The secret of effective diagnosis and troubleshooting is to have a logical plan. The secret of effective diagnosis and troubleshooting is to have a logical, well-ordered system. Following a logical step-by-step procedure will get you to the root cause of a problem quickly and efficiently. Repair manuals will have a diagnostic tree that goes in a logical progression. It will ask a question, usually yes or no, and depending on the answer will branch off in two or more directions. The last box in the tree will have the problem and how to correct it. The example shown is a simple one. A more complicated system will have branches going into specific tests and then have 2 or more branches from there depending on test results. You will need some basic test equipment to perform your diagnosis. A 12-volt test will tell you if a circuit has power or, when hooked up in reverse, will tell you if a ground circuit is good. News source: Auto Repair About A good volt-ohm-meter (VOM) will be needed to perform specific voltage and resistance tests. You can get a good meter at any Radio Shack or Best Buy store. A digital meter is an excellent choice because they are easier to read than an analog meter. I have both digital and analog meters in my toolbox because sometimes an analog meter is best for a certain job. Most VOM’s have an ammeter that will test the alternator output and test for current draws. Make sure the one you buy has it. If you have an older car with a point equipped ignition system, you will need a dwell meter as well to measure and adjust the dwell angle of the points. As with any piece of equipment, read the instructions that come with your meter. It will tell you what the various functions are and how to connect the meter to the circuit for accurate test results. Most meters have a fuse in them to protect them from an incorrect connection. Make sure the one you buy has one and get a couple of spare fuses. You will, at some point, hook it up wrong and be very thankful you have the spares. I know I have. Most of the troubleshooting on today’s cars will be electrical in nature. A good wiring diagram is essential to properly troubleshoot any electrical circuit. They usually come in two parts, a schematic and the wiring diagram. The schematic shows the different components of a system and how they relate to each other. The wiring diagram shows the actual wire colors and connections. For testing the mechanical side of the engine, you will need some more specialized equipment. A vacuum gauge with several adapters can be used to test manifold vacuum and test vacuum operated circuits. A hand vacuum pump is handy for testing vacuum operated components such as EGR valves and heating and air conditioning systems.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.Sponsored LinksFree Auto Repair InfoAnswers to Auto Repair FAQ Free Information & Advicedigitalprecision.net/auto_repairAuto Repair ManualGet answers to your car problems Free info on Auto Repair ManualAuto-Repair-Manuals.big.comAutomotive Repair GuideAuto Repair Answers, Software Free Info & Resource, Manualswww.theoffering.com/auto_repairMake 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. Do the same thing for electrical problems. Check the fuses and fusible links first. Check connections to see that they are clean and tight. Check light bulbs to see if they are just burnt out and the correct type. I had a customer bring a car in and said every time he stepped on the brake his dash lights came on. What he did was put the wrong type of bulb in his brake light and it would feed back into the dash. A dishonest mechanic would have had a field day with this one. He would replace the bulb and charge 5 hours labor locating and repairing a short. In short, check all the stupid things first. Don’t take anything for granted. Car won’t start? Check the gas gauge first. That one burned me a couple of times. When you look for an electrical problem look at it from all angles. Literally look at it forward and backwards. Will it be easier to trace from the component to the fuse box or vice versa? If you are tracing a wire, is the connector buried in the dash? Look at the wiring diagram and find another location to make the same test in a more accessible location. You’ll get the same results in a much shorter time. Lastly check the computer for Diagnostic Trouble Codes (DTC’s). For this you will need a scanner or a service manual that explains how to pull the DTC’s up manually. If you get a bad injector circuit code, don’t assume it’s a bad injector. That code is telling you it’s in the injector circuit and that includes the wiring, injectors, dropping resistors (on older EFI cars) and computer. Any one of which will throw that code. Get your wiring diagram out and check the whole circuit. Too many parts get replaced because “the computer said it was the fuel pump.” Don’t get burned buying an expensive part only to have it not fix your problem. When you have found the problem and completed making the repair, check it again. Make sure it is fixed. Sometimes one fault will cause another one that you couldn’t see at first. For example, there is a shorted wire between the injector and the computer. You fix the wire and take it for a ride and it still misses. Well you didn’t see that the shorted wire burned out the injector. When you test the circuit again, you will see that the injector needs to be replaced also. Double-check your diagnosis; double-check your work and double-check the repair. Troubleshooting a problem can be tough, even in the best of circumstances, but by following some simple rules, using the right test equipment properly and some common sense, you will locate and repair most problems with your vehicle yourself.
Category Archives: DYI
That time of year to discuss engine coolant There are several different types of coolant Good old ethylene glycol the old standby and works great but has a short life span worse in newer aluminum engines(drain and refill every 2 years)Extended life great for aluminum engines and has a longer life span but GM has expressed some concerns about how long that is ( drain and refill every 3 years)Notice I said drain not flush The so called power flush at most chains ends up to be a drain and refill a few do it correctly but this is rare Drain and refill is a simple task you can do yourself the hardest part is being sure you have all the air removed and bleeding if necessary. As a general rule if the heater is blowing hot the system is OK and on most newer vehicles there is a bleed screw in the area of the stat. Worse case scenario leave the cap off overnight and usually the air will bleed out of its own accord.Last but not least dont check the coolant for strength only but also have the condition checked yearly. Dont count on it to look bad as many times it will look fine and be worn out.Last but not least check the parastic voltage of the coolant. Using a lab scope or a good Vohm meter go from the coolant to ground the voltage present will surprise you check it clean so you have a reference point also consider a seperate ground from the rad
We have had several questions on grounds lately. Poor grounds account for a majority of the electrical problems that involve several circuits When you check a ground dont just look at it take it apart and clean all surfaces until they are bare metal or do a voltage drop test( more on this later)A shot of clear lacquer over the connection is also a good idea or clear spray paint I aslo do this to the battery connections it is not as messy as battery protector and I think it covers better
The three city libraries in Waterloo Region are launching a new electronic database which provides information for most of the major manufacturers of domestic and imported vehicles, with repair information for most vintage makes as far back as 1954.The new database, Auto Repair Reference Centre, is now available through the websites of the Waterloo, Kitchener and Cambridge library systems. The three libraries have been able to make this electronic resource available through a collaborative purchasing agreement with other public libraries in the province.Auto Repair Reference Centre can be accessed from computer workstations within any of the libraries, or from home or work. It provides step-by-step procedures suitable for both the do-it-yourself mechanic and professional technicians. It is also a good resource for consumer information for the car-buying public.For more information, visit the Waterloo public library’s website [url”>www.wpl.ca. News source: Waterloo Chrononicle
Computer diagnostics — what are they? how are they done, and what do they cost. Most cars have some form of a computer to operate the performance system. Computers have evolved in recent years, so there are any number of operating systems running from primitive to very high tech depending on the age of the vehicle News source: Woman Motorist What are computer diagnostics? Computers generate signals called data streams. These streams of data flow through the operating system of the car at all times, constantly adjusting and re-adjusting the engine. Diagnostic computers that are interfaced with the car’s computer read the data streams flowing through the system. When a problem with a computer-controlled car crops up, it shows up either in the form of a drivability problem or a lit check-engine light on the dashboard. The problem could be in the form of a bad sensor, malfunctioning electrical or mechanical component, or damaged wiring and plugs. The system is designed to generate a trouble code when it “sees” a problem in the system. This code is supposed to lodge in the onboard computer’s memory for retrieval at a later date, aiding in diagnostics. The shop must have access to information either in book form or online to decipher what the codes mean and how to go about diagnosing the particular problem area. Sounds simple right? Hook the car up to “Da Machine” and it will tell you what’s wrong — hold on, not so fast, it’s not that easy! What happens when there is no evidence of a trouble code stored in the car’s computer and no check-engine light is lit, but a drivability problem still exists? This is where the men are separated from the boys in the world of onboard computer diagnostics. How are computer diagnostics performed? Effective computer diagnostics and repair demands state-of-the-art equipment, cutting edge training, and up-to-date information. Equipment: Cars of the 90s can’t be fixed with 1968 equipment. Necessary equipment for the diagnostician includes: Oscilloscopes and lab scopes to read wave patterns omitted by sensors DVOM (Digital Volt-Ohm Meters) to measure electricity in minute amounts Sensor stimulators which actuate sensors to make sure they are functioning properly Diagnostic computers to read the data streams of the car’s performance system Training: All the latest equipment is worthless without a trained diagnostician. Today’s diagnosticians must keep abreast of rapidly-changing technology to remain in the field. The average student coming out of a technical college needs two years to get “up to speed” after joining the workforce. Information: Diagnosticians must have access to over a million pages of technical information to fix computer-related problems. Transmissions, ABS brakes, HVAC (Heating Ventilation and Air Conditioning), Traction Control, Fuel Delivery Systems, and Performance Systems are all computer-controlled. Car manufacturers and vendors are constantly coming out with TSBs (Technical Service Bulletins) alerting the diagnostician of repair strategies and fixes for computer glitches. The technician takes the tools, training, and information and diagnoses your car’s problem. The diagnosis may start with a basic check of the computer’s memory for any stored codes. In a perfect world, there are codes and the simple replacement of a sensor is all that is needed. But what is there are no codes!? Now the quest starts! The technician might perform a “flight test,” hooking the car’s performance system up to a handheld computer and test driving the car, monitoring the data stream for anything out of the ordinary. Hopefully the problem will show up in the form of a code or poor reading of a particular function. Next a “sensor stimulator test” might be in order. The car is hooked up to a machine which stimulates all the sensors, simulating the car driving down the road. Maybe a check of a particular component’s electrical value with a digital volt-ohm meter is in order to see if it’s operating within manufacturer’s specifications. What do computer diagnostics cost? Equipment, training, information, and qualified technicians cost money — a lot of money! Consequently, this kind of service is not cheap. Most shops charge for diagnostics, justifiably so!!!! It usually goes like this: Initial computer scan for codes — $50.00 No codes? Diagnosis at the skilled labor rate of $80.00 per hour Installed at the skilled labor rate of $80.00 per hour News source: Woman Motorist
Brought to you by: Patrick Parish – Capitol Air Conditioning If your old R12 Air Conditioning system has failed, a retrofit to R134a may be the best answer. This site documents what is generally involved – parts, procedures, etc. – whether you plan to tackle this yourself or have a professional do it for you.Includes a whole series of steps involved for retrofit in general, as well as separate pages for retrofit issues unique to Acura, Chrysler, Ford, General Motors, Honda, Nissan, Toyota, and Volvo News source: Patrick Parish/Capitol Air Conditioning