Engine fault diagnostics (VW Transporter T4)

If the engine does not start, you should look for the cause, systematically narrowing the search circle. In order for the engine to start at all, two basic conditions must be met. The air-fuel mixture must enter the cylinders and a spark must jump at the spark plugs. The check should always begin with the presence of fuel supply. How to proceed in this case is described in subsection 2.17.3.2.

1. To determine the presence of a spark, unscrew the spark plugs, insert them into the spark plug connector and apply them sequentially to the ground. It is not recommended to hold the connector with your hand. It is necessary to use well-insulated pliers. With outside help, turn the engine with the starter.

2. If there is no spark, see. subsection 2.14.8.

3. For diesel engines, check the spark plug preheating system.

Caution! When diagnosing, pay attention to the safety instructions for handling electronic ignition systems (see subsection 2.14.2).

Cause	Method of elimination
The engine starts poorly or does not start at all
Gasoline engine
Errors when starting	Turn the ignition key and start until the engine starts, then release the ignition key. During starting, the clutch pedal must be depressed. Do not give gas.
	Only when the engine is hot, add a little gas after starting.
Diesel engine
Errors when starting	On a cold engine: pull the cold start accelerator valve all the way out. Turn on the ignition until the pre-heating indicator lamp goes out. Press the clutch. Start the engine immediately after the indicator lamp goes out, do not press the gas. As soon as the engine warms up to operating temperature, push the cold start accelerator valve all the way in. If the engine starts irregularly when starting, continue turning the starter (max 1/2 min.), until the engine starts on its own. If the engine does not start, preheat it again and repeat the start as described.
	When the engine is warm: no preheating is required. The engine can be started immediately.
The fuse is faulty:	Check the fuses (see subsection 10.10).
- electric fuel pump
- electronic fuel injection system
- preheating systems
Engine power supply system is faulty
Contaminated, fuel line is kinked, filter is clogged	Check the engine power supply system according to the fault diagnostics.
The starter turns too slowly	Charge the battery. If seasonal oil is poured in, winter oil must be poured in during the cold season. Check the starter.
Compression pressure too low	Check hydraulic lifters, overhaul the engine.
Malfunction of the valve timing mechanism	Check the valve timing mechanism, check the timing belt tension.
The cylinder head gasket is blown	Replace the gasket.