SOME BASICS OF TROUBLESHOOTING DICK RANDALL I decided to pull these ideas together because I have spent plenty of hobby time figuring out things that did not work or that needed repair. This process and these tips should also be useful for solving other issues or problems. Troubleshooting is defined as a form of problem solving using a logical, systematic search for the source of a problem in order to solve it and make the item operational again. The typical steps in troubleshooting are: 1. Plan and prepare 2. Verify that a problem actually exists. 3. Isolate the cause of the problem. 4. Correct the cause of the problem. 5. Verify that the problem has been corrected. 6. Follow up to prevent future problems. PLAN AND PREPARE The secret of effective diagnosis and troubleshooting is to follow a logical step-by-step procedure to get you to the root cause of a problem quickly and efficiently. The first step - preparation In troubleshooting, as in any other endeavor, you must have the right attitude to succeed. The best way to get and maintain the attitude is to remember that it is a mathematical certainty that you will solve any reproducible problem there is always an explanation. It is important to know as much as you can about the situation before you jump headlong into trying to fix it. Gathering information and preparing is the first step in successful troubleshooting. Consulting available resources is a vital part of obtaining knowledge about the product and about the specific issue you are troubleshooting. Those resources may include shop manuals, wiring diagrams and Internet research. Use appropriate safety precautions and equipment when troubleshooting. For example, disconnect the battery, use jack stands under the car and wear safety glasses. As you start, take pictures or notes to remember how it came apart so you can put it back together. As you attempt troubleshooting, if things are not going well remember to take a breather and walk away from the problem for a while. You may find that after a short break you can think of solutions that you were too close to the situation to see. VERIFY THAT A PROBLEM ACTUALLY EXISTS Is something actually wrong? A problem usually is indicated by a change in performance or lack of performance (not working). Verification of the problem will provide you with indications of the cause if a problem actually exists. The number one rule in any troubleshooting procedure is to confirm the problem. Once you understand what the problem is and have a more detailed the description, the sooner you can narrow down the problem. Understanding the problem in detail may mean less work to do and a better ability to find the problem.! 1
IDENTIFY AND LOCATE THE CAUSE OF THE PROBLEM One of the core principles of troubleshooting is that reproducible problems can be reliably isolated and resolved. Often considerable effort and emphasis in troubleshooting is placed on reproducibility...on finding a procedure to reliably induce the symptom to occur. Determining the most likely cause is a process of elimination eliminating potential causes of a problem. Check all the easy things first to look for an easy and simple answer, working towards the more complex. Check only one area at a time and don't move on to something else until you've eliminated the specific system or component as the cause for your problem. There are some steps to take in looking for symptoms of the problem, starting with what you know: How long has the symptom existed? A sudden symptom usually means a sudden defect. When did it start happening? What else happened around that time? What work or incident accompanied the symptom? Reproducing the problem The next step is to reproduce the symptom. If there is a procedure to consistently reproduce the symptom, the problem is said to be reproducible. If there is no way to consistently reproduce its symptom it is Intermittent. Intermittent problems are the most difficult to diagnose. Identifying and isolating the cause A basic principle in troubleshooting is to start from the simplest and most probable possible problems first. While troubleshooting takes a systematic approach, a short-cut to save time and expedite finding a solution is to begin by investigating the easiest items to check. If that does not find the problem, the next thing is to turn to a step-by-step search through the system or equipment. A sequential search involves systematic testing, starting from one end of the equipment and working item by item to the other end. On-Board Diagnostics testing Since 1996, cars sold in the U.S. have been required to provide a connection for mechanics to measure and monitor parts of the chassis, body and accessory devices, as well as the diagnostic control network of the car. The system is called On-Board Diagnostics generation two (OBD-II). The data provided by OBD-II can often pinpoint the specific component that has malfunctioned, saving substantial time and cost compared to guess-and-replace repairs. CORRECT THE CAUSE OF THE PROBLEM After you confirm the problem, then develop a logical plan to test the parts to solve the problem. It is very important to correct the cause of the problem, not just the effect or the! 2
symptom. This often involves replacing or repairing a part or making adjustments. The quick fix A quick fix is not necessarily the most likely solution to the issue, but because it is easy to perform and involves little time or expense, it is worth trying. You can try one or more quick fixes before taking on the more time-consuming tasks involved with isolating the issue. Some examples of quick fixes are: checking fuses, switching batteries, adjusting controls, and cleaning contacts. If a quick fix works, time has been saved. If not, little time has been lost and there is knowledge that some parts are not the cause of the trouble. VERIFY THAT THE PROBLEM HAS BEEN CORRECTED Make sure it is fixed. When you have found the problem and completed making the repair, check it again. Repeating the same check that originally indicated the problem can often verify the correction or repair. If the fault has been corrected, the part or system should operate properly. Sometimes one fault will cause another one that you couldn't see at first. So by verifying the proper operation of the repaired equipment, the troubleshooter can be relatively sure the problem has been resolved correctly. FOLLOW UP TO PREVENT FUTURE PROBLEMS Double-check your diagnosis, double-check your work and double-check the repair. The final step is to follow up to prevent future problems. This step involves taking preventive measures and actions that could help keep the equipment from failing. Although the system retest and preventative measures taken may not seem as vital as fixing the problem these steps are vital to a long-term solution. SUMMARY Troubleshooting a problem can be difficult. By following some simple rules, a process, using the right test equipment properly and some common sense, you will locate and repair most problems.! 3
EXAMPLES OF THE PROCESS Following are two real examples of the process. The first was with a Nash Metropolitan, which was my father s daily driver for a number of years. The second was with our 1966 Pontiac GTO. PROBLEM 1 - Nash Metropolitan quits running in the rain then later restarts Troubleshooting Step 1: Plan and prepare Understanding that the engine needs three things to run: fuel, spark and air. Lack of one of those is causing the problem. Troubleshooting Step 2: Verify that a problem actually exists. The car quits running in heavy rain or after going through a water puddle. After 15 to 20 minutes the car starts again and runs fine. This problem is repeatable most times when it is raining and the car is driven through a puddle. Troubleshooting Step 3: Isolate the cause of the problem. It was determined that there was no issue with fuel or air, thus the focus was on the ignition system. The distributor was mounted low on the engine and would get wet from splashing water from the tires. After the car sat for 15 to 20 minutes, the heat from the engine would dry out the distributor and the car would start. Troubleshooting Step 4: Correct the cause of the problem. A simple splash shield was fabricated and installed. In addition, a spray sealant was applied to the distributor. Troubleshooting Step 5: Verify that the problem has been corrected. Driving in heavy rain or through a puddle did not affect engine running, although deep puddles were avoided in the future. Troubleshooting Step 6: Follow up to prevent future problems. There was no further repetition of the issue. The problem was resolved. PROBLEM 2: Gas gauge in Pontiac GTO not registering properly Troubleshooting Step 1: Plan and prepare A review of the wiring schematics showed that there were three components to this system: the gas gauge in the dashboard, the wiring harness between the gas gauge and the gas tank sending unit, and the sending unit in the gas tank. Troubleshooting Step 2: Verify that a problem actually exists. The gas gauge would not register full when the gas tank was filled. It did not register properly as the car was driven and gas was used. This condition existed every time the tank was filled or the car driven. Troubleshooting Step 3: Isolate the cause of the problem. There were three things to check that could cause the problem: 1. The gas gauge in the dashboard 2. The wiring harness between the gas gauge and the gas tank sending unit, 3. The sending unit in the gas tank. Easy things first - The easiest thing to check was the wiring connections. All connections were clean and tight. The grounding wires were secure. Thus we could eliminate a bad connection.! 4
After the easiest test, we moved on to more difficult tests: The next thing to check was the continuity of the wiring harness. A separate wire was run from the sending unit to the dash gauge. The gauge still did not register correctly, so we could eliminate the wiring harness as the cause. The gas sending unit uses resistance with the float to send a varying signal to the gauge. When the sending unit was bypassed, the gauge still did not register correctly as full or empty, so we could eliminate the sending unit as the problem. Had the problem been in the sending unit, it would have required removing the sending unit from the gas tank. That is not a difficult job, but with limited accessibility it would have been challenging. Those tests left us with the gas gauge as the issue. Since replacing the gas gauge required removing the instrument panel, this was the most difficult solution, thus the last we tested. Troubleshooting Step 4: Correct the cause of the problem. Those tests left us with the gas gauge as the issue. Since replacing the gas gauge required removing the instrument panel, this was the most difficult solution. However replacing the gas gauge with a new assembly solved the problem. Troubleshooting Step 5: Verify that the problem has been corrected. The new gas gauge registered correctly when the tank was full or when partially full. The problem was corrected. Troubleshooting Step 6: Follow up to prevent future problems. Since the gas gauge was the cause of the problem and was replaced, and the wiring and tank sending unit were checked and worked, we determined that the problem was fixed.! 5