My friend's 5.0 started knocking and I did a compression test on it. The haynes manual says that compression should be minimum 101psi. I tested #1 cyl and got 55psi. On #2 I got 60 psi, and on #3 I got 65psi. Then I was like woah, this is half of what it should be. To check to make sure the guage was reading right, I went over to my LX5.0 which runs perfectly fine and tested #2 and got 75psi. Do I have a faulty guage? Or is my friends engine really bad and just found out mine is going bad too? Will the engine seem to run fine with such low compression? I'm a little worried

 

make sure you have all spark plugs out and turn the engine over a min of 3 times. Thats how you get an accurate reading.

 

I actually started the engine and let it run for 3-4 seconds

 

Good idea! I think i'm going to take a compression test tomorrow....so you suggest to take out all the plugs and crank it over 2-3 times each cyl?

 

Correct, Remove all plugs, remove coil wire, turn engine overa MIN of 3 times per cyl, not 2-3

 

Get engine warm, remove spark plugs, remove coil wire, turn engine five revolutions, and prop pedal to WOT.