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eurotecknik
05-06-2008, 09:25 AM
Hey guys, how do you get a compression test done? Did you give it to a mechanic to do it? I called a local tuner and they said they can do it. It would take an hour of labor x $109/hour. So I am looking at $109 to get this test done.
What do you think? Particularly people who have done this.

mike-2ptzero
05-06-2008, 09:28 AM
Just go buy a compression test gauge from your local auto parts store or sears, they cost around $25. Doing the test is very easy, you just pull all 4 spark plugs out and test 1 cylinder at a time by cranking the motor till the gauge stops moving.

You can hang the gauge from the latch on the hood using a bungee cord so you can see it from the driver seat.

eurotecknik
05-06-2008, 09:33 AM
Thanks Mike, I will see what I can do

djwimbo
05-06-2008, 09:33 AM
It's worth the time and effort to do it yourself. Unless for whatever reason you're not comfortable doing this test on your vehicle. If so I'd say find a local automotive training facillity and have them do it. Labor is "free" there.

I bought mine for $25 and it came with instructions. Just make sure while you're cranking to disable the ignition and the fuel injectors. Pull the primary side of the coil harness to disable the coils. In a COP setup just unplug them.

mike-2ptzero
05-06-2008, 09:38 AM
It's worth the time and effort to do it yourself. Unless for whatever reason you're not comfortable doing this test on your vehicle. If so I'd say find a local automotive training facillity and have them do it. Labor is "free" there.

I bought mine for $25 and it came with instructions. Just make sure while you're cranking to disable the ignition and the fuel injectors. Pull the primary side of the coil harness to disable the coils. In a COP setup just unplug them.

Correct, you can also just unplug the cam sensor harness or just unplug all 4 injectors so that there is no fuel being sprayed into the cylinders while cranking the engine.

eurotecknik
05-06-2008, 09:46 AM
So, what specification range per cylinder should I be looking at? What is considered good or bad?

Ewok_Fetus
05-06-2008, 09:59 AM
So, what specification range per cylinder should I be looking at? What is considered good or bad?

As long as they are within 10% of each other, you are fine... And the Bentley states to unplug the cam position sensor, this disable the coils AND the injectors. Also, when cranking, it is best to go WOT...

iin10ded
05-06-2008, 02:25 PM
where is the CPS? and why would you go WOT?


And the Bentley states to unplug the cam position sensor, this disable the coils AND the injectors. Also, when cranking, it is best to go WOT...

ILoveT
05-06-2008, 02:28 PM
So you can compress as much air as possible.

iin10ded
05-06-2008, 02:32 PM
duh.. because engines do not work on fuel alone. =)

djwimbo
05-06-2008, 02:46 PM
So you can compress as much air as possible.

Kinda, It's more to the effect of maintaining the same amount of air supply to each cylinder as you move from #1 to #4. If you do the test with 1 & 2 w/ the throttle plate closed and 3 & 4 @ WOT, the readings will be different.
Do all 4 under the same conditions. If you have a battery charger available, hook it up as well. This is to try and maintain battery voltage so the cranking speed will not slow down as you progress.

pac1085
05-06-2008, 02:55 PM
and try not to crank the engine for more than 5 seconds at a time or you could damage the starter

mike-2ptzero
05-06-2008, 03:32 PM
You don't need to press the throttle(does nothing on the DBW anyway), if you take all 4 spark plugs out while doing the test the amount of air being supplied to all 4 cylinders will be equal.

Ewok_Fetus
05-06-2008, 04:41 PM
and try not to crank the engine for more than 5 seconds at a time or you could damage the starter

I swore it was 10 seconds. And you must wait 30 seconds between cranks... At least that is what my owners manual is saying...

Mike, have you looked at the throttle body while doing a compression test on a DBW? It does open and stays open while cranking...

pac1085
05-06-2008, 04:44 PM
I swore it was 10 seconds. And you must wait 30 seconds between cranks... At least that is what my owners manual is saying...

Mike, have you looked at the throttle body while doing a compression test on a DBW? It does open and stays open while cranking...

Well, it's something like that. Either way, don't crank it over for like 30 seconds.. lol

djwimbo
05-06-2008, 08:50 PM
By the book it's 15 seconds, but it also calls for 5 compression cycles. Which is less than 3 sec anyways.
After 10 Sec the windings in the starter get too hot and you can damage the armature and such.

mike-2ptzero
05-06-2008, 09:02 PM
I swore it was 10 seconds. And you must wait 30 seconds between cranks... At least that is what my owners manual is saying...

Mike, have you looked at the throttle body while doing a compression test on a DBW? It does open and stays open while cranking...

The ecu controls the dbw throttle body during cranking so it isn't like your food on the pedal is doing anything at that point.


BTW yes I did CR's all the time back when I was dbw.

Seerlah
06-18-2008, 06:20 AM
Bump: I am a noob and am about to attempt this properly. I looked in the Bently manual and it said that the cam sensor is located behind the top of timing belt cover. I looked and is that the sensor that is on the top right area which is sticking out from behind the cover? If you need pics, just request. Thanks!

*I bumped this thread because it says I need to remove cam position sensor and am requesting if it is correct plug

Mawhitey
06-18-2008, 06:24 AM
Yes thats the one, pull that, or pull the ICM plugs just need to stop it starting up or anything

mike-2ptzero
06-18-2008, 07:02 AM
Yes that would be it. You can pull that, or unplug the injectors or even just pull the fuel pump fuse. You just want to make sure the injectors are not spraying while cranking the car.

Seerlah
06-18-2008, 08:49 AM
Just did it. And I am amazed a shop would charge $110 for a simple job like that. Autozone even let me rent thier compression tester for free (well, $35 deposit. going to go and get money back now)

Cylinder 1-165
Cylinder 2-165
Cylinder 3-170
Cylinder 4-165/170

Nebone
06-18-2008, 09:20 AM
Do you have to pull the cam position sensor? Coils will be disconnected anyways so I'd just pull the injector connectors.

Seerlah
06-18-2008, 09:27 AM
I just did the easiest route and took Mike's suggestion to pull the fuel pump fuse. If I did not go that route, I would have just unplugged the cam position sensor and did it.

317ssayzarc
06-18-2008, 09:32 AM
Do you have to pull the cam position sensor? Coils will be disconnected anyways so I'd just pull the injector connectors.

word, thats the way i did it...

and for the record, throttle open vs shut is the same even on DBC, i tested it both ways... and the proper way to do a comp test is to crank it until it stabilizes, which is usually 4-5 cranks for me... the 1st puff is also key, but youll need someone else to record it, they should all be within 15% on the 1st puff [up]

dougyfresh
06-18-2008, 10:15 AM
Here is a DIY:

http://www.audigeeks.com/forums/index.php?topic=2769.0