Diagnose car starting problems

Written by don bowman
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Diagnose car starting problems
Car starting problems are among the most common. (holding car key image by Photosani from Fotolia.com)

A starting problem is one of the most likely problems that can occur at some point in the life of a car. It can be caused by a multitude of malfunctions, from the battery to a sensor. Following this procedure will expedite the process of diagnosing a starting problem.

Skill level:
Moderate

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Things you need

  • Voltmeter
  • Battery load tester
  • Hydrometer
  • Set of either 1/4- or 3/8-inch drive sockets
  • 6-inch extension
  • Ratchet
  • Common screwdriver

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Instructions

  1. 1

    Turn the key on until the lights on the dash come on. If the dash lights fail to come on, the battery or battery connections are suspect, and you have eliminated an engine performance problem. If the lights come on, try to start the engine. If the engine does not turn over (it just makes a clicking sound), the battery is suspect. If the lights are on, and the engine turns over, but does not start, the issue is with performance. Go to Step 2 if the engine does not turn over. Go to Step 6 if the engine cranks but does not start.

  2. 2

    Inspect the battery terminal for corrosion and security. Clean the terminals if necessary by wetting them with water and pouring baking soda on the terminals. The baking soda neutralises the acid and cleans the terminals. Wait for the terminals to stop foaming and clean with water. Take off the negative terminal and clean it with a wire brush. Leaving the negative terminal off, remove the positive and clean it with a wire brush. Reinstall the terminals with the positive first. Check to see if that solved the problem. If not take the voltmeter and check the voltage across the terminals, red lead of voltmeter on positive terminal and black on negative. There should be showing 12.3 or better volts. If the voltage is low it is under charged or incapable of holding a charge. Take the caps off the battery and check the cells one at a time with the hydrometer. The hydrometer reading should be the same on all cells if all cells are good. A fully charged battery will show 1,260 specific gravity on the hydrometer. Check the water level in the battery and fill as necessary with distilled water.

  3. 3

    Replace the caps on the battery and hook the load tester to the battery. Watch the voltage as you press the load button for five seconds. Note how much the voltage dropped while the load was being applied. Look on the battery label on top and look for the CCA, or cold cranking amps. Compare this with the diagrams on the load tester for that size battery. For example, a 550 cold cranking amp battery should not drop below 10.5 volts when a load is applied. This would indicate a bad cell in the battery and require replacement of battery.

  4. 4

    Check the black negative cable where it attaches to the engine and make sure it is tight. Check the positive cable and be sure it is tight on the starter.

  5. 5

    Disconnect the small wire from the starter solenoid. Clip the red lead on the voltmeter to the small wire and clip the black lead on the voltmeter to the battery. Have a friend turn the key to the start position. There should be power to the wire every time the ignition is turned to start. If there is power then the starter is the problem and needs to be replaced. If there is no power, check the fuse in the relay box on the driver's side fenderwell. If it is good then pull the starter relay out and check for power at one terminal. Put the red positive lead of the voltmeter in the relay terminal and touch the negative to the negative battery post to check for power. If there is power then have the assistant turn the key to the start position and check to see if another terminal has power. There should be two terminals with power when the ignition is in start. If there is power at a second terminal turn the key off. Take a jumper wire and jump the terminal with the power on constantly with one of the terminals that had no power. Try the next terminal if no response at the starter. When jumped, if the starter engages, the relay is at fault and needs to be replaced. If there was no power to the relay when the key was in the start position, then the ignition switch is at fault.

  6. 6

    Insert an extra spark plug into the end of one of the spark plug wires. Do not take a spark plug out of the engine for this test. If it is a coil over system, remove the 10 millimetre bolts from the coil and pull it out of the head and insert the plug and lay it on the valve cover or in a spot where the plug is grounded by touching metal. Do not touch this during this test or you will get shocked. Have the helper turn the engine over. Look at the plug for a spark every few revolutions. If there is no spark, there is an issue with the engine management system. Take the car to a shop with the right test equipment. If you see spark, the problem is in the fuel system.

  7. 7

    Look at the top of the engine and locate the fuel rail on the injectors. There should be a Schrader valve on the rail. Make sure to extinguish any cigarettes or heat source like an electric light bulb during this step. Take a small screwdriver or a nail and push in on the Schrader valve. Have the helper turn the key on and look for fuel pressure at the valve. If there was no Schrader on the rail, just loosen the fuel line for the same results. If there is no fuel expelled, check the fuel pump fuse and relay located in the relay box. If these are not faulty, the fuel pump has failed and is need of replacement.

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