You turn the key or press the start button.
Nothing.
Maybe there's a click.
Maybe the engine turns over but refuses to start.
Perhaps it starts and immediately cuts out.
Or, most frustratingly:
IT STARTS PERFECTLY WHEN IT GETS TO THE WORKSHOP.
“Car won't start” sounds like one problem.
Diagnostically, it isn't.
One of the first things we need to establish at The Cape Brake Co is what the vehicle actually does when you try to start it.
Because:
DOESN'T CRANK
CRANKS BUT DOESN'T START
and
STARTS THEN CUTS OUT
can send the diagnosis in very different directions.
WHAT DOES “CRANKING” MEAN?
When you attempt to start the vehicle, the starter motor turns the engine.
That turning action is called cranking.
You'll normally hear the engine rotating:
rrr-rrr-rrr-rrr
before it starts running under its own power.
This gives us our first important question:
DOES THE ENGINE ACTUALLY TURN OVER?
WHAT DOES “NO CRANK” MEAN?
A no-crank condition means you attempt to start the vehicle but the starter doesn't turn the engine normally.
You might experience:
- Complete silence
- One click
- Rapid clicking
- Dashboard lights dimming
- Dashboard lights remaining normal but nothing happening
- Intermittent starting
Possible areas requiring investigation can include:
- Battery
- Battery terminals
- Cables and earths
- Starter motor
- Starter circuit
- Relays or fuses
- Ignition/start request
- Clutch or park/neutral interlocks
- Immobiliser/security system
- Wiring
- Control modules
That's already considerably more than simply:
“IT NEEDS A BATTERY.”
DOES CLICKING MEAN THE BATTERY IS FLAT?
It can, but not always.
Rapid clicking when attempting to start can be associated with insufficient voltage or current reaching the starter system.
A weak battery is one possible cause.
But battery-terminal condition, cable resistance, earth connections and other electrical issues can also matter.
A single heavy click may lead the investigation in a different direction.
The sound is useful information.
It isn't the complete diagnosis.
CAN THE LIGHTS WORK EVEN IF THE BATTERY CAN'T START THE CAR?
Absolutely.
Your lights and infotainment system require far less current than the starter motor.
A battery may therefore have enough available energy to illuminate the dashboard while struggling badly when asked to crank the engine.
So:
“THE LIGHTS WORK, SO THE BATTERY MUST BE FINE”
isn't a reliable battery test.
DOES A FLAT BATTERY ALWAYS MEAN THE BATTERY IS BAD?
No.
If the battery is discharged, we still need to ask:
WHY?
Possibilities can include:
- Battery deterioration
- Charging-system problems
- Something being left switched on
- Electrical drain while parked
- Poor connections
- Vehicle standing for an extended period
Replacing a battery without understanding why it went flat can sometimes result in another flat battery.
WHAT IF THE ENGINE CRANKS BUT WON'T START?
Now the problem changes considerably.
The starter is turning the engine.
So the question becomes:
WHY IS THE ENGINE NOT RUNNING?
Depending on the vehicle, diagnosis may involve areas such as:
- Fuel delivery
- Ignition
- Engine-speed or position information
- Air-management systems
- Engine-management electronics
- Immobiliser authorisation
- Wiring
- Power supplies
- Mechanical engine condition
Modern engine management relies on multiple inputs and conditions before the engine can operate correctly.
That's why cranks but won't start needs systematic diagnosis.
CAN A CRANKSHAFT SENSOR STOP A CAR FROM STARTING?
Potentially.
Engine-management systems need to know engine position and speed.
Sensors such as crankshaft and camshaft position sensors can provide information required for ignition, injection and engine synchronisation.
But if a diagnostic code mentions a crankshaft or camshaft signal, that doesn't automatically mean:
BUY A SENSOR.
The problem could involve:
- Sensor
- Wiring
- Connector
- Power supply
- Signal integrity
- Timing relationship
- Mechanical issue
- Another system affecting the signal
Again:
CODE = CLUE.
CAN AN IMMOBILISER STOP MY CAR FROM STARTING?
Yes.
An immobiliser is designed to prevent unauthorised operation of the vehicle.
Depending on the vehicle, starting may require successful communication or authorisation between components such as:
- Key or transponder
- Immobiliser system
- Body control module
- Engine control module
- Antenna/reader
- Other security-related electronics
If the vehicle doesn't recognise or authorise the key, it may prevent starting in different ways depending on the system.
Some vehicles may not crank.
Others may crank but not start.
Some may start and then stop.
HOW DO I KNOW IF IT'S AN IMMOBILISER PROBLEM?
Possible clues can include:
- Security/key warning light
- “Key not detected” message
- Immobiliser warning
- One key works and another doesn't
- Vehicle starts intermittently depending on the key
- Engine starts and immediately stops
- Security-related diagnostic faults
But not every no-start accompanied by a key symbol is necessarily a failed key.
Proper diagnosis still matters.
CBC also has key-coding and immobiliser diagnostic capability for supported vehicles.
SHOULD I TRY MY SPARE KEY?
If you have one, yes.
If the vehicle won't recognise one key but starts normally with another known-good key, that is valuable diagnostic information.
Tell us.
Don't throw the non-working key away, though. We may still want to examine what the vehicle is recognising.
WHAT IF THE CAR STARTS AND THEN IMMEDIATELY DIES?
This can have several possible causes.
Security authorisation is one possibility on certain vehicles.
But engine-management, fuel, air or other faults may produce superficially similar behaviour.
Tell us exactly what happens:
“IT STARTS FOR TWO SECONDS AND CUTS OUT.”
That's much more useful than:
“IT DOESN'T START.”
WHY DOES MY CAR SOMETIMES START AND SOMETIMES NOT?
Intermittent faults can be some of the most challenging problems to diagnose.
They may depend on:
- Temperature
- Battery voltage
- Engine temperature
- Vibration
- Wiring movement
- Component position
- Moisture
- Time
- Electrical load
A vehicle that starts perfectly ten times in the workshop can still have a genuine intermittent starting fault.
The challenge is reproducing it or finding evidence left behind by the failure.
WHY WON'T MY CAR START WHEN IT'S HOT?
A temperature-related starting complaint is particularly useful diagnostic information.
Certain electrical and mechanical components can behave differently as they heat up.
If the vehicle:
STARTS PERFECTLY COLD BUT WON'T RESTART HOT
tell us exactly that.
Similarly, if the opposite occurs:
STRUGGLES FIRST THING IN THE MORNING BUT STARTS FINE ALL DAY
that's useful too.
Patterns matter.
WHY WON'T MY CAR START AFTER SITTING OVERNIGHT?
If the battery is repeatedly discharged after the vehicle stands, we may need to investigate why electrical energy is being lost.
That could potentially involve:
- Battery condition
- Charging performance
- Electrical drain
- Module behaviour
- Accessories
- Wiring faults
An electrical drain that occurs while the vehicle is switched off is often referred to as a parasitic draw.
Finding one can require methodical testing because the offending circuit may not remain active all the time.
COULD THE ALTERNATOR BE THE PROBLEM?
Possibly.
The alternator is responsible for supplying electrical power and charging the battery while the engine is running.
If the charging system isn't operating correctly, the battery may gradually discharge.
Eventually, there may not be enough energy left to restart the vehicle.
But replacing the alternator because the battery went flat is still guessing.
Charging-system performance can be tested.
COULD IT BE THE STARTER MOTOR?
Yes, particularly in a no-crank complaint.
A starter motor or its associated solenoid can fail or become intermittent.
But before condemning the starter, we need to know whether it is receiving the correct:
- Power
- Earth
- Start command
A perfectly good starter can't operate if the electrical supply to it is poor.
Likewise, replacing the starter won't fix a faulty control circuit.
CAN A BAD EARTH STOP A CAR FROM STARTING?
Absolutely.
Electrical current needs a complete circuit.
Poor earth connections can cause:
- Slow cranking
- Clicking
- Voltage drop
- Intermittent starting
- Strange electrical behaviour
Corrosion, damaged cables or poor connections can sometimes create symptoms that look like component failure.
This is why voltage-drop testing can be so valuable.
CAN A BLOWN FUSE CAUSE A NO-START?
Potentially.
Depending on which circuit is affected, a fuse or power-supply problem can prevent important systems from operating.
But if a fuse has blown, we also want to know:
WHY DID IT BLOW?
Simply fitting another fuse without considering the underlying cause may result in the replacement failing again.
WHY DOES MY CAR SAY “KEY NOT DETECTED”?
On keyless-start vehicles, communication must occur between the vehicle and the key.
Possible issues can involve:
- Key battery
- Key itself
- Antenna/receiver systems
- Vehicle battery voltage
- Security system
- Communication faults
Some vehicles also provide an emergency key-detection location or procedure if the key battery is weak.
The correct procedure is vehicle-specific.
SHOULD I KEEP TRYING TO START IT?
Repeatedly cranking a vehicle that isn't starting isn't always helpful.
It can:
- Further discharge the battery
- Overheat the starter
- Complicate diagnosis
- Potentially create additional issues depending on the fault
A couple of attempts can help establish the symptom.
Twenty increasingly desperate attempts generally don't.
WHY IS A VIDEO USEFUL?
No-start faults have an annoying habit of disappearing when the vehicle reaches the workshop.
If it's safe to do so, record the dashboard and sound while attempting to start the vehicle.
We may be able to see:
- Warning lights
- Security messages
- Instrument behaviour
and hear:
- Normal cranking
- Slow cranking
- Clicking
- Silence
- Engine firing and stopping
A 15-second video can sometimes provide extremely useful information.
HOW DOES CBC DIAGNOSE A NO-START?
There isn't one universal test.
We first classify the complaint.
NO CRANK?
Investigate the starting circuit and conditions required for cranking.
CRANKS BUT WON'T START?
Investigate what the engine is missing or why operation isn't being authorised.
STARTS THEN CUTS OUT?
Look at the systems capable of causing that specific behaviour.
INTERMITTENT?
Look for patterns, stored evidence and conditions under which the failure occurs.
Testing may involve:
- Battery and electrical testing
- Diagnostic scanning
- Live data
- Circuit testing
- Voltage-drop testing
- Immobiliser diagnostics
- Key recognition
- Engine-management testing
- Mechanical checks where appropriate
The exact process follows the evidence.
DO I NEED A NEW BATTERY, STARTER OR KEY?
Maybe.
But we don't want to decide that before testing.
At The Cape Brake Co, we don't believe:
NO START = BATTERY
CLICK = STARTER
KEY LIGHT = NEW KEY
or
FAULT CODE = NEW SENSOR.
Instead:
WHAT DOES THE VEHICLE ACTUALLY DO?
DOES IT CRANK?
IS THE BATTERY SUPPLY HEALTHY?
IS THE STARTER CIRCUIT WORKING?
IS THE ENGINE MANAGEMENT RECEIVING WHAT IT NEEDS?
IS THE VEHICLE AUTHORISING THE KEY?
Then we repair the fault we've actually found.
WHAT SHOULD I SEND CBC?
If your vehicle won't start, send us:
- Make
- Model
- Year
- VIN
- Approximate mileage
- Whether it cranks
- Whether you hear clicking
- Whether it starts and then stops
- Any dashboard warning or message
- Whether a spare key works
- Whether the problem is intermittent
- Whether it happens hot or cold
- Whether the battery has recently gone flat
- Whether the vehicle was recently jump-started
- Any recent repairs or electrical work
And, if possible:
SEND US A SHORT VIDEO OF WHAT HAPPENS WHEN YOU TRY TO START IT.
That can be incredibly useful.
CAR WON'T START?
Don't worry about deciding whether it's the battery, starter, key, immobiliser, sensor or something else before contacting us.
Tell us what the vehicle does.
We'll work from there.
Ask the Workshop Assistant or WhatsApp The Cape Brake Co.
0 comments