Engine fault diagnostics (Peugeot 305)

The engine does not turn over with the starter

• The battery is dead
• The battery terminal contacts are loose or corroded
• A break in the wiring to the starter or poor grounding of the engine or battery
• The starter or solenoid is faulty (see chapter 10)
• The ignition/starter switch is faulty
• Major mechanical failure (the engine seized up)
• The piston rings are rusted to the cylinder liners (after the car has been idle for a long time)

The starter turns the engine slowly

• The battery is dead
• The battery terminal contacts are loose or corroded
• A break in the wiring to the starter or poor grounding of the engine or battery
• The wrong brand of oil was poured into the engine. Starter malfunction (see chapter 10)

The engine turns over normally with the starter, but does not start

• The ignition wires are damp or dirty
• The breaker contacts are dirty or incorrectly adjusted
• Spark plugs are fouled or have an incorrect spark gap
• Broken spark plug wires
• Other malfunctions of the ignition system (see chapter 4)
• The fuel tank is empty or the fuel pump is faulty
• Excessive or insufficient suction
• The air damper drive mechanism is incorrectly adjusted
• The air purifier is clogged
• The carburetor jet(s) are clogged
• Other fuel system faults (see chapter 3)
• Incorrectly adjusted valve clearances
• The valve timing is incorrectly adjusted (after engine overhaul)
• Poor compression in the cylinders

The engine catches but does not start

• Loose ignition wire contacts or internal break in the wire
• The intake manifold or carburetor gasket is leaking air
• The fuel pump is faulty
• Other fuel system faults (see chapter 3)

Rough idle

• The carburetor is out of adjustment or clogged (see chapter 3)
• The ignition timing is incorrectly adjusted (see chapter 4)
• Incorrectly adjusted valve clearances
• The intake manifold or carburetor gasket is leaking air
• The air filter is clogged
• Different compression in the cylinders due to wear or gas leakage
• The distributor is worn out
• The timing mechanism components or valve mechanism are worn out

Flash skip

• Spark plugs are fouled or have an incorrect spark gap
• High voltage wires are damp, dirty or have internal damage
• The breaker contacts are blocked or incorrectly adjusted
• Other malfunctions of the ignition system (see chapter 4)
• The intake manifold or carburetor gasket is leaking air
• The carburetor is poorly adjusted or the jet(s) are clogged
• Dirty fuel
• Other fuel system faults (see chapter 3)
• Incorrectly adjusted valve clearances
• The valve is sticking, not seated correctly, or is burnt
• The valve spring(s) is broken
• Different compression in the cylinders due to wear or gas leakage

The engine does not develop the required power

• The ignition timing is incorrectly adjusted
• The air purifier is clogged
• Engine overheating
• The carburetor is poorly adjusted or the jet(s) are clogged
• Incorrectly adjusted valve clearances
• The distributor is not working properly (automatic ignition regulators do not work)
• The brakes are sticking
• Excessive carbon deposits in the cylinder head
• Poor compression
• The valve timing is incorrectly adjusted (after engine overhaul)

Detonation or knocking when increasing engine speed

• Incorrect octane rating of fuel
• Too early ignition or automatic ignition regulators do not work
• The carburetor is incorrectly adjusted
• Overheat
• Excessive carbon deposits in the cylinder head
• The valve timing is incorrectly adjusted (after engine overhaul)

The engine makes an unusual noise

• Unintended metal contact (for example, fan blades)
• The drive belt is worn out
• Peripheral equipment failure (for example, a water pump or a generator)
• Excessive valve clearances (knocking sound)
• The sprockets or timing chain are worn out
• Broken piston ring(s) (ticking sound)
• The connecting rod bearings are worn out (knocking, may decrease under load)
• The main bearings are worn out (heavy, dull thuds that may increase under load)