Diesel Engines |
Basic Maintenance + Repair
A tune-up is the process by which all mechanical, electrical/electronic, chemical, and fluid dynamic systems (both liquid and gaseous) are returned to normal condition in order to bring engine performance to its optimum level. Car systems wear or suffer loss of adjustment due to such things as heat, vibration, etc. We need to periodically restore these systems to keep our cars at peak performance.
If you have not established a tune-up schedule for your car, learn to look for and recognize the signs that tip you off that service is needed. Keep a record of your fuel mileage. When it begins to drop off, a tune-up is probably needed. Learn the “response” of your car. If it doesn’t accelerate as rapidly or as smoothly as usual, perhaps a tune-up is just the thing that’s needed for the car and your peace of mind as well.
Tune-ups are easy to perform even on today’s complex cars. Easy, however, doesn’t imply that doing sloppy or careless work will get the job done. To get maximum benefit and performance from a tune-up, accuracy and precision are required. To do a good tune up, a carefully planned sequence of tests and adjustments must be performed. Every system must be checked in order and proper adjustments or parts replacement made without exception for optimum results. The advantages in proceeding this way are twofold.
First, by following a prescribed sequence, trouble spots cannot be easily overlooked. Use a checklist. That way, if the next item on the list is spark plugs, for example, only by deliberately skipping them would you fail to look at and adjust or clean them. Second, the correct adjustment of some tune-up items depends on whether previous checklist items were done correctly or even at all. As an example, adjusting a carburetor before properly setting the timing is generally a waste of time. The timing needs to be adjusted before any adjustments to the carburetor can successfully be made.
Proper and timely tune-ups are the car owner’s solution to the “pay me now or pay me later” dilemma advertised so well on television. Tune-ups faithfully performed can reduce future repair bills because minor problems are caught before they become major problems. And that’s doubly important for those of us who do mostly city stop- and-go driving. In this case, the engine might not reach operating temperature quickly or even at all on very short trips, causing valves to stick, compression to drop, etc.
Some tips are in order before proceeding. First, never tune up a car in a closed garage. With the engine running, carbon monoxide fumes can build quickly and strike suddenly. You might not even realize you’re about to be overcome; you’ll simply pass out. You could die within minutes.
Next, make sure you know what you’re doing. Review the shop manual section on tune-ups the night before the tune-up. If you still feel uneasy, ask a knowledgeable friend to help out. Doing an improper tune-up is worse, in most cases, than not doing one at all. And remember those vocational-technical courses at night school; they provide professional training at low cost.
Practice makes perfect. Practice and become familiar with all your test instruments and equipment. Know what meters or gauges to use to perform tests or checks. Just reading the instructions that come with the instruments and equipment is usually not enough, unless you already have broad knowledge and experience doing tune-ups. It normally is necessary to review the shop manual to discover what instruments or equipment to use for a particular tune-up or service function. If any of the instruments are battery-operated, make sure the batteries are in good shape before you plan to use them.
Familiarize yourself with the tune-up specifications for your car and have them handy. The shop manual will have a list of them. They are the values of such things as spark plug gap (in inches or millimeters), idle speed settings, alternator output, timing settings, etc. To provide your car with a good tune-up, you must adhere to all the specifications as closely as possible.
Lastly, don’t wait until Saturday morning to run down all the parts you will need. There is no better way to kill your enthusiasm for doing any work on your car than by wasting time tracking down parts at the last minute. Make a parts list the weekend before you plan to do the tune-up. Then spend some leisurely time during the week gathering the parts together. You’ll have time to check the newspaper for auto store rates and time to make any special trips to pick up parts from the dealer or maybe the junk yard. What a terrific feeling it will be to face Saturday morning with a complete set of tune-up parts.
THE CORRECT STEPS
Stick to the following sequence for the tune-up work. The benefits, as explained above, will be obvious.
1. Remove the battery cables from the battery terminals.
2. Inspect the case, cable vent caps, clamps, and holder. Clean and/or repair as necessary.
3. Install the cables.
4. Perform the specific gravity and electrical tests outlined in the service manual.
5. Recharge or replace the battery as necessary.
1. Perform an engine compression test following the instructions in the service manual.
2. It doesn’t make much sense to proceed further if the engine shows signs of poor compression. Have the engine repaired to bring the compression up to specification before the next step.
Electrical Connections and Tests
1. Check all important electrical connections for tightness and continuity.
2. Clean or replace any connectors found faulty.
3. Some connections to check are:
- All battery cable connections to battery and engine or starter solenoid.
- All ignition cables.
- Any wiring to the carburetor.
- All distributor wiring.
- Gauge wiring such as temperature and pressure of the engine.
- Wiring and connections to relays, alternators, generators and starters.
4. Check all fuses and circuit breakers according to the instructions in the service manual.
5. Replace any frayed, oil-soaked, or torn wires or cables before proceeding.
6. Check the alternator, regulator, and ignition coil for proper output and resistance via the directions in the service manual.
1. Check the torque of the cylinder head bolts. If they require tightening, torque them to the value and according to the sequence in the service manual.
2. Check and, if necessary, tighten the intake and exhaust manifold bolts to the torque values in the service manual.
3. Properly torque the base of the carburetor to the intake manifold. Check for leaks following directions in the service manual. Repair leaks before proceeding.
4. Check and tighten the fuel and vacuum connections at the carburetor and fuel pump (if mechanical type).
5. If the car is equipped with a manifold heat control valve make sure it is free to move. Otherwise, free it with penetrating oil.
1. Inspect all the V-belts for wear and tension.
2. Replace any belts at this time. Note: It’s not worth the risk to try to get a few more miles out of a worn V-belt. If it fails while you’re on the road, you’ll be stuck. Replace V-belts at the very first signs of trouble.
1. Check all heater hoses, radiator hoses, and hoses to the carburetor or other equipment. Replace as necessary.
2. Inspect the radiator for signs of corrosion. Repair if needed.
3. Check the thermostat. Replace if necessary.
4. Check the radiator cap. Replace if necessary.
5. Inspect the overflow hose and overflow tank. Replace the hose and/or clean the tank, if necessary.
6. Remove dead bugs and other debris from the radiator.
7. Make sure the entire cooling system is leak-free. Repair any leaks before proceeding.
1. Replace all the air filters on the engine. There might be two or three of them. Refer to the service manual.
2. With the main air filter off and the engine running, spray some carburetor cleaner into the carburetor. Repeat this until the inside of the carburetor looks clean.
3. If the engine uses an oil-wetted or oil-bath main air filter, refer to the service manual for proper maintenance.
Pollution Control System (PCS)
We cover four systems here:
(Warning: in some states you cannot legally perform tune-up services on a car unless you are licensed to do so by the state.)
1. Positive Crankcase Ventilation (PCV)—Check the PCV valve for proper operation. It can’t be cleaned, replace it if it doesn’t move freely. Refer to the service manual.
2. Exhaust Gas Recirculation (EGR)—Check the operation of the EGR valve according to the instructions in the service manual. Some models can be cleaned. Otherwise, replace them. A dirty EGR valve will affect engine performance.
3. Air Injection or Thermactor System—This system promotes more complete burning of exhaust gases and, therefore, reduces the carbon monoxide and hydrocarbon content of the exhaust gases. It does this by pumping fresh air under pressure into the exhaust manifold, which helps burn any unburned fuel, resulting in further oxidation of the fuel. The system is made up of the following parts: A belt-driven air pump; an air filter located on the air pump behind the drive pulley wheel; air delivery hoses; a check valve in the hose between the air pump and exhaust manifold; an air distribution manifold located on the exhaust manifold or internally within the exhaust manifold; a bypass valve that acts both as a pressure relief valve and a shut-off valve on low vacuum.
The Thermactor System usually performs trouble-free. Service it during the tune up as follows:
- Remove the air delivery hose and start the engine.
- Check for air flow through the hose.
- Inspect and tighten drive belts to specification.
- Using soapy water, check for air leaks around the air filter and at all connections. Repair if necessary.
- Inspect the check valve. Remove it and try blowing through it in the opposite direction—back toward the air pump. If you can blow through, it’s defective and needs to be replaced.
4. Evaporative Control System (ECS)—this system is designed to control the leakage of fuel vapors to atmosphere. American Motors, General Motors, and Ford use a charcoal storage system to absorb fuel vapors. Other manufacturers use a crankcase system requiring no maintenance. If your car has a crankcase system you can proceed beyond this step. The charcoal-based systems are made up of the following parts: a charcoal storage unit, an air filter usually located at the bottom of the charcoal storage unit, a special fuel tank cap, and tubing lines.
The ECS system usually performs trouble-free. Service it as follows:
- Make sure all tubing is in good condition and tight.
- Replace the air filter element.
- Check the fuel tank cap for leaks. Refer to the service manual. Replace the cap if it’s damaged or lost.
- Unclog any tubing lines that are restricted.
1. Remove all the plugs and inspect them for signs of engine trouble.
2. Clean and re-gap the plugs, if necessary.
3. If the plugs are too worn, replace them.
4. Reinstall the plugs, being careful not to strip threads, and make sure the correct cables are installed on each plug.
5. At the end of this step, check the manifold vacuum for proper value according to the procedure in the service manual.
Distributor and Timing
1. Remove and clean the distributor cap and rotor. Make sure the cap is not cracked.
2. Replace the cap if it’s cracked and the rotor if the copper contact is worn, pitted, or corroded.
3. If the car uses breaker points, clean and adjust them. Replace if the points are pitted or burned.
4. Check the breaker point spring tension and adjust, if necessary.
5. Lubricate according to the service manual instructions.
6. Reassemble carefully.
7. Check and adjust the timing to specification. The service manual will provide complete instructions.
1. Clean the carburetor sediment bowl and fuel filters. Given their low cost, re place the fuel filters rather than cleaning them. In-line fuel filters must be re placed, they cannot be cleaned.
2. Clean and adjust all the carburetor linkage and the choke mechanism.
3. Make sure the fuel pump works properly. Tests are outlined in the service manual.
1. Check the muffler(s), catalytic converter(s), and pipes for damage and leakage.
2. Make sure the system is tight and doesn’t bounce around when the car is moving.
Note: Consider changing the oil and oil filter, and performing a grease job at tune-up time to top off a good job.
1. Drive the car under all normal driving conditions for 15 to 20 minutes. Be sensitive to things like uneven acceleration or engine misses. Recheck trouble areas, if necessary.
2. Check for oil, fuel, and coolant leaks.
SUMMARY OF RECOMMENDATIONS
• Perform a tune-up faithfully twice a year.
• Keep a record of fuel mileage. When it begins to drop off a tune-up may be in order.
• Perform the tune-up according to a sequence of events.
• Never tune up a car in a closed garage; carbon monoxide poisoning may result.
• Become knowledgeable about tune-ups. Study the service manual or take a course at the local vocational school or community college.
• Familiarize yourself with your tools and test equipment.
• Have a complete set of tune-up specifications at ready reference.
• Gather all the replacement parts you think will be needed before you start to work. Don’t wait until the last minute to hunt down parts.
• Mark spring-type clothes pins with cylinder numbers and then snap them on the spark plug wires in order not to lose track of which wires go where. Remember to remove them before operating the car.
• Use a fender cover when leaning over the car. And don’t wear a belt with a met al buckle because it could scratch the paint on the fender.
• Consider cleaning the engine with degreaser before you perform a tune-up.
• To better read the appropriate timing marks of the timing pulley, etch them with a dab of phosphorescent paint. They will show up nicely in the light of the timing gun.
• Have plenty of rags available. Keep your hands clean, especially when working with electrical parts. Consider using a pair of light cotton gloves as added dirt protection.