2uniq

Hey guys!
I did a compression test today but wondering if it was done correct....
What i did was before the compression test i went for a nice hard drive so the car can reach operating temps quickly and when i had it at about 190-200F i shut the car off and parked it..
Then i removed all 4 spark plugs and disconnected the plug on the coil pack...
I then installed the compression gauge and while i had my gas pedal ALL the WAY to the floor i was cranking the motor for about 5-10 sec on each cylinder until it reached its MAX psi...
The engine cranked about 5 times to get 190psi but the funny thing is on all 5 cranks it preety much was reading like this.....First crank 120psi then 150,170,180 and then 190..The needle kept on jumping so it was it was building up pressure
It did the same on all 4 cylinders and was wondering if its normal that it needs to BUILD up the pressure on the gauge while cranking the motor for 5 -10sec...
OR should it jsut shoot up to 190psi


Thanks in advanced

faithofadragon

thats why you need to crank it a few times

did you disable the fuel pump?

2uniq

I didnt disconnect the fuel pump becuase i didnt think this would of affect my readings
What i also wanted to know is if im driving the car hard for about 10-15 minutes to bring up the operating temps and then doing a compression test would the test be accurate as opposed to actaully JUST letting the car idle and when it raeches operating temps of 190F then performing the compression test....
Is there ant difference at all?

Finally so i guess the gauge raeding 120,150,180,190psi is normal while cranking is normal because its building up pressure?

12SecRD

I allready told you it was normal. drillsergeant.gif

And by not disconecting the fuel supply you were dumping fuel down your motor. fing02.gif

Dmitry

what readings do you have by cylinders?

2uniq

Well i did another compression test today and on the compression gauge instructions it says to crank the motor for 5 cranks per cylinder to get a reading....
Now on all cylinders on the 5th crank over it reads 180psi but if you let it crank 1-2 more times it reads 190psi...
When doing a compression TEST do i have to wait till the needle on the gauge stops to actualy get the CORRECT reading per cylinder like 5 or more cranks, OR just what ever the 5 cranks show...

Finally i did pay attention to the gauge and my first crank was about 50-90psi then 120,160,180,190psi

Does it really matter what PSI you get on the first crank even if its pretty low and then building pressure to get to 190psi?
Thanks!

Dmitry

it doesn't metter first crank's pressure, cause engine need time to get 250-400 RPM

probably you need max pressure on cylinder. Webtech just said - crank engine and reed pressure.

180 is a bit low.

2uniq

Cool
Thanks guys!
I just thought that the first crank if its LOW was a bad thing...
BTW Dmitry im running Weisco Pistons which are low compression at about 8.8:1 and 190PSI is pretty good and normal smile.gif
Oh and BTW i forgot to mention that when i checked my spark plugs the tips had a grey white color to it and all around the threads on the Spark plug was black

Not sure if this is a LEAN condition or Rich....
I know if the plug including the tip is ALL black then its running Rich but the grey white color i think means its lean or a good mix with it being black all around the threads!

Dmitry

190 psi for low comp pistons is good fing02.gif

but, spark plags tips of white color can be result of:
• Too lean a fuel mixture
• Advanced ignition timing
• Insufficient plug tightening

Normal color of the tip is a bit brown-orange without black dots.

01tibby

id think that the reading are going up because fuel is being added each time to the combustion chamber. disconnect the fuel pump relay underneath in the pass. compartment relay "box" up above the clutch pedal.