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.

[adobedero]

After a lot of searching, I found this to be the best source of information in the world regarding SD22 compression test adapters.

In a moment when my brain went soft, I bought two 1982 pickups with SD22 diesels. One was complete and runs.

The other had been in a front end crash. No radiator, etc.

With a new set of nozzles, even without a cooling system I got it to run. That is, run ... but not run well.

I've been working with VW (and other) diesels for many years, and had collected several different diesel compression testers. Including one HEC (hecho en china) set with many adapters. But nothing fit.

So I went searching the web for diesel compression adapters. It turns out there are three different couplers: otc/snap-on; tu-15/apex; and jet.

The injector adapters in my HEC didn't fit. The M10 glow plug adapters in my HEC kit wouldn't work. None of the other glow plug adapters I bought would fit the #1 and #2 cylinders.

Apparenltly, the OEM solution was an M22 x 1.5 injector-adapter, so I kept searching. I finally found an automotive tool supplier in Australia who was selling made-in-Taiwan adapters, and their website included enough dimensions that I thought it might fit. So I ordered two M22 (plus an Isuzu 2.23) adapters. About $200 delivered.

The M22 adapters didn't fit, but they had the right thread and the right 'projection' on the nose to seal at the copper washer. But the body diameter was too big to fit in the SD22 injector bore.

So I spent an hour or so on the bench grinder, grinding down the hex and flared shoulder to fit into the 25mm injector bore. The adapter would then screw into the head until the top went into the bore.

Then I ground a 19mm hex on the top end so that I could tighten it up. (A 19mm deep socket fits in the injector bore.)

But it wouldn't tighten enough to seal.

I wound up taking a diamond file and cutting the leading thread off. Then it screwed in far enough to seal against the copper washer.

I attach a picture with an SD22 injector, my modified adapter, and an untouched adapter.

It turns out that my HEC adapter kit already had the same adapter that I wound up modifying. Oh well. Live and learn.

At least I now have an injector adapater for testing compression on an SD22.

The good news is that the compression turned out to be 220-180-350-200. Enough to get it to run. Sort of.

The bad news is that with no cooling hoses in place, its slowly pumping engine oil out of the cooling system.

Does anyone have an SD22 oil cooler laying around?

[waynosworld]

I believe I have always used the glow plug hole to do my compression tests.

I can look to see if I have an oil cooler for an SD22 for a US engine around, where are you located?