compression tester problem

[cobcorsa]

hey guys been tyring to get my skyline fixed up lately so today went out and bought a compression tester , i tested cylinder 1 2 3 5 , i didnt do 4 and 6 as i was in a hurry and they were alkward
cyl 1 110
cyl 2 138
cyl 3 139
cyl 5 138
so then i went back to cyl 1 to double check it and the reader went to about 30 so i was very confused , i tried cyl 2 again and again got about 20 is my reader broke or what , im very confused

and info appreciated

 

[the snooper]

sounds like it could be
did you remove all plugs then just crank until it peaked

 

[cobcorsa]

i removed the plug of the cylinder i was testing then put in back in and tested the next one , i disconnected the coilpacks , i pressed the accelerator pedal and cranked for 5 seconds

 

[the snooper]

remove all the plugs and just crank, the accelerator pedal doesnt need to be pressed crank until the max reading has been reached

 

[cobcorsa]

ok cool i was told only 5 seconds , but even the 2nd time i tried i was cranking for about 10 secs and only 30 psi was reached

 

[the snooper]

5 seconds will probably be enough anyway

 

[Kafer_meister]

ok cool i was told only 5 seconds , but even the 2nd time i tried i was cranking for about 10 secs and only 30 psi was reached

I would ensure that the tester was properly seated and that you had a good seal. There's little that would cause that sort of compression drop without an associated large bang

 

[wheresmejumper]

remove all the plugs and just crank, the accelerator pedal doesnt need to be pressed crank until the max reading has been reached

ive been told too to keep WOT,im trying to remember the reason

 

[wheresmejumper]

google says The reason the throttle must be wide open is to ensure that each cylinder fills completely. If the throttle is partially open, a vacuum will be generated in the inlet manifold and the pressures indicated will be lower than expected.

 

[the snooper]

wide open throttle for those that dont understand WOT

it makes no difference as it will still compress enough air to give the correct reading, its to measure psi not cfm and at cranking speed it will pull all the air it needs

 

[the snooper]

try it both ways you wont see a difference

 

[Country Joe]

wide open throttle for those that dont understand WOT

Nice one Snooper, you must be a mind-reader!
I'd settled on Working On That, but suspected I'd be wrong!
CJ

 

[wheresmejumper]

not going to argue,just the way i was taught

 

[the snooper]

i figured some people wouldnt know i find abbreviations on a forum tend to leave people out of a conversation, as some dont know what they mean and some people dont like to ask because they feel asking makes them look daft

 

[the snooper]

not going to argue,just the way i was taught

me neither

 

[Country Joe]

asking makes them look daft

I've been rumbled!
CJ

 

[brightspark]

wide open throttle for those that dont understand WOT

it makes no difference as it will still compress enough air to give the correct reading, its to measure psi not cfm and at cranking speed it will pull all the air it needs

if it didnt it would soon buckle the butterflies

 

[the snooper]

yeah or pull them open its self

 

[cobcorsa]

ok went at it again today and the tester started giving all different kinds of readings, one time i test the cylinder it reads 140 try it next time and it reads 100 , then 150 on the same cylinder , im puzzled

 

[the snooper]

tester no good by the sound of it is it a screw in tester or a push and hold type