WORKSHOP MANUAL Porsche K-Jetronic

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 beflat . The chamfered edge of the sensor plate must facedown . The word 'top' or five punch marks arestamped on the top of the sensor plate .The sensor plate must pass through the narrowestpart of the funnel without touching the sides . If thesensor plate touches the sides of the funnel, loosenthe sensor plate fastening screw . Insert the appropriate guide ring (see Too/List) . Hold the fastening screwas shown to prevent the sensor plate from movingdown . When the guide ring is in place, tighten thefastening screw to 5 .0 - 5 .5 Nm (3 .7 - 4 .0 ft Ibs) . Then,loosen the screw and retorque to the same value . Theair flow sensor plate must not now be able to beturned 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 project up asmuch as 0 .5 mm above the beginning of the uppercone, but the lower edge of the sensor plate (abovethe chamfer) must not project down into the lowercone at all .If the sensor plate is too high, very carefully tap theguide pin (arrow) deeper into the housing . Caution :Make this adjustment very carefully . Adjustment several times in both directions will loosen the press fit ofthe pin, possibly causing engine damage .K-JetronicPorscheKNW4ROBERT BOSCH 15

AUXILIARY AIR VALVECold Operation . Test the auxiliary air valve first withthe engine cold (not run for several hours, preferablyovernight) . Disconnect the electric plug from the auxiliary air valve and from the warm-up regulator . Remove both air hoses from the auxiliary air valve .Using a flashlight and a mirror, look through the valveas shown . When the engine is cold, the valve must beopen . If not, replace the auxiliary air valve .Warm Operation . Attach the electric plug to the auxiliary air valve . Bridge the electric safety circuit (seeElectric Wiring Diagram) . Turn the ignition on . Theauxiliary air valve must be completely closed within10 minutes.If the auxiliary air valve does not completely closewithin 10 minutes, test the supply voltage (approximately 11 .5 volts, ignition off) available to the auxiliary air valve at the electric plug .If sufficient voltage is available to the auxiliary airvalve and the valve still does not close, replace theauxiliary air valve .16 ROBERT BOSCHPorscheK-Jetronic

FUEL PUMPThe test point for fuel pump operation depends on thetype of fuel distributor . Fuel distributors WITH pushvalves (most vehicles since 1978) have two fuel linesconnecting with the warm-up regulator . Fuel distributors WITHOUT push valves have only one fuelline connecting directly to the warm-up regulator ; theother fuel line connects to a "T" and returns to the gastank. Determine whether the vehicle to be tested isfitted with or without a push valve before proceedingfurther.-I K, z1 Z Disconnect the return fuel line leading to the gas tankat the appropriate test point, as indicated below forthe specific vehicle .Test Point for 911 : Disconnect the union fitting on thefuel return line from the fuel distributor (see Compo-nent Location) . Connect a temporary hose with anappropriate fitting (M 14 x 1 .5) to the line coming fromthe fuel distributor .Fuel Pump Test Point WITH Push ValveTest Point for 924 : Clean and disconnect the unionfitting located above the front axle (see ComponentLocation) .Test Point for 928: Disconnect the fuel line from theHfuel distributor which leads to the gas tank (seeComponent Location) . Connect a temporary fuel linewith an appropriate fitting (M 14 x 1 .5) to the outlet onthe fuel distributor .Hold the line coming from the fuel distributor in a1500 cc or larger graduate . Inflexible metal fuel linesmay require a rubber hose to reach the graduate .Remove the electric plug from the warm-up regulatorand the auxiliary air valve . Bridge the electric safetycircuit (see Electric Wiring Diagram) .Turn the ignition on for the amount of time specifiedfor Fuel Pump on the test sheet .Fuel Pump Test Point WITHOUT Push ValveIf fuel quantity is not within specification, check forsufficient voltage supply to the fuel pump (minimum11 .5 volts) or a dirty fuel filter . If all the above aresatisfactory, replace the electric fuel pump .K-JetronicPorscheROBERT BOSCH 17

COLD START SYSTEMThermo-Time Switch . This instruction applies only toRobert Bosch thermo-time switches .Remove the thermo-time switch from the engine .Engine coolent will spill out when the switch is removed from the engine . Find the design numberstamped on the flats of the thermo-time switch housing . Use the design number to find the appropriatetest values from the thermo-time switch chart below .Using an ohmmeter, check the resistance at both .temperatures indicated on the thermo-time switchchart . Use warm water to heat the switch as required .If any resistance does not fall within the specifiedtolerance, replace the thermo-time switch .THERMO-TIME SWITCH CHARTDesign NumberTemperature45 C/9 .5 sbelow 104 F30 - 4055 - 850120 - 160below 86 Fabove 104 F25 - 4050 - 800100 - 16050 - 80below 55 Fabove 73 F50 - 7050 - 700infinite50 - 7050 - 70below 50 Fabove 68 F50 - 7050 - 700infiniteinfiniteabove 122 F35 C/8 s18 C/8 s15 C/8 sResistance in ohmsfrom terminal from terminal from terminalG to Ground W to GroundG to W30-4055 - 8525 - 40infiniteCold Start Valve . Disconnect the electric plug fromthe cold start valve . Remove the cold start valve fromthe intake manifold . Hold the cold start valve in agraduate . A rubber hose may be required to reach thegraduate .Temporarily connect one start valve terminal toground and the other terminal to the " " terminal ofthe ignition coil . Bridge the electric safety circuit (seeElectric Wiring Diagram) . Turn the ignition on for notmore than 30 seconds . If the cold start valve does notspray, replace the cold start valve . Caution : Keep thecold start valve and connecting wires away from the" " battery terminal to prevent sparking .Turn the ignition off and disconnect the temporaryelectrical wires from the cold start valve . Wipe thecold start valve dry . With the electric safety circuit stillbridged, switch the ignition on for one minute . If thecold start valve drips or leaks, replace the cold startvalve .18 ROBERT BOSCHPorscheK-Jetronic

WARM-UP REGULATOR (CONTROLPRESSURE)Porsche uses several warm-up regulators on its vehicles . The testing procedure and test specifications aredifferent for each type of warm-up regulator. Find thewarm-up regulator type to be tested from the oneslisted below and proceed with the test instructions forthat specific type .Standard Warm-Up Regulator. Connect pressure tester KDEP 1034 (see Mounting Pressure Tester) . Usethe test specification for the specific warm-up regulator .Cold Control Pressure : The engine must be cold (notrun for several hours, preferably overnight) . Disconnect the plug from the warm-up regulator . Open bothvalve screws on the three-way valve of the pressuretester . Bridge the safety circuit (see Electric WiringDiagram) .Switch the ignition on to run the electric fuel pumpand read the cold control pressure on the gauge . Thepressure must be within the tolerance band given onthe appropriate test specification graph . Turn theignition off.to pressure gaugefWarm Control Pressure : Engine temperature is notimportant . Attach the plug to the warm-up regulator .Bridge the safety circuit . Open both valve screws onthe pressure tester as shown .Switch the ignition on to operate the electric fuelpump . When the pressure stops increasing, readwarm control pressure on the gauge . The warmcontrol pressure must be within the tolerance givenon the test sheet . Turn the ignition off.If the warm control pressure does not fall within thespecified tolerance, test the supply voltage (approximately 14 volts) available to the warm-up regulator .fto warm-upregulatorKDEP 1034from fueldistributorOpening Both Valve Screws(measuring control pressure)If sufficient voltage is available to the warm-up regulator, and the warm control pressure still does notfall within the specified tolerance, replace the warmup regulator .K-JetronicPorscheROBERT BOSCH 19

,e!P VacuumWarm-Up Regulator with Full Load Enrichment . Connect pressure tester KDEP 1034 (see Mounting Pressure Tester) . Use the test specification for the specificwarm-up regulator .Cold Control Pressure : The engine must be cold (notrun for several hours, preferably overnight) unlessotherwise indicated on the test sheet . Disconnect theplug from the warm-up regulator . Open both valvescrews on the three-way valve of the pressure tester .Bridge the safety circuit (see Electric Wiring Diagram) .Switch the ignition on to run the electric fuel pump .Apply the vacuum indicated on the test sheet (if any)to the warm-up regulator with a vacuum pump asshown . The cold control pressure indicated on thegauge must be within the tolerance band shown onthe appropriate test specification graph . Turn the ignition off .43 AtmosphereWarm Control Pressure : Test warm control pressurewith the warm-up regulator plug attached . Enginetemperature is not important . Bridge the safety circuit . Open both valve screws on the pressure tester asshown .Switch the ignition on to run the electric fuel pump .Apply the vacuum indicated on the test sheet (if any)to the warm-up regulator with a vacuum pump asshown . When the pressure stops increasing, read thewarm control pressure on the gauge . The warmcontrol pressure must be within the tolerance givenon the test sheet . Turn the ignition off .Warm Control Pressure WITH Throttle ActivatedValve: Test warm control pressure with the warm-upregulator plug attached . Position throttle plate againstidle stop .Switch the ignition on to run the electric fuel pump .When the pressure stops increasing, read the warmcontrol pressure on the gauge . If the warm controlpressure is not within the tolerance given for idle onthe test sheet, remove both fastening screws on thethrottle activated valve and turn the valve in the areaof the slots . If the idle value cannot be obtained,replace the throttle activated valve and readjust to thevalue given for idle on the test sheet.Position the throttle plate by hand about halfway . Ifthe pressure does not rise to the partial load valuegiven on the test sheet, replace the warm-up regulator .Completely open the throttle to the full load position .If the pressure does not drop to the full load valuegiven on the test sheet, replace the throttle activatedvalve and recheck the idle pressure .If the warm control pressure does not fall within thespecified tolerance, test the supply voltage (approximately 14 volts) available to the warm-up regulator .If sufficient voltage is available to the warm-up regulator, and the warm control pressure still does not20 ROBERT BOSCHPorscheK-Jetronic

fall within the specified tolerance, check the vacuumsource for a leak .If warm control pressure cannot be brought intospecification, replace the warm-up regulator .Warm-Up Regulator with Full Load and AltitudeCompensator. Connect pressure tester KDEP 1034(see Mounting Pressure Tester) . Use the test specification for the specific warm-up regulator .Cold Control Pressure: The engine must be cold (notrun for several hours, preferably overnight) unlessotherwise indicated on the test sheet . Disconnect theplug from the warm-up regulator . Open both valvescrews on the three-way valve of the pressure tester .Bridge the safety circuit (see Electric Wiring Diagram) .Switch the ignition on to run the electric fuel pump .Apply the vacuum indicated on the test sheet (if any)to the warm-up regulator with a vacuum pump asshown . The cold control pressure indicated on thegauge must be within the tolerance band shown onthe appropriate test specification graph . Turn theignition off.to pressure gaugeWarm Control Pressure : Test warm control pressurewith the warm-up regulator plug attached and theengine warm . Use station pressure from the localairport or weather bureau, NOT the correctedbarometric pressure reported to the public, whenreading the warm control pressure graph on the testsheet . Bridge the safety circuit . Open both valvescrews on the pressure tester as shown .Switch the ignition on to run the electric fuel pump .Apply the vacuum indicated on the test sheet (if any)to the warm-up regulator with a vacuum pump asshown . When the pressure stops increasing, read thewarm control pressure on the gauge . The warmcontrol pressure must be within the tolerance givenon the test sheet (use upper curve when testing WITHvacuum) . Turn ignition off.fF 1:21to warm-upregulatorOO3KDEP 1034ffrom fueldistributorOpening Both Valve Screws(measuring control pressure)If the warm control pressure does not fall within thespecified tolerance, test the supply voltage (approximately 14 volts) available to the warm-up regulator .If sufficient voltage is available to the warm-up regulator, and the warm control pressure still does notfall within the specified tolerance, check the vacuumsource for a leak .If the high control pressures required for high altitudes cannot be obtained, increase system pressureto the high side of the tolerance band (see SystemPressure) .If warm control pressure cannot be brought intospecification, replace the warm-up regulator .K-JetronicPorscheROBERT BOSCH 21

SYSTEM PRESSURETesting System Pressure . Engine temperature is notimportant . Connect pressure tester KDEP 1034 asindicated in Mounting Pressure Tester . Bridge theelectric safety circuit (see Electric Wiring Diagram) .Close the pressure tester valve screw leading to thewarm-up regulator as shown .to pressure gaugeTurn the ignition on . Read the system pressure on thegauge and compare this reading with the valueshown on the test sheet .2rJfto warm-upregulatorKDEP 1034from fueldistributorClosing Valve Screw to Warm-up Regulator(measuring system pressure)If system pressure is lower than the value given onthe test sheet, test the fuel pump . If the fuel pump iswithin specification, adjust the system pressure asindicated below .If system pressure is higher than the value shown onthe test sheet, check the gas tank return line for arestriction . If there is no restriction in the return line,adjust the system pressure .Adjusting System Pressure . If the fuel distributor isfitted WITH a push valve, unscrew the large screwplug with attached push valve assembly . Change theadjusting shim as required . A 0 .1 mm increase in shimthickness will increase system pressure 0 .15 bar (2 .2PSI) . Use a new O-ring and copper gasket whenreinstalling the large screw plug and push valve .Note : The piston in front of the shim is matched to thehousing and is not replaceable.SYSTEM PRESSURE REGULATOR(without push valve)If the fuel distributor is fitted WITHOUT a push valve,remove the screw plug and change the adjusting shimas required . A 0 .1 mm increase in shim thickness willincrease system pressure 0 .15 bar (2 .2 PSI) . Use a newcopper gasket when installing the screw plug . Tightenthe screw plug to 13 - 15 Nm (10 - 11 ft Ibs) . Note : Thepiston in front of the shim is matched to the housingand is not replaceable.1 Fuel distributor housing2 0-ring3 Control piston4 Spring5 Retainer6 Retaining ring7 Spring8 Shims10 Valve needle11 Seal ring12 Screw plug13 Screw plug14 Flat seal ringa from fuel distributorb from warm-up regulatorc fuel return22 ROBERT BOSCHPorscheK-Jetronic

LEAKAGE TESTThe engine must be warm, but not hot . Connectpressure tester KDEP 1034 (see Mounting PressureTester) . Bridge the electric safety circuit (see ElectricWiring Diagram) . Open both valve screws on thethree-way valve as shown .to pressure gaugefTurn the ignition on . When warm control pressure isreached, turn the ignition off. After the specified time,the control pressure must NO

6 Ignition Distributor 7 Exhaust Gas Recirculation Valve (only California) 8 Changeover Dump Valve 9 Vacuum Limiter 10 Vacuum Takeoff for Auxiliary Air Valve and Auxiliary Air Device 11 Vacuum Takeoff Power-assisted Brake System-Lzz:z" b 6 Ill it 11 10 F-1 8 [74 t I K-Jetronic Porsche ROBERT BOSCH 9