Problem, help appreciated
Discussion
Just to put a fly in the ointment, I'm not convinced that your problem is a failed pre-cat. Not that I have ever seen the results of a pre-cat breaking down. A red hot manifold is usually a sign of fuel not burnt in the combustion chamber which carries on into the manifold where it is ignited by the flames from cylinders that are firing. I just can't see how a failed cat would glow hot. If the cat is fully blocked then there would be no air flow from the cylinders (no air no fire) perhaps if it is partially blocked then fire could exist but I would have thought a partial blockage would allow the engine to idle when air flow is low but cause problems when the revs rise. I would be checking plugs, are they all the same colour? Manifold vacuume, an air leak can make a manifold glow red. Would also be good to check fuel pressure isn't decaying away when engine is shut off indicating a leaking injector. Have you still got your old ignition components to try in case you have faulty new stuff?
Of course I could be thinking about it the wrong way but as I said I haven't seen the affects of a blocked pre-cat.
The only experience I have with blocked cats is on four cylinder single bank engines which I'll fire a couple of shots when trying to start then when back pressure builds no more firing. Good luck.
Of course I could be thinking about it the wrong way but as I said I haven't seen the affects of a blocked pre-cat.
The only experience I have with blocked cats is on four cylinder single bank engines which I'll fire a couple of shots when trying to start then when back pressure builds no more firing. Good luck.
NZ fan said:
Just to put a fly in the ointment, I'm not convinced that your problem is a failed pre-cat. Not that I have ever seen the results of a pre-cat breaking down. A red hot manifold is usually a sign of fuel not burnt in the combustion chamber which carries on into the manifold where it is ignited by the flames from cylinders that are firing. I just can't see how a failed cat would glow hot. If the cat is fully blocked then there would be no air flow from the cylinders (no air no fire) perhaps if it is partially blocked then fire could exist but I would have thought a partial blockage would allow the engine to idle when air flow is low but cause problems when the revs rise. I would be checking plugs, are they all the same colour? Manifold vacuume, an air leak can make a manifold glow red. Would also be good to check fuel pressure isn't decaying away when engine is shut off indicating a leaking injector. Have you still got your old ignition components to try in case you have faulty new stuff?
Of course I could be thinking about it the wrong way but as I said I haven't seen the affects of a blocked pre-cat.
The only experience I have with blocked cats is on four cylinder single bank engines which I'll fire a couple of shots when trying to start then when back pressure builds no more firing. Good luck.
^^^^THIS^^^^Of course I could be thinking about it the wrong way but as I said I haven't seen the affects of a blocked pre-cat.
The only experience I have with blocked cats is on four cylinder single bank engines which I'll fire a couple of shots when trying to start then when back pressure builds no more firing. Good luck.
The problem is way more likely to be ignition related.
Remember there's little to be learned about the quality & strength of spark by observing it at atmospheric pressure. This is because the raised pressures under compression when the plug is fitted in the head can kill easily kill what looks like a reasonable spark out in the open.
I used to have an old Champion spark plug tester where you fitted an airline then raise the pressure while sparking the plug, it's amazing to see how easily you can extinguish it as the pressure increases.
I'd focus on the ignition side, start by getting rid of those completely unsuitable shrouded electrode 7 heat range plugs TVR fitted, replacing them with a projected electrode 6 from NGK (BPR6ES).
Then move onto the extenders which can often be a point of failure, replacement is the answer here although I have deleted mine altogether, but this does require extra protection of the HT lead ends.
If you haven't done so already replace the HT leads with something decent, then make your way to the distributor, replace the cap & the rotor arm with a new old stock original or a red one from the distributor doctor.
After that lot you may as well replace the coil too, go for a Bosch one from a Range Rover parts specialist, finish off by checking and adjusting your ignition timing using a strobe.
I bet you'll find your problem will disappear.
ChimpOnGas said:
^^^^THIS^^^^
The problem is way more likely to be ignition related.
Remember there's little to be learned about the quality & strength of spark by observing it at atmospheric pressure. This is because the raised pressures under compression when the plug is fitted in the head can kill easily kill what looks like a reasonable spark out in the open.
I used to have an old Champion spark plug tester where you fitted an airline then raise the pressure while sparking the plug, it's amazing to see how easily you can extinguish it as the pressure increases.
I'd focus on the ignition side, start by getting rid of those completely unsuitable shrouded electrode 7 heat range plugs TVR fitted, replacing them with a projected electrode 6 from NGK (BPR6ES).
Then move onto the extenders which can often be a point of failure, replacement is the answer here although I have deleted mine altogether, but this does require extra protection of the HT lead ends.
If you haven't done so already replace the HT leads with something decent, then make your way to the distributor, replace the cap & the rotor arm with a new old stock original or a red one from the distributor doctor.
After that lot you may as well replace the coil too, go for a Bosch one from a Range Rover parts specialist, finish off by checking and adjusting your ignition timing using a strobe.
I bet you'll find your problem will disappear.
Will any of the above cause the manifold to glow red hot? Plugs & leads are less than a year old & decent stuff, the plugs are NGK. Same goes for the distributor cap & rotor arm, not sure about the quality of the latter though,.The problem is way more likely to be ignition related.
Remember there's little to be learned about the quality & strength of spark by observing it at atmospheric pressure. This is because the raised pressures under compression when the plug is fitted in the head can kill easily kill what looks like a reasonable spark out in the open.
I used to have an old Champion spark plug tester where you fitted an airline then raise the pressure while sparking the plug, it's amazing to see how easily you can extinguish it as the pressure increases.
I'd focus on the ignition side, start by getting rid of those completely unsuitable shrouded electrode 7 heat range plugs TVR fitted, replacing them with a projected electrode 6 from NGK (BPR6ES).
Then move onto the extenders which can often be a point of failure, replacement is the answer here although I have deleted mine altogether, but this does require extra protection of the HT lead ends.
If you haven't done so already replace the HT leads with something decent, then make your way to the distributor, replace the cap & the rotor arm with a new old stock original or a red one from the distributor doctor.
After that lot you may as well replace the coil too, go for a Bosch one from a Range Rover parts specialist, finish off by checking and adjusting your ignition timing using a strobe.
I bet you'll find your problem will disappear.
Edited by hot metal on Monday 24th November 21:33
Edited by hot metal on Monday 24th November 21:35
hot metal said:
Will any of the above cause the manifold to glow red hot?
Yes!!!As a number of people have already pointed out, its highly likely the reason your manifolds are glowing is because raw unburnt fuel is finding its way to them.
The only way this can happen is because one or more cylinder is failing to ignite it's quoter of fuel or failing to ignite it at the correct point in the cycle (ignition timing), other cylinders are combusting correctly so they are heating the manifolds to a level where the unburnt fuel from the problem cylinder or cylinders can burn inside the manifold.
In effect you have created a petrol heater, it's working just like a workshop space heater.
Burn the fuel in the combustion chamber at the right point in the cycle and your manifolds will stop glowing, unsurprisingly you'll also find the car will start better, use less fuel and perform substantially better too.
The place to burn fuel is in the combustion chamber not the exhaust manifolds, the most likely reason unburnt fuel is finding to the exhaust manifolds is because you have an ignition fault on one or more cylinders.
hot metal said:
Plugs & leads are less than a year old & decent stuff, the plugs are NGK. Same goes for the distributor cap & rotor arm, not sure about the quality of the latter though
Never assume because you've replaced a component previously its working correctly, start from scratch and be systematic in your diagnosis, avoid blind assumptions and going def to logic.When you are 100% happy you have a good spark at every cylinder you then need to make sure its happening at the correct point in the cycle, this means checking & adjusting your ignition timing.
If you have a good spark at all 8 cylinders and that spark occurs at the correct time your manifolds will stop glowing, start with replacing the totally inappropriate NGK B7ECS spark plugs used by TVR with the far more suitable NGK BPR6ES.
http://www.pistonheads.com/gassing/topic.asp?h=1&a...
Then follow what I suggested in my previous post.
I agree that fuel igniting in the exhaust would cause it to glow but I was of the impression that the car had only made it as far as the driveway when you observed this. Imo a blocked cat would heat up a lot quicker than unburnt fuel would, I've only seen unburnt fuel glow manifolds after driving.
s p a c e m a n said:
I agree that fuel igniting in the exhaust would cause it to glow but I was of the impression that the car had only made it as far as the driveway when you observed this. Imo a blocked cat would heat up a lot quicker than unburnt fuel would, I've only seen unburnt fuel glow manifolds after driving.
This is correct, only on the left side too. What chimpongas says is very convincing though..............sod it 
One thing that is easy to check is the plug extention, I can try it without them briefly.
Edited by hot metal on Tuesday 25th November 20:27
Edited by hot metal on Tuesday 25th November 20:29
As COG says the combustion is in the manifold, but the crux of the matter is the catalyst is doing exactly what its designed to do and igniting unburnt fuel within its body to reduce the HC content of the exhaust, as part of the catalyst sweep cycle the ECU swings the mixture in normal running lambda cycle. Obviously it would not glow read hot if the amount of unburnt fuel was normal.
Edited by blitzracing on Tuesday 25th November 20:56
blitzracing said:
As COG says the combustion is in the manifold, but the crux of the matter is the catalyst is doing exactly what its designed to do and igniting unburnt fuel within its body to reduce the HC content of the exhaust, as part of the catalyst sweep cycle the ECU swings the mixture in normal running lambda cycle. Obviously it would not glow read hot if the amount of unburnt fuel was normal.
I have never known such an extreme reaction to what people are saying is a simple misfire, I want to believe this though.Edited by blitzracing on Tuesday 25th November 20:56
A few years ago when I had a TR6, it would always get airlocks in the fuel injection pipes causing one or more cylinders to not fire. The easiest way I found to identify the faulty cylinder was to make the exhaust manifold wet with water or spray it with WD40 (although a bit smoky) then start the engine and quickly observe which pipe was evaporating slower than the others. I know it sounds a bit crude but it used to work for me, and it was quite obvious as to what cylinder is not firing correctly.
Good luck
Good luck
I went to investigate a glowing exhaust manifold issue on my friends chimaera. We pulled out one of the spark plugs and it looked brand new, on further investigation the injector associated with that cylinder / spark plug had not been plugged in (at a well known TVR specialist) which was causing the lambda to read lean on that bank of cylinders. In an attempt to correct this the ECU will over fuel the remaining working injectors, the unburnt fuel then uses the the "free oxygen" from the cylinder not being provided with fuel to ignite and hey presto you have a very hot manifold in this primary. So, if you definitely have a good spark on that cylinder I would like to suggest that your injector is either not receiving a signal feed (not plugged in) or is faulty. Cheers.
Mr Supercharged said:
I went to investigate a glowing exhaust manifold issue on my friends chimaera. We pulled out one of the spark plugs and it looked brand new, on further investigation the injector associated with that cylinder / spark plug had not been plugged in (at a well known TVR specialist) which was causing the lambda to read lean on that bank of cylinders. In an attempt to correct this the ECU will over fuel the remaining working injectors, the unburnt fuel then uses the the "free oxygen" from the cylinder not being provided with fuel to ignite and hey presto you have a very hot manifold in this primary. So, if you definitely have a good spark on that cylinder I would like to suggest that your injector is either not receiving a signal feed (not plugged in) or is faulty. Cheers.
I booked the car into garage early this year to investigate what I thought was overfueling, the smell of petrol out of the exhaust was quite strong.They faffed about with it a bit, changed the fuel filter, checked the pressure of the fuel system (ok) & reported that if anything it was running lean. I have not looked into this any further since as the car was running well enough although a bit thirsty at 12mpg around town (compare that to the 15mpg my previous Griffith 500 did) .Something in the above post rings a bell there
Hi,
I'd follow ChimpOnGas suggestions with fault finding.
And don't assume that new kit is good kit, our cars are very temperamental with ignition components. How many times have we heard on here a bad running car cured by the correct model of dizzy cap & arm?
I have a 430 Pre-Serp & have had the same symptoms & the fix was reconnecting the loose HT lead.
If you do take the Pre-Cats out, you will remove the evidence of your fault... as the unburnt fuel will go down to the main cat instead. (But if you're nearly there I'd carry on) but even if you do that I'd still be checking the ignition system.
HTH
Mark
I'd follow ChimpOnGas suggestions with fault finding.
And don't assume that new kit is good kit, our cars are very temperamental with ignition components. How many times have we heard on here a bad running car cured by the correct model of dizzy cap & arm?
I have a 430 Pre-Serp & have had the same symptoms & the fix was reconnecting the loose HT lead.
If you do take the Pre-Cats out, you will remove the evidence of your fault... as the unburnt fuel will go down to the main cat instead. (But if you're nearly there I'd carry on) but even if you do that I'd still be checking the ignition system.
HTH
Mark
Mr Supercharged said:
I went to investigate a glowing exhaust manifold issue on my friends chimaera. We pulled out one of the spark plugs and it looked brand new, on further investigation the injector associated with that cylinder / spark plug had not been plugged in (at a well known TVR specialist) which was causing the lambda to read lean on that bank of cylinders. In an attempt to correct this the ECU will over fuel the remaining working injectors, the unburnt fuel then uses the the "free oxygen" from the cylinder not being provided with fuel to ignite and hey presto you have a very hot manifold in this primary. So, if you definitely have a good spark on that cylinder I would like to suggest that your injector is either not receiving a signal feed (not plugged in) or is faulty. Cheers.
Quality response, very interesting Relevant too
OP should pay attention here.
Gassing Station | Chimaera | Top of Page | What's New | My Stuff