A Home Compression Test

**ozcity** · May 16th, 2003 04:32 PM

i just found this in the internet..hth..hehehehe

Home Compression Test

Think you messed something up? Think you may have lost compression in one of your cylinders? Well, there is one easy way to tell without having to drive to your mechanic to get a compression test. Do as follows:

1- Turn on ignition and start motor.

2- Let the car idle until warm, and have a steady idle.

3- Starting with cylinder 4 on the left side of the motor, pull out each spark plug wire one by one, and listen for idle drop. Replace spark plug wire before testing next.

What should happen is the following:

1- If your motor is alright, when you pull out the spark plug wire in each cylinder, the idle should drop significantly.

2- If the motor is damaged, and one or two cylinders in particular are the culprit, then when you pull out that spark plug wire from that cylinder, the idle will NOT change, but it will remain constant, and that means that you are NOT getting compression in that cyldiner, and that is the root of the problem.

If you try this, and the idle drops each time, then your bottom end is not the root of your problem. If it does not drop in any particular cylinder, then that cylinder could be cracked, scratched hard, or that piston ring could be burnt beyond belief.

**papichulo168** · May 16th, 2003 06:29 PM

Safe ba gawin ito kahit naka ECU?

**GoThicbLuE** · May 16th, 2003 10:12 PM

Ito ginaagawa to test what cylinder ang may problema pag pumapalya. if these things happen most of the time spark plug ang problema at hindi always compression.- my 2 cents

**SunTzu** · May 16th, 2003 10:14 PM

ozcity, thanks for the info! :D

**wildthing** · May 19th, 2003 09:34 AM

it makes sense....so even if you change to new plugs and the idle still drop, then there is something wrong with that cyclinder (either loose compression nga or the plug wires have problem)

**Doc Diesel** · May 19th, 2003 08:10 PM

IMHO,
compression testing is best done when the engine is cold. Why?

1. When the engine is warm already, the compression tends to go up thereby giving you a much higher ratio reading.

2. When the engine is cold, you get readings that are 95% accurate. This is what we do with diesel and petrol compression testing.

This is based on our experience..

Doc Diesel