Foul plugs - the story continues.
Discussion
Sorry to keep posting, but I seem to have solved my hesitation/miss problems by replacing all plug leads with Magnacor 8.5mm and new Champion plugs, however whilst changing the plugs I noticed that I have a cracked exhaust manifold on the RHS and that the plugs that apparently have only been in for 4400 miles, according to the invoices that came with the car, look, to say the least, knackered.
I've never seen plugs quite this bad before, and I'm a little concerned that it's a tell tail sign of expensive engine work just over the horizon.
Your comment would be most welcome.
[b]Plugs 1, 2 & 3[/b] sooty but not too bad.
[b]Plug 4[/b] heavy deposits and a lot of oil on the thread when the plug was removed.
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo4.jpg[/pic]
[b]Plug 5[/b] very heavy deposits, worse of all 8!
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo5.jpg[/pic]
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo5v2.jpg[/pic]
[b]Plug 6[/b] heavy deposits
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo6.jpg[/pic]
[b]Plug 7 near perfect[/b] ceramic around electrode still white!
[b]Plug 8[/b] sooty but good
Once again, comments/diagnosis/action suggestions welcome.
Tim
I've never seen plugs quite this bad before, and I'm a little concerned that it's a tell tail sign of expensive engine work just over the horizon.
Your comment would be most welcome.
[b]Plugs 1, 2 & 3[/b] sooty but not too bad.
[b]Plug 4[/b] heavy deposits and a lot of oil on the thread when the plug was removed.
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo4.jpg[/pic]
[b]Plug 5[/b] very heavy deposits, worse of all 8!
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo5.jpg[/pic]
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo5v2.jpg[/pic]
[b]Plug 6[/b] heavy deposits
[pic]http://www.tjgraphics.net/TVR/CerberaSparkPlugs/PlugNo6.jpg[/pic]
[b]Plug 7 near perfect[/b] ceramic around electrode still white!
[b]Plug 8[/b] sooty but good
Once again, comments/diagnosis/action suggestions welcome.
Tim
I know it's quite incredible, isn't it?
I've just spent a week in Shropshire (I live in Kent) with no hick-ups and have covered 2000 miles since the end of April, which is when i bought the car.
My wife followed me back from the Welsh boarders last weekend and said the only time the car put out any smoke was when i nailed it, when there was a very brief cloud, so I don't think there's much oil going down the exhaust!
Will do 100 miles or so and pull the plugs and see what state they're in.
Tim
PS: Will do Gary, 'tis on my todo list for tomorrow
Are we thinking top or bottom end?
The last owner said the car had been used for lots of short runs, I might expect some bore glaze from that but nothing that would cause this.
>> Edited by TT Tim on Friday 22 July 20:29
I've just spent a week in Shropshire (I live in Kent) with no hick-ups and have covered 2000 miles since the end of April, which is when i bought the car.
My wife followed me back from the Welsh boarders last weekend and said the only time the car put out any smoke was when i nailed it, when there was a very brief cloud, so I don't think there's much oil going down the exhaust!
Will do 100 miles or so and pull the plugs and see what state they're in.
Tim
PS: Will do Gary, 'tis on my todo list for tomorrow
Are we thinking top or bottom end?
The last owner said the car had been used for lots of short runs, I might expect some bore glaze from that but nothing that would cause this.
>> Edited by TT Tim on Friday 22 July 20:29
What is the oil consumption like? I would just hope that these plugs have been in a lot longer than the paperwork reflects.
I think if there was anything seriously wrong you would have high oil consumption and smoke on start up and over-run.
(I reserve the right to talk total b@ll@cks at anytime)
I think if there was anything seriously wrong you would have high oil consumption and smoke on start up and over-run.
(I reserve the right to talk total b@ll@cks at anytime)
I think you hit the nail on the head there Nick, the oil consumption isn't bad, I'm not driving around in clouds of oil smoke and the oil consumption doesn't seem off the scale, I've topped up with about 3/4 litre over the past 2000 miles.
My diagnosis based on the plugs seems to be oil ingress from either valves or up past the rings, along with incorrect mixture/over fueling.
If the rings were on their way out surely, as you say, the car would look like an old Vauxhall and smoke all the time, or at least when under load?
If it's heads it's probabally a job I'll tackle at home myself, if it's bottome end then i guess it's time to pull the engine and get it off to a specialist.
Tim
PS: Good site for Spark plug 'stuff': <a href="www.spark-plugs.co.uk/pages/technical/diagnosis.htm">www.spark-plugs.co.uk/pages/technical/diagnosis.htm</a>
>> Edited by TT Tim on Saturday 23 July 09:31
My diagnosis based on the plugs seems to be oil ingress from either valves or up past the rings, along with incorrect mixture/over fueling.
If the rings were on their way out surely, as you say, the car would look like an old Vauxhall and smoke all the time, or at least when under load?
If it's heads it's probabally a job I'll tackle at home myself, if it's bottome end then i guess it's time to pull the engine and get it off to a specialist.
Tim
PS: Good site for Spark plug 'stuff': <a href="www.spark-plugs.co.uk/pages/technical/diagnosis.htm">www.spark-plugs.co.uk/pages/technical/diagnosis.htm</a>
>> Edited by TT Tim on Saturday 23 July 09:31
Tim, I have the exact same problem, but with only one of the plugs - the one nearest the driver on the off side. I also don't get any discernable smoke from the exhaust (except a puff at full chat + high revs) however my oil consumption is pretty poor at about 1 litre every 200 miles!!!! About once a month the plug fails and when removed looks exactly like the one you've posted. When replaced the car runs perfectly, and the performance, idling etc is bang on. I've checked the compression on the cylinder and it is the same as all the others, all I have left to do is a leak down test. I'm hoping a valve stem seal has let go, although that is still a relatively big job to fix isn't it??? Does the engine have to come out to remove a cylinder head???
Not sure.... I know on some engines you can replace the seals in situ, but not sure with the ajp. One thread I read somewhere recommended pressurising the cylinder with compressed air and then applying pressure to the valve spring to get to the collets beneath the shim. Can anyone confirm what work is needed to replace valve stem seals on the ajp8?? Cheers
I'll have to investigate, but I can't see any reason why the stem seal would need the engine removing, I have heard about pressurising the cylinder but haven't had any direct experience of it.
I'm inclined to think that this is stem seals rather than rings, so will be monitoring it with a view to removing the heads come the winter.
When you did the compression test what was the difference across the cylinders and what pressures were you getting?
Tim
I'm inclined to think that this is stem seals rather than rings, so will be monitoring it with a view to removing the heads come the winter.
When you did the compression test what was the difference across the cylinders and what pressures were you getting?
Tim
Hi Tim, well before I say anything else I know Xsnowman was having the exact same symptoms as me a while back which resulted in his engine being removed for a rebuild - he started a thread regarding plug fouling, I'm sure you can find it, it wasn't long ago. I beleive it got so bad in the end it wasn't practical for him to keep changing a plug every week or so. Xsnowman if you read this, let us know what the diagnosis was please!!!! Right, the compression test was done using an ordinary gauge from halfords, all 8 plugs out and the injection and ignition fuses pulled out. With the throttle fully opened, a few cranks of the engine gave very very high readings on all cylinders - I was totally gobsmacked at the time. Every cylinder was in the top of the red band above the green band!!! Can't remember the exact pressure, but it was nearly off the scale. The readings were all virtually the same across all 8 cylinders though which I was happy with. I'm still not sure why this is, I'm sure you are supposed to fully open the throttle while cranking aren't you???? Well anyway, as I said the performance and manners of the car are A1 right up until the point where the plug gives up, when obviously there is a huge loss of power and change of engine note. I've just spotted the thread on the main TVR listings about Al Mellings lecturette at the Museum of Army Flying on the 14th Aug, so I plan to ask him a few questions regarding the AJP8 and his input into TVR Crafts stroker conversions etc. Should be interesting....
The high pressure reading is caused by the 'coke' deposits taking up space in the 'unswept' area and raising the efective compression . high readings arent allways a good thing.Yes readings should be done with the throttle open and another reason for high readings is cam timing or wear issues.
RGDs Peter
RGDs Peter
Pete, I've read that coke deposits can raise the CR, and to be honest this is my biggest concern with the engine running as it is, as without a knock sensor any CR induced detonation will be fatal. However, the other 7 plugs are a perfect 'tan' colour with no deposits at all, infact the insulators are still white! So I doubt all of the cylinders are suffering from excess deposits. As far as cam timing and wear is concerned, the cams were replaced about 2 years ago for the whisper cams and subsequent to that the engine had a total factory rebuild following a snapped crankshaft less than 15k miles ago. The car was recently dynoed at the Cerb rolling road day at 359bhp / 330lb and as mentioned it runs really sweet for a Cerb, idles perfectly with no jerkiness at low revs etc. So I am pretty sure it is simply an oil leak into the cylinder, most likely the intake valve. Hopefully I'll get a chance to do a leak down test within the next fortnight - this will confirm whether its coming in through the valve or the rings.....
longbow said:
Pete, I've read that coke deposits can raise the CR, and to be honest this is my biggest concern with the engine running as it is, as without a knock sensor any CR induced detonation will be fatal. However, the other 7 plugs are a perfect 'tan' colour with no deposits at all, infact the insulators are still white! So I doubt all of the cylinders are suffering from excess deposits. As far as cam timing and wear is concerned, the cams were replaced about 2 years ago for the whisper cams and subsequent to that the engine had a total factory rebuild following a snapped crankshaft less than 15k miles ago. The car was recently dynoed at the Cerb rolling road day at 359bhp / 330lb and as mentioned it runs really sweet for a Cerb, idles perfectly with no jerkiness at low revs etc. So I am pretty sure it is simply an oil leak into the cylinder, most likely the intake valve. Hopefully I'll get a chance to do a leak down test within the next fortnight - this will confirm whether its coming in through the valve or the rings.....
I may well have this same prob on one of my cylinders but I recently changed to 20w-50 fully synthetic and I am hoping that might help.
What weight oil are you guys using?
I had a lot of piston slap noise that has quietened right down since the 20w-50 btw
. Duncan
You didn't say what the actually compression readings were, but I'd say that getting a similar reading from all cylinders is a very good sign. I don't know what the normal CR is for that engine, but could well be higher than the average production engine that the halfwits gauge was designed for, so going into the 'red' isn't immediately worrying.
Given that there's only one plug showing signs of fouling and it gave the same compression reading as the other cylinders I wouldn't worry too much about carbon build-up raising the compression.
From the symptoms it sounds like you've got a significant oil leak into the cylinder, and your problem now is to work out where it is coming from.
Given that there's only one plug showing signs of fouling and it gave the same compression reading as the other cylinders I wouldn't worry too much about carbon build-up raising the compression.
From the symptoms it sounds like you've got a significant oil leak into the cylinder, and your problem now is to work out where it is coming from.
Yes, I totally agree with you GreenV8s, I just wish I knew where the oil was getting into the cylinder from. Obviously not knowing how the valve system is built up means I'm just guessing!! So Billy, if there are no stem seals then what mechanism does the ajp use to stop oil seeping past the valves then?? As far as oil is concerned I am using Castrol RS 0w40 at the moment, having changed the oil just over two weeks ago. I thought at the time that a good high quality synthetic would burn off cleaner and leave less deposits, but the plug fouling rate and appearance have not changed at all. Here's an idea I'm trying to discount though - could a weak spark on a single cylinder cause an 'apparent' oil burning problem? I.e. if the mixture is only partially igniting (enough not to misfire, but not enough to burn cleanly) could the mixture then wash the oil from the bore leading to high oil consumption and plug fouling?? I guess I could swap the HT lead and coil between banks and see if this changes anything......
longbow said:
Yes, I totally agree with you GreenV8s, I just wish I knew where the oil was getting into the cylinder from. Obviously not knowing how the valve system is built up means I'm just guessing!! So Billy, if there are no stem seals then what mechanism does the ajp use to stop oil seeping past the valves then?? As far as oil is concerned I am using Castrol RS 0w40 at the moment, having changed the oil just over two weeks ago. I thought at the time that a good high quality synthetic would burn off cleaner and leave less deposits, but the plug fouling rate and appearance have not changed at all. Here's an idea I'm trying to discount though - could a weak spark on a single cylinder cause an 'apparent' oil burning problem? I.e. if the mixture is only partially igniting (enough not to misfire, but not enough to burn cleanly) could the mixture then wash the oil from the bore leading to high oil consumption and plug fouling?? I guess I could swap the HT lead and coil between banks and see if this changes anything......
I don't want to get into a massive oil debate but I personally wouldn't use a 0w-40 oil in the Cerb!
They're are dirty oil burners at the best of time let alone when problems like this are arising.
Get yourself some nice 10w-60 or 20w-50 in there
. Duncan
DuncanM said:
Yes, I totally agree with you GreenV8s, I just wish I knew where the oil was getting into the cylinder from. Obviously not knowing how the valve system is built up means I'm just guessing!! So Billy, if there are no stem seals then what mechanism does the ajp use to stop oil seeping past the valves then?? As far as oil is concerned I am using Castrol RS 0w40 at the moment, having changed the oil just over two weeks ago. I thought at the time that a good high quality synthetic would burn off cleaner and leave less deposits, but the plug fouling rate and appearance have not changed at all. Here's an idea I'm trying to discount though - could a weak spark on a single cylinder cause an 'apparent' oil burning problem? I.e. if the mixture is only partially igniting (enough not to misfire, but not enough to burn cleanly) could the mixture then wash the oil from the bore leading to high oil consumption and plug fouling?? I guess I could swap the HT lead and coil between banks and see if this changes anything......
I don't want to get into a massive oil debate but I personally wouldn't use a 0w-40 oil in the Cerb!
They're are dirty oil burners at the best of time let alone when problems like this are arising.
Get yourself some nice 10w-60 or 20w-50 in there
Duncan
0w-40 is too thin in my opinion.Gassing Station | Cerbera | Top of Page | What's New | My Stuff