Download Engine Performance Diagnosis and Testing

Engine Performance Diagnosis and Testing
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Figure 31–2 Diagnostic funnel. Step
#1 is to verify the problem. If the
problem cannot be duplicated,
obviously the repair cannot be
performed.
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Check everything that does and does not
work. This step involves turning things on and
observing that everything is working properly.
Look for evidence of previous repairs. Any
time work is performed on a vehicle, there is
always a risk that something will be disturbed,
knocked off, or left disconnected.
Check oil level and condition. Another area
for visual inspection is oil level and condition.
Oil level—Oil should be to the proper level.
Oil condition—Using a match or lighter, try to
light the oil on the dipstick; if the oil flames
up, gasoline is present in the engine oil. Drip
some engine oil from the dipstick onto the
hot exhaust manifold. If the oil bubbles or
boils, coolant (water) is present in the oil.
Check for grittiness by rubbing the oil
between your fingers.
NOTE: Gasoline in the oil will cause the engine to run
rich by drawing fuel through the positive crankcase
ventilation (PCV) system.
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Check coolant level and condition. Most
mechanical engine problems are caused by
overheating. The proper operation of the cooling
system is critical to the life of any engine.