Testing Compression

[plenzen]

Not too sure how often Al comes on here these days. You may want to try the PM option.

[asavage]

It's still available for loan (I have loaned it out several times over the years). I have contacted you via email.

[1981kingcabsd22]

Does cold compression testing yield any meaningful information? Does anyone know what those numbers should be? Just curious.

[asavage]

You want even: no more than 10% variation between cylinders (that's a generic spec, not necessarily a Nissan one). So, cold testing is valid to determine if a valve is stuck or burned, or one or two cyls have big gouges. If they're all very low, you could be facing widespread/even wear -- and hard starting! -- or all the compression rings stuck, which is not likely going to be fixed via snake-oil methods (but won't keep us from trying them, right?).

But if you're looking to compare to OEM numbers, the engine has to be near operating temperature. Even then, since we're usually testing via the GP holes -- and not pulling hot injectors for this test -- the OEM numbers are merely guidelines and not hard-n-fast rules.