Compression Test Results

[rn240sx]

Warmed up the motor, Unplugged fuel and distributor, Went and did comp test on all 4 but then realizing that i was NOT at wot while testing

Went WOT while testing and came out with 210 on all 4 cylinders....

Now i remember when i did it the 1st time and i forgot that i was NOT on wot... i got 190 on the # 1 cylinder.... but i didnt do the rest..

Is this good or bad..???

[:: orion ::]

Standard is ~179...new rebuild is ~190 or so.

...but don't get too excited yet...readings higher than normal are usually a gauge that's out of whack.

The thing to look for is consistency...the fact that they are all close to the same number is good.

- Brian

[chmercer]

can somone say exactly what one should do to perform a proper compression test? unplug the wires, disconnect the fuel pump, WOT, etc? how many times to crank it?

[Structure240sx]

my way of doing a compression test:

unplug injectorspull plugs and wiresunplug dist. install guagewotcrank average 7 times

[Craving4Boost]

why do you unplug the distr.?

[:: orion ::]

So you don't shock the hell out of yourself...think, you have your plug wires laying in the engine bay, and you lean over to watch the gauge as your buddy turns the key...as the engine start to rotate, the plug wires start arcing across to the nearest ground...which may be your hand!

...

And to add to "Structure240sx"s list...

Warm up motorUnplug injectors (or just pull fuel pump fuse)Pull plugs and wiresUnplug distributorInstall guageWOTCrank average 7 times

...and iof you have a battery charger, hook it up. The more consistent the cranking amps/voltage, the more accurate the readings will be.

- Brian

[hannibal]

Can I ask what you unplug from the distributor?Do you just unplug the four spark plug wires??

[:: orion ::]

The harness leading into it...so the ECU can;t tell the dist to fire.

If you unplug the wires, it can still arc ontot he head and shock you.

On an S13, with an external coil...you can just unplug the coil wire, and the coil.

On S14...unplug the 2 plugs on the dizzy.

- Brian

[candela]

also just to note, higher numbers dont necessarily mean a bad gauge at all.

My 95' KA had 210 across the board with over 90k on it. After pulling the head, I found that it was due to carbon buildup (making the CC effectively smaller).

To reiterate, the MAIN reason we disable the distributor is that its not good to have it fire without any load and so fast. Similar to how you dont want to spin a starter very long if its not connected to the flywheel.