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All Info About Auto Repair: Basics of Troubleshooting
All Info About Auto Repairs
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Basics of Troubleshooting

Learn what you need to have to have and how to diagnose a problem quickly and efficiently.
» Part 1
» Part 2
» Part 3

A fuel pressure tester is needed to test the fuel system. Most cars have a test port on the fuel rail to connect the tester. Some require that it be installed in-line with the fuel system. Make sure it comes with the correct adapters for your particular vehicle.

A timing light will be needed to check the engines timing. On some engines the timing is not adjustable and is completely computer controlled. On other engines there are specific conditions that the timing should be checked under. These may involve jumping certain switches and or sensors to get an accurate reading.

Okay, now that you have an idea of what you will need to diagnose a problem, let's talk about some procedures. The number one rule in any troubleshooting procedure is "Confirm the problem." In order to find the problem, you need to define and understand it. Duplicate the conditions when the problem occurs. Be it at start up, cold, hot, rain or sunshine. These are all clues in finding the problem. If the car won't start when it's raining, then that puts you into the ignition system ballpark. If it bogs down or hesitates when you step on the gas that will put you in the fuel system ballpark. Once you understand what the problem is, your chances of finding it greatly improve.

Once that is done, you need to check the basics. I don't know how many people get burned looking for a complicated answer when it's a simple answer. If your house started leaning to the left, you wouldn't check the roof first. You would check the foundation. Same thing with a car, the foundation has to be sound before you look anywhere else.

With a drivability problem, the first thing you should check is the spark plugs. They will tell you a lot about the condition of the engine if you know how to read them. Check to make sure they are the correct plugs for that car. Don't automatically get the same ones that were in there. Check them. Maybe the guy who tuned it up before you put the wrong ones in. Use AC Delco plugs in GM, Champion in Chrysler, Motorcraft in Fords and NGK's in Japanese cars.

After the spark plugs you need to check the ignition wires, distributor cap and rotor. Make sure the plug wires are tight on the plugs and there are no cracks or burns on them. A quick test is while the car is running, spray water from a spray bottle on them. If the car starts to stumble or run rough, or you see sparks arcing, you need new wires. Look inside the distributor cap for cracks and burns. If you see any, replace it. The same goes for the rotor. If the tip is burned out, replace it. If in doubt, replace any of these parts. The cost is small and you will know that they are in good shape to continue troubleshooting. These are the most common causes of misfires and rough engine performance. The next thing to check is the vacuum lines. Make sure they are connected and in good shape. Trace the whole line for cracks, breaks and collapsed areas. Murphy's Law stipulates that a cracked or broken vacuum line will be in the most hidden place in the car. After that you need to check for loose electrical connections. Unplug the connectors and look at the terminals. Dirty, loose or corroded connections will cause a world of strange symptoms and intermittent problems.

Check the filters as well. A new air and fuel filter will solve quite a few drivability problems.

Spark Plugs Tell A Story
Sample Diagnostic Tree

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Additional Information provided courtesy of
ALLDATAdiy.com and Warranty Direct
© 2000-2007 Vincent T. Ciulla

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