Classic Car Diagnostics – Carb, Ignition & Electrical
Classic cars behave very differently from modern ones. Their fuelling, timing and electrical systems are mechanical, simple on paper, and sometimes full of character. Our diagnostic service focuses on getting to the true cause of common classic faults — poor running, misfires, rough idling, charging problems, lighting failures and more.
We specialise in carburettors, ignition systems, and vintage electrical faults, including those famous quirks from Lucas electrics, often jokingly known as the Prince of Darkness. We like to call the bill for sorting it out the price of darkness.
Why specialist diagnostics?
Older vehicles have aged wiring, worn tolerances, analogue fuel systems and ignition components that behave differently under heat or load. A rough idle might be carburetion, vacuum leaks, coil weakness, timing drift or even a dying alternator. We inspect systems as a whole to find the root cause – not just the most obvious symptom.
Carburettor Diagnostics
We work with SU, Stromberg, Weber, Solex and most period carburettors.
Typical checks include:
- Float level and needle valve inspection
- Jet cleanliness and sizing
- Synchronisation of multi-carb setups
- Choke mechanism function and cold-start behaviour
- Idle mixture and pilot jet adjustments
- Fuel delivery rate testing from tank to carb
Quick carb tips:
• Varnish from old petrol clogs small passages — a thorough clean often transforms running.
• Fuel delivery issues often mimic carb faults, so we test flow and pressure first.
Ignition Diagnostics
A strong spark and correct timing make the biggest difference to drivability. We test:
- Points, condenser and distributor cam wear
- Coil strength and secondary leakage
- Distributor cap, rotor and carbon-tracking faults
- Static and dynamic ignition timing
- Advance curve behaviour (centrifugal and vacuum)
- Advice and fitting of sympathetic electronic ignition upgrades
Pro tip:
If your engine backfires on acceleration, weak ignition or poor timing is often the cause — not the carb.
Electrical Diagnostics
From intermittent headlights to dead charging systems, electrical issues are extremely common in classics.
We test:
- Battery load and cranking capability
- Alternator/dynamo output and regulator health
- Main earthing points and continuity
- Switchgear, relays and fuse boxes
- Lighting circuits, instrument clusters and heater fans
- Voltage drop throughout the harness
Lucas Electrics – The Price of Darkness
Lucas systems have an infamous reputation, but much of it comes from age, corrosion and worn-out connectors rather than bad design. We deal with:
- Early alternator and dynamo regulator faults
- Weak or inconsistent earth paths
- Aged insulation and brittle wiring
- Failing wiper motors, heater switches and headlamp contacts
- Dash light flicker and voltage-drop issues
We repair or refurbish components sympathetically, keeping originality where possible.
Diagnostics Process
- Symptom discussion and background assessment
- Baseline checks — compression, timing, charging, carb function
- Targeted testing: oscilloscope ignition traces, fuel pressure, voltage drop
- Root-cause report with recommendations and options
- Follow-up testing after repair (optional)
Typical Symptoms We Solve
- Starts, then cuts out
- Poor idle or uneven running
- Backfires on acceleration
- Dim, flickering or dead lights
- Flat spots when driving
- Charging lights glowing at idle
- Intermittent electrical failures
Fees & Booking
Diagnostics from £65 for a basic half-hour inspection.
Half-day and full-day investigations are quoted based on vehicle complexity and required testing.
You receive:
- A written diagnostic report
- Oscilloscope ignition analysis
- Carburettor sync and mixture checks
- Charging system under-load testing