Simon Blythe
Zorg Guru (I)
I'm going to do a compression test on the Z later but I'm unsure as to what to disconnect to stop it firing so I can do the test. It's the single vanos engine, can anyone offer a little guidance please?
Quick question
- Thread starter Simon Blythe
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- Model of Z
- Z3M Imola and Z4 (e89)
Pull the coil packs off you'll need to anyway to remove the plugs in turn for the test. (I would put them back on in the same position they came off)
Simon Blythe
Zorg Guru (I)
Cheers Niall,
I've removed all the plugs now and the seem fine. Do I need to disconnect anything else before I connect the gauge and crank the car?
I've removed all the plugs now and the seem fine. Do I need to disconnect anything else before I connect the gauge and crank the car?
I think that if you've disconnected the coils that should stop the fuel pump running. I might be wrong here so just be careful, and if any fuel is injected into the cylinders you will have to follow Brian's recommendations.
Tony.
Tony.
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Agree or at least put 5 of the plugs back in and only remove the one on the cylinder your testing or you'll be pumping air/fuel out of the others actually I think thats how you're suppose to do it ie.e.one removed at a time
I haven't done a compression test on a car in 15 years. At that time, I never had to deal with coil packs. I don't feel that you will have any trouble performing the test once the packs are removed and set aside. Keep all the plugs out so the engine turns freely without the resistance of compression in any of the cylinders except the one you are testing. I think the compression should read around 150 psi but check the specifications for this to be sure. It is important that all the readings are similar among all the cylinders and that one cylinder doesn't vary drastically with the others. One cylinder being off reading could indicate valve trouble or head gasket. Two adjoining cylinders being off usually means head gasket. If you see a bad cylinder, take a good look at your engine oil for any milky looking substance or your coolant for oil contamination. Good luck with it. .........................Frankie
PS. Compression can be lost if the rings are bad, but you would already have known this by blowing smoke from oil being burned as it gets past the rings as you are driving. If you see oil smoke but only when you first start the car or when you are stopped at a light and begin to drive after the light changes, this indicated valve problems such as valve guides or seals.
PS. Compression can be lost if the rings are bad, but you would already have known this by blowing smoke from oil being burned as it gets past the rings as you are driving. If you see oil smoke but only when you first start the car or when you are stopped at a light and begin to drive after the light changes, this indicated valve problems such as valve guides or seals.
Last edited:
Simon Blythe
Zorg Guru (I)
Thanks guys for your help, the readings are as follows - from the scuttle the the front of the car in bars, 15, 15, 14.5, 14.5, 15 and 15. Not sure if this indicates a failing between 3 and 4 as its not a significant difference however, I may be wrong.
The plugs look fine too- so I'm leaning towards faulty injector or coil pack.
Top plug is next to the scuttle panel.
The plugs look fine too- so I'm leaning towards faulty injector or coil pack.
Top plug is next to the scuttle panel.
- Joined
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- Model of Z
- Z3M Imola and Z4 (e89)
Have you got a misfire?
Simon Blythe
Zorg Guru (I)
Yep - it's definately running on 5
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Ok well your compression is over 200 psi thats good. I would say its a coiil pack even its intermittent, find the offending pack by running the car and disconnecting each pack in turn, if the engine note doesn't change you've found it, of course it could be a plug, same test will finf that too.
- Joined
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- Model of Z
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The absolute min compression is I believe?? 10.1 bar approx 146 psi so you have very good compression.
Simon Blythe
Zorg Guru (I)
Thanks Niall - I'll disconnect each coil in turn and see what happens
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The only other advice is a code reader if you have access to one that will tell you whats going on.
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Dont know if its just the picture but when zoomed in plugs look a little worn
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True that the gaps do look a little big. worth checking
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New plugs rule that out all together
- Joined
- Apr 1, 2016
- Points
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- Location
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- Model of Z
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Don't know what you get plug wise for the 6cyl engines but my 4 pot come with 3 options
Standard plug. Single tip
Platinum. Twin tip (look bit like yours )
Iridium. 4 tip plug (dear to buy £52 for my 4 but extended run period)
These are the ones i took out mine when i got it .Iridium plug has a 60k change period got my zed with 84k plugs well worn possibly originals
Standard plug. Single tip
Platinum. Twin tip (look bit like yours )
Iridium. 4 tip plug (dear to buy £52 for my 4 but extended run period)
These are the ones i took out mine when i got it .Iridium plug has a 60k change period got my zed with 84k plugs well worn possibly originals
Simon Blythe
Zorg Guru (I)
I'll pop it on later Niall.
Looks like a faulty plug, I disconnected the 2nd pack from the scuttle and the engine note didn't change - I change the pack for a good one and it improved slightly but was still missing when revved (suspect injector too) She does sound like she's sucking a lot of air in somewhere also but that's all for another day.
Positives from today are finding out - with help from those here - that the engine is good and that she drives beautifully so pretty much everything else can be rectified from here on in.
Thanks again for the help.
Looks like a faulty plug, I disconnected the 2nd pack from the scuttle and the engine note didn't change - I change the pack for a good one and it improved slightly but was still missing when revved (suspect injector too) She does sound like she's sucking a lot of air in somewhere also but that's all for another day.
Positives from today are finding out - with help from those here - that the engine is good and that she drives beautifully so pretty much everything else can be rectified from here on in.
Thanks again for the help.