I sold an old pair of tow mirrors the other day, and I was talking powerstrokes with the fellow who picked them up. I​​​​​​ told him I was thinking about having a compression test done on my truck in the near future, cuz at it's mileage I wanna see just how worn out it is before I have a transmission go bad or something else that costs a good bit to fix.

At that point he told me a good shop could do a compression and leakdown test just with the right scan tool, via the obd, and not need to pull the valve covers, etc. And he was saying this in relation to the 7.3, not just like generic engines.

Is this true with the 7.3s? I had always been under the impression from the reading I'd done you had to do a manual check with the correct gauges and going into the glow plugs ports, etc.


My truck is currently running fine, and the blowby looks normal, I'm just thinking about doing the compression test sometime just so I know.

 

A Compression and Leak-Down Test are Manual Tests on all Internal Combustion Engines. These are the most accurate; real-time pressure measured in the Cylinder at specific times.

Other Options Available for Diagnosis is a Cylinder Contribution Test. Which, could indicate the Need for either of the above.

A Cranking Compression Test is done with an Oscilloscope. This Graphs the Rotational Resistance of the Cylinders while Cranking the Engine. This test is used to diagnose which cylinder, if any, would require a Mechanical repair.

 

So... Someone was talking out his butt? That's kinda what I figured. He said he had an auto shop in a city near me. Guess I know not to go there, lol.

 

Well, actually no.

What he was referring to is a cylinder balance test to determine if any further diagnostics is needed. Most professional scan tools now have this feature.

 

Correct me if I am wrong but I'm thinking that a balance test would only be helpful if one or some of the cylinders had issues and would be useless if all were equally worn out.

 

Yes.

On older engines you would either have to short out the cylinder(s) or just bite the bullet and get on with it.

If the engine is that worn, why even bother?

 

Lol, ouch, that sucks. Cross my fingers.
How bad was your #8, and did you expect anything before starting your tests?