Hi Guys

 

I've got an issue with the number 5 cylinder not firing (first one on the pass side looking from inside) and when I do a bit of research I find that that cylinder seems to have a disproportionate amount of failure from the other ones, is this common knowledge or just luck...

 

Rich

That's number 6 cylinder.

Hi Guys

 

I've got an issue with the number 5 cylinder not firing (first one on the pass side looking from inside) and when I do a bit of research I find that that cylinder seems to have a disproportionate amount of failure from the other ones, is this common knowledge or just luck...

 

Rich

 

number 6 is always the 1st to go bad...furthest away from the throttle bodies and can get the leanest A/F charge.

Yep No 6 !

I had that go on me in my first Z!

From experience I've found it's number 5 that has a higher failure rate. I know that when there's a fuel delivery issue it seems that 5 fails before 6. Generally, it seems that cyl 5 is the lowest in terms of compression on an overall tired engine.

 

Heat due to insufficient coolant flow plays a massive part in the failure of the rear cylinders. It would be interesting to note if the rear cylinders receive more air than the front four, and the effect of the Bernoulli Principle on fuel flow at cyl 5 at WOT and different duty cycles.

Edited February 14, 201510 yr by Noz

Ive never really studied hard the lubrication circut in these engines and maybe the next time i have a block i should...underskirt oiling on these motors play a crucial role in keeping piston temps down and maybe the rear 2 cylinder oil squirters might have starvation issues being the furthest from the oil pump.

That's number 6 cylinder.

 

Sorry, first hit on Google from the Nico site. So the one i'm looking at is number 6. With all this knowledge about the failure's of these rear cylinders, has anyone got some idea what the problem could be.

 

Rich

Sorry, first hit on Google from the Nico site. So the one i'm looking at is number 6. With all this knowledge about the failure's of these rear cylinders, has anyone got some idea what the problem could be.

 

Rich

 

What's the compression of that cylinder?

Noz, sorry, haven't got that far yet, I'll let you know.

 

Rich

I think the thoery is of cooling issues. The water pipe flashing is awful on these engines done worse than others so the rear cylinders get hotter than they should esp once you start ramping up the boost. Don't quote me on it but I think the plenum has an odd shape runner back there too, meaning it's more restricted than the others. Excess heat plus poor breathing, recipe for disaster esp once you throw in 25 years of aging, a crappy generic chip and some failing components/poor maintenance. Not saying that's YOUR particular issue, just generally.

 

Interestingly mine failed on cyl 3. I know a chap with a collection of blocks, not one has the same cyl failed. Six is the most probe to failure but it's not always the fail point.

 

"Today, 02:55

Noz, sorry, haven't got that far yet, I'll let you know.

 

Rich"

 

Does that mean you haven't done a compression, if so what leads you to the conclusion it's failed?

"How do I know its number 6"

 

Well the exhaust for the drivers side is behaving normally, ie when I put my hand to the output its smooth and gentle, however when I placed my hand up to the passengers side, it was not as it should be, ie its was thumping in a bang bang bang , against my hand.

Now I removed one of the electrical connections to a cylinder on the drivers side and the exhaust output was bang bang bang against my hand, just like the passenger side. I then replaced the connector and the exhaust was back to normal. I then pulled the connectors on , I think, 2 and 4 ie the accessible cylinders on the pass side. Once off, the engine noise dropped on both of them, so after I can get access to cylinder 6 ill be in a better position to asses the problem.

 

That's how I deduced it was a cylinder fail and which one. if there's something wrong with my method, please advise

 

Regards

 

Rich

 

ps, oh when these cylinders at the rear fail, what exactly fails?

Ringlands

Could it not just be a case of a failed coilpack or injector on number 6 cylinder?

Definitely could be electrical, first thing that needs to be done is a compression check. 15mins is all that is required to determine if it's injector, plug, coil pack or compression.

Noz, are you trying to tell me its the piston rings? if it is can you tell me the connection, coz noz, ive never heard of that one

 

Rich

Edited February 15, 201510 yr by Rev1Richie

Right so it's too early to jump to conclusions. It could be a faulty connection or a duff injector etc all of those need to be checked. A compression test will identify if you have compression and that may be the answer. However for the sake of an hour with a cup of tea and multimeter it's a road that has to be taken.

 

Get the balance bar out the way. Then check the ohm resistance of the injector, check the coil pack and injector connectors for corrosion clean them up. Pull the plug and have a look at it, note it's appearance. Is it wet with fuel, gunked with out etc. Try swapping over the coil pack and plug to a known working cyl, see if the issue follows you or stays. Once you have clearly established you have both spark and fuel you know things should work. If they don't the missing piece if the puzzle is compression. Test it, you will want all 6 plugs out for this and the fuel relay. Note them all and look for abnormally low or big differences between cylinders.

 

If you find that compression is the route cause, see if you can borrow a leak down tester this will tell you roughly where it's failed. It may be you don't need a full engine rebuild, HG failure or a damaged valve etc. Good luck. I expect you will find that one of those brittle old connectors is green as hell and causing the fault. Don't panic be logical.

Noz, are you trying to tell me its the piston rings? if it is can you tell me the connection, coz noz, ive never heard of that one

 

Rich

 

Definitely could be electrical, first thing that needs to be done is a compression check. 15mins is all that is required to determine if it's injector, plug, coil pack or compression.

 

Posted again.

 

You're talking about failed cylinders. Thread title is "broken cylinder". If it's compression-related, it will be the ringlands most likely. You need to detrmine what the issue is.

Use a long screwdriver to listen to the injectors "clicking". Is cyl 6 the same as others?

Remove balance bar.

Check all connections visually. Close up the female terminals, scrape away any green oxidisation.

Remove plug, place in coil pack, ground on plenum, crank engine, do you have spark?

Swap coil pack, does issue change to different cylinder?

Remove all plugs, compression check entire engine, throttle open.

Check resistivity for all injectors.

 

Injector, injector connector, spark plug, coil pack, coil pack connector, loom (inc at PTU), compression (ringlands, valve). These are possible causes. Time for basic health check. You only need basic hand tools until compression test or ohm test. Literally takes a couple of minutes to rule out injector, spark plug or coil pack failure for a single cylinder.

Edited February 15, 201510 yr by Noz

Stephen, Noz. Thanks very much, those instructions are just what I need as ive not really played around with the cylinder/electrical area.

 

Noz, broken, failed... does it matter, Broken was the first word that came to mind. lets just leave it.

 

Thanks

 

Rich

Stephen, Noz. Thanks very much, those instructions are just what I need as ive not really played around with the cylinder/electrical area.

 

Noz, broken, failed... does it matter, Broken was the first word that came to mind. lets just leave it.

 

Thanks

 

Rich

 

You asked me a question directly and said you've never heard of failed piston rings. I answered. Yes, terminology matters for swift diagnosis. Broken, failed cylinder = ring or bore damage and low compression, typically. Cylinder not firing, could be various issues.

Noz..oh god. I've just looked for the first time at the thread listing under "my threads" and saw my last listing "Broken Cylinder" and I have to say, when you look at it that way, I can see your point. so I do apologise for getting arsie about the title. Normally I got to the thread via my email box which takes me straight to the post in the thread, bypassing the index. I could have PM'ed this but thought it right for everyone to see what a right twerp I can sometimes be. Sorry

 

Rich