Symptom-led fault-finding
Diagnostics
Every interactive flowchart in the archive, grouped by what the car is actually doing. Start from the symptom, answer a few questions, and the tree narrows the fault down to something you can test.
Answer a few questions and this will point you to the most likely cause, and the guide that covers the fix.
Interactive troubleshooter
Start from the symptom
6 steps
What is the car doing?
Ignition light stays on, or the battery keeps going flat
Most likely area
Charging system
An ignition light that stays on, or a battery that keeps going flat, points to the charging system: the fan belt (is it actually turning the dynamo?), the dynamo itself, the control box (the RB106 regulator), or the wiring between them. Check the belt first, then the dynamo output and the control box.
Ignition and charging →When you turn the key, what happens?
Nothing at all, no lights
Most likely area
Battery or earth
No lights usually means no power is getting through. On a positive-earth car the usual culprit is a poor battery connection or a corroded earth strap. Check the battery is charged, and that both terminals and the earth strap are clean and tight.
Wiring and loom colour codes →Turning the key to start, do you hear a click, or nothing?
A single click, or silence
Most likely area
Starter or its circuit
Lights but no crank points to the starter side: a battery too weak under load, a poor connection at the starter or solenoid, or the starter itself. Check the battery under load and the heavy cables and earth before condemning the starter.
Wiring and loom colour codes →It cranks, but slowly
Most likely area
Battery or connections
Slow cranking is usually a tired battery or poor connections, or simply thick oil on a cold morning. Charge and test the battery, then clean and tighten the terminals and the earth strap.
Wiring and loom colour codes →It cranks well. To split fuel from spark: pull a plug lead, hold it near bare metal and crank. Is there a fat blue spark?
Yes, a good blue spark
Most likely area
Fuel
A good spark but no start points to fuel. Check there is petrol in the tank, that the SU pump ticks when you switch on and then falls silent, that fuel reaches the carburettors, and that the float chambers are neither dry nor flooded. A stuck float or a blocked jet is common after the car has stood.
SU carburettor tuning →No spark, or a weak yellow one
Most likely area
Ignition
No spark points to the ignition side. On a T-Series that means the contact points (gap, burnt, or not opening), the condenser (a dead one kills the spark even when the points look fine), the coil, the cap and rotor, or the low-tension wiring. Start with the points and condenser.
Ignition and charging →I'd rather not test that
Most likely area
Fuel and spark
An engine needs both to fire. Fuel: petrol in the tank, the SU pump ticking, fuel reaching the carbs. Spark: the points opening with a clean gap, a sound condenser and coil, a good cap and rotor. Work through both in turn.
Technical Library index →How does it run badly?
Misfires or stumbles
Most likely area
Ignition or fuelling
A misfire is usually ignition (plugs, leads, points, condenser, cap) or fuelling (a blocked jet, a weak mixture, or an air leak at the manifold). Start with the plugs and points, then look at the carburettors.
Ignition and charging →Won't idle, or stalls
Most likely area
Carburettors
Poor idling on a T-Series nearly always comes back to the SU carburettors: the idle mixture and speed, worn throttle spindles drawing in air, or a piston that is sticking. Check the carbs and for air leaks.
SU carburettor tuning →Down on power
Most likely area
Tune, fuel or compression
Low power is usually tune (ignition timing and mixture) or a restricted fuel supply; if it persists and the tune is good, tired compression is the next suspect. Check timing and mixture first.
XPAG and XPEG settings and torque figures →When does it get hot?
Only in slow traffic
Most likely area
Airflow: fan and radiator
Overheating only in traffic points to airflow: a slipping fan belt, a tired fan, or a radiator core partly blocked so it cannot shed heat without road speed. Check the belt tension first, then the radiator.
Cooling and overheating on the XPAG and XPEG →All the time, even cruising
Most likely area
Cooling system or tune
Hot all the time suggests the cooling system or the tune: low coolant, a failing water pump, a stuck thermostat, a furred block or radiator, or ignition timing too retarded and a weak mixture making it run hot. Check coolant, timing and mixture.
Cooling and overheating on the XPAG and XPEG →It won't start
BeginnerMG T-Type Won't Start? A Step-by-Step Diagnosis
Start by reading how the engine refuses, dead silence, a slow churn, or spinning happily without firing, then split the fault between supply, spark and fuel.
- Nothing at all
- Turns slowly
- Cranks but won't fire
- Fires then dies
It misfires or runs rough
IntermediateMG T-Type Misfire & Rough Running: Finding the Cause
Misfires on the XPAG and XPEG are diagnosed by pattern. The tree asks when the misfire appears, then narrows it to ignition, mixture or a single dead cylinder.
- Rough at idle
- Stumbles under load
- Breaks up at high revs
- One dead cylinder
It's running hot
IntermediateKeeping the MG T-Series Cool: Cooling & Overheating
Overheating is almost always a system fault rather than a design one. The flowchart works from when the temperature climbs, in traffic, at speed, or always.
- Hot in traffic
- Hot at speed
- Losing coolant
- Gauge always high
The fuel pump has gone quiet
IntermediateThe SU Fuel Pump: Why It Stopped, and What to Do at the Roadside
The most famous failure in British classic motoring: the silence where the tick used to be. A roadside checklist you can work through at the kerb.
- No tick
- Continuous ticking
- Fuel starvation uphill
- Hot-weather stall
It runs, but never quite right
IntermediateMG XPAG Tuning: Stage 1, Stage 2 and Engine Specs
For a car that starts and runs but feels flat, heavy on fuel or reluctant to rev, the tuning troubleshooter works back from the symptom to the setting.
- Flat response
- Heavy on fuel
- Won't pull top gear
- Idles unevenly
There is a patch under the car
BeginnerOil and Fluid Leaks on the MG T-Series: What Is Dripping, and From Where
A puddle on the garage floor is the quickest symptom to spot, but not the easiest to read. The guide works from colour, smell and location to the likely source and how urgent it is.
- Dark oil
- Clear or green coolant
- Reddish brake or clutch fluid
- Fuel smell
Fix-it guides
Single-fault guides for the two systems that generate most of the letters: the Lucas charging circuit and the SU fuel side. No flowchart, just the ordered sequence of checks, and what each result rules out.
Transmission
The clutch judders, slips or drags
Which of the four clutch symptoms you actually have, why oil and mountings cause most judder, and the 7¼in to 8in change that decides which parts you order.
Electrics
Wiring and loom colour codes
What each loom colour carries on a TD or TF, how the TC differs, the RF95 and RB106 terminal letters, and a sequence for tracing a dead circuit.
Electrics
The dynamo isn’t charging
Ignition lamp on: belt, earths, brushes, the output test and field flashing, and how to tell a tired dynamo from a regulator fault.
Fuel system
The carburettor is flooding
Petrol dripping from a float chamber: sticking needle valve, punctured float, float level and pump pressure, in the order to check them.
These trees are a way of thinking, not a substitute for the Workshop Manual. Every setting they mention should be confirmed against the manual for your car before you adjust anything. For the full topic index, see the Technical Library.