clairetoo
|
| posted on 25/10/12 at 04:14 PM |
|
|
Non-firing cylinder
After all the faffing about with my V6 Mx5 , which has got me nowhere (  ) , I seem to tracked down the basic problem - one cylinder isnt firing
.
I have changed everything - injector , wiring , plug , swapped the plug leads , and just done a leak-down test .
It was the same as the next cylinder - just over 10% - with no audible leaks from the throttle body , exhaust or breather .
So - what the fudge is going on ? Pulling a plug lead off any other cylinder causes the engine to nearly stop , but has no effect on that cylinder ,
which also pops flame from the throttle body when revved .
Any suggestions welcome !
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
|
|
Jon Ison
|
| posted on 25/10/12 at 04:22 PM |
|
|
Got a spark ?
The next thing I would look at is can you see the injector down the inlet tract ? If so is it injecting, in my experience its usually lack of fuel
rather than lack of spark on fuel injected cars cuasing this problem.
|
|
|
clairetoo
|
| posted on 25/10/12 at 04:29 PM |
|
|
I have a spark , and on removal from the engine the plug from the offending cylinder is wet - so I have spark , fuel and compression .
I just checked my TDC mark , and its spot-on - checked the timing with a timing/advance light and its spot-on .
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
rb968
|
| posted on 25/10/12 at 04:37 PM |
|
|
Weird one Claire. Spark and wet plug?
Have you got a spare coilpack to try? In case its broken down on that one lead?
Sorry only thing I can think of on top of what you have tried.
Rich
|
|
|
clairetoo
|
| posted on 25/10/12 at 04:42 PM |
|
|
I have tried swapping the two leads on that part of the coil , and nothing changed - I've spent two days off and on swapping and changing stuff
, to no effect
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
jollygreengiant
|
| posted on 25/10/12 at 04:56 PM |
|
|
Are the valves on that cylinder opening properly, First garage I worked in one mechanic had a V8 Yank with a misfire on 1 cylinder. He changed the
distributor, serviced the carb, removed the head and over-hauled them, changed the coil, changed the leads, did the heads again. Then one day he was
running the engine with the rocker covers off and noticed one of the valve rockers was barely moving. Turned out one of the cam lodes almost made a
perfect bearing cos' it had worn round(ish).
Just a thought.
Beware of the Goldfish in the tulip mines. The ONLY defence against them is smoking peanut butter sandwiches.
|
|
|
DIY Si
|
| posted on 25/10/12 at 05:07 PM |
|
|
Could it over-fuelling that one cylinder? An injector sticking open would cause roughly what you're seeing.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
|
|
|
clairetoo
|
| posted on 25/10/12 at 05:34 PM |
|
|
quote:
Originally posted by DIY Si
Could it over-fuelling that one cylinder? An injector sticking open would cause roughly what you're seeing.
I've now tried four different injectors in that cylinder !
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
ashg
|
| posted on 25/10/12 at 05:56 PM |
|
|
you say you have spark. is that when you pull the ht lead off? have you actually checked that the spark plug is working? hows the finger getting
on?
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
|
|
|
DIY Si
|
| posted on 25/10/12 at 05:56 PM |
|
|
Ummmm.......
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
|
|
|
clairetoo
|
| posted on 25/10/12 at 06:01 PM |
|
|
quote:
Originally posted by ashg
you say you have spark. is that when you pull the ht lead off? have you actually checked that the spark plug is working? hows the finger getting
on?
I've gone through a complete set of plugs from a spare engine , tried the old trick of heating the plug before fitting - I have a good spark at
the plug , but nothing once its in the engine .
Edit to add - the fingers are still sore , two of them dont bend at all
[Edited on 25/10/12 by clairetoo]
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
on_eighty_runner
|
| posted on 25/10/12 at 06:05 PM |
|
|
assuming spark plug is ok, (swap with one from another cylinder)
The inlet valve make be stuck open . You mentioned flames in its inlet tract,
No other route for flames unless timing on that individual cylinder is miles out. (spark during induction stroke)
|
|
|
clairetoo
|
| posted on 25/10/12 at 06:15 PM |
|
|
quote:
Originally posted by on_eighty_runner
assuming spark plug is ok, (swap with one from another cylinder)
The inlet valve make be stuck open . You mentioned flames in its inlet tract,
No other route for flames unless timing on that individual cylinder is miles out. (spark during induction stroke)
Thing is - the leak-down test showed no problems . I've been pulling and swapping plugs all day.........and surely a timing issue would effect
all the cylinders , not just one ?
[Edited on 25/10/12 by clairetoo]
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
Nickp
|
| posted on 25/10/12 at 06:22 PM |
|
|
Has it got hydraulic lifters? Faulty one keeping a valve open maybe? You've done a leak down test, but have you done a compression test?
[Edited on 25/10/12 by Nickp]
|
|
|
clairetoo
|
| posted on 25/10/12 at 06:29 PM |
|
|
quote:
Originally posted by Nickp
Has it got hydraulic lifters? Faulty one keeping a valve open maybe? You've done a leak down test, but have you done a compression test?
[Edited on 25/10/12 by Nickp]
Could that happen - it does have hydraulic followers , could they `pump up' when running , but leak out when stopped ?
One `test' I have done is simply to place the palm of my hand on the top of the throttle body , it sucks my hand hard to the `body , but doesnt
slow the engine at all .
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
Nickp
|
| posted on 25/10/12 at 06:35 PM |
|
|
quote:
Originally posted by clairetoo
quote:
Originally posted by Nickp
Has it got hydraulic lifters? Faulty one keeping a valve open maybe? You've done a leak down test, but have you done a compression test?
[Edited on 25/10/12 by Nickp]
Could that happen - it does have hydraulic followers , could they `pump up' when running , but leak out when stopped ?
One `test' I have done is simply to place the palm of my hand on the top of the throttle body , it sucks my hand hard to the `body , but doesnt
slow the engine at all .
It is possible. Does it spit back against your hand when you do that test? Mind those pinkies 
|
|
|
sebastiaan
|
| posted on 25/10/12 at 06:38 PM |
|
|
Blocked exhaust primary maybe?
We're running out of options here.... Maybe it's voodoo? 
|
|
|
britishtrident
|
| posted on 25/10/12 at 07:09 PM |
|
|
Just because you get a spark testing with the plug out doesn't mean there is a spark under compression, the voltage required to jump the
spark plug gap is much higher under compression. At these high voltages the insulation of the coil pack or distributor cap as to be in top class
order or the spark will jump to earth.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
clairetoo
|
| posted on 25/10/12 at 07:10 PM |
|
|
quote:
Originally posted by Nickp
quote:
Originally posted by clairetoo
quote:
Originally posted by Nickp
Has it got hydraulic lifters? Faulty one keeping a valve open maybe? You've done a leak down test, but have you done a compression test?
[Edited on 25/10/12 by Nickp]
Could that happen - it does have hydraulic followers , could they `pump up' when running , but leak out when stopped ?
One `test' I have done is simply to place the palm of my hand on the top of the throttle body , it sucks my hand hard to the `body , but doesnt
slow the engine at all .
It is possible. Does it spit back against your hand when you do that test? Mind those pinkies
Nope , no spitting at all (at tickover)
I am being careful - I'm using the other hand for testing stuff
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
Nickp
|
| posted on 25/10/12 at 07:12 PM |
|
|
A colourtune kit might help you see what's happening spark wise.
|
|
|
rusty nuts
|
| posted on 25/10/12 at 07:24 PM |
|
|
As Jolly green giant has already suggested check that the valves are opening, I wouldn't be suprised if the exhaust valve isn't opening
which would give you compression but not allow the cylinder to fire properly causing spitting back through the throttle body and a wet plug.
I've had similar symptoms a few times, a couple of times it was due to worn(read non existent )cam lobes and another was due to a tappet
adjuster coming loose
|
|
|
adithorp
|
| posted on 25/10/12 at 07:48 PM |
|
|
quote:
Originally posted by rusty nuts
As Jolly green giant has already suggested check that the valves are opening, I wouldn't be suprised if the exhaust valve isn't opening
which would give you compression but not allow the cylinder to fire properly causing spitting back through the throttle body and a wet plug.
I've had similar symptoms a few times, a couple of times it was due to worn(read non existent )cam lobes and another was due to a tappet
adjuster coming loose
Agreed. Seen it years ago on a RangeRover that had 2 exhaust cam lobes worn down to nothing. had compression, spark and fuel but wouldn't fire
on those 2 cylinders.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
|
|
|
clairetoo
|
| posted on 25/10/12 at 07:59 PM |
|
|
Thanks for the suggestions guys - looks like tomorrows job is to pull the cam cover off that bank , and have a good look .
I do have plenty of spares - the Fury engine just happens to have dead rings and a broken cam belt
Its cuz I is blond , innit
Claire xx
Will weld for food......
|
|
|
ashg
|
| posted on 25/10/12 at 11:53 PM |
|
|
Not having much luck at the moment are you.
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
|
|
|
MikeRJ
|
| posted on 25/10/12 at 11:59 PM |
|
|
An air leak on the inlet manifold/throttle body is a possibility. That would account for both the flame spitting activities and not running at idle,
as well as not affecting a leak down test.
[Edited on 25/10/12 by MikeRJ]
|
|
|
.jpg)
