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Starter works but engine does not start

Step 1: Is ignition system in proper condition?

Check battery voltage, ignition distributor, spark plugs, ignition coil, ignition timing, etc.

  • Yes: Go to Step 2
  • No: Repair or replace damaged ignition components

Step 2: Is engine in proper mechanical condition?

If engine still does not start or starts only poorly after the electrical test, check for mechanical problems: Compression, basic adjustment of valves and engine oil pressure.

  • Yes: Go to Step 3
  • No: Repair or replace damaged components

Step 3: Are all hose lines attached? Are these lines in proper condition?

Check whether hoses in the air intake system are attached properly, tightened firmly in place, not kinked and not damaged.

  • Yes: Go to Step 4
  • No: Repair or replace damaged lines and hoses

Step 4: Check the fuel pressure according to the Test Chart. Is the fuel pressure correct?

  • Yes: Go to Step 5
  • No: Go to Step 4-A

Step 4-A: Crank engine. Check whether fuel pump operates (aural check). Is it running?

  • Yes: Check fuel line and filter to be sure they permit throughflow. Filter in tank clogged? Corrosion in tank?
    Check pressure regulator according to the Test Chart.
  • No: Go to Step 4-B

Step 4-B: Crank the engine. Check whether voltage is present at the disconnected pump plug.

  • Yes: Replace fuel pump
  • No: Go to Step 4-C

Step 4-C: Check whether voltage is present at the pump fuse and at the double relay terminals 88y and 88d.
  • No: Replace the pump fuse and/or double relay

Step 5: Is the start valve in the proper condition?

  • Yes: Go to Step 6
  • No: Go to Step 5-A

Step 5-A: Check cold start valve according to Test Chart. Voltage at cold start valve OK?

  • Yes: Test the start valve mechanically.
    Remove the valve from the intake manifold and hold it in a container (Caution: fire risk!).
    During starting and with engine temperature below 50 F the valve must spray fuel for max. 20 seconds. At a temperature above 104 F the valve must not spray fuel.
    Carry out the spray test at temperatures above 104 F as follows: remove the plug from the thermo-time switch and connect terminal "W" to ground.
    If spray test cannot be carried out, see cold-start relay.
  • No: Check cable 45 for continuity to thermo-time switch terminal G. Check cable 46 for continuity to thermo-time switch terminal "W"

Step 6: Is the thermo-time switch in proper condition?

  • Yes: Go to Step 7
  • No: Go to Step 6-A

Step 6-A: Check thermo-time switch according to Test Chart. Does the switch check out OK?

  • Yes: Check cables 45 and 46 from the start valve for continuity (see Wiring Diagram).
  • No: Replace the thermo-time switch

Step 7: Is the auxiliary air device in proper condition?

  • Yes: Go to Step 8
  • No: Go to Step 7-A

Step 7-A: Visual check of the auxiliary air device: in the cold condition the device must be open, with the engine warm it must be closed.
  • No: Replace auxiliary air device

Step 8: Is the air intake system leak-tight?

Check the intake manifold, components attached to the intake manifold, and all hose connections for leaks. Using compressed air and soapy water localize any leaks present.

  • Yes: Go to Step 9
  • No: Repair leaks

Step 9: Is the air-flow meter in proper condition?

Check pump contacts in air flow meter according to Test chart. Remove the upper section of the air filter.
Open the air-flow meter flap by hand. It must be possible to open the air-flow meter flap with uniform ease from its fully closed position to its fully open position, and then this flap must close completely by itself. When the air-flow meter flap is opened it must not catch at any point. Watch for any indications of abrasion or rubbing.

When air flow-meter flap is opened, if the inside of the air-flow meter is very dirty, clean it.