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Quick noob compression test question..

3K views 11 replies 7 participants last post by  dannanw 
#1 ·
Hi there.
I want to perform a compression test on my truck today... I researched a lot how to do it, but I have a few noobs questions...

Should I disconnect and take out all the glow plugs to perform the test?, then install the tester on each glow plug port to test?

Or should I just disconnect all the glow plugs, but take them out one by one in order to put the tester on each port?

With disconnect i mean electric...
Also, how can I do the cranking test and dont start the truck?.. and then how can i start to check the compression with the engine running???

I know is very basic, but I want to be 100% sure

Thanks a lot!
 
#2 ·
Hi there.
I want to perform a compression test on my truck today... I researched a lot how to do it, but I have a few noobs questions...

Should I disconnect and take out all the glow plugs to perform the test?, then install the tester on each glow plug port to test?

Or should I just disconnect all the glow plugs, but take them out one by one in order to put the tester on each port?

Disconnect one at a time and reinstall when done with that cylinder because you want the engine to be just like it is when running rather than no compression in the other cylinders.

With disconnect i mean electric...
Also, how can I do the cranking test and dont start the truck?.. and then how can i start to check the compression with the engine running???

You have to disconnect the GPs electrically to even remove them so yes. You dont need to test while running just cranking. In order to do that you can do it a few ways.

If its just you by yourself just use a screw driver to bump the starter relay on the passenger fender wall and it will crank and not start as long as you dont have the key on. Just be careful not to shock yourself

If you have a helper, just disconnect the pcm connector and have them crank it with the key.

I know is very basic, but I want to be 100% sure

Thanks a lot!
Answers in red
 
#4 ·
Very true sir good call. Same results as unpluging the connector
 
#5 ·
Thanks a lot guys.
So remove one by one and crank with the screwdriver or without fuse 22..
perfect!
 
#8 ·
I couldnt perform the test :(
I followed the instruction on this thread to make the adapter for our trucks, but it didnt work. Homemade Compression Adapter - PowerStrokeNation : Ford Powerstroke Diesel Forum

The adapter is bigger than the glow plug port... I used a grinding machine, but in the process I damaged the thread and now only goes 2 turns, so it doesn't seal proper...

im on a friend house with a shop full of tools, so I think Im going to make my own adapter..
Can I use a glow plug to make something to get in there?

I have the harbor freight diesel compression tester...
WHat are you guys using to test?

:confused:
 
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