Need advice on compression testing
22-Dec-2002, 10:45 PM
#1
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Join Date: May 2002
Location: Toronto
Posts: 326
Need advice on compression testing
I've taken the plugs outta my B18B and screwed in my compression testing gauge.
This engine has been out of a car for a while, lying on my garage floor (on a carpeted dolly) and not started in 1 month. I turned the engine over with a wrench on the crankpulley, and it moves, but I get a low compression reading like 10 psi.
Is this because I'm not using the starter and turning the motor over quickly? Does the speed of the turnover greatly effect the pressure that develops in the cyclinder? I hope so!
Regardless, if anyone has any advice on how I can turn this engine over, without a battery, since its outta the car, I'd appreciate it.
So far, I've briefly tried directly connecting a 12v 35a batter charger to the starter solenoid +ve terminal, the -ve to the engine ground, and of course touching the starter soleniod sender wire to the positive trigger. All I get is a loud click... not enough juice I guess to turn it over, even with the spark plugs out!? I'm only tapping it on though, since I don't wanna burn out my starter. My next guess is to pull my buddies car battery and connect that instead of the cheesy car battery charger. A battery probably has higher amperage, right?
When I bypassed the solenoid and hooked 12 v up to the starter motor directly, I can hear a whizzing (probably the motor tunring but not being engaged), which provides evidence my starter is working.
So if you could give me some adice on how to compression test, without a leakdown test, and what psi I should expect COLD, I'd appreciate it,
-j, toronto
This engine has been out of a car for a while, lying on my garage floor (on a carpeted dolly) and not started in 1 month. I turned the engine over with a wrench on the crankpulley, and it moves, but I get a low compression reading like 10 psi.
Is this because I'm not using the starter and turning the motor over quickly? Does the speed of the turnover greatly effect the pressure that develops in the cyclinder? I hope so!
Regardless, if anyone has any advice on how I can turn this engine over, without a battery, since its outta the car, I'd appreciate it.
So far, I've briefly tried directly connecting a 12v 35a batter charger to the starter solenoid +ve terminal, the -ve to the engine ground, and of course touching the starter soleniod sender wire to the positive trigger. All I get is a loud click... not enough juice I guess to turn it over, even with the spark plugs out!? I'm only tapping it on though, since I don't wanna burn out my starter. My next guess is to pull my buddies car battery and connect that instead of the cheesy car battery charger. A battery probably has higher amperage, right?
When I bypassed the solenoid and hooked 12 v up to the starter motor directly, I can hear a whizzing (probably the motor tunring but not being engaged), which provides evidence my starter is working.
So if you could give me some adice on how to compression test, without a leakdown test, and what psi I should expect COLD, I'd appreciate it,
-j, toronto
23-Dec-2002, 01:19 AM
#3
No better ideas...never tested one out of the car before. However, it is safe to say that the speed of turnover will affect compression, since the valves are now opening and closing slowly, so all the compresion that should build will escape though the open valves. That's the only thing I can think of...
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