Andi
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| posted on 3/12/14 at 11:10 PM |
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Compression test methods
Probably a bit of a basic question, but I have seen many slight variants in compression testing on t web
ie all plugs out, just one plug out, WOT, disconnect fuel pump etc
I have a zetec with fuel injection and I know I have to disable the spark, but do I disable fuel pump as well?
and I was going to go for all plugs out and do one cylinder at a time.
What are your thoughts please.
Andi
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bart
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| posted on 3/12/14 at 11:24 PM |
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no straight answer depends on what you suspect is the problem ie : rings - valves
for a general check
all spark plugs out , allows quicker turn over and less drain on the battery
disconnect the spark and petrol for safety
if you suspect rings not valves post again.
BE ALERT > BRITAIN NEEDS LERTS
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Nickp
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| posted on 4/12/14 at 07:43 AM |
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Warm engine
All plugs out
Disable fuel pump, especially if FI
Crank 1/2 dozen turns with wide open throttle
If readings are low then squirt oil down bores to see if they improve. If they do then suspect rings.
Job done 
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DW100
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| posted on 4/12/14 at 12:09 PM |
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What you are aiming for is to make the test as consistent as possible. Same amount of engine drag, same throttle opening and same length of cranking
etc.
As said before fuel and sparks are disconnected for safety.
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steve m
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| posted on 4/12/14 at 02:18 PM |
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Compression tests need to be done with "wot" wide open throttle
personly I always do mine with all 4 plugs out and just spin the starter 3 seconds
Steve
Thats was probably spelt wrong, or had some grammer, that the "grammer police have to have a moan at
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