I've done compression tests before but I've always just pulled one plug at a time then replaced them when moving on to the next cylinder. I'm wondering if warming up the engine, then pulling ALL the plugs, then replacing them one at a time after testing each cylinder will ruin the readings. I.E. so when testing the first cylinder the other 7 have no spark plugs in, and by the time I'm testing the last cylinder the other 7 all have their spark plugs in. This obviously creates huge vacuum leaks when those cylinder's intake valves are open, I'm just wondering if this matters. If it's necessary or not to have the other cylinders sealed up while testing compression.

 

Shouldn't matter ur testing that particular cylinder's compression...

 

the instructions for my compression tester say to warm up the engine to running temp, then turn it off, and remove all spark plugs, and go from cylinder to cylinder and check what they read.

 

So that means I've been doing it wrong up until now. Sounds about right

Thanks for the replies.

 

no prob that's what we're here for

 

Thats the way I have always done it, I check ALL cylinders and get readings, THEN put the plugs back in.

 

ase standard also removing all plugs

 

Thanks. That's the way I did it. Compression test came out good. 140 as a low and 160 as a high. Engine was cold and no oil was put in cylinders for a second test. I was happy enough with those numbers to not bother.