7.3 idi compression test numbers and discussion

[jaluhn83]

It's ok, don't stress about it.

Compression test is never really about absolute pressure, it's about differences because there's so many variables. #6 is the only one that's really out of family. Book spec is within 75% of max, i.e. with 440 max, 330 should be minimum, so it's low out of spec, but not badly so. No specific value you should see or number of strokes to get there.

I would want to do a head job on it since I would bet the problems is worn valve seats, but unless there's other symptoms of a problems you should be fine for a while.

 

[The_Josh_Bear]

I responded to your other post on the same thing but I'll go into more detail here.

1. Not good on cylinder 6
2. Not good on 21 strokes, a motor is usually within 6-7 strokes before it tops out and not more than 10
4. Upload a video of the gauge while you do it if you have a smart phone
5. Do a leak down test if you have a tester
6. Doesn't matter that your motor is cold

Compression usually builds quick and even. Generalizations.. Leaking piston rings will build slow on the first stroke and take many strokes to get to the peak. Leaking valves will be low on the first stroke but stay low. You don't have adjacent low compression so probably not that.

This is my video if you want to see what it's suppose to look like. You can scroll past my explanations on how to hot wire start and grind the harbor freight adapter

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Just watched your video. Why leave the other GP's installed when cranking?

 

[hacked89]

Just watched your video. Why leave the other GP's installed when cranking?

No particular reason

 

[The_Josh_Bear]

@hacked89 I bought the same kit as you did(i think) and cut down the long glow plug adapter, but that removed the schaeder core from the equation. Now my gauge won't keep a cumulative pressure-- how'd you get around that? Mayne our kits aren't the same after all.

 

[The_Josh_Bear]

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