Misfiring When Warm
Discussion
Hi,
Although this is related to a recent post on electronic ignition, I think it is sufficiently different to justify a separate post.
My 2500 misfires when warmed up and is also sometimes difficult to start when warm.
The problem started a little over two years ago, on MOT day! The fault was diagnosed as no output from the coil. My MOT tester kindly replaced the coil and the problem seemed to be resolved. The car had Neutronic electronic ignition fitted at the time.
I had covered around 1000 miles since buying the car. Some journeys were long and some were taken on hot days. Up until this point there had been no ignition problems.
In January this year, I drove about 2 miles to get petrol. After putting some fuel in, the car wouldn't restart. The RAC came out and checked the car over. Again, it was established that here was no spark (some of the time) when warm. The king lead was unlpugged fron the distributor cap and held close to the rocker cover when cranking. There was power supply to the coil but no HT output. The coil was warm but not excessively hot.
The coil was fairly new so the next suspect was the electronic ignition, which was of unknown age.
I ordered and fitted a Lumenition Optronic kit - module, optical switch, coil and ballast resistor. When fitting I noticed the chopper blade was sitting too low and likely to drag against the top of the optical switch or the mounting screw. I phoned Autocar (Lumention). They asked if the distributor had been rebuilt. I don't know if it has but the chopper and optical switch from the old Neutronic system fitted correctly. Ultimately, they didn't seem too concerned about this.
I finished installing the Lumenition, started the car, tweaked the timing and the engine seemed to run OK. I let it warm up and switched off. It wouldn't restart. Both the RAC and Autocar (Lumenition) suggested running in an extra earth wire. I did this and it seemed to cure the problem.
The coil on the Triumph 2500 engine is mounted to the side of the engine block. I didn't like the idea of this so I mounted the Lumenition coil and module away from the engine.
Since then, I've driven the car a couple of miles around the block, switched off and restarted with no problems.
A few weeks ago, I took it for its first drive in a long time. After about ten miles it started to misfire. This gradually got worse resulting a major loss of power. With feathering the throttle, the car would still drive but only just. If I pressed the throttle at all, the misfire got worse and the car slowed down. It made the 10 miles or so home though.
Back home in the (dark) garage, with the engine running I looked under the bonnet. There were no sparks flying and nothing obviously wrong. The engine seemed to rev freely in neutral but was barely able to pull the car along. The coil and module were both warm but not hot.
On checking the car over (a week later), the battery voltage was 12.5. The voltage at the ballast resistor was about 11. Is a drop of about 1.5 volts after going through the loom, ignition switch and battery isolator switch about right?
I checked the battery switch on its own and it seemed to be losing about 1/3 of a volt. The output from the ballast resitor is about 5.5 volts. I hope the coil runs on 6 and not 9 volts!
The underside of the chopper blade has score marks so it's definitely been dragging against either the optical switch or the mounting screw. If it is dragging against the switch, could this raise the temperature beyond 125 celcius which is its maximum specified operating temperature?
Another possible issue could be where the thin wires from the optical switch exit the distributor cap. They are within a milimetre or two of the cylinder head. Could heat from the engine cause a problem here?
As the battery isolator switch was losing about 1/3 of a volt and it cuts the -ve supply, I thought it likely to have a detrimental effect on the earth. I bypassed the switch and took the car on the same run as a few weeks previously. This time it did the 22 miles without issue. Back in the garage I switched off and restarted it easily. It's too early to say at this stage whether I've found the problem though.
Has anyone else had heat related ignition problems? Does anyone else have a Triumph six cylinder engine with Lumenition or Neutronic ignition and a battery isolator switch?
Apologies for the length of this post.
Any ideas or suggestion swould be appreciated.
Thanks,
Chris
Although this is related to a recent post on electronic ignition, I think it is sufficiently different to justify a separate post.
My 2500 misfires when warmed up and is also sometimes difficult to start when warm.
The problem started a little over two years ago, on MOT day! The fault was diagnosed as no output from the coil. My MOT tester kindly replaced the coil and the problem seemed to be resolved. The car had Neutronic electronic ignition fitted at the time.
I had covered around 1000 miles since buying the car. Some journeys were long and some were taken on hot days. Up until this point there had been no ignition problems.
In January this year, I drove about 2 miles to get petrol. After putting some fuel in, the car wouldn't restart. The RAC came out and checked the car over. Again, it was established that here was no spark (some of the time) when warm. The king lead was unlpugged fron the distributor cap and held close to the rocker cover when cranking. There was power supply to the coil but no HT output. The coil was warm but not excessively hot.
The coil was fairly new so the next suspect was the electronic ignition, which was of unknown age.
I ordered and fitted a Lumenition Optronic kit - module, optical switch, coil and ballast resistor. When fitting I noticed the chopper blade was sitting too low and likely to drag against the top of the optical switch or the mounting screw. I phoned Autocar (Lumention). They asked if the distributor had been rebuilt. I don't know if it has but the chopper and optical switch from the old Neutronic system fitted correctly. Ultimately, they didn't seem too concerned about this.
I finished installing the Lumenition, started the car, tweaked the timing and the engine seemed to run OK. I let it warm up and switched off. It wouldn't restart. Both the RAC and Autocar (Lumenition) suggested running in an extra earth wire. I did this and it seemed to cure the problem.
The coil on the Triumph 2500 engine is mounted to the side of the engine block. I didn't like the idea of this so I mounted the Lumenition coil and module away from the engine.
Since then, I've driven the car a couple of miles around the block, switched off and restarted with no problems.
A few weeks ago, I took it for its first drive in a long time. After about ten miles it started to misfire. This gradually got worse resulting a major loss of power. With feathering the throttle, the car would still drive but only just. If I pressed the throttle at all, the misfire got worse and the car slowed down. It made the 10 miles or so home though.
Back home in the (dark) garage, with the engine running I looked under the bonnet. There were no sparks flying and nothing obviously wrong. The engine seemed to rev freely in neutral but was barely able to pull the car along. The coil and module were both warm but not hot.
On checking the car over (a week later), the battery voltage was 12.5. The voltage at the ballast resistor was about 11. Is a drop of about 1.5 volts after going through the loom, ignition switch and battery isolator switch about right?
I checked the battery switch on its own and it seemed to be losing about 1/3 of a volt. The output from the ballast resitor is about 5.5 volts. I hope the coil runs on 6 and not 9 volts!
The underside of the chopper blade has score marks so it's definitely been dragging against either the optical switch or the mounting screw. If it is dragging against the switch, could this raise the temperature beyond 125 celcius which is its maximum specified operating temperature?
Another possible issue could be where the thin wires from the optical switch exit the distributor cap. They are within a milimetre or two of the cylinder head. Could heat from the engine cause a problem here?
As the battery isolator switch was losing about 1/3 of a volt and it cuts the -ve supply, I thought it likely to have a detrimental effect on the earth. I bypassed the switch and took the car on the same run as a few weeks previously. This time it did the 22 miles without issue. Back in the garage I switched off and restarted it easily. It's too early to say at this stage whether I've found the problem though.
Has anyone else had heat related ignition problems? Does anyone else have a Triumph six cylinder engine with Lumenition or Neutronic ignition and a battery isolator switch?
Apologies for the length of this post.
Any ideas or suggestion swould be appreciated.
Thanks,
Chris
Hi,
Thanks for your reply. I appreciate the time you've taken to give such an informative response. There is a lot for me to take in and hopefully learn from in your answer.
One thing that particularly puzzles me though is if the starter draws several hundred amps and the ammeter in the car only reads between -45 and +45, how can the two work together without causing problems?
Thanks again,
Chris
Thanks for your reply. I appreciate the time you've taken to give such an informative response. There is a lot for me to take in and hopefully learn from in your answer.
One thing that particularly puzzles me though is if the starter draws several hundred amps and the ammeter in the car only reads between -45 and +45, how can the two work together without causing problems?
Thanks again,
Chris
Thanks both for the further replies.
Penelope Stopit - is it normal for the ammeter to read around -15 when cranking? I'm hoping that this is merely showing that the batttery is discharging. When the engine fires, the reading goes over to the positive for a few seconds and then settles at around 0.
I'll try to run the tests you suggested when I get a chance.
Stew - the electronic ignition is using the supply from the wiring loom (if that's what you mean). I have run an extra wire from the module earth wire to the chassis. I have also run a wire from the same point on the chassis to the battery isolator switch.
Using relays to connect to the battery and bypassing the loom might be worth considering. Similarly using points and a condensor would be an option if I can't sort this. I have read though that the quality of points is poor these days. Also it would be a shame to use points after spending £200+ on new Lumenition.
As for plugs and leads, I changed them a coupe of years ago and have only covered a small mileage since. The car completed a 22 mile run recently with the battery isolator switch bypassed and there were no issues.
Thanks again both,
Chris
Penelope Stopit - is it normal for the ammeter to read around -15 when cranking? I'm hoping that this is merely showing that the batttery is discharging. When the engine fires, the reading goes over to the positive for a few seconds and then settles at around 0.
I'll try to run the tests you suggested when I get a chance.
Stew - the electronic ignition is using the supply from the wiring loom (if that's what you mean). I have run an extra wire from the module earth wire to the chassis. I have also run a wire from the same point on the chassis to the battery isolator switch.
Using relays to connect to the battery and bypassing the loom might be worth considering. Similarly using points and a condensor would be an option if I can't sort this. I have read though that the quality of points is poor these days. Also it would be a shame to use points after spending £200+ on new Lumenition.
As for plugs and leads, I changed them a coupe of years ago and have only covered a small mileage since. The car completed a 22 mile run recently with the battery isolator switch bypassed and there were no issues.
Thanks again both,
Chris
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