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[Allenm]

I need to test the compression on my 2.5 V6 to see if any valves got bent when the cambelt sipped, but am not sure on how.

Questions..

1.  Will this do the job ?

http://www.halfords.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&langId=-1&catalogId=10151&productId=199553&categoryId=31477

2.  How do I actually perform the test?  (only ever used one on a single pot motorbike)

3.  How the hell do I get the the passenger side bank???

Many thanks
Merv

[Matchless]

That gauge should be fine.

Unbolt the cable tray on the passenger side to improve access.

All plugs out.
Unplug the injection relays (purple ones in ecu box) to stop injectors.
Hold throttle wide open then crank for 2-3 seconds.

[Markjay]

The access is the same as for changing spark plugs.

The testing method is as above, but also make sure that the HT leads are insulated and tucked safely away from any part of the body to avoid a spark.

The easiest is a compression tester that has a screw fitting as opposed to a rubber cone, the screw fitting allows you to do this test yourself without the need for a helper.

(With the rubber cone type, you can still short-circuit the starter motor and do this as a one-man job, but on automatic cars this can be risky because the starter motor short-circuit method by-passes the gear selecor inhibitor so the car could be started in gear by mistake - though obviosuly not while while the plugs are out)

Then carry-out a dry and wet test on any low-compression cylinder by adding a couple of spoonful of engine oil through the spark plug hole - if the problem is due to compression rings' wear, the oil will boost the compression on re-testing, if the low compression is due to leaky valves (or HG) then the added oil will have no effect on the compression which will remain low on the re-testing.

[Allenm]

Thanks for the replies.  I've just gone and bought the one from halfords shown in the link above.

One slight query.. The instructions of the tester say to remove only the spark plug on the pot being tested then replace before removing the next etc.  Is this wrong? I suspect it is but just want to confirm I should remove all the plugs and then just test each pot in turn without replacing the plugs.

Finally ( ) is there an easy way to disable the spark to all six leads?  a fuse or relay somewhere?

Cheers
Merv

[Markjay]

...One slight query.. The instructions of the tester say to remove only the spark plug on the pot being tested then replace before removing the next etc.  Is this wrong? I suspect it is but just want to confirm I should remove all the plugs and then just test each pot in turn without replacing the plugs...

Interesting... I always did the compression test with all plugs removed, the engine cranks much easier this way and there is less strain on the battery. Not sure why they say to do this one at a time - I can't see how this could affect the compression reading for the cylinder tested, perhaps they wanted to prevent petrol from being spitted-out through the plug holes (which will not be the case anyway if you remove the injectors relay)?

[Markjay]

...is there an easy way to disable the spark to all six leads?  a fuse or relay somewhere?...

I would say disconnect the multi-plug feeding the DIS pack, though I am not sure how easy is the access to it. Alternatively, just tie them together with a cable tie and make sure they are well out of the way.

[TheBoy]

Pull the fuses that feed Motronic??

[Matchless]

If you pull the two purple relays it will inhibit both fuel injection and spark.

[Allenm]

Cheers guys,  Will give it a go in a while and post the results.

[Allenm]

Quick Check..

What is this, and will having disconnected it affect testing the compression?

[Marks DTM Calib]

Idle valve and no it wont.....

[TheBoy]

Thats ICV (Idle Control Valve) - it won't affect compression test, but remember to reconnect when done, as the car will run like a sack of shit...

[TheBoy]

bugger, mark beat me, and the word censor doesn't like s h i t.

[Marks DTM Calib]

bugger, mark beat me, and the word censor doesn't like s h i t.

Word censor fixed for that word (which isnt a bad one in my book!)

[TheBoy]

bugger, mark beat me, and the word censor doesn't like s h i t.

Word censor fixed for that word (which isnt a bad one in my book!)

Thats better - my wording above didn't make sense when it swaps words!

[Allenm]

well that took ages to get the f'ing plug out of 6!!  does it matter that the engine is now nearly cold and how do these damn relays come out?

[Andy B]

well that took ages to get the f'ing plug out of 6!!  does it matter that the engine is now nearly cold and how do these damn relays come out?

Just be thankfull it's V6 and not a C30SE straight 6 - that really is a PITA to get out.

[Allenm]

Test done..  result posted back in the original thread, here

http://www.omegaowners.com/forum/YaBB.pl?num=1153140766/220#220

[v6man54deg Geffd]

bit late i know but best to take all 6 plugs out and also to unplug the crankspeed sensor - that way you get no spark or fuel injection, the fuel pump relays are quite tight / hard to remove.

 

Test done..  result posted back in the original thread, here

http://www.omegaowners.com/forum/YaBB.pl?num=1153140766/220#220