Ford could not do a relative compression test because for some reason there cpu would not let them. So I want to do a compression test just to make sure that is not one of my issues.
What tools do I need to do this? Does anyone know if Auto zone has them on their loaner program.

 

It will probably take you a long time to run a compression test.

You need a good compression tester. I have a Snap On unit that has different quick disconnect hoses depending on the spark plug thread. You'll probably need something that separates like that. The proper way to do it is to take out each spark plug first. Then start at Cyl 1. Thread the tester in, crank the engine so it completes about 5 revolutions and then check the compression. Make sure you crank the same amount of revolutions for each cyl or the results may be affected. Then go on down the line until you are done with number 8.

I am not sure what the normal compression is for these trucks. But at least you will see how close each cyl is to each other. Hope that helps.

Edit: The set I have looks like this

and the adapter is like this


I think it was like $250 or something, but that was about 10 years ago.

 

Thanks,

So I remove all the plugs then start, right?

 

HI!... When I do a compression test on my truck I 1ST pull the fuel pump fuse. This way the truck won't start and you won't flood the cylinders with fuel. I pull all 8 plugs. I have a long enough hose on my compression tester that I can position it so I can see it while I crank over the engine. I just keep cranking till it won't go any higher on the gauge. Usually this takes about 10 seconds or so. I then usually let the compression gauge sit for a few minutes and watch the needle to see if the pressure drops off slowly, quickly, or not at all. The last time I did the test I had 182 PSI on all cylinders but the two center ones on the passenger side. They were only 135PSI. I'm glad I'm currently building a new BUILT 5.4, because this one I got now is hurt.

 

Are you guys using the compression tester that screws into the spark plug hole or the ones that you hold in place while someone else cranks the engine?


I remember doing it on my old Sentra one day, 4 cylinders and screwing in each one, even that was a pain. Don't want to think about doing that on the L.

 

4 ........LOL... when I raced go-karts , I only had 1 cylinder to check and it was pretty easy to get too. LOL

The G-Kart is gone (too fat hehe) but I still have the compression checker.


VINNIE

 

Right. Pulling the fuel pump fuse is a good idea. It's impossible for the truck to start without any spark plugs installed, but at least you won't be smelling fuel. Or you could trip the shutoff switch behind the passenger kick panel.

 

Remove all plugs

install compression test device

HOLD THROTTLE WIDE OPEN!!!!!!!

count revolutions (6 to 10 should be good)

record readings.


************************************************
Don't know about these coil packs laying around while cranking?

Carefull with the fuel!!!!

Why in the world would you wait after pump up? Most good compresion testors have a check valve to hold reading. Be sure and reset to zero between cylinders.

Most test hoses have an 0-ring on the end so you just hand tighten.

Be sure and post your readings. This will be interesting.

Have you gentelman that are giving advice ever done a compression test before?

 

WTF would you hold the throttle wide open??? What do you think that can possibly do to the test?

And I would assume that the coil packs would have been removed when the plugs were removed. The connectors that trigger the coil pack are not connected to anything with the coil pack removed from the engine area, (Coil pack unplugged and sitting on floor) and therefore not a fire hazard.

Who are you referring to? Pretty much everyone that responded to this thread said the same thing you did.

 

As I was reading through this thread, I was waiting to see if anyone brought this up. I'm with EZGZ, holding the throttle open is proper procedure.

 

I stand corrected, my face is red.

I don't know what I was thinking when I read EZGZ's instruction.

 

Excuse me fellas I didn't mean to come off as a smart a$$. Well, maybe I did but I shouldn't have.

Just try it sometime on something that is a little easier to get the plugs out of and do some back to back testing on your own.

Try it without having your throttle wide open and your readings will be 30 or more pounds lower than if you have it open. If you still have the instruction sheet that came with your testor it will probably say something about that.

Sometimes I just get a little frustrated when I see miss information.

I apologize if I offendid anyone. It's been a long week

 

i think putting it at wot also make it so there is no spark sent to the coils.

 

actually unless I'm mistaken, cranking the engine while holding WOT makes the injectors stop firing.

this would help in a "flooded" situation. more air, but no more fuel.

later,
chris

 

You block the throttle wide open so that the maximum amount of air can enter the cylinder during the test. More air = better representation of what the compression is on that cylinder.
Plus the throttle must be opened exactly the same during the entire test, or the readings will be off...