Michigan sos engine repair
Question 1.
Compression test
ANSWER
Remove all spark plugs, throttle must be WOT, crank though 4 compression strokes. Usually max difference is 20% between lowest and highest.
Question 2.
Where can the engine loose compression?
ANSWER
Intake or exhaust valves, piston rings, & cylinder head gasket
Question 3.
All cylinders must have what compression?
ANSWER
Equal
Question 4.
Wet compression test
ANSWER
Done if low compression is found on one or more cylinder(s) to help determine the cause. Using 3 squirts of oil to help seal piston rings.
Question 5.
After preforming a Wet compression test the readings improve, what does this indicate?
ANSWER
The engine is loosing compression through the piston rings.
Question 6.
Cylinder leak test
ANSWER
Injecting air pressure into the cylinders one at a time to help determine the condition of the engine. Must be done at operating temp and with the cylinder at
TDC & by firing order.
Question 7.
What percentage range is considered acceptable in a cylinder leak test?
ANSWER
20% or less of a difference is the acceptable range: 10% is optimal and less than 30% is poor.
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, Question 8.
Where can air escape on a cylinder leak test?
ANSWER
Oil cap, radiator cap, throttle body, and tailpipe.
Question 9.
During a cylinder leak test the tech finds air escaping through the oil cap what does this condition indicate?
ANSWER
Piston rings are worn or broken, causing the engine to loose compression.
Question 10.
During a cylinder leak test the tech finds air escaping through the radiator cap what does this condition indicate?
ANSWER
Blown head gasket or cracked cylinder head, causing the engine to loose compression.
Question 11.
During a cylinder leak test the tech finds air escaping through the throttle body what does this condition indicate?
ANSWER
Intake valves are damaged or defective, causing the engine to loose compression.
Question 12.
During a cylinder leak test the tech finds air escaping through the tail pipe what does this condition indicate?
ANSWER
Exhaust valves are damaged or defective, causing the engine to loose compression.
Question 13.
After preforming a dry compression test the readings are as follows. Cylinder 1: 140 psi, Cylinder 2: 200 psi, Cylinder 3: 180 psi,
Cylinder 4: 190 psi. What do these readings indicate?
ANSWER
Cylinder 1 has an issue since its readings are over 30% worst than Cylinder 2. A wet compression test or leak down test should be done to determine the
cause.
Question 14.
During a dry compression test Cylinder 1 reads 180 psi. After preforming a wet compression test Cylinder 1 reads 185 psi. What does
this reading indicate considering the highest psi value was 220 psi?
ANSWER
Cylinder 1 is not loosing compression through the piston rings since the readings only improved slightly. A leak down test should be preformed.
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Question 1.
Compression test
ANSWER
Remove all spark plugs, throttle must be WOT, crank though 4 compression strokes. Usually max difference is 20% between lowest and highest.
Question 2.
Where can the engine loose compression?
ANSWER
Intake or exhaust valves, piston rings, & cylinder head gasket
Question 3.
All cylinders must have what compression?
ANSWER
Equal
Question 4.
Wet compression test
ANSWER
Done if low compression is found on one or more cylinder(s) to help determine the cause. Using 3 squirts of oil to help seal piston rings.
Question 5.
After preforming a Wet compression test the readings improve, what does this indicate?
ANSWER
The engine is loosing compression through the piston rings.
Question 6.
Cylinder leak test
ANSWER
Injecting air pressure into the cylinders one at a time to help determine the condition of the engine. Must be done at operating temp and with the cylinder at
TDC & by firing order.
Question 7.
What percentage range is considered acceptable in a cylinder leak test?
ANSWER
20% or less of a difference is the acceptable range: 10% is optimal and less than 30% is poor.
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, Question 8.
Where can air escape on a cylinder leak test?
ANSWER
Oil cap, radiator cap, throttle body, and tailpipe.
Question 9.
During a cylinder leak test the tech finds air escaping through the oil cap what does this condition indicate?
ANSWER
Piston rings are worn or broken, causing the engine to loose compression.
Question 10.
During a cylinder leak test the tech finds air escaping through the radiator cap what does this condition indicate?
ANSWER
Blown head gasket or cracked cylinder head, causing the engine to loose compression.
Question 11.
During a cylinder leak test the tech finds air escaping through the throttle body what does this condition indicate?
ANSWER
Intake valves are damaged or defective, causing the engine to loose compression.
Question 12.
During a cylinder leak test the tech finds air escaping through the tail pipe what does this condition indicate?
ANSWER
Exhaust valves are damaged or defective, causing the engine to loose compression.
Question 13.
After preforming a dry compression test the readings are as follows. Cylinder 1: 140 psi, Cylinder 2: 200 psi, Cylinder 3: 180 psi,
Cylinder 4: 190 psi. What do these readings indicate?
ANSWER
Cylinder 1 has an issue since its readings are over 30% worst than Cylinder 2. A wet compression test or leak down test should be done to determine the
cause.
Question 14.
During a dry compression test Cylinder 1 reads 180 psi. After preforming a wet compression test Cylinder 1 reads 185 psi. What does
this reading indicate considering the highest psi value was 220 psi?
ANSWER
Cylinder 1 is not loosing compression through the piston rings since the readings only improved slightly. A leak down test should be preformed.
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