just checked my compression (2 Viewers)

[concretejungle]

my truck has just at 160,000 miles on it. I blew the PHH around 148,000 miles. I feel lucky with these results:

#1 - 181
#2 - 180
#3 - 179
#4 - 180
#5 - 180
#6 - 181

 

[Heffenoche]

I don't recall what spec is but I think your close, the consistancy across cyliders looks great.

 

[photogod]

When you did the test, how long did you crank the engine to get your result? Just curious as I did a test on my old 60 and cranked it for aprox 3 seconds each cyl. It had 84000 on the odo and the comp was at or near original spec.

 

[fzj80kidpen]

I thought factory spec was 170-175?
I saw a post awhile back where someone was talking up 190.
This seems odd.
I had mine tested prior to purchase and they were all around 160.

 

[sixsracing]

General rule of thumb for a compression test:

Remove all plugs and disconnect power to coil

Hold throttle wide open

Turn key and count 10 cycles. RUR RUR RUR... you get the idea.

Repeat for each cylinder

 

[roncruiser]

http://www.geocities.com/SiliconValley/2072/carcomp.htm

Questions for the more knowledgeable:

In step 2, is it necessary to ground the wire coming from the coil?
In step 3, is it necessary to pull the fuse for the EFI? Is there such a fuse? i don't recall.

 

[e9999]

any useful advice on how to reach these deeply buried holes?

 

[concretejungle]

Here's how i did it, and not the compression tester is brand-new, so it should be very accurate:

1. Remove all plugs (might as well remove the intake since it's right over the top of #3 and #4.

2. Remove the EFI fuse.

3. Put compression tester in cyclinder, and place the dial on top of the motor so i could see it under the hood from inside the truck.

4. Crank on motor, with gas pedal pressed 100% watching dial until it reaches the highest pressure and will not climb any higher (this was an average of about 4 to 6 seconds of cranking).

5. that's it, continue this for each cylinder.


Ron, i don't think it's necessary to ground the coil, just be sure the ends of the plug wires are not touching any metal or anything (i just let mine hang to the side).

This is very easy, i was surprised after i did it just how simple it was.

 

[sixsracing]

You can pull the EFI relay in the box just as easy as a fuse.

Grounding the coil wire can have adverse results, an open is better than a ground. Unplugging the coil from the vehicle harness essentially leaves an open.

On mulit-point fuel injected cars fuel is sprayed at a fairly high velocity into the intake manifold just upstream of the valve. When you remove all the plugs the fuel now has an exit and will create vapor in and around the engine compartment. Should any of the spark plug wires decide to throw a spark in the right place at the right time you may experience a slight flash of fire. It's surprising let me tell you. I've seen it happen on a Subaru XT. (No I didn't do it)

 

[concretejungle]

any useful advice on how to reach these deeply buried holes?

I have a socket extension that is approximately 24 inches long. It's perfect for the front 4 cycl. but it's too long for the back too, especially the very back one. I had to use a shorter extension, a swivle socket and an extensioin on the swivel to get #6 .

 

[concretejungle]

You can pull the EFI relay in the box just as easy as a fuse.

Yea, that's what i meant to say. It's right there and easy to pull.

 

[robbie]

It is a good thing to also disconnect the coil, for no spark and no damage to the inginitor circuit. If you pull the EFI fuze then no fuel gets sprayed into the cylinders to mess with. I use the 10 cycles also. By using 10 cycles you remain consistant. Even new compression testers can be off by a few % points. 175 new is the book value. a few over could mean carbon build up, or the testor is off a little. But having them consistant is a great thing. later robbie

 

[Rookie2]

Is there a certain tester that should be used for doing a compression test on IFZ setup (i.e. 5" or so deep plug holes)? I was going to borrow one from a dude at work, but it looked like it would be hard to get the end of his tester down in the hole and screwed into the plug threads.

Thanks,
Rookie2

 

[e9999]

that's what I meant too. My tester (15 yrs old Sears) has a curvy flex hose ending in a threaded connector. But it would be interesting to try and thread this thing correctly 6" down with the flex, and I'm not keen on cross-threading. Do you guys have testers with rigid extensions?

 

[IdahoDoug]

My testes have a VERY rigid extension.

DougM

 

[HZJ60 Guy]

Are those good numbers for a gasser?

Interesting that my diesels numbers would be more than three times those values.

Good info to know.


TB

 

[concretejungle]

that's what I meant too. My tester (15 yrs old Sears) has a curvy flex hose ending in a threaded connector. But it would be interesting to try and thread this thing correctly 6" down with the flex, and I'm not keen on cross-threading. Do you guys have testers with rigid extensions?

That's how mine was,....well the one that i borowed. Friend who owns it rigged this little threaded peice at the bottom which made it a breeze to screw in.

 

[sixsracing]

Diesels generally have twice to three times the compression of a gas motor.

Your usual grocery getter will have somewhere around 9:1 or less.

Your average passenger car diesel will be 23:1.

Don't know if anybody cares but it came up.

 

[GXO]

Duramax is 18:1 stock.

 

[cruiserman]

I used the Sears tool, which worked fine until the adapter got stuck in the #1 cyl hole. Luckily I was able to get it out.

Those are excellent numbers.