TR6 ticks over fine but won't drive for long
Discussion
Hi All
I need help!
I have been having a look at my friend's TR6 2.5 PI. It starts OK and will sit at tickover or rev up nicely. It comes up to temperature fine and I have had it ticking over on the drive for half an hour without issue.
The problems comes when the car is driven. Initially it runs fine. It has a fast road cam I think therefore idle is slightly lumpier than a standard cam but it's OK and regular. However after 1/4 of a mile or so it starts to misfire and this gets worse until it is a real struggle to keep it going.
I have checked numerous things including draining the fuel and checking there is no sediment in the tank.
We tested it again tonight and had the same problem. But as soon as it got back onto the drive it ticked over fine again. Slightly lumpier when revved, but not too bad.
I swapped the coil for another I had lying around and that made no difference.
It strikes me that the problem is subtle. Maybe a contact heating up and then being jogged when the car is run or not having enough contact to cope with the extra load going through it when the car is driven.
Otherwise, perhaps a split air pipe which opens up on load.
Timing seems fine and plugs and contacts have been cleaned and checked and are fine.
Any ideas would be very welcome as I am running out of ideas!!
Cheers
Adrian
I need help!
I have been having a look at my friend's TR6 2.5 PI. It starts OK and will sit at tickover or rev up nicely. It comes up to temperature fine and I have had it ticking over on the drive for half an hour without issue.
The problems comes when the car is driven. Initially it runs fine. It has a fast road cam I think therefore idle is slightly lumpier than a standard cam but it's OK and regular. However after 1/4 of a mile or so it starts to misfire and this gets worse until it is a real struggle to keep it going.
I have checked numerous things including draining the fuel and checking there is no sediment in the tank.
We tested it again tonight and had the same problem. But as soon as it got back onto the drive it ticked over fine again. Slightly lumpier when revved, but not too bad.
I swapped the coil for another I had lying around and that made no difference.
It strikes me that the problem is subtle. Maybe a contact heating up and then being jogged when the car is run or not having enough contact to cope with the extra load going through it when the car is driven.
Otherwise, perhaps a split air pipe which opens up on load.
Timing seems fine and plugs and contacts have been cleaned and checked and are fine.
Any ideas would be very welcome as I am running out of ideas!!
Cheers
Adrian
Thanks guys
Lots and lots of money has been spent on this car and lots of things have been replaced. I believe that includes the fuel pump and filter. You're right that it probably merits another filter change and I also want to disconnect either end of teh fuel line running under the car and blow it through with compressed air as I do wonder whether the shaking around and generrally higher revs when you drive the thing is causing muck to be stirred up.
I wondered if anyone had come across possible half broken joints in the distributor or elsewhere that may allow idle current through but not like revving current, or something similar to that?
Cheers
Adrian
Lots and lots of money has been spent on this car and lots of things have been replaced. I believe that includes the fuel pump and filter. You're right that it probably merits another filter change and I also want to disconnect either end of teh fuel line running under the car and blow it through with compressed air as I do wonder whether the shaking around and generrally higher revs when you drive the thing is causing muck to be stirred up.
I wondered if anyone had come across possible half broken joints in the distributor or elsewhere that may allow idle current through but not like revving current, or something similar to that?
Cheers
Adrian
The quantity of current pulled through the points isn't very big, and doesn't vary according to engine speed/load. HT side of the Distributor, there have been a lot of rogue rotor arms around (black, with a rivet on the top) which allow tracking to earth. My TR6 had this issue, solved for £6 or so with a red rotor arm from Martin Jay the distributor doctor. If a condensor is on the way out, then it will run a bit rough, but it will run.
I would check the fuel filter, any corrosion or gummed up rubbish in the fuel tank will have found its way in there, and if you have a Bosch pump, they aren't the best at drawing fuel. Most Bosch kits sold will have a pre and a post filter, with the pump between.
You could always see that 100psi or so is arriving at the metering unit. Im assuming that you have Lucas PI and not carbs?
I would check the fuel filter, any corrosion or gummed up rubbish in the fuel tank will have found its way in there, and if you have a Bosch pump, they aren't the best at drawing fuel. Most Bosch kits sold will have a pre and a post filter, with the pump between.
You could always see that 100psi or so is arriving at the metering unit. Im assuming that you have Lucas PI and not carbs?
Right I have had another look at it.
I did drain all teh fuel out and the tank looked fine. However, I shall replace the fuel fileter as this is low cost and can't do any harm!
I also blew the fuel pipe through which runs under the car and although there were a few bits of debris there was nothing significant. Certainly nothing that would cause the ongoing problems.
A friend of a friend had suggested fuel injectors. I don't know much about these so thought I would remove each of them and investigate. 5 of them had teh same code number on them (73125 I think!!) and were gold passivated finish. The sixth one was black anodised and had no code number. It also looked subtley different at the needle end.
There was also another injector which had no needle at the end of it. Whether it had broken off or never been there I don't know.
The other thing which I wondered about was with regard to the fitting of the injectors into the inlet manifold. They fit into a nylon boss which is sealed into teh inlet manifold with an 'O' ring. Now 3 of the injectors were such a tight fit in the nylon boss that when I pulled the injector out of the inlet manifold it bought the boss with it. One of them was not such a tight fit so that although it pulled the boss out it easily came out the nylon boss when pulled. But the remaining 2 just pulled straight out of the nylon boss, leaving teh boss in the inlet manifold. I am wondering whether under load excess air is being drawn into the engine via the gap down the sides of these injectors. I'm not sure if this is likely or would cause the symptons the car has, but it didn't seem right. Any thoughts? I can only imagine that as the nylon boss has an 'O' ring to seal it to the inlet manifold there should be a similarly air-tight fit between the injector and boss.
Also, for information the car has a Bosch fuel pump fitted.
I am thinking that I sould get the injectors tested and I believe there is somewhere in Portsmouth. Any thoughts on this aswell?
Cheers
Adrian
I did drain all teh fuel out and the tank looked fine. However, I shall replace the fuel fileter as this is low cost and can't do any harm!
I also blew the fuel pipe through which runs under the car and although there were a few bits of debris there was nothing significant. Certainly nothing that would cause the ongoing problems.
A friend of a friend had suggested fuel injectors. I don't know much about these so thought I would remove each of them and investigate. 5 of them had teh same code number on them (73125 I think!!) and were gold passivated finish. The sixth one was black anodised and had no code number. It also looked subtley different at the needle end.
There was also another injector which had no needle at the end of it. Whether it had broken off or never been there I don't know.
The other thing which I wondered about was with regard to the fitting of the injectors into the inlet manifold. They fit into a nylon boss which is sealed into teh inlet manifold with an 'O' ring. Now 3 of the injectors were such a tight fit in the nylon boss that when I pulled the injector out of the inlet manifold it bought the boss with it. One of them was not such a tight fit so that although it pulled the boss out it easily came out the nylon boss when pulled. But the remaining 2 just pulled straight out of the nylon boss, leaving teh boss in the inlet manifold. I am wondering whether under load excess air is being drawn into the engine via the gap down the sides of these injectors. I'm not sure if this is likely or would cause the symptons the car has, but it didn't seem right. Any thoughts? I can only imagine that as the nylon boss has an 'O' ring to seal it to the inlet manifold there should be a similarly air-tight fit between the injector and boss.
Also, for information the car has a Bosch fuel pump fitted.
I am thinking that I sould get the injectors tested and I believe there is somewhere in Portsmouth. Any thoughts on this aswell?
Cheers
Adrian
Look for a rivet on the top of the rotor arm holding the copper contact in place. If its there, then you might have a dud rotor arm.
The O rings on the injector bushes are easy to inspect, and if you suspect them, then just smear them with grease to provide a temporary seal, it should work for long enough to point you in that direction if there is a problem, but unless they are obvously knackered, they should be OK, generally problems in the manifold vac area lead to crap tickover.
Ive just been through all this with my TR6, turned out to be a dud injector with mine.
You can feel a pressure pulse in the injector plastic pipes when they are working properly, so if they are all pulsing, then they must be bled and functioning, pulling them out with the engine running should show a nice spray cone of fuel, but mind the hot exhaust manifold!
The injectors are sometimes different, some have pips on and some don't, I wouldn't worry about a mixture, providing they all open with the same pressure behind the valve.
A recon set of injectors can be had for as little as £60 from ebay.
The O rings on the injector bushes are easy to inspect, and if you suspect them, then just smear them with grease to provide a temporary seal, it should work for long enough to point you in that direction if there is a problem, but unless they are obvously knackered, they should be OK, generally problems in the manifold vac area lead to crap tickover.
Ive just been through all this with my TR6, turned out to be a dud injector with mine.
You can feel a pressure pulse in the injector plastic pipes when they are working properly, so if they are all pulsing, then they must be bled and functioning, pulling them out with the engine running should show a nice spray cone of fuel, but mind the hot exhaust manifold!
The injectors are sometimes different, some have pips on and some don't, I wouldn't worry about a mixture, providing they all open with the same pressure behind the valve.
A recon set of injectors can be had for as little as £60 from ebay.
You can test your injectors by using a pressure guage, and a pipe fitting to screw the injector into, and using a foot pump to pressurise the fuel inlet side of the injector, I forget the precise figure but about 50psi is about right before the valve on the end opens.
The injectors come apart with a small grub screw inside, accessed from under the nut where the pipe fits, then tap out the inner part of the injector with its spring and O ring. Its also possible to adjust the pressure that they open at by changing the preload on the spring.
You can buy new kits of seals to recon your own injectors.
It might be beneficial to check the synchronisation of the throttle butterflies also, and you can do this with a set of motorcycle vacuum guages and a little ingenuity, but the easiest way is to pull the plenum chamber off the throttle bodies, and look down the inlets and then put a 2 thou feeler guage into each of the chokes under the butterfly, then adjust till they are all the same.
I think it might be a dud rotor arm though.
:
The injectors come apart with a small grub screw inside, accessed from under the nut where the pipe fits, then tap out the inner part of the injector with its spring and O ring. Its also possible to adjust the pressure that they open at by changing the preload on the spring.
You can buy new kits of seals to recon your own injectors.
It might be beneficial to check the synchronisation of the throttle butterflies also, and you can do this with a set of motorcycle vacuum guages and a little ingenuity, but the easiest way is to pull the plenum chamber off the throttle bodies, and look down the inlets and then put a 2 thou feeler guage into each of the chokes under the butterfly, then adjust till they are all the same.
I think it might be a dud rotor arm though.
:Edited by Chewykneeslider on Sunday 9th June 17:46
My concern with the injectors wasn't so much the 'O' rings as much as the hole where the injector goes in. The tolerance here seems to vary and i am wondering whether it might be getting worse when the engine heats up. That said, the engine will tickover and rev on the drive for ever and a day. It is only when it is driven and the engine is under more load.
If there is an 'O' ring on the outside of that nylon boss then it is to prevent air/fluid leakage. Therefore the same should be the case around the injector.
The rotor arm is black but the top connection doesn't have a rivet holding it in place. Did that issue occur when driving aswell? Or just a constant problem? To save time I shall probably get my friend to take the injectors to be tested. I could set myself up to do it but I am working on this car as a favour and with limited time!! Quite fun though!
Cheers
Adrian
If there is an 'O' ring on the outside of that nylon boss then it is to prevent air/fluid leakage. Therefore the same should be the case around the injector.
The rotor arm is black but the top connection doesn't have a rivet holding it in place. Did that issue occur when driving aswell? Or just a constant problem? To save time I shall probably get my friend to take the injectors to be tested. I could set myself up to do it but I am working on this car as a favour and with limited time!! Quite fun though!
Cheers
Adrian
Some cars have a ballast resistor, some don't. Mine doesn't... Because I've never seen one, I can't tell you what its supposed to do!
I spent ages trying to chase down my misfire, give me a pair of carbs to play with any day.
You could try hotwiring the coil by just taking a 12v supply to the coil, that would sort out wether or not the ignition circuit is playing up?
Is the timing correct? I run 12°btdc static, is it advancing? The advance bobweights have been known to be a bit sticky.
The injectors fit tightly into the nylon bushes, so should seal like that without needing an additional O ring. I still don't think that is your issue though.
Have you tried measuring the resistance of the primary side of the coil?
I spent ages trying to chase down my misfire, give me a pair of carbs to play with any day.
You could try hotwiring the coil by just taking a 12v supply to the coil, that would sort out wether or not the ignition circuit is playing up?
Is the timing correct? I run 12°btdc static, is it advancing? The advance bobweights have been known to be a bit sticky.
The injectors fit tightly into the nylon bushes, so should seal like that without needing an additional O ring. I still don't think that is your issue though.
Have you tried measuring the resistance of the primary side of the coil?
I need to get my Megger tester to test the coil primary because my standard tester isn't accurate enough. I will do that.
I checked the ignition timing to find that it was consistent and lined up with a tippex mark that someone had put on the crank pulley and when the engine was warmer and happend to be idling a bit faster (after we had got back from a drive and encountered the problem again) it had advanced. So I assume that is OK. Not a specific test and I may need to be more thorough but it seemed to indicate all OK.
Where are the bob weights? In the dizzy?
As far as the injectors were concerned I thought I would fit and 'O' ring under the injector clamp around where the injector goes in. That would seal it, even if not a long term fix! As I said, not all the injectors are a tight fit in the bushes and one of them can even be moved when teh clamp is tight!!!
The engine has a fast road cam, so idle is not as smooth as it might be, but it is consistent and in line with what I woudl expect from that kind of cam.
A.
I checked the ignition timing to find that it was consistent and lined up with a tippex mark that someone had put on the crank pulley and when the engine was warmer and happend to be idling a bit faster (after we had got back from a drive and encountered the problem again) it had advanced. So I assume that is OK. Not a specific test and I may need to be more thorough but it seemed to indicate all OK.
Where are the bob weights? In the dizzy?
As far as the injectors were concerned I thought I would fit and 'O' ring under the injector clamp around where the injector goes in. That would seal it, even if not a long term fix! As I said, not all the injectors are a tight fit in the bushes and one of them can even be moved when teh clamp is tight!!!
The engine has a fast road cam, so idle is not as smooth as it might be, but it is consistent and in line with what I woudl expect from that kind of cam.
A.
The OE cams are quite wild anyway, with loads of overlap, so maybe a performance cam is a step too far?
I think that specialists recommend recalibrating the metering unit to cope with the performance cam...
Bobweights fling out centrifugally when the engine revs, and they are under the baseplate the points are bolted to in the distributor.
You can check the advance with a strobe, and pull the rotor arm around to advance the system to check its not stuck.
I wonder if anyone else is going to contribute? Heheh!
I think that specialists recommend recalibrating the metering unit to cope with the performance cam...
Bobweights fling out centrifugally when the engine revs, and they are under the baseplate the points are bolted to in the distributor.
You can check the advance with a strobe, and pull the rotor arm around to advance the system to check its not stuck.
I wonder if anyone else is going to contribute? Heheh!
Yes, you have done pretty well!!!!
I know what you mean by bob weights now.
I will check the timing again both before taking the car for a run and afterwards. Not sure what the advance should be for this cam but I'll work to your 12 deg BTDC for a start and see where we go from there.
I still don't think that injector fit is right so I will have a look at sealing the possible gap.
My friend is going to get me insured on the car so it will be easier to check thinkgs out that way.
A.
I know what you mean by bob weights now.
I will check the timing again both before taking the car for a run and afterwards. Not sure what the advance should be for this cam but I'll work to your 12 deg BTDC for a start and see where we go from there.
I still don't think that injector fit is right so I will have a look at sealing the possible gap.
My friend is going to get me insured on the car so it will be easier to check thinkgs out that way.
A.
I will have to check that, thanks.
I was looking at getting a replacement rotor arm. But I'm having trouble identifying what type of dizzy it is. It doesn't have a vacuum unit on the side like the Lucas ones shown on the Rimmer. What it does have is a knurled nut on the side marked up 'AR', which I assume is advance/retard.
My plan now is to replace the rotor arm and contacts, check the bob weights and check/blow through the fuel vent. I also want to check out the injectors. The place I thought would test them for me only deals in diesels, so I will have to rig something up.
I added an 'O' ring to try to seal the injectors which were loose in their nylon boss this evening. 2 out of 3 sealed fine and when i got back after a drive (yes, my friend has got me insured!!) the 3rd of the injectors was leaking. A bit scary considering the exhaust manifold is just below!!!!! So that needs sorting tomorrow!
A.
I was looking at getting a replacement rotor arm. But I'm having trouble identifying what type of dizzy it is. It doesn't have a vacuum unit on the side like the Lucas ones shown on the Rimmer. What it does have is a knurled nut on the side marked up 'AR', which I assume is advance/retard.
My plan now is to replace the rotor arm and contacts, check the bob weights and check/blow through the fuel vent. I also want to check out the injectors. The place I thought would test them for me only deals in diesels, so I will have to rig something up.
I added an 'O' ring to try to seal the injectors which were loose in their nylon boss this evening. 2 out of 3 sealed fine and when i got back after a drive (yes, my friend has got me insured!!) the 3rd of the injectors was leaking. A bit scary considering the exhaust manifold is just below!!!!! So that needs sorting tomorrow!
A.
I will have to check that, thanks.
I was looking at getting a replacement rotor arm. But I'm having trouble identifying what type of dizzy it is. It doesn't have a vacuum unit on the side like the Lucas ones shown on the Rimmer. What it does have is a knurled nut on the side marked up 'AR', which I assume is advance/retard.
My plan now is to replace the rotor arm and contacts, check the bob weights and check/blow through the fuel vent. I also want to check out the injectors. The place I thought would test them for me only deals in diesels, so I will have to rig something up.
I added an 'O' ring to try to seal the injectors which were loose in their nylon boss this evening. 2 out of 3 sealed fine and when i got back after a drive (yes, my friend has got me insured!!) the 3rd of the injectors was leaking. A bit scary considering the exhaust manifold is just below!!!!! So that needs sorting tomorrow!
A.
I was looking at getting a replacement rotor arm. But I'm having trouble identifying what type of dizzy it is. It doesn't have a vacuum unit on the side like the Lucas ones shown on the Rimmer. What it does have is a knurled nut on the side marked up 'AR', which I assume is advance/retard.
My plan now is to replace the rotor arm and contacts, check the bob weights and check/blow through the fuel vent. I also want to check out the injectors. The place I thought would test them for me only deals in diesels, so I will have to rig something up.
I added an 'O' ring to try to seal the injectors which were loose in their nylon boss this evening. 2 out of 3 sealed fine and when i got back after a drive (yes, my friend has got me insured!!) the 3rd of the injectors was leaking. A bit scary considering the exhaust manifold is just below!!!!! So that needs sorting tomorrow!
A.
Two suggestions not mentioned yet, both from experience.
1/ The choke lever on the metering unit. If it is even slightly pulled open, the car will reproduce your symptoms. Foxed me for months, when the cable was kinked in the outer and didn't shut.
2/ Fuel pressure. Pi has critical need for at least 100psi. Any less will do what you are experiencing. Mine was due to faulty fuel filter, again difficult to spot. Can you check Fuel pressure? There are expensive guages on sale, but an oil pressure gauge and a T-piece will do the job. Insert a damping orifice in the line to suppress the pulses from the pump, which will oscillate the needle off the gauge! Piece of copper from central heating pipe, flattened and with the smallest hole you can drill thorught the middle will do it, in one of the connectors to the gauge.
JOhn
1/ The choke lever on the metering unit. If it is even slightly pulled open, the car will reproduce your symptoms. Foxed me for months, when the cable was kinked in the outer and didn't shut.
2/ Fuel pressure. Pi has critical need for at least 100psi. Any less will do what you are experiencing. Mine was due to faulty fuel filter, again difficult to spot. Can you check Fuel pressure? There are expensive guages on sale, but an oil pressure gauge and a T-piece will do the job. Insert a damping orifice in the line to suppress the pulses from the pump, which will oscillate the needle off the gauge! Piece of copper from central heating pipe, flattened and with the smallest hole you can drill thorught the middle will do it, in one of the connectors to the gauge.
JOhn
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