Editing Leakdown tester homemade engine cylinder troubleshooting tool

{{youcanedit}}
If you have a cylinder in the engine that is not as strong as the rest, and you have determined that it is getting spark, here's how to make a simple tool that may aid in locating the problem.  This gives you some of the functionality of a leakdown tester.

#Take an old spark plug that fits the engine, and remove all of the porcelain and the center electrode, leaving just the outer shell.
#Braze an air fitting onto the shell.
#Turn the engine over until the piston in the suspect cylinder is at TDC on the compression stroke.
#Insert the modified plug and apply 60-80 psi air to the cylinder. Be certain not to use so much air that it turns the engine.
#With air pressure in the cylinder, look and listen:

*If you hear air bubbles, it may be a leaking head gasket. You can also remove the radiator cap and look for bubbles.
*If you hear air in the exhaust (at the exhaust outlet), it may be a leaking exhaust valve.
*If you hear air coming up through the carb (open the throttle) it may be a leaking intake valve.
*If you hear a hissing noise from the oil fill tube, or the dipstick tube, it may be a piston or piston ring problem.


This simple homemade device can save a lot of time in diagnosing a problem.

[[Category:Engine]]
[[Category:Tools]]

There is also a tool called a "differential cylinder pressure tester" (AKA leakdown tester), that operates on the same principles, but it regulates the pressure entering the cylinder, and monitors the pressure that remains, the balance being the amount of "leakdown". A GOOD healthy motor will leak less than 3~5%, more than about 10~15% is in need of repair, but as was stated above, you can listen to ''where'' it's leaking, so you know whether to go after head gaskets, valves or valve adjustment, or rings. This is a Car Craft article about using a leak down tester: http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/index.html

http://image.carcraft.com/f/8883467/116_0406_leak02_z.jpg