Omega Owners Forum - Compression Testing V6

Allenm

Senior Member

Offline

Posts: 591
Milton Keynes
Gender: male

Drives: '99 2.5 V6 CDX saloon manual

Compression Testing V6
22. Aug 2006 at 11:29

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&l...

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??? Shocked

Many thanks
Merv

Back to top

IP Logged

Matchless Omega Knight Offline Posts: 1746 Nottingham Gender: Drives: The one at the end of the drive	Re: Compression Testing V6 Reply #1 - 22. Aug 2006 at 11:43 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.
Back to top	IP Logged

Markjay

Omega Lord

Offline

Posts: 5452
London
Gender: male

Re: Compression Testing V6
Reply #2 - 22. Aug 2006 at 13:36

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.

Back to top

Alas, no more Omegas....

IP Logged

Allenm

Senior Member

Offline

Posts: 591
Milton Keynes
Gender: male

Drives: '99 2.5 V6 CDX saloon manual

Re: Compression Testing V6
Reply #3 - 22. Aug 2006 at 14:04

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 ( Roll Eyes

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

Cheers
Merv

Back to top

IP Logged

Markjay

Omega Lord

Offline

Posts: 5452
London
Gender: male

Re: Compression Testing V6
Reply #4 - 22. Aug 2006 at 14:12

Allenm wrote on 22. Aug 2006 at 14:04:

...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)?

Back to top

Alas, no more Omegas....

IP Logged

Markjay

Omega Lord

Offline

Posts: 5452
London
Gender: male

Re: Compression Testing V6
Reply #5 - 22. Aug 2006 at 14:14

Allenm wrote on 22. Aug 2006 at 14:04:

...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.

Back to top

Alas, no more Omegas....

IP Logged

TheBoy Administrator Offline TBE has an MOT! Posts: 64817 Brackley, Northants Gender: Drives: 98 MV6, 03 Elite, 00 25, 89 ZX10	Re: Compression Testing V6 Reply #6 - 22. Aug 2006 at 14:25 Pull the fuses that feed Motronic??
Back to top	If you are going to kick a car, remember to wear appropriate footwear Any posts are the result of my own views as a member of OOF, which may or may not be the same as my views as part of the Admin Team. IP Logged

Matchless Omega Knight Offline Posts: 1746 Nottingham Gender: Drives: The one at the end of the drive	Re: Compression Testing V6 Reply #7 - 22. Aug 2006 at 14:25 If you pull the two purple relays it will inhibit both fuel injection and spark.
Back to top	IP Logged

Allenm Senior Member Offline Posts: 591 Milton Keynes Gender: Drives: '99 2.5 V6 CDX saloon manual	Re: Compression Testing V6 Reply #8 - 22. Aug 2006 at 14:28 Cheers guys, Will give it a go in a while and post the results.
Back to top	IP Logged

Allenm Senior Member Offline Posts: 591 Milton Keynes Gender: Drives: '99 2.5 V6 CDX saloon manual	Re: Compression Testing V6 Reply #9 - 22. Aug 2006 at 15:54 Quick Check.. What is this, and will having disconnected it affect testing the compression?
Back to top	IP Logged

Marks DTM Calib Administrator Offline Ex Member Posts: 25671 Northern Hemisphere Gender: Drives: Astra J, Mum Bus, Dexta Tractor, 108 DMU wip	Re: Compression Testing V6 Reply #10 - 22. Aug 2006 at 15:55 Idle valve and no it wont.....
Back to top	IP Logged

TheBoy Administrator Offline TBE has an MOT! Posts: 64817 Brackley, Northants Gender: Drives: 98 MV6, 03 Elite, 00 25, 89 ZX10	Re: Compression Testing V6 Reply #11 - 22. Aug 2006 at 15:56 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...
Back to top	If you are going to kick a car, remember to wear appropriate footwear Any posts are the result of my own views as a member of OOF, which may or may not be the same as my views as part of the Admin Team. IP Logged

TheBoy Administrator Offline TBE has an MOT! Posts: 64817 Brackley, Northants Gender: Drives: 98 MV6, 03 Elite, 00 25, 89 ZX10	Re: Compression Testing V6 Reply #12 - 22. Aug 2006 at 15:56 bugger, mark beat me, and the word censor doesn't like s h i t.
Back to top	If you are going to kick a car, remember to wear appropriate footwear Any posts are the result of my own views as a member of OOF, which may or may not be the same as my views as part of the Admin Team. IP Logged

Marks DTM Calib Administrator Offline Ex Member Posts: 25671 Northern Hemisphere Gender: Drives: Astra J, Mum Bus, Dexta Tractor, 108 DMU wip	Re: Compression Testing V6 Reply #13 - 22. Aug 2006 at 15:58 TheBoy wrote on 22. Aug 2006 at 15:56: 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!)
Back to top	IP Logged

TheBoy Administrator Offline TBE has an MOT! Posts: 64817 Brackley, Northants Gender: Drives: 98 MV6, 03 Elite, 00 25, 89 ZX10	Re: Compression Testing V6 Reply #14 - 22. Aug 2006 at 16:02 Marks DTM Calib wrote on 22. Aug 2006 at 15:58: TheBoy wrote on 22. Aug 2006 at 15:56: 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!
Back to top	If you are going to kick a car, remember to wear appropriate footwear Any posts are the result of my own views as a member of OOF, which may or may not be the same as my views as part of the Admin Team. IP Logged

This is the old site. Please use the new site.

This is the old site. Please use the new site.

www.omegaowners.com/forum/index.php.

This is the old site. Please use the new site.

	Welcome, Guest. Please Login