Me[kk]A

do you leave the spark plugs in the caps and ground them to the engine head during the test?

imported_nsxvtec

No
Just remove all of the spark plugs from the engine and have the TP plate fully open.

Why would you want to ground the spark plug caps / wires???

lazyjai123

disconnect the electric connector beside ur disturbutor. that disables the coil so there will be no spark

chris_si98

^ those clips are stubborn..

Just disconnent the ecu fuse=no fuel and no spark.

Don't forget to do the test at operating temperate and at WOT

imported_starboy869

I heard you could damage your ignition coil if you don't. However I don't do it I just pull the connection. I do my compression tests on a warm engine (if possible), fuse pump fuse pulled, Throttle plate fully open, all plugs pulled, start with cylinder #1 and work my over. Write the reading down and if there's a problem. Redo the test 'wet'. A squirt of oil in each cylinder.

Also if there's an issue I follow the compression test with a leakdown test.


I never thought about pulling the ecu fuse. thanks.

chris_si98

Yes that is true.. because the voltage has to find a ground somewhere.. And if it can't jump the gap at the spark plug.. it has to go somewhere

imported_janz3n

what will happen with the compression reading if you dont push the gas wile cranking the motor?

chris_si98

it'll be lower than what it should

imported_starboy869

Since the throttle plate won't be open your creating a restriction in air flow for the intake. You reading won't be as high. This would give you a possible false problem since your compression psi #s shouldn't be where it should be.

imported_janz3n

ok cool. thanks. im dumb

imported_nsxvtec

No you are not.

Better to ask and get help. Now you know.

imported_janz3n

im dumb because i knew about that i just forgot or just thought it didnt matter.