If you're doing a cranking compresion test, all of the sparkplugs
would be removed, throttle wide open and fuel and spark delivery
If you're doing a running compression test, only the sparkplug
for the cylinder being tested would be removed.
If you're doing it electronically, no sparkplugs need to be
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.