drewfrink@mac.com wrote:
>To further highlight my lack of automotive knowledge, I was wondering if
>anyone could point me in the direction of some instructions on how to do a
>compression test on my TR4. I have a compression guage, but don't know how to
>use it yet. After I do my fluid change/topup next week, I want to run a good
>test and gap plugs, check points (assuming I can figure that one out) and
>essentially baseline where the engine is right now. I think I'm making myself
>paranoid, so I want to make sure I know what's going on with the heart of the
>beast.
>
Drew, here you go:
- Put the car in neutral, engage the handbrake.
- Label the spark wires so you get them back in the same order, then
disconnect (most parts shops have little plastic numbers that clip onto
the plug wires to save later embarrassment).
- Remove all the spark plugs, keep them in order, and note overall
condition.*
- Screw the compression gauge into a cylinder, carefully so you don't
screw up the threads.
- Crank the engine (either turn the key or use the pushbutton starter
solenoid if you have one).
- Record the reading for that cylinder, move to the next one.
- Replace clean, regapped plugs and wires, threading the plugs by hand
so you don't screw up the threads.
You're looking for consistent readings across all cylinders, variation
within 5 or 10, and maybe a reading of 100-120. For example, with my
burnt valve, the reading in that cylinder was 35 and 120 in the others.
If the readings aren't what you expect, you could always check a known
good, modern engine to see what readings you get there -- not all gauges
are created equal.
* Here's a nice web site with an NGK 1977 spark plug reading handout,
good detail:
http://www.dansmc.com/Spark_Plugs/Spark_Plugs_catalog.html
Steven Newell
Littleton, CO USA
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