Engine Systems Flashcards
When it comes to mechanical problems It is necessary to what?
to evaluate whether the mechanical problem will cause an accident or breakdown versus the need to get the load moved.
How can you minimize deadline situations?
By listening to the driver and technician and making decisions based on the given facts and possible consequences.
Who should perform pre-trip inspection and where should it start?
The driver should perform a pre-trip inspection. The inspection should start at the left front of the vehicle and work in a counterclockwise direction around it.
How valuable are permanent records?
Are invaluable from a performance standpoint. A study of failures of individual components can alert the manager of the need to take corrective action. It also highlight components the have performed satisfactorily.
Where should any repair procedures be noted?
Must be noted using a sign-off sheet before the vehicle is put back into Service. If the problem noted did not require repair, but was still looked at, then this must be recorded as well. A copy of the inspection report must remain with the vehicle.
What should be included in service logs and why are they important?
Should affect work performed on a vehicle. Active complaints/problems should always be addresses immediately with quick visual inspection to determine if the repair can be made quickly and easily. The check the vehicle records if it appears that quick repair cannot be made. All information that can be obtained could be invaluable to the timely repair the vehicle.
Federal Motor Carrier safety Regulations
Part 393, States that anything mechanical component that can either cause or prevent an accident is a safety item. All vehicle safety problems should be addressed, no matter how minor they appear. Section 396.19, States it is the fleets manager’s responsibility to ensure that all personnel doing annual inspections are qualified to preform those inspections. They should understand the inspection criteria and be able to identify defective components and systems.
Federal Highway Administration
Has set up a minimum inspection standards program, under which each vehicle must carry proof that an inspection was completed. Proof can either be copy of the inspection form kept on the vehicle or a decal. If using decal , a copy of the inspection form must be kept on file and should indicate where an inspector can get a copy of it. The only requirement of a decal itself is that it be legible. Each vehicle must be inspected separately. This means a tractor/trailer is considered to be two vehicles, each requiring a decal; a converter dolly is separate vehicle. The decal must show the following information: date vehicle passed inspection, name and address to contact concerning inspection record, and VIN.
Regulation
Places a greater emphasis on the post-trip inspection, most operators agree the pre-trip inspection in more important. Because the driver is doing the inspection will be operating that particular vehicle, the incentive to ensure that the vehicle is safe is probably greater. Repairs are cheaper and less time-consuming if the driver finds them on the pre-trip before inspectors levy fines or impose penalties.
Today’s Diesel trucks contain
A verity of computerized control systems to operate engines. transmissions, antilock brakes, etc. According to Society of automotive engineers(SAE) Standard J1930, diagnostic codes are known as diagnostic trouble codes (DTCs). DTC access may be by blink codes or read off the chassis data-bus. You need to understand how to check, record, and clear DTCs.
At what RPM should engine should crank?
Electronic diesel and gasoline-fueled engines will not inject fuel until at least 150 rpm.
And Using ether can cause detonation (Loud hammering sound). It should never be used on glow plug applications.
What are the Exhaust smoke colors?
White smoke is an Indication of unburned fuel exiting the exhaust pipe. Blue smoke is an in dictation of burning oil. Black smoke is caused by air starvation or rich-fuel mixture.
Governed RPM
The Maximum engine RPM that an engine is rated for and the fuel or engine-management system will attempt to limit speeds above that setting.
Vibration Damper
Mounted on the front of the engine, balancing harmonic vibrations caused by torsional loads of the rotating crankshaft.
All accessory belts
Should be checked for obvious signs of wear, tension, and/ or correct application(if suspected). A belt tension gauge should be used whenever possible for most accurate readings. If one is not available, Then the normal deflection points at the specified locations and measurements should be observed. an idler hub should be checked for loos or worn bearing, condition of belt surfaces, cracks from fatigue of deterioration, and the correct application.
What two types of leaks should an engine be checked for while doing an inspection?
Static (while it’s running) and Dynamic (while it’s off) Leaks
What is mandatory, when checking for fuel leaks on an engine?
It is mandatory that the engine is running, thus making the leak very apparent.
Why is a fuel leak more hazardous while the engine is running?
Due to the higher fuel pressure.
What should inspection of the cooling system include?
A check of the: cooling system maintenance history coolant change intervals component replacement (s) past diagnosis
Although a leak in the cooling system a serious problem, why is it not the criteria for deadlining?
It is not safety-related.
What is the most effective way of diagnosing a vehicle with defective engine mounts?
Observe the engine mounts while torquing the engine with the brakes applied. This will allow a broken or deteriorated engine mount to be quickly observed and noted for replacement.
Why is checking the engine oil level a critical part of a PMI?
The correct oil level is essential for proper engine lubrication and cooling.
What are the effects of an oil level too low?
Oil level too low may allow air to be drawn into the pump and a loss of oil circulation.
What are the effects of an oil level too high?
Oil level too high may allow the oil to be whipped by the crankshaft, which could cause oil aeration.
What does aerated oil do?
It is not compressible and does not provide a continuous flow of oil to the various components that depend upon oil for lubrication, cooling, or hydraulic operation, which could result in engine failure or accelerated wear..
What is the recommended procedure for checking the oil level?
Be sure that the vehicle is on level ground and has not been operating for at least five minutes. Remove the dipstick and wipe with a clean rag to remove any oil from the previous operation. Fully insert the clean dipstick and remove to obtain the correct reading.
Why is it careful examination of the wiring harnesses essential?
Many systems on a modern truck depend upon the electrical circuit in one way or another.
What is the procedure for checking wiring harnesses?
- Pay particular attention to any areas where the wiring harness contacts anything metal.
- Wiring harnesses should be covered with protective armor and secured in place with brackets and loom holders.
3, Make sure all wiring is properly routed to avoid damage from moving parts and hot exhaust manifolds
Why are connectors constructed with waterproof seals?
To prevent corrosion.
Why should seals on connectors always be in good condition?
Many electrical problems are traced to problems at the connectors.
What should you do to remove a wire from a connector for repair or placement?
Be sure to use the proper tools and replacement parts. Wherever a splice or repair is made to the wiring, it should be sealed to weatherproof it
What should you look for when checking fuel tanks during a PMI?
- Signs of leakage at any point, with special attention to all seams and any damaged areas.
- The fuel tank mounts should be attached to the frame and the tank should be free from any cracks, corrosion, and damage that could cause failure.
- There should be no sign of tank shifting and all mounting bolts should be in place and tight.
- Check the tank fuel supply for moisture contamination by the use of a rod or probe coated with water detection paste, which is designed to change color when it comes in contact with water.
- If more than the tip changes color, the tanks may require draining to remove the water.
- Water in the fuel tank can be drained by the use of a suction pump with a long sump that reaches to the bottom of the tank where the water would accumulate, or by a tank drained.
What should you look for when checking the fuel tank cap during a PMI?
- The fuel tank cap should be easily installed and removed and should be able to provide a good seal.
- Check to ensure that the cap seal is in place and in good condition.
The fuel lines, including the crossover line, must be leak-free and should be secured by loom or brackets.
Inspect all routing to ensure that no line damage will occur due to contact with other objects.
If the line is chafed but no leak is present, a replacement decision should be made on the severity or probability of a future leak or breakdown.
What should you do when inspecting a water separator/fuel heater during a PMI?
- Routine water draining and changing the filter element when the other engine filters are changed is a good practice.
- The aftermarket filter element that has a longer service life, should be changed at specified intervals.
3,. Fuel contamination can occur easily if the canister is primed with unfiltered fuel or dirt is allowed to enter when the element is being changed.
The filters must be primed before the engine can be started.
Why do some manufacturers recommend that the secondary filter be installed dry and primed with a hand pump?
To ensure that only filtered diesel fuel enters the secondary filter.
How would you ensure that no air bubbles are present at the fitting?
A line fitting upstream from the pump should be cracked open and priming should continue until no air bubbles are present
What is the procedure for inspecting the crankcase ventilation system during a PMI?
- The PV valve should always be checked when any inspection of the emission control system.
What does improper operation of the PCV cause?
Erratic engine operation as well as higher than normal gasoline exhaust emissions, causing fines and penalties due to violations.
How should you check exhaust system mountings for looseness and damage?
- Use a pry bar to check exhaust pipes and support brackets for looseness.
- All mounting brackets should be examined for cracks and clamps must be tight.
- The complete system should be visually inspected for rust, damage, and cracks.
What happens when an exhaust system is leaking in front of below the driver/sleeper compartment and the floor plan has potential for cab entry of exhaust fumes?
The fumes can result in a drowsy o asphyxiated driver, which could cause an accident.
How should the exhaust routing be checked and assembled?
The exhaust routing must be checked and assembled in a way that does not allow contact of the exhaust system with any wiring, air lines, fuel lines, or combustible materials.
The Commercial Vehicle Safety Alliance (CVSA) our-of-service criteria would deadline a vehicle for any of these faults.
What depends on whether the truck air induction ducts need to be cleaned on every PMI?
The conditions the vehicle is driven in.
What should you do, concerning the truck air induction systems during a PMI?
- Give a full visual inspection to the air induction for blockage and/or deterioration.
- The air inlet restriction should be checked with a water manometer or accurate vacuum gauge.
- If the restriction exceeds the maximum specifications, the air filter should be checked.
What will tapping on the floor or blowing with air pressure to dislodge dirt do to restricted dry filters?
It will result in filter damage and dirt bypassing the filter if it is reinstalled.
How does a turbocharger operate?
A turbocharger operates on the principle of thermal expansion to drive a turbine wheel, located in the turbine housing.
This, in turn, spins the compressor wheel in the impeller housing.
Where is the compressor wheel located and what does it do?
The compressor wheel is located in the inlet side and draws in fresh air and pressurizes it.
Where is it necessary to contain the pressurized air?
It necessary to contain the pressurized air in hoses, manifolds, and an intercooler.
A turbocharger can operate within manufacturer’s specifications and still have acceptable leakage. True or False?
True
How would you test for proper leak rate?
Follow the most current information provided in the manufacturers’ service bulletins and do not exceed the recommended test air pressure.
How should clamps be torqued?
The clamps used are spring-loaded and should be torqued to specifications and placed in a way as to not chafe through other hoses or components with engine movement.
At what speed can modern diesel engine turbochargers perform?
Modern diesel engine turbochargers perform at very high speeds and can reach well over 100,000 rpm.
What should you do when running the engine without the air intake?
Be sure to install an intake guard over the turbocharger inlet.
How much air by volume do engines require?
- Engines require approximately 9,000 to 10,000 gallons of air by volume for every gallon of fuel consumed.
- This results in a volumetric air-fuel ratio of approximately 10,000to 1 for both gasoline and diesel engines.
What is the stoichiometric ratio?
Air fuel ratio by mass of approximately 15:1
What is dusting; what causes it; How can it be prevented??
When a large volume of air enters an engine, it is important to provide good filtration, as airborne dust, sand, and other debris ingested into the cylinders will lead to premature engine failure called “dusting” caused by loose clamps or ill-fitting air filter assemblies.
What causes a rich fuel condition and causes a cylinder wash down of the oil film on the cylinder walls?
Obstructions such as restricted air filter will reduce airflow/volume and cause an engine to operate in a rich fuel condition, and cause cylinder wash down of the oil film on the cylinder walls, leading to engine failure.
What are typical restriction specifications for naturally aspirated and boosted engines?
Typical restriction specificationsare15inches of water vacuum for naturally aspirated engines and 25 inches of water vacuum for boosted engines.
What is EGR?
EGR is a method of reducing oxides of Nitrogen (NOx) by circulating a small amount of exhaust gases back through the intake manifold to dilute the intake charge and lower the combustion temperature.
