No-Start & Crank-No-Start Diagnostics

A car that cranks but will not start may require checks of battery voltage, ECU communication, crank and cam signals, immobiliser status, fuel-system data and relevant power supplies. Sunderland Vehicle Diagnostics carries out mobile no-start fault finding across Sunderland and nearby areas, subject to safe access to the vehicle.

“Will not start” can describe different faults

A vehicle that does not crank is different from one that cranks at normal speed but does not fire. A slow crank, a single click, no response, a start-and-stall condition and an intermittent no-start each point the investigation in different directions. Describing the exact behaviour is an important first diagnostic step.

Areas that may be checked

Checks are selected from the evidence and are not a list of parts assumed to have failed. Depending on the vehicle and symptom, useful diagnostic areas may include:

• battery voltage and voltage behaviour during an attempted start;
• starter or cranking information available from the vehicle;
• relevant immobiliser-related fault indications and authorisation status;
• crankshaft and camshaft signal information;
• fuel-related data and commanded values;
• communication with the engine and other relevant control modules;
• ECU and system power supplies and grounds; and
• relevant temperature, pressure or position sensor readings.

None of these is automatically the cause. The purpose of testing is to find which requirement for starting is missing, incorrect or not being recognised.

What to do before the visit

Avoid repeatedly flattening the battery by making long starting attempts. Note whether the engine turns, whether dashboard lights dim, whether a security or key symbol appears and whether the problem followed battery work, fuel filling, a repair or a period of non-use. If it started after a jump, say how long it then ran.

What mobile diagnosis can establish

A mobile visit can often narrow the fault and identify a sensible next step without transporting the vehicle purely for an initial scan. However, access, battery state, intermittent behaviour or the need for mechanical measurements can affect what is possible on the first visit.