how to get a compressiion test? [Archive] - GrandAmGT.com Forum

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snowaholic
04-05-2005, 05:17 PM
i was wondering how would i go about getting a compression test for my engine? are they free or do they cost money to get them checked? also where could i go to find a compression test?

digitalballz
04-05-2005, 05:24 PM
local garage. Probly not free.

GrahamKracka
04-05-2005, 05:27 PM
they are pita to do...def not free

Rogue9
04-06-2005, 12:57 AM
buy a gauge and do it urself, lol.
pull each spark plug one by one, put in the tester and crank it.

tenspeed
04-06-2005, 06:47 AM
Not to start a big debate but don't you pull all the plugs and put a charger on the battery?

Having the plugs out reduces the drag and the charger keeps the starter at a constant speed.

snowaholic
04-06-2005, 11:42 PM
umm i dont know if anyone answered my question??

Malaclypse
04-07-2005, 12:09 AM
Buy a Haynes manual. I'm sure the instructions for a compression test are in there. You can usually buy a compression gauge at large retail hardware stores (sears) and some automotive parts houses.

The basic steps are this.
1. Remove all spark plugs.
2. Disable spark and fuel.
3. Thread tester adapter into cylinder head.
4. Hold throttle completely open and crank engine. Allow four puffs into the compression gauge to take your reading.
5. Releive pressure from the gauge and repeat for all cylinders.

Tenspeed: Yes, removing all the spark plugs helps the engine out but isn't necessary to perform the test. Holding the throttle wide open is more important. The battery charger is a good idea if you have a weak battery.

2002AmSE
04-07-2005, 09:49 AM
I've done the compression test myself with just the front 3 because a buddy of mine owns a tester. The back three are a PITA, if I had a 4 cylinder it would be easy because they would all be on top... I didn't remove the back plugs and I unplugged the fuel pump and ignition fuses, removed the front plugs, put the tester on and cranked it WOT until the level peaked and then repeated that with the other ones.

The battery *should* have plenty of power to crank the engine with plugs in for at least the amount of time to complete this test, just make sure you drive the car to charge the battery or charge it with a charger afterwards if you took an extended amount of time cranking the engine.

I personally think it isn't safe to the electronics in the car to be starting the car with a charger connected unless it was a charger designed for that purpose because some chargers aren't regulated to change output amperage fast enough.