Ka24de VERY Low compression. HELP!!!

[fatsalmon15]

So before I begin to tear the motor out of my car (91 hatch) for a ka-t build I decided it would be a good idea to compression test the car before I start. I bought a compression tester and proceeded on my way. I let the car idle for 10 minutes or so to bring the temperature up a bit, pulled the spark wires and did my compression test. I got 98-103,109,101. I made sure that I held the throttle wide open when I did the test as well. I have never seen numbers this low and it doesn't make any sense to me. The engine runs great, doesn't smoke, and seems to have plenty of power. It does idle a little funky when its cold but besides that I haven't noticed anything wrong with it. The car is a dedicated drift car so the engine does get beat on but I have never see compression this low and the engine even run. The car did have some mods when I purchased it from the previous owner. The engine may have been turboed previously but I'm not too sure. Would low compression pistons or an aftermarket cam cause this? Did I do the test wrong!? I'm stumped. any help would be greatly appreciated.

[anthony_240]

So before I begin to tear the motor out of my car (91 hatch) for a ka-t build I decided it would be a good idea to compression test the car before I start. I bought a compression tester and proceeded on my way. I let the car idle for 10 minutes or so to bring the temperature up a bit, pulled the spark wires and did my compression test. I got 98-103,109,101. I made sure that I held the throttle wide open when I did the test as well. I have never seen numbers this low and it doesn't make any sense to me. The engine runs great, doesn't smoke, and seems to have plenty of power. It does idle a little funky when its cold but besides that I haven't noticed anything wrong with it. The car is a dedicated drift car so the engine does get beat on but I have never see compression this low and the engine even run. The car did have some mods when I purchased it from the previous owner. The engine may have been turboed previously but I'm not too sure. Would low compression pistons or an aftermarket cam cause this? Did I do the test wrong!? I'm stumped. any help would be greatly appreciated.



Hey bud. I’m sorry this doesn’t answer your question, but for your tester did you use a 12mm adapter for the plug hole, or a 14mm?


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[fatsalmon15]

The fittings where not labeled. I just used the one that seemed to match the spark plug and that threaded into the hole and tightened up! I guess I could double check but I really hope not (or hope so) cause I would feel really dumb lol

[anthony_240]

The fittings where not labeled. I just used the one that seemed to match the spark plug and that threaded into the hole and tightened up! I guess I could double check but I really hope not (or hope so) cause I would feel really dumb lol



No I’m sure you used the right one dude, I’m just asking cuz I’m trying to buy a leakdown tester, but I’m trying to find the right fitting for the ka , good luck tho man I’m sure you’ll get your answer shortly


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[fatsalmon15]

No I’m sure you used the right one dude, I’m just asking cuz I’m trying to buy a leakdown tester, but I’m trying to find the right fitting for the ka , good luck tho man I’m sure you’ll get your answer shortly


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Whatever leakdown tester you buy it will probably have the right fitting! I got my compression tester at harbor freight and it had the right fitting so id assume most any leakdown tester will have the right one.

[anthony_240]

Whatever leakdown tester you buy it will probably have the right fitting! I got my compression tester at harbor freight and it had the right fitting so id assume most any leakdown tester will have the right one.



It’s cuz the two I’m looking at either come with a 10mm, 12 & 16 OR 10, 14, 16 ...


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[kyral]

Check to make sure the O rings are on the fittings to make a tight seal.
- also just a quick warning
DO NOT USE ANY ADAPTERS THAT ARE NOT LONGER THAN THE SPARK PLUG TUBES.
i did this and got an adapter fitting stuck in my head for a couple days

i would give another tester a try cause it sounds like you did it right holding it at WOT while you crank it. I know small engines run at 100 psi but your down almost 50% comp so i cant imagine the engine would pull very hard

[fatsalmon15]

Check to make sure the O rings are on the fittings to make a tight seal.
- also just a quick warning
DO NOT USE ANY ADAPTERS THAT ARE NOT LONGER THAN THE SPARK PLUG TUBES.
i did this and got an adapter fitting stuck in my head for a couple days

i would give another tester a try cause it sounds like you did it right holding it at WOT while you crank it. I know small engines run at 100 psi but your down almost 50% comp so i cant imagine the engine would pull very hardOk i will try to run another test tonight and i will post what i find out. The only other thing i could think of is if my timing is advanded a tooth that maybe it is opening my exhaust valve too early? Because i would think that would affect the compression test but driveabilty would still be fine.

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[fatsalmon15]

I did another test this evening. Got the exact same results as last time. Put a cap full of oil in each cylinder and it hardly affected the number at all. 2-3 psi tops. I started to tear the motor out of the car also. So i guess i will see what i can find once i get the motor out unless anybody has any suggestions

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[gaz_moose]

does it start ok? eg,, don't need loads of cranking to get going? ive seen Sr's with compression that low due to knackered rings and valve seats that still ran ok but took ages to get to start.

does it look like it been rebuilt? could have low compression bits inside it.

or your timing could be out causing your valves timing to overlap etc..

[kyral]

I did another test this evening. Got the exact same results as last time. Put a cap full of oil in each cylinder and it hardly affected the number at all. 2-3 psi tops. I started to tear the motor out of the car also. So i guess i will see what i can find once i get the motor out unless anybody has any suggestions

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did you use a different tester? i said a different unit not a retest. eliminate variables. and i am only suggesting that because youre saying it runs smooth and has power. which at 100 psi it would be very lacking in power