Looking for instructions for testing compression...

Post by **EstVolvo** » 28 Mar 2011, 17:41

"The engine must be fully warmed-up to normal operating temperature ... and the spark plugs must be removed."
Isn't it bad for the threads?

Post by **polskamafia mjl** » 28 Mar 2011, 17:58

I think it's ok to remove plugs from a warm engine. The danger comes from trying to put them back in to a warm engine.

Post by **LamboSE5** » 24 Apr 2011, 11:54

How do I disconnect the "positive lead from the coil"? I wanna make sure I do this test right. Does this mean the long "bougiecord" cord that leads from the distributor (and it's 5 cords) to somewhere?

Here's what I have:

Warm engine to operating temperature, and perform the following test after.

“Dry” test
1) Remove all 5 spark plugs.

2) Remove the fuel pump fuse, Unplug the Injectors (Just pop off that metal cover and disconnect each one) AND the Positive lead from the Coil.

3) Screw in the compression tester

4) With throttle fully open, turn the engine over 5-6 times (or about 7-8 seconds). After about a half dozen spins you should have a good compression reading. Make sure it’s within the specifications or within at least 10% or them.

Is there some other connector (electrical) I have to disconnect?

Post by **kcodyjr** » 24 Apr 2011, 11:58

Not the question you asked, but related: there is a wire lead near the driver's side fender that, if connected to positive, will crank the engine without having to go inside the car. Search around for exact details on where to find it; it should be somewhere in the loom between airbox and firewall.

Post by **kcodyjr** » 24 Apr 2011, 12:00

Oh, positive lead on the coil: no, not the Bougi, the connector of ordinary wires. Actually, if you're feeling paranoid, disconnect the coil entirely. Feeling a spark plug discharge through your skin is unpleasantly like being drunk. You ask what's so unpleasant about it? Ask the glass of water. (credit for the quip: Douglas Adams)

Geevs · Post by **Geevs** » 24 Apr 2011, 23:14

[quote="Alecw81"]Just picked up a compression tester today, is it possible to do this solo?[/quote]
Yes, I just did my compression test today and used a bungee cord hooked to the latch on the hood and the other end hooked around the tester so it is "standing" upright. Unfortunately, the tester wasn't oriented to face the driver seat, so I just cranked it 10 times which should be enough to get the gauge needle as far as it can go (mine has a "hold peak" feature with a release/reset valve).

I was surprised to get a consistent 180psi across all cylinders give or take 2-3 psi. Car is a 96 850R 5-speed.

My tester is quite new but I want to test it for accuracy. Any idea how to do this? Just hook it up to an air compressor?

Post by **LamboSE5** » 25 Apr 2011, 10:56

Geevs - That sounds awesome for a 96 850R, lucky man.

I still don't know what is meant by "positive lead on the coil". Is it the longer cord that leads to the distributor, and looks like the 5 cords that go from the distributor to the spark plugs/cylinders?

Anyone have a picture? I don't wanna get shocked today

Geevs · Post by **Geevs** » 25 Apr 2011, 11:09

Yes, the "positive" coil is the cord that runs from the ignition coil to the distributor. Just pull off the cord from the ignition coil as it is easier to access. Also remove fuse #2 from the fuse box located near the driver side windshield- this will disable the fuel pump. The purpose is to stop fuel delivery why you crank the starter several time during the compression test. Removing the ignition coil is just an additional safeguard.

Yes, I'm surprised at the consistent 180psi +/-2-3 psi across all cylinders for a 15 year old engine with 225K kms. That's why I would like to have my compression tester tested. I bought this one

http://www.princessauto.com/workshop/ha ... ion-tester

which is similiar to Harbour Freight house branded tools.

Post by **LamboSE5** » 25 Apr 2011, 11:18

Thanks for clearing that up, and quickly

I'm actually sitting here waiting to do this test. Might try it without a helper.

Wow, funny - I almost bought the exact same one from princess auto - are you in Canada too, or are the international? Hmm

I bought the "Innova" one from Canadian tire, it was 5$ more but had a couple adapters and a colored gauge (fancy, I know).
I hope it isn't your tester, that sounds like good numbers eh?

Thanks again Geevs.

Geevs · Post by **Geevs** » 25 Apr 2011, 12:15

Yes, I'm in Canada also.

If you can get a helper to crank the car while you monitor the gauge - I think that is ideal.

Can someone confirm if the manner which the needle rises to peak psi is important or not? As I cannot see the needle climb while I'm cranking, I just crank it 10 times assuming the needle no longer climbs at this point.

Looking for instructions for testing compression...

Re: Looking for instructions for testing compression...