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Discussion Starter · #1 ·
I have an 1990 si wi/ 189k

how do I checkk the compression? I have the gauge and i know i have to crank it. but for how long?

Can somebody please tell me the right steps on how to do a wet and dry com
pression test? also, What is the average compression it should have?
 

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You will want to disconnect your fuel and spark. Then crank the car over for a couple seconds.

You really want all the cylinders to read the same, if you have a large gap between the cylinders, something is off. My car was reading 120~... honda states the minimum allowed is 132
 

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OK I can chime in on this one.
Check the "dry" compression first.
The easiest way to disconnect the spark is to loosen and slide the dizzy cap away from the dizzy base.
Remove all four spark plugs(This makes it easier for the starter to crank the motor over).
Start at #1:Thread the compression guage in and crank the motor for a few seconds(say like 3 to 4 seconds)
Record the reading and move on down the cylinders.
Now "wet".
Either spray or squirt a little oil in the cylinder,and repeat the earlier processes.

The reason for a dry and wet reading is this.If you take a "dry" reading and get a good compression,but do the wet and the reading goes up a lot like 20+ psi then your cylinders are probably seriously scratched up.
I hope that helps.

I really dont know what Honda says is a bare minimum for a cylinder psi,but I do these tests at work and anything less than 150 is considered weak.
Good luck and I hope my lil lession in compression testing helps you.
 

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ollie said:
The easiest way to disconnect the spark is to loosen and slide the dizzy cap away from the dizzy base.
[...]
crank the motor for a few seconds(say like 3 to 4 seconds)
Since nobody else seemed to mention it, you want to do the test with the engine fully warmed up. You probably won't get the same numbers on a cold engine as a warm one... Metal expands when heated, which affects the clearance between various parts - the piston and cylinder wall included.
The easiest way to disable the ignition that I've found is to unplug the distributor's 2 pin electrical connector. The heavy blk/yel wire is the distributor's power feed coming from the ignition switch. Without it, the ignition coil can't be energized so no spark can be generated. Sliding back the distributor cap simply prevents the high voltage pulse from being transfered to the spark plug wires... Who knows where it's going instead.
To cut off the fuel, remove the "ECU" fuse from the underhood fuse box. Without it, the fuel pump won't prime and the injectors won't fire. In truth, the ignition shouldn't work either, but I prefer to unplug the distributor connector just to be safe.
As for cranking time, I've always positioned the compression gauge in such a way that I can see the needle from the drivers seat. Then simply crank the engine until the needle stops twitching... It's typicly 8-10 seconds. With all the spark plugs out, there's a good bit less load on the starter motor, so cranking the engine doesn't run the battery down nearly as much.
 

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bluecrxnc said:
Don't forget to hold your gas pedal all the way down while cranking.
If you disable the system that is not necessary.
 

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You have to have something to compress... :idea:

Holding the throttle wide open insures the cylinder
is full of air...
 

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ehh, late chiming in. Everyone already caught everything needed to happen for reliable results (warm engine, plugs out, WOT, ecu disabled)
jvillarr said:
I think you're fine with it if it's just a daily driver. Memory serving, stock figures should be at 175. If performance is desired, a leak down test is in order. From those numbers I suspect worn compression rings as a primary.
 

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Discussion Starter · #13 ·
My main concern is this...

I'm going to need a head gasket soon. I was thinking, since i'm going to have to remove the heads, i might as well go mini me. But if the rings are bad, why even bother with the gasket.

It's just for daily driver. I don't race at all. But I would also like to experience the mini me. I had a ZC in my previous CRX and I loved it. It has come to my attention that it's hard to find a reliable ZC now. And the shipping on a ZC is about $250.

That is why I wanted to check my compression to see if it would be worth going mini me.

Thanks A lot. Still waiting for more suggestions.
 
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