Compression test prep
Thread Starter
Burning Brakes
Joined: Apr 2014
Posts: 828
Likes: 189
Compression test prep
I will be doing a compression test on a 94 LT1. I’ll remove all spark plugs and make sure the battery is juiced up good. If I pull the pcm fuse, will that disable the ignition coil and injector pulse during the cranking process?
thanks
thanks
Team Owner
Joined: Aug 2004
Posts: 21,543
Likes: 3,214
From: Park City Utah
probably. There shoudl be injector fuses too. Also, if you disconnect the opti harness, you won't get any spark or inj pules.
Thread Starter
Burning Brakes
Joined: Apr 2014
Posts: 828
Likes: 189
8-155 7-150
6-155 5-150
4-155 3-155
2-160 1-150
Here are the test results. It’s a 125k mile engine. So, how are we looking here? All in reasonable range of each other, that’s for sure. Is 155psi average cranking compression indicate a healthy LT1?
6-155 5-150
4-155 3-155
2-160 1-150
Here are the test results. It’s a 125k mile engine. So, how are we looking here? All in reasonable range of each other, that’s for sure. Is 155psi average cranking compression indicate a healthy LT1?
Thread Starter
Burning Brakes
Joined: Apr 2014
Posts: 828
Likes: 189
On a 94 LT1, anyone know if the factory installed spark plugs were AC 41-906 iridium? And would these have a date code? The ones I took out have “Made in USA“ then numbers either 08 or 10.
Im wondering is those numbers indicate the year of manufacturer ie, 2008 and 2010. I’m trying to determine if these had ever been replaced.
Thanks
Im wondering is those numbers indicate the year of manufacturer ie, 2008 and 2010. I’m trying to determine if these had ever been replaced.
Thanks
Le Mans Master
Joined: Aug 2017
Posts: 6,928
Likes: 1,486
From: New Jersey
I don't know about the plugs but the compression seems good. I look more for how even each cylinder is vs what the actual number is. Granted if they're all 80 you have a problem too but its an even one lol. 
