203f - Diesel Engine & Fuel Testing & Adjusting Flashcards
A properly tuned engine has what benefits? (4)
- Low exhaust emissions
- Efficient engine operation - fuel economy
- Maintains rated power output
- Reliable and maximum service life
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An engine tune-up could include what services?
- Valve & injector adjustment
- Governor adjustment
- Engine brake adjustment
- Injection pump timing check
- Injector nozzle test
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Governors are designed to work through the full range of throttle travel. If throttle linkage wear affects the range of travel, what should be done before making adjustments?
Replace the throttle linkage
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What do some throttle linkages use that allows full throttle travel regardless of engine movement in the chassis?
A spring-loaded overtravel device
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What does a fuel injector cut-out test consist of?
Momentarily crack open one injection line at a time with engine running. A cylinder that exhibits no change in rpm indicates a faulty injector or other issues in that cylinder.
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How could an infrared thermometer be used to test for misfiring cylinders?
Check exhaust manifold temperature at each cylinder. A drop of more than 50 degrees Celsius indicates a cylinder that is not firing correctly.
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How is injector back leakage tested?
Bring the pressure up to 2000psi and let drop to 1500psi. Time the pressure drop.
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What is the maximum allowed variation in cracking pressures between a set of injectors?
50 psi
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What is injector nozzle chatter?
A series of popping or chattering sounds caused by the rapid pulsation of the needle.
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How is injector needle seat to face leakage tested?
Maintain pressure at 150-200 psi lower than cracking pressure. Time for 10 seconds and check for leakage. There should be no leakage.
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Why is injector back leakage important?
Back leakage fuel cools and lubricates the injector
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To properly test and diagnose an engine for performance, you must put the engine under _____.
Load
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What three basic components to dynos have?
- A power absorption unit
- A load control
- A torque-measuring device
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Two common types of load cells used in heavy-duty diesel engine dynos are:
- Hydraulic
- Electric
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In a water brake dyno, engine power output is converted to ______ in the load cell.
Heat
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What style of dyno has a permanent frame on the shop floor and requires long setup time?
Stationary dyno
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What style of dyno is usually compact, has integral instrumentation, and minimal hookup?
Portable dyno
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What style of dyno is embedded in the shop floor and has a set of rollers to support the rear wheels of the vehicle?
Chassis Dyno
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What style of dyno is typically used in the agricultural industry?
PTO dyno
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What units are engine power output typically measured in?
- Horsepower (hp)
- Kilowatts (kW)
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What units are engine torque output typically measured in?
- Pound-feet (lb-ft)
- Newton meters (Nm)
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Why should engines be operated at their rated horsepower level?
Ensures that it performs at maximum efficiency.
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How do most diesel engine manufacturers rate the fuel economy of an engine?
Brake Specific Fuel Consumption (BSFC). The amount of fuel used per hour per brake horsepower.
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How much should a naturally aspirated engine be de-rated at 1000 feet above sea level?
3%
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What should be inspected on a vehicle before performing any dyno tests?
- Vehicle powertrain
- Suspension
- Tire condition
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What four main uses are there for dyno testing?
- Testing engine performance
- Diagnosis
- Troubleshooting
- Break-in after a rebuild
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What four basic steps should be followed when performing engine diagnosis?
- Gather relevant information
- Perform operating tests to verify the problem
- Determine possible causes
- Perform tests based on the results of your diagnosis
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