see System Pressure)0-Fuel system pressure leakage (see Fuel Leaks)10.000No.No11o.Injection valve(s) leaking, opening pressure too low (seeTesting Injectors).Unequal fuel delivery between cylinders (seeComparative Test)Basic idle and/or CO adjustment incorrect (see Idle andCO Adjustment)Throttle plate does not open completely10 ROBERT BOSCHPorscheK-Jetronic

VACUUM LEAKSThere must be no air leaks in the air intake system .Any air drawn into the engine without passingthrough the air flow sensor will cause a lean air-fuelmixture condition and improper engine operation .To test for air leaks, remove the outlet hose from theauxiliary air valve and pressurize the hose with compressed air. Hold the throttle plate open and coat allair fittings (arrows below) with soapy water . Bubblesindicate a leak.Replace any defective hoses, gaskets or seals .K-JetronicPorscheROBERT BOSCH11

AIR FLOW SENSOR (updraft only)Sensor Plate/Plunger Movement . Engine temperaturemust be above 20 C (68 F) . Remove the rubber bootfrom the air flow sensor . Bridge the electric safetycircuit (see Electric Wiring Diagram) . Switch the ignition on for 10 seconds to apply control pressure to theplunger .Fully lift the sensor plate up by hand to its maximumdeflection as shown . Even resistance must be felt overthe entire lever movement . If not, the air flow sensorplate is not moving freely, (see below) .Now push the sensor plate down rapidly, almost backto its rest position . The plunger will not follow therapidly moving sensor plate, but the shock of theplunger hitting the sensor plate lever when it doescome down must be felt . If this cannot be felt, theplunger is not moving freely, (see below) .Fully lift the air flow sensor plate up to its maximumdeflection . When released, the sensor plate must fallback to its rest position after bouncing once or twiceon the spring stop . If not, the air flow sensor plate isnot moving freely, (see below) .If the air flow sensor plate does not move freely,loosen the mounting screws around the air flowsensor housing to check if housing warpage is causing the lever to bind . If necessary, replace the gasketunder the air flow sensor and uniformly tighten thefastening screws .If the plunger does not move freely, remove the fueldistributor from the air flow sensor (see Fuel Distributor Repair) . Remove the plunger from the fueldistributor. If it is necessary to blow compressed air inthe control pressure connection hole to free theplunger, hold the plunger with your hand as shown toprevent the plunger from falling out of the fuel distributor. Clean the plungerwith an appropriate solvent .If the plunger still binds in its barrel, replace the fueldistributor.12 ROBERT BOSCHPorscheK-Jetronic

Air Flow Sensor Plate Position . Remove the rubberboot from the air flow sensor . The sensor plate mustbe flat and pass through the narrowest part of thefunnel without touching the sides .If the sensor plate touches the sides of the funnel,loosen the sensor plate fastening screw . Insert theappropriate guide ring (see Too/List) . Hold the fastening screw with pliers to prevent the plate from movingdown as shown . When the guide ring is in place,tighten the fastening screw to 5 .0 - 5 .5 Nm (3 .7 - 4.0 ftIbs) . Then, loosen the screw and retorque the fastening screw again to the same value . The air flow sensorplate must not now be able to be turned by hand .Bridge the electric safety circuit (see Electric WiringDiagram) . Switch the ignition on for 10 seconds toapply control pressure to the plunger .The upper edge of the sensor plate should be flushwith the beginning of the upper cone as shown . Theupper edge of the sensor plate may be as much as 0 .5mm below the beginning of the upper cone, but mustNOT project up into the cone at all .Adjust the sensor plate position by removing the airfilter and bending the wire loop on the spring stop(arrow) or turning the adjusting screw (1) . Tighten thelock nut before rechecking the sensor plate position .K-JetronicPorscheROBERT BOSCH 13

AIR FLOW SENSOR (downdraft only)Sensor Plate/Plunger Movement . Engine temperaturemust be above 20 C (68 F) . Remove the air filter fromthe air flow sensor . Bridge the electric safety circuit(see Electric Wiring Diagram) . Switch the ignition onfor 10 seconds to apply control pressure to theplunger .Fully push the sensor plate down by hand to itsmaximum deflection as shown . Even resistance mustbe felt over the entire lever movement . If not, the airflow sensor plate is not moving freely, (see below) .Now pull the sensor plate up rapidly, almost back toits rest position . The plunger will not follow therapidly moving sensor plate, but the shock of theplunger hitting the sensor plate lever when it doescome down must be felt . If this cannot be felt, theplunger is not moving freely, (see below) .Fully push the air flow sensor plate down to itsmaximum deflection . When released, the sensor platemust fall back to its rest position after bouncing onceor twice on the spring stop . If not, the air flow sensorplate is not moving freely, (see below) .If the air flow sensor plate does not move freely,loosen the mounting screws around the air flowsensor housing to check if housing warpage is causing the lever to bind . If necessary, replace the gasketunder the air flow sensor and uniformly tighten thefastening screws .If the plunger does not move freely, remove the fueldistributor from the air flow sensor (see Fuel Distributor Repair) . Remove the plunger from the fueldistributor. If it is necessary to blow compressed air inthe control pressure connection hole to free theplunger, hold the plunger with your hand as shown toprevent the plunger from falling out of the fuel distributor. Clean the plunger with an appropriate solvent .If the plunger still binds in its barrel, replace the fueldistributor.14 ROBERT BOSCHPorscheK-Jetronic

Air Flow Sensor Plate Position . Remove the air filterfrom the air flow sensor . The sensor plate must bef