VW Digifant I, II Service Repair Manual

VW Digifant I, II Service Repair Manual PDF free online

Fuel systems can be repaired by following the step-by-step procedures shown in this book.

Make Sure You Understand The Customer’s Complaint

— Identify the symptoms as you follow the diagnosis procedure. Try to determine the cause of the problem.
— Repair the problem after you have identified the symptoms.
— After completing repairs, always road test the vehicle before returning it to the customer.

Preliminary Checks

A complaint may be caused by a minor detail. Before starting the fault finding procedure, make a fev visual checks, such as:

— Are all electrical connections clean and tight? Spark plug wires not hanging loose, etc.
— Are all hoses OK? Check vacuum, crankcase ventilation, fuel tank ventilation, and air intake hoses for restrictions, cracks, or looseness.
— Are all the ground connections OK?
— Is there adequate fuel supply?

Pinpointing The Problem
Remember the basics:

— No matter how advanced the system, to start and run an engine you need correct spark timing, anc the proper fuel-to-air ratio.
— Get as much information as possible from the customer.
— Gather as many symptoms as possible.
— Check the simple things first.
• Look for spark.
• Listen for the fuel pump.
• Feel the injectors operating.
— Make logical deductions, not assumptions.

Intermittent Engine Performance Complaints

Intermittent performance complaints can be caused by any part of the electrical, ignition, or fuel systems. Therefore, obtain as much information as possible from the customer. Find out under wha conditions the problem occurs, how often, and for what duration. For example: engine cold?,dunn» warm-up?, under load?, light acceleration?, highway driving?, only in hot weather?, only at high altitude j etc…. If possible, road test the vehicle to duplicate the condition.

When troubleshooting intermittent engine performance complaints:

— Pay very close attention to electrical connections on the fuel injection harness. Connectors whicl have insufficient tension, are bent, or show signs of corrosion should be replaced and not repaire.
— Corroded and/or loose ground connections should be cleaned and tightened.
— The complete fuel system should be checked, including the fuel quality.


  • System Components/Operation
    • System Description
    • Electronic Control Unit (E.C.U.)
    • Coolant Temperature Sensor
    • Fuel Pump
    • Air Flow Sensor
    • Intake Air Temperature Sensor
    • Fuel Pressure Regulator
    • Fuel Injectors
    • Throttle Switch
    • Fuel Filters
    • Oxygen Sensor
    • Ignition System
    • Idle Stabilization
    • Crankcase Emission Control/Vent-Line Heating Element
    • Evaporative Emission System
  • Checking/Adjusting
    • Throttle Valve
    • Throttle Switch (Adjusting)
    • Throttle Switch (Wiring And E.C.U. Check)
    • Coolant Temperature Sensor
    • Air Flow Sensor/lntake Air Temperature Sensor
    • Fuel Injectors (Spray Pattern, Quantity)
    • Fuel Injectors (Leak Checking, Wiring Test)
    • Deceleration Fuel Cut-Off
    • Full Throttle Enrichment
    • Oxygen Sensor System
    • Fuel Pump (Pressure, Volume Test, Current Draw)
    • Fuel Pump (Electrical)
    • Fuel Pressure Regulator
    • Residual Fuel Pressure
    • Ignition System
    • Idle Stabilization System
    • Evaporative Emission System
  • Basic Engine Adjustments
    • Ignition Timing, Idle Speed, CO Content
  • System Check With Volt/Ohmmeter
    • System Test Chart
    • Functioning Wiring Diagram
    • Special Tools Required
    • Glossary/Component Location


Driveability problems that occur even when all engine specifications are in order may be caused by injector tip gum-up or carbon build-up on the intake valves and injector tips. These deposits are related to the use of gasoline with insufficient cleaning additives and can be prevented by:

— Using only major brand gasolines that advertise their additive packages are effective for cleaning fuel injection systems.
— Avoiding fuels that contain alcohol.
— Regular use of supplemental additives such as Autobahn Fuol Additivo, which is specially formulated to prevent carbon, gum or varnish build-up and help break down existing deposits.

Once formed, many deposits cannot be removed by normal preventative measures such as the use of fuel additives. Most injector deposits can be removed by using a special cleaning system like our G-16 Fuel Injection System Cleaner. Carbon build-up may require mechanical removal.

Check Group 24 of your Technical Information Book for further information on injection system cleaning and de-carbonization.

Language: English
Format: PDF
Pages: 51

VW Digifant I, II Service Repair Manual PDF free online