1979 Vw Beetle Fuel Injection Wiring Diagram

1979 Vw Beetle Fuel Injection Wiring Diagram – A dual relay provides power to the fuel pump and the ECU (Electronic Control Unit). There are two magnetic coils, one for each relay, named CR1 and CR2. Each relay has a normally open contact that is shown separately from the coil on the diagram. There is nothing magical about the “double relay.” Volkswagen simply decided to put two normal relays in a box

When the ignition switch is turned to the start position, voltage is applied to the starter solenoid and also to relay CR1 via terminals 86a, 86. A diode in series with coil CR1 prevents backflow. The cold start valve is also activated when the starter motor is cranked. The cold start is controlled by a thermo-time switch. The cold start valve will only inject fuel when the temperature is low enough to require it, and injection will stop after a preset time due to heating of the thermal timer during the cycle. If you start for a long time and the engine still does not start, the cold start injection will turn off to prevent flooding.

1979 Vw Beetle Fuel Injection Wiring Diagram

1979 Vw Beetle Fuel Injection Wiring Diagram

When the engine starts itself, the pump switch on the airflow sensor (airbox) closes from 39 to 36. This contact closure provides a “hold” circuit to relay CR1. Due to the holding circuit, current can now be removed from terminal 86 when the starter is disconnected. The hold circuit has a resistor built into the relay housing that provides enough current to hold current CR1.

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This circuit provides a safety feature in that the fuel pump will automatically shut off if the engine stalls. Also, when the ignition is on, the pump does not start. The starter motor should turn just before the pump starts.

Note: If the wire at the ECU terminal no. 1 is not connected to the correct terminal of the ignition coil, the engine will not run. The injectors fire at alternate point holes. All injectors light up at the same time. The ECU controls how long the injectors stay open after calculating factors such as engine temperature, RPM, airflow, and throttle opening.

The diagram shows the controls for the EGR valve and the maximum throttle switch. They were only like that for a few years. Also, in the early years there was no temperature sensor located on the airflow sensor.

A test light or voltmeter is useful for testing various parts of a circuit. If you are using an ohmmeter to test the dual relay out of circuit, be aware that the diodes will affect the resistance reading of the relay coil. The actual resistance of the relay coils is between 50 and 80 ohms. However, when measuring the resistance of the dual relay pins, the resistance will be between 100 and 500 ohms, depending on the scale and type of meter used.

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You can also check the hold circuit between pins 86b and 85. You should also measure between 100 and 500 ohms.

It is not possible to accurately measure the operation of the airflow sensor potentiometer with ohms, due to the design of the resistive elements. So if you’re trying to measure it and get erratic readings when you operate the airflow flap, there’s probably nothing wrong with that.

If the air flow sensor has 7 terminals (latest style), the resistance of the air temperature sensor can also be measured. At room temperature, the reading should be about 2500 ohms between terminals 6 and 27.

1979 Vw Beetle Fuel Injection Wiring Diagram

A double relay is usually a problem, but with a little patience and the use of a test lamp, problems in your circuitry can be isolated.

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A quick test is to have someone crank the engine while you feel for the electric fuel pump. If it works, you will be able to feel the pump motor turning.

Another common cause of the engine stalling or misfiring is the temperature sensor on the left side (#3) in the cylinder head. When cold (room temperature) the sensor should measure around 2500 ohms. At operating temperature the resistance will drop rapidly to about 100 ohms. If either test fails, replace the sensor. In an emergency, the sensor (Radio Shack) can be replaced with a variable resistor.

Don’t ignore bad connections when you have problems. Any one of the many snap fasteners may be loose or making poor contact. (Don’t forget the two pressure connectors on the fuel pump.) Note that there is no fuse anywhere in the IF circuit. You should check the ignition points.

Points with hard plugs or that are incorrectly spaced may fire, but still won’t reliably trigger the ECU to start the injectors. Also, visually inspect the carbon track rotor/cap and replace if they look suspicious.

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For a more detailed description of the other FI system controls, see the Robert Bentley manual for his car. 1978 FI System: Wiring Simplified FI: AFM (Air Flow Meter) 7-Pin AFM from AMSkeptics Dual Relay Tutorial Dual Relay Ignition Simplified. Running Engine Off: Dual Relay Starter: Dual Relay Starter: Dual Relay Wire Colors: Dual Relay Plugs: White wire is another wire found on the 79 Calif? FUEL FLOW LEAK TEST _________________________________________________________________________________________________________________ – VACUUM HOSE DIAGRAMS VACUUM HOSES 73-74 CARBURETOR VACUUM HOSES 75 DVDA SVDA VACUUM HOSES TO 76 VACUUM HOSES 76 1/2 TO 6 VACUUM HOSES TO 7/1/ 2 VACUUM HOSES 757 Model CA. DVDA by RATWells Vacuum Tube Vacuum Tubes Page 1 Review Steam Tubes Steam Tubes T: Air Regulator: Coal Steam Tubes: Pressure Regulator: SVDA: Deceleration and Vent Valve: ECU DI RAM CONTROL UNIT: https :///vw/forum/viewtopic .php ?p=8575116#8575116 “The Bosch L-Jetronic technical instruction manual has a very good overview of this. You can find it in PDF format online and read pages 16 and 17 for more information, but that’s about it. Related to this diagram and the fact that the basic injector timing is calculated and then corrected by certain mono factors, which are a combination of the engine status read from the sensors.” http://www.cardiagnostics.be/-now/Educational_site…Manual.pdf “The best L-Jetronic ECU block diagram I have found is not from Bosch, but from a 1977 Datsun 280Z manual. It is a 6 cylinder, but the logic is the same Absolutely (just think 4 cylinder and instead of engine temperature): “_________________ 73 Baja Beetle, Ghia front brakes, Type 3 rear brake, 1776, Solex 34 Pict-3, Bosch SVDA ’97 Mustang seats [77 Westy M license plate decoded] error error for vw virgin: index last edited by mal evolent on May 28, 2012 at 5:56 PM. m.; Held once in total

As always, great job! __________________ Toby http://www.aircoolednut.com/ Did I mention I’m an original Darksider? 72 VW Squareback 2007 cc 5 speed GB soft top; ’76 VW Riviera Sundowner 2.0L; 2015 Audi S5 Cabby with APR Stage II; Ducati Sport Classic 1000 from 2006; 2014 Ducati Diavel Strada http://www.type3registry .com/ – first foray

Nice collection, thanks for putting them together. _________________ > 78Gr┬Án Westphalia `Donkey’. It may be greater than you and it may be greater than me, but it is not greater than you and me; Can you dig it?

1979 Vw Beetle Fuel Injection Wiring Diagram

Great job gathering information. One suggestion would also be to include a key so others can know what the letters mean. _________________ Special thanks to: Headflow Masters – Vista, CA www.headflowmasters.com

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I found this in a gallery and thought it was cool… I’ve got some stuff on another computer too bad to try to dig it up. _________________ Sage Green Westy ’76 2.0 FI ’76 Creamsicle 7 Passenger 2.0 CS FI ’85 Tan Westy

In my opinion the most useful is the IF circuit shown in the standard current trace diagram. It would be quite useful to separate the FI part from the standard drawing. Another thing that would be great would be a troubleshooting chart similar to the one on the Vanagon Bentley. Using the Vanagon diagram requires almost no thinking, whereas using the information in the Bentley bay window can be an effort.

Dang, I wasn’t sure about that air filter =) Here are a few more, probably breached by rats in the wells, I found it helpful. 85 – Ground 86 – Thermal Timer and ECU Pin 4 86a – Jump Starter 86b – AFM Harness Connector #36 86c – Ignition Coils (+12v) Terminal 15 88a – AFM Harness Connector #39 88b – Resistors in Series and 8 Pins ECU 8 – 10 Governor Air 88d – Fuel Pump 88y – Battery +12v 88z – Battery +12v _________________ ’76 Sage Green Westy 2.0 FI ’76 Creamsicle 7pass 2.0 CS FI ’85 Tan Westy

Really nice, but too bad you didn’t post it on FI sticky so everyone could find it 2 years later. __________________ The deck contains 52 cards and 2 Jokers. No matter how much you argue about how to shuffle them, to be fair, there are only 52 cards and 2 jokers in a single suit.

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78 California ECU Scheme/thanks ratwell Last edited by Tcash on Thursday, Jul 7, 2016 at 4:32 PM; edited

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