Performing a compression test....

[Silverado]

Canadian Tire has a compression tester kit on sale this week. I think I'll pick one up and do a test on my truck for kicks, and replace the spark plugs.

Once the fuel system has been unpressurized and the ignition disconnected, I presume it's normal to use the starter to turn over the motor for the test?

Is there a way to do this from the engine bay, or do I need a helper to turn the key?

 

[fordwheelinman]

You can do it by yourself. Like you said, pull the fuel pump fuse and crank the motor a couple times, then pull the plug out of the coil pack to disable the ignition. Pull the spark plugs (all if you want or just one at a time either way) and screw in the hose to the spark plug hole. Attach the gauge to the extension hose and route the gauge between the hood and the cowl and rest it on the cowl or windshield wiper (or even the windshield with a towel under it) and then crank the engine over. Watch the needle to "bounce" 4 times and that will be your compression reading. Repeat as needed for the remaining cylinders.

 

[Silverado]

Thanks for the tip. It sounds like I might need a longer hose than the one the kit comes with for that to work though... it looked like it had about 16" of hose.

I'm sure I can find someone to give me a hand in any case.

 

[shadetree]

Check the compression with the engine warm.

Remove all plugs.

Use a remote starter button on the fender relay. You can make your own, or buy one from auto parts, and you can do the test yourself.

Spin the engine at least four revolutions on each cylinder.

Readings should be within 15% of each other on all cylinders.

shady

 

[Silverado]

Use a remote starter button on the fender relay. You can make your own, or buy one from auto parts, and you can do the test yourself.

Can you give me some more details on this?

 

[85_Ranger4x4]

Can you give me some more details on this?

Ours is like a pistol grip with a button on top, with wires and aligator clips that go on each pole of the starter relay. You push the button and and engages the starter without you turning the key. I saw them at Sears the other day too, I don't remember what they wanted for them however.

 

[shadetree]

You should be able to get a cheapie from auto parts for about 5 bucks. They are very handy to have.

Any single contact button or trigger will work. Attach two long wires w/alligator clips. One of the wires will go to the small wire connection on the fender relay which is the start wire from the ignition switch. The other wire will go to the battery positive. With the button depressed the engine will spin over. If a manual trans, make sure it is out of gear. shady