Morris Minor Running Badly Fault Diagnosis | Blind Man Morris

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Fault Diagnosis

Help - My Morris is Running Badly

First Checks

What have you recently worked on?

What component have you worked on or replaced immediately before this issue occurred?

Are there any obvious loose wires or hoses in the engine bay?

Has the dashpot got oil in it?

My Morris is Misfiring

The misfire is regular in rhythm

If this is the case, this narrows the issue down to one cylinder area.
The likely causes are:
- Bad spark plug or sparkplug lead
- Disconnected sparkplug lead
- Issue with valves in one cylinder
- Defective head gasket affecting one cylinder

The misfire is irregular in rhythm

If this is the case, the issue is more likely to be system wide rather than cylinder specific

The likely causes are:
- Distributor
  - Check rotor arm, condenser, distributor cap, all leads
- Fuel system
  - Mixture set incorrectly
  - Incorrect jet adjustment
  - Air leaks between the carburettor and manifold or at the exhaust connection
  - Blockage due to sediment in the float bowl
- Mechanical
  - Consider an issue with the head gasket
  - A broken valve or spring
  - Or incorrect valve clearances

My Morris is backfiring

The backfire (snapback) is heard coming out of the carburettor, with fuel smelt in the engine bay

Likely Causes:
- Weak fuel mixture
- Weak spark due to an issue with the ignition system
- Valve sticking or broken/worn
- Air leaks

The backfire is coming from the exhaust tail pipe

This is due to unburnt fuel/air mixture, likely causes:
- Weak fuel mixture
- Weak spark/ignition
- Valve sticking or broken/worn

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