I am trying to do a compression test, car is leaking coolant so dealer suggested doing a compression test to see if the headgasket is going. But they refuse to tell me what my stock compression is, and I googled it and all it came up with was 9? I've never done this before but the meter reads in PSI...so if someone could help me out with a step by step, and tell me what it's supposed to be at it'd be much appreciated. car is 1996 Mustang GT, 4.6L 2V motor 5 speed, with a few bolt ons. thanks in advance

 

Remove all spark plugs. Disconnect power to coils, unplug if cops if you have. Block TB wide open, this also shuts off fuel to injectors. Attach gauge to each spark plug hole, one at a time, crank engine til gauge reads no higher (4 compression strokes or so should do it). Make chart of each cylinder reading. All should be within approximately 15 (+-) psi of each other. The number depends on cam, C/R, and other factors, so is not a given psi range, but I would expect to see somewhere around 150 give or take.

 

How do I disconnect power to the coils? And what are cops?? Also how do I tell if it has been 4 compression strokes? Im not even sure I know what I compression stroke is....sorry to be asking dumb questions, Im just very precise in what I do and want to learn how to do it right. Thank's for bearing with me.

 

Without looking, Im not sure if you have 2 individual coils, for 4 cylinders each, or the coil on plug setup. 96, I think, has 2 separate ignition coils. Whichever you have, there is a connection to the coil(s), a small plug, not the spark plug wires. Unplug the connection. If you have a helper, when you have guage attached, and said helper cranks engine, you will hear when it hits compression. If helper is cranking engine, you can observe the gauge. It will jump up in PSI, each time it hits compression. After 3 or 4 hits, the gauge wont go any higher. This is the reading you are looking for.

 

i just did a compression test on my 5.0 gt mustang and was 150 psi
but its 15(+)(-) on the highest number to the lowest if its higher or lower theres something wrong with the heads

 

johnny092097;6918849]i just did a compression test on my 5.0 gt mustang and was 150 psi but i lest the spark plugs in and took the plug of the egr

 

srry took of the power coil. its better that way so no drit gets in your heads if you take all the spark plugs out