How do you diagnose crank no start?

If your vehicle's engine fails to start when you turn the key, it's likely experiencing a "crank no start" issue. This can be caused by a variety of problems, from electrical issues to mechanical failures. Diagnosing the root cause is crucial to getting your car back on the road. In this article, we'll guide you through the steps to identify and address a crank no start problem.

Symptoms of a Crank No Start

When you turn the key in the ignition, you may hear the starter cranking, but the engine doesn't start. This is the hallmark of a crank no start issue. Other symptoms may include:

• The engine may crank slowly or not at all


• The dashboard lights may dim when you try to start the engine


• You may hear clicking or other unusual noises when attempting to start the vehicle

These symptoms can point to a range of potential problems, from a dead battery to a faulty starter or fuel system issues. Identifying the root cause is the key to resolving the crank no start problem.

Diagnosing a Crank No Start

To diagnose a crank no start issue, you'll need to systematically check various components and systems in your vehicle. Here are the steps to follow:

1. Check the battery: Ensure the battery is charged and the connections are clean and tight. Use a voltmeter to test the battery's voltage, which should be around 12.6 volts when the engine is off.


2. Inspect the starter: Listen for the starter engaging when you turn the key. If you hear nothing, the starter may be faulty and need replacement.


3. Verify fuel delivery: Check that fuel is reaching the engine by removing the fuel pump fuse and listening for the pump to activate when the key is turned. If the pump doesn't run, there may be a problem with the fuel system.


4. Check for spark: Use a spark tester to check if the engine is receiving a spark. If there's no spark, the issue may be with the ignition system, such as a faulty ignition coil or spark plugs.


5. Inspect the engine's mechanical components: If the electrical and fuel systems appear to be functioning correctly, the problem may be mechanical, such as a seized engine or a broken timing belt.

By systematically working through these diagnostic steps, you can identify the root cause of the crank no start issue and take the appropriate steps to resolve it.

Resolving a Crank No Start

Once you've identified the underlying problem, you can take the necessary steps to fix the issue. This may involve replacing a faulty component, such as the battery, starter, or ignition coil, or addressing a more complex mechanical problem. If you're unsure of the best course of action, it's always a good idea to consult a professional mechanic who can provide expert guidance and ensure your vehicle is repaired correctly.

What sensors can cause crank no start?

Sensors that can cause a crank no start include the crankshaft position sensor and camshaft position sensor, which are critical for spark and fuel timing. Other sensors like the mass air flow (MAF), throttle position sensor (TPS), manifold absolute pressure (MAP), and engine coolant temperature sensor can also prevent a vehicle from starting. A fault in any of these can send incorrect data to the engine control unit (ECU), causing it to cut fuel or spark to prevent the engine from running. 
This video explains the common causes of a crank no start, including sensor malfunctions: 59sEasyAutoFixYouTube · Sep 9, 2023
Most critical sensors 

• Crankshaft Position Sensor (CKP): This is one of the most common culprits. It tells the ECU the position and rotational speed of the crankshaft. If it fails, the ECU doesn't know when to fire the spark plugs or inject fuel, and the engine won't start. 
• Camshaft Position Sensor (CMP): This sensor works with the CKP to ensure the fuel injectors and spark are timed correctly, especially on modern engines with sequential fuel injection. A failed CMP sensor can result in no start. 

This video explains how to diagnose a crank no start issue: 54s1A Auto: Repair Tips & Secrets Only Mechanics KnowYouTube · Dec 10, 2022
Other relevant sensors

• Mass Air Flow (MAF) Sensor: This sensor measures the amount of air entering the engine to calculate the correct air-fuel mixture. A failed MAF sensor can cause a no-start condition. 
• Throttle Position Sensor (TPS): This sensor tells the ECU how much the throttle is open. If it fails, the ECU may not receive the correct information to start the engine. 
• Manifold Absolute Pressure (MAP) Sensor: This sensor measures pressure in the intake manifold. A faulty MAP sensor can lead to a no-start. 
• Engine Coolant Temperature (ECT) Sensor: This sensor tells the ECU the engine's temperature. If it fails and incorrectly signals that the engine is extremely hot, the ECU might prevent it from starting. 

This video demonstrates how to diagnose a crank no start issue, including checking sensor functionality: 49sBudget MechanicYouTube · Dec 8, 2023
What to do

• Check for codes: Use an OBD-II scanner to read any trouble codes. These codes can point directly to a specific sensor issue. 
• Inspect wiring: Check for any visible damage, loose connections, or corrosion on the sensors and their wiring harnesses, as this can mimic a sensor failure. 
• Consult a professional: If the problem is not immediately obvious, a mechanic can perform a more detailed diagnosis, such as using a voltmeter to test the sensors. 

How to diagnose no crank no start?

A "no crank, no start" diagnosis typically involves first checking the battery, terminals, and fuses, as these are the most common causes. If those are okay, the issue could be a faulty starter motor or solenoid, a problem with the ignition switch, or a safety switch like the neutral safety switch (automatic) or clutch pedal position sensor (manual). Less common but possible issues include bad wiring, a seized engine, or anti-theft system problems. 
Common issues and initial checks

• Battery: A dead or weak battery is the most frequent cause. Check if the lights come on or if there are any sounds when you try to start the car. A clicking sound often points to the starter solenoid, but can also be a weak battery not able to provide enough power. 
  • Action: Ensure the battery terminals are clean and tight. Test the battery voltage with a multimeter. 
• Fuses and relays: Blown fuses or a faulty starter relay can prevent the starter from engaging. 
  • Action: Check the fuse box for any blown fuses related to the starting system. You can also try swapping the starter relay with a similar, identical relay from another circuit to test if it's working. 
• Ignition switch: A bad ignition switch can fail to send the signal to the starter. 
  • Action: This can be harder to test and often requires professional diagnosis or checking for voltage at the starter when the key is turned. 
• Safety switches: For automatic transmissions, the neutral safety switch prevents starting in gear. For manual transmissions, it's the clutch pedal position sensor. 
  • Action: Try starting the car in neutral (for automatics) or with the clutch fully depressed (for manuals). 

This video explains the most common causes for a no crank no start condition and demonstrates how to check the battery: 57sEasyAutoFixYouTube · May 27, 2023
Less common issues

• Starter motor or solenoid: The starter motor itself can fail, preventing the engine from cranking. 
  • Action: You can test the starter motor by applying power directly to it or having a mechanic bench-test it. 
• Wiring problems: Corroded, loose, or damaged wiring can interrupt the electrical circuit to the starter. 
  • Action: Inspect all wiring connections, especially around the battery and starter, for any signs of damage. 
• Anti-theft system: Some anti-theft systems can immobilize the vehicle, preventing it from starting. 
  • Action: Check if the security light on your dashboard is flashing, and consult your owner's manual on how to reset it. 
• Seized engine: In rare cases, the engine may be "seized" and cannot be turned over by the starter. 
  • Action: This usually requires professional mechanical diagnosis to determine. 

When to seek professional help

• If you are uncomfortable with electrical diagnostics or working on your car, it is best to have a professional mechanic diagnose the issue. 
• A professional can use specialized tools to accurately diagnose the problem, saving you time and potential further damage. 

What is the first thing you check on an engine with a no start issue?

First, Check the Basics - The very first step to diagnose a “cranks but won't start” problem is to find if something's missing – Spark, Fuel and Compression (which includes cam timing). These three things are required for an engine to start.
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What is the corrective action for the engine cranks but does not start?

Check your fuel gauge to ensure you are not running out of fuel. Fuel Pump Failure: The fuel pump may fail to deliver fuel to the engine, resulting in cranking without starting. Clogged Fuel Filter: A blocked fuel filter can restrict fuel flow to the engine.