Today I visited some workshop to kill time , and I saw the mechanic there did a compression test using rotary comp tester (comp 07S).

He pulled the fuel pump relay located at the front bumper fuse box. Then I watch he cranked the engine for 5 seconds (the tester got count down timer) without accel pedal to the floor.

I always thought that we must pull the the EGI relay and when doing the test we must open the throttle (accel pedal to the floor) ?

Is there any difference doing the test with and without opening the throttle?

 

nope.

 

I am new to all this but I just learned something new, thank you for the information.

 

I hate to disagree but I do!.I was taught Wide open throttle so that the engine can Get air,no restriction and therefore give you a Good Comp Test.A closed TB( at idle) will not let the engine get Good air.
I would do another test with Open Throttle.It can variate the Test by at least 15PSI.

 

if the throttle is not open, it will pull vacuum and thus a resistance to turn and will not crank as fast and not give as high of a compression.