ASE A1 flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Wet compression test
- A compression test performed after adding a small amount of oil to each cylinder; if compression rises significantly, worn piston rings are indicated rather than valve or head gasket leakage.
- Cylinder leakage test
- A test that applies compressed air to a cylinder at top dead center and listens for escaping air at the oil filler, intake, exhaust, or radiator to locate ring, valve, or head gasket leaks.
- Vacuum gauge fluctuation
- A vacuum gauge needle that fluctuates rhythmically at idle often indicates a leaking valve, weak valve spring, or uneven compression, while a steady low reading suggests an intake leak or late valve timing.
- Positive fuel trim
- Positive long-term fuel trim means the powertrain control module is adding fuel to correct a lean condition, commonly caused by vacuum leaks, low fuel pressure, dirty injectors, or unmetered air entering the engine.
- Rod bearing knock
- A deep, low-pitched knock that increases with engine load and is often loudest during acceleration or deceleration indicates excessive connecting rod bearing clearance.
- PCV blowby check
- Removing the oil filler cap with the engine running and feeling strong pressure or seeing smoke indicates excessive crankcase blowby from worn rings or damaged pistons.
- Valve seat width
- Intake valve seat width is typically about 1/16 to 3/32 inch and exhaust about 3/32 to 1/8 inch; too narrow causes overheating and too wide causes carbon buildup.
- Valve stem seal symptom
- Worn valve stem seals commonly cause blue exhaust smoke at startup after idling and during engine deceleration, because oil is drawn past the valve guides into the cylinders.
- Cylinder head warpage
- Cylinder head flatness is checked with a straightedge and feeler gauge; warpage beyond the manufacturer's limit, often around 0.002 to 0.004 inch, requires resurfacing or replacement.
- Hydraulic lifter preload
- Hydraulic lifter preload is the distance the pushrod compresses the lifter plunger, typically 0.020 to 0.060 inch, and incorrect preload can cause valve noise or a valve held open.
- Cam lobe lift
- Cam lobe lift is calculated by subtracting the base circle diameter from the maximum lobe diameter; valve lift equals cam lobe lift multiplied by the rocker arm ratio.
- Cylinder taper measurement
- Cylinder taper is found by measuring bore diameter at the top, middle, and bottom with a bore gauge; excessive taper or out-of-round requires boring or honing the block.
- Ring end gap rule
- A common ring end gap rule is about 0.004 inch per inch of cylinder bore for the top ring, with the second ring slightly smaller and the oil ring larger.
- Plastigauge bearing clearance
- Plastigauge is a crushable plastic strip placed across a bearing journal; the compressed width is compared with a scale to determine oil clearance, typically 0.001 to 0.003 inch.
- Crankshaft endplay
- Crankshaft endplay is measured with a dial indicator while prying the crankshaft fore and aft; excessive endplay indicates worn main thrust bearing surfaces or a damaged crankshaft.
- Crosshatch honing angle
- Cylinder honing should produce a crosshatch pattern of about 45 to 60 degrees included angle, which helps retain oil and seat new piston rings.
- Pressure cap boiling point
- A cooling system pressure cap raises coolant boiling point by about 3 degrees Fahrenheit for each pound per square inch of pressure, so a 15 psi cap raises boiling point about 45 degrees.
- Thermostat opening test
- A thermostat should begin opening at its rated temperature and be fully open about 15 to 20 degrees Fahrenheit higher; a thermostat stuck open causes slow warm-up and poor heater performance.
- Blown head gasket coolant
- Combustion gases in coolant can be detected with a block tester fluid that turns from blue to yellow when hydrocarbons are present, indicating a leaking head gasket or cracked casting.
- Oil pressure low causes
- Low oil pressure can result from a worn oil pump, restricted pickup screen, excessive bearing clearance, diluted or wrong viscosity oil, or a stuck-open pressure relief valve.
- Water pump weep hole
- Coolant leaking from the water pump weep hole indicates a failed pump shaft seal and usually requires water pump replacement rather than sealing the hole.
- Coolant freeze point
- A coolant hydrometer or refractometer measures freeze point; a 50/50 ethylene glycol mixture typically protects to about minus 34 degrees Fahrenheit and raises boiling point.
- Exhaust backpressure test
- Exhaust backpressure measured at the oxygen sensor port should be low, typically under 1 to 2 psi at idle; higher readings indicate a restricted catalytic converter or muffler.
- Oxygen sensor switching
- A good upstream oxygen sensor switches rapidly between about 0.1 and 0.9 volt; a slow or flat response indicates a lazy sensor, exhaust leak, or fuel control problem.
- Spark plug reading
- Spark plug electrode color and wear reveal combustion conditions: tan-gray indicates normal, black soot indicates rich mixture, and white blistered porcelain indicates overheating or lean mixture.
- Fuel pressure volume test
- Fuel pressure must meet specification and the pump must deliver adequate volume, often about one pint in 15 seconds, because a pump can produce pressure but insufficient flow.
- Injector resistance test
- Measuring fuel injector resistance with an ohmmeter identifies open or shorted coils; resistance outside the manufacturer's specified range, often 12 to 16 ohms, indicates a faulty injector.
- Battery state of charge
- A fully charged 12-volt battery rests at about 12.6 volts; 12.4 volts is about 75 percent, 12.2 volts about 50 percent, and 12.0 volts about 25 percent state of charge.
- Battery load test
- A battery load test applies half the rated cold cranking amps for 15 seconds; at 70 degrees Fahrenheit the battery should stay above about 9.6 volts.
- Parasitic draw limit
- After modules sleep, normal parasitic draw is usually less than 50 milliamps; excessive draw can discharge the battery overnight and is found by measuring voltage drop across fuses.
- Charging voltage range
- A properly charging alternator typically produces 13.5 to 14.5 volts at the battery with the engine running and accessories off; higher or lower voltage indicates a charging system fault.
- Starter current draw
- A typical starter draws about 150 to 250 amps during cranking; excessive current draw suggests a seized starter, bad cable connection, or mechanical engine drag.