compression check

[snipershrk1]

I'm slowly creeping up on the timing belt change mark and thought that I'd check the condition of the motor prior to the required maintenance. Why? No real reason to but I figure if things needed to be changed now is the time to do it. I've been boosting on the stock motor for the last 80k with rather minor issues along the quest for HP path. (knock on wood)

So my question is this. Do I only have to disconnect the front and rear bank injector harnesses to pull this off. I think that's the case but could be wrong and thought I'd get a little feedback prior to the compression check.

Any input welcomed much thanks

[NC[Spyder]GT]

I'm dying to see a how to for this... Been wanting to check mine for awhile.

[snipershrk1]

lol I just looked. Maybe I'll take pics in the process. I'm probably only going to check the front bank right now. #4 is really only my main concern at this point and if anything looks off I guess I'll start ordering parts

[FlashBlueRS]

With the car idleing, I pull the fuel pump fuse before I do a compression test or anything with the fuel system. Leave the fuse out while you do the test and you won't have to worry about fuel.

[snipershrk1]

Originally Posted by FlashBlueRS

With the car idleing, I pull the fuel pump fuse before I do a compression test or anything with the fuel system. Leave the fuse out while you do the test and you won't have to worry about fuel.

ohh. I didn't realize you were doing this with the car running. I was under the impression the starter turned everything without ever actually turning over the vehicle. Maybe I shouldn't be doing this

or are you killing the engine by pulling the fuse?

[Jetblackness]

He has the car idling so that the engine will evacuate all the fuel. You will basicly be left with a bone dry engine.

[snipershrk1]

ah ok. that 's what I thought after I posted the first part.

[FlashBlueRS]

Sorry, I wasn't too clear. Pulling the fuse kills the motor.

[MattS00]

I usually just unplug the crank position sensor wire. This stops the injectors/spark plugs from firing. Also, make sure that the throttle body is all the way open when you are cranking. Otherwise you will get incorrect readings.

[snipershrk1]

now we have that much out of the way.

what's next I "assume"
Pull a plug and screw in the tester.
Bump the starter (how much/long?)
Get the reading
Release the pressuer
Remove the tester
Move on to another cyl.

Is that about it? Please fill in the missing blanks.

[MattS00]

Pull all of the plugs first. Then it will take 3 to 5 pulses to reach max compression. You need to look at and remember the first, 2nd 3rd compression, and max compression. Then write down all of the numbers for each cylinder.

[NC[Spyder]GT]

Originally Posted by fasteclipse00

Pull all of the plugs first. Then it will take 3 to 5 pulses to reach max compression. You need to look at and remember the first, 2nd 3rd compression, and max compression. Then write down all of the numbers for each cylinder.

Can anyone explain the "3 to 5 pulses to reach max compression"? Does that mean turn the starter/ignition on 3 to 5 times or what? I just got a compression tester and am hoping to get this test done before this w/e (prepping for SDS). I did some searching and this thread seems to have the most info on how to do the test.... but I am still confused. I have no problems accessing all the plugs, just not sure what to do when I get there other than:

1) disconnect crank position sensor
2) remove all spark plugs
3) fix throttle body valve so it is held wide open
4) install compression fitting into a cylinder
5) ??? (pretty sure its not steal underpants or make profit)

[1LarryLB]

this is pretty close, subsitute as needed,

Engine Compression Testing

[FlashBlueRS]

Fixing the throttle body open is easy. Just hold the gas pedal down while your in the car cranking it. You'll know what that 3 to 5 pulses means when you are doing it. You'll hear it

[NC[Spyder]GT]

Many thanks guys. I'll try and snap some pics while I do this and maybe we can get a How To made up for the Garage section.

[IAmTheSTIG]

even though it's not necessary i usually have a friend of mine go inside the car to crank it while i look at the gauge.

[steadly2004]

Originally Posted by fasteclipse00

I usually just unplug the crank position sensor wire. This stops the injectors/spark plugs from firing. Also, make sure that the throttle body is all the way open when you are cranking. Otherwise you will get incorrect readings.

Thats what the manual said to do for the 4cyl. It works like a charm, cuts spark/injectors.

and cranking the engine.... sounds like: "rawr...rawr...rawr...rawr...rawr"

[NC[Spyder]GT]

keep the tips coming!

Steadly: Is that "rawr" the "pulse" others are talking about? Just trying to get a much info as possible before I start this. I'd hate to kill something due to ignorance.

[steadly2004]

Its the sound of the engine turning over. It happens in short spurts. At least on a 4cyl it does. Not really difficult. It kinda sounds like when a car won't start, infact it is because the car won't start because there isn't any spark/injection occuring. Just the starter turning over the engine.

Your list pretty much sums it up

1. remove plugs
2. unplug crank position sensor
3. install compresson gauge
4. hold pedal to the floor
5. crank over several times (make sure you do each cylinder the same number of turns, this helps get an accurate comparison between cylinders)
6. release pressure and repeat step 3-5 on all cylinders.
7. re-install everthing
8. erase SES light from the crank position sensor being removed.


If you have any questions on if you're not doing it right, or if you want the acceptable values, go the the service manual.Online 3G Service Manual *Now with GT-S info* Its under engine mechanical 3.0 page 11c-7

Disable your fuel pump (fuse works)
Disable primary ignition (harness to dist)
Remove the plug for the cyl you are testing
Replace it with your gauge.

Now you can either tap the ignition and try to reach TDC or you can manually crank it.

so long as you disable fuel and spark you'll be fine. doesnt matter which way you do it.

[NC[Spyder]GT]

Thanks again guys. Another question.... The FSM says to start and idle the engine until it warms up to normal temp. How can they expect you to do that and then have the manifold off in time to plug your guage into a rear cylinder?? LOL! I must be missing something here. If you all don't bother warming the engine up then do you think doing a compression test in 30-50F degree weather would be ok?

I'm holding off on the comp check until I get a new cap/rotor and plugs to install (1 week or so).

[steadly2004]

Its supposed to be operating temperature because metal expands and closes the clearances between the piston/cylinder/rings ect and provide more of a compression when compared to a cold engine.

I guess you just have to let it idle until it is at normal temperatures, then AS QUICK AS POSSIBLE get to the rear cylinders. At least you can do the fronts, then warm it again and the rear three might be different from the front, but within specs from eachother.

I personally have never done it on a V6, but thats the theory behind it.

[NC[Spyder]GT]

Last question before I go do this compression test:

The upper manifold/TB assembly can be left unbolted from the engine while doing the cranking, correct?

I assume this because:
-fuel pump relay removed so no fuel
-crank angle sensor disconnected so no spark
-all plugs removed so definately no fuel/spark mixture!
-TB valve clamped wide open so it doesn't seem like air pressure would be required on the manifold side of things

Please let me know! Car is on jacks now awaiting this test. If all is well then SDS gets bolted on tomorrow

[steadly2004]

Originally Posted by NC[Spyder]GT

Last question before I go do this compression test:

The upper manifold/TB assembly can be left unbolted from the engine while doing the cranking, correct?

I assume this because:
-fuel pump relay removed so no fuel
-crank angle sensor disconnected so no spark
-all plugs removed so definately no fuel/spark mixture!
-TB valve clamped wide open so it doesn't seem like air pressure would be required on the manifold side of things

Please let me know! Car is on jacks now awaiting this test. If all is well then SDS gets bolted on tomorrow

Sounds like you have it figured out bro.

[repforenzo]

Here's a question: what brand of tester works the best for our deep spark plug setup?

[GSXROFDFW]

Pretty much all the ones I have even seen is the kind that have the small hose (10' long or so) that quick connects to the gauges hose.

I have Snap On compression and Cylinder Leak down testers and I can say this.

My compression gauge came with 2 of those hoses.
1) for long threaded spark plugs.
2) for short thread spark plugs.

My Cylinder leak down tester came with only the hose for short style plugs and a little metal adaptor at the end for the long style plug. THAT LITTLE ADAPTOR GETS STUCK DOWN IN THERE and can be a bitch to get out.

When you are done cranking and you get the reading off the gauge always press the pressure release button to relieve the pressure. If you just disconnected the quick disconnect then it always blows the schrader valve out on mine. Everytime I loan it to someone at work they bring it back saying it doesn't work! Fuckin' rookies!

[NC[Spyder]GT]

Doesn't our car take the short thread type spark plugs? I noticed that my tester comes with an adapter for each type. I am hesitant to use the deep adapter because it mentions damage would occur if it was used in a short type spark plug hole.

I am planning to use the short version unless you all say the deep one is needed. 1 more hour and I will be trying my 1st compression check

[repforenzo]

Originally Posted by NC[Spyder]GT

Doesn't our car take the short thread type spark plugs? I noticed that my tester comes with an adapter for each type. I am hesitant to use the deep adapter because it mentions damage would occur if it was used in a short type spark plug hole.

I am planning to use the short version unless you all say the deep one is needed. 1 more hour and I will be trying my 1st compression check

yes, we have the short shaft.

[GSXROFDFW]

Originally Posted by repforenzo

yes, I have the short shaft.

Wow dude that sucks.
At least you are man enough to admit it though.
You want me to forward all those emails I get from Max Gains to you?

[repforenzo]

Originally Posted by GSXROFDFW

Wow dude that sucks.
At least you are man enough to admit it though.
You want me to forward all those emails I get from Max Gains to you?

Wow, did you come up with that by yourself? Go back to OT, newbie. You can talk about all the cocks you want over there.

[NC[Spyder]GT]

After warming up the engine I ripped off the mani/TB/intake and started pulling plugs. On the very last one I discovered my plug socket would not grip the plug. I grab a light and look into the hole to find an old rubber plug "gripper" (found inside spark plug sockets) had been left on that plug! I guess the heat caused it to expand and now it has moved down toward the bottom and is blocking the socket portion of the plug. I'm suprised I wasn't throwing misfire codes What a MOFO!!!! I tried getting it out with some flatheads for about 1/2 hour with no luck. Back needs a break... trying again tomorrow. WTFOMGBBQ~!

BTW, The threads on my "M12LR" Actron gauge/plug-hole adapter match my spark plugs so I think we may have the "long reach" type spark plug threads. Thoughts?

[repforenzo]

Sorry to hear about the issues. If you can get to Auto Zone, they sell a 'hook -n- pick' set. Something similar happen to me and the hook easily got it out.

[icemanrld19]

get a clothes hanger and fish it out

[GSXROFDFW]

So if the old rubber "gripper" is down in there just get a regular 16mm socket and unscrew your plug. If it was the rubber deal and inside a spark socket at one time then it should just slid back in any 16mm socket or if you have the old spark plug socket that it slid out of.

Some deep sockets have a shelf very shallow inside and some are hex all the way through. Usually the cheaper ones are hexed all the way through. Get one that is hexed all the way through and pull that plug out.

Is the rubber melted and deformed? If not then it should be cake.

Let us know or take a picture.

[NC[Spyder]GT]

Originally Posted by GSXROFDFW

If it was the rubber deal and inside a spark socket at one time then it should just slid back in any 16mm socket or if you have the old spark plug socket that it slid out of.

Is the rubber melted and deformed? If not then it should be cake.

Let us know or take a picture.

The problem was that the prolonged heat deformed/expander the rubber ring. So now the walls of the socket will not fit around the plug as the rubber "boot" is way too wide. It pretty much fills the spark plug tube diameter. I will try a hacked up clothes hanger today at lunch. If that doesn't work then off to the store for the "hook-n-pick" set! A hook of some sort will definately be required. Thanks for the suggestions guys

[rc_maniac]

Bust up the rubber with a screw driver if you can. Then suck it out with a shop vac.

[GSXROFDFW]

+1 on that!

Even if you have to get an old screw driver and sharpen the tip a little.

[NC[Spyder]GT]

coat hanger FTW! I picked up a pick and hook set but they were too dang short to rach the bottom of the tube. Problem solved. Checking compression this evening. Thanks again guys!

[NC[Spyder]GT]

So that was MUCH easier than I was expecting LOL!
#1 188psi
#2 188psi
#3 191psi
#4 194psi
#5 191psi
#6 194psi

They all seem to be pretty close so I think its time to boost this beyatch! Thx again for all the help! +repped where I could.

[steadly2004]

Glad to hear everything worked out well!

Imagine how easy it is to do that on a 4cyl... lol

[NC[Spyder]GT]

Now I am curious about this "leak down" test and what the differences are

[steadly2004]

I just searched and found an informative writeup
http://honda-tech.com/zerothread?id=1491041
Its from a honda forum, but still gets the gist across

[GSXROFDFW]

We have a tool here at work that you connect to the starter wire and a trigger clip to the #1 cylinder. Then you crank the engine with the fuel pump fuse pulled put and it measures starter amperage (sp) on every fire and can calculate compression. I have checked it with a real compression gauge and it is in the ballpark but not perfect.

Some of the newer engine control modules at work have this feature in them and can calculate this as a test plan with out addition tools. How farcking sweet is that!!!!

[NC[Spyder]GT]

I checked that link and it looks like TDC for each cylinder is required Based off the how to I'm not sure what he had to remove the valve cover Or maybe we have to remove the manifold but not the covers? I guess I'll check the FSM for more info on TDC and compression testing. Hopefully it sheds more light.

Originally Posted by GSXROFDFW

How farcking sweet is that!!!!

That would certainly make things easier. What is the model of that tool?