Ignition Amplifier - Recurring Fault
Discussion
Ok you lot out there, I need help!!!
I've had a '98 Chimp 500 for over 2 years now to the pleasure of my ears and to the annoyance of the neighbours!!! Done a few mods over the time including carbon plenum trumpets, no pre cats and cat replacement pipe (JP exhausts)and had soooooo much fun - Until recently!!!
The ignition amp blew about 12 months ago (commonish problem) replaced it and again I was happy. It went again 3 moths later and is now going virtually everytime I take it out - The AA, RAC and Greenflag are less than impressed and so am I. Put on a new coil and done various other stuff to no avail - A well respected specialist now has it, done the diagnostic stuff and had his maechanic broken down in it.
So....come on you Pistonheaders!!!! Any ideas?????? Mike.
I've had a '98 Chimp 500 for over 2 years now to the pleasure of my ears and to the annoyance of the neighbours!!! Done a few mods over the time including carbon plenum trumpets, no pre cats and cat replacement pipe (JP exhausts)and had soooooo much fun - Until recently!!!
The ignition amp blew about 12 months ago (commonish problem) replaced it and again I was happy. It went again 3 moths later and is now going virtually everytime I take it out - The AA, RAC and Greenflag are less than impressed and so am I. Put on a new coil and done various other stuff to no avail - A well respected specialist now has it, done the diagnostic stuff and had his maechanic broken down in it.
So....come on you Pistonheaders!!!! Any ideas?????? Mike.
biglump said:
Ok you lot out there, I need help!!!
biglump said:
A well respected specialist now has it
I think it was very sensible to get a specialist to sort it out, no doubt they'll soon get to the bottom of it. Why do you need our help, you planning to take it back and fix it yourself?
>> Edited by GreenV8S on Wednesday 8th December 20:41
Thinking out loud, what the amplifier does it take a low power signal from the pickup inside the distributor, and short the -ve side of the coil to earth (sinking several amps in the process) and then un-short it (which gives it one heck of an inductive jolt).
Different coils take different amounts of current. If you have the wrong spec coil, or the right spec but without a ballast resister when it is designed to use one, then it will take too much current which could overheat the ignition module.
You can get different spec ignition modules too. For example RPI do a high current version designed to cope with very long dwell angles at low rpm without overheating. If you are fitting the wrong spec amplifier, it might not be able to handle the current.
The ignition module puts out a lot of heat, which it dissipates by being bolted hard onto a big lump of metal. If it's not mounted properly it could overheat.
The ignition module does its thing each time the pickup pulses. If there was a fault with the pickup, or a wiring fault between it and the ignition module, the module might see a series of weak pulses instead of one single strong one. That might trigger it to fire multiple times, which would produce a cr@p spark and also put out more heat.
The common theme here is that things that blow up the ignition module cause overheating. You could monitor the external temperature of the module to see whether or not it is obviously overheating. (If it is just an internal component giving up the heat may not be enough to be obvious, but if you do feel the whole thing heating up more than normal this is a clue that the problem is caused by overloading.)
I would check for obvious overheating, chop one of the failed units open and see whether there is any obviously blown component to suggest overloading, check the current it is taking from the coil, put a scope on the inputs and outputs and see whether it is getting a clean signal and whether the dwell angle looks right (i.e. compared to other healthy cars).
This is probably a bit out of reach of the average DIYer but a professional mechanic should be able to take this sort of stuff in his stride.
Different coils take different amounts of current. If you have the wrong spec coil, or the right spec but without a ballast resister when it is designed to use one, then it will take too much current which could overheat the ignition module.
You can get different spec ignition modules too. For example RPI do a high current version designed to cope with very long dwell angles at low rpm without overheating. If you are fitting the wrong spec amplifier, it might not be able to handle the current.
The ignition module puts out a lot of heat, which it dissipates by being bolted hard onto a big lump of metal. If it's not mounted properly it could overheat.
The ignition module does its thing each time the pickup pulses. If there was a fault with the pickup, or a wiring fault between it and the ignition module, the module might see a series of weak pulses instead of one single strong one. That might trigger it to fire multiple times, which would produce a cr@p spark and also put out more heat.
The common theme here is that things that blow up the ignition module cause overheating. You could monitor the external temperature of the module to see whether or not it is obviously overheating. (If it is just an internal component giving up the heat may not be enough to be obvious, but if you do feel the whole thing heating up more than normal this is a clue that the problem is caused by overloading.)
I would check for obvious overheating, chop one of the failed units open and see whether there is any obviously blown component to suggest overloading, check the current it is taking from the coil, put a scope on the inputs and outputs and see whether it is getting a clean signal and whether the dwell angle looks right (i.e. compared to other healthy cars).
This is probably a bit out of reach of the average DIYer but a professional mechanic should be able to take this sort of stuff in his stride.
Hi Biglump, mine did this, called the AA 5 times in 3 months, broke down on way back from garage that allegedly fixed it.
What are the symptoms - is it running fine for a while then just cutting dead with an electrical fault, no spark, not starting?
This was what mine was doing, a multimeter whizz found a signal reaching the ignition amplifier but nowt coming out.
The ignition amplifier is mounted on a small ally backplate. This backplate has various 2 and 3 pin connectors on it, with short bits of wire linking components including coil and distributor.
We EVENTUALLY found (12.00 midnight in a remote pub car park, thank you Captain Sideways and Wildeep) that one of these short bits of wire had broken inside its insulation, just where it met the top of the black 3-pin connnector (which only uses 2 of the connections, btw).
So the broken wire was still more or less held together by its insulation, every time someone pulled the connector apart to test it the wire touched inside the insulation and it worked, every time someone swapped a component they were inadvertantly wiggling the relevant wire and it worked. Then over the next 100 miles the vibration parted the wire inside its insulation, the engine cut until someone started wiggling again.
So my suggestion is borrow a ignition amplifier complete with backplate and associated short wires and connectors off a car known to work. Put it on your car. If it runs, substitute one of your supposedly faulty ignition modules, keeping the donor backplate and wiring. If it still works, it's the wiring or connectors on your backplate, like mine.
"mine" is a '99 500, with the ignition module mounted away from the distributor near the coil, don't know if all the details are exactly the same on yours.
Good luck, Dean.
>> Edited by deeen on Thursday 9th December 11:15
What are the symptoms - is it running fine for a while then just cutting dead with an electrical fault, no spark, not starting?
This was what mine was doing, a multimeter whizz found a signal reaching the ignition amplifier but nowt coming out.
The ignition amplifier is mounted on a small ally backplate. This backplate has various 2 and 3 pin connectors on it, with short bits of wire linking components including coil and distributor.
We EVENTUALLY found (12.00 midnight in a remote pub car park, thank you Captain Sideways and Wildeep) that one of these short bits of wire had broken inside its insulation, just where it met the top of the black 3-pin connnector (which only uses 2 of the connections, btw).
So the broken wire was still more or less held together by its insulation, every time someone pulled the connector apart to test it the wire touched inside the insulation and it worked, every time someone swapped a component they were inadvertantly wiggling the relevant wire and it worked. Then over the next 100 miles the vibration parted the wire inside its insulation, the engine cut until someone started wiggling again.
So my suggestion is borrow a ignition amplifier complete with backplate and associated short wires and connectors off a car known to work. Put it on your car. If it runs, substitute one of your supposedly faulty ignition modules, keeping the donor backplate and wiring. If it still works, it's the wiring or connectors on your backplate, like mine.
"mine" is a '99 500, with the ignition module mounted away from the distributor near the coil, don't know if all the details are exactly the same on yours.
Good luck, Dean.
>> Edited by deeen on Thursday 9th December 11:15
I also hope that it is a genuine Lucas part as all the pattern ones have lifetimes less than a few minutes. They are simply not up to the job.
Steve
www.tvrbooks.co.uk
Steve
www.tvrbooks.co.uk
GreenV8S said:
I would check for obvious overheating, chop one of the failed units open and see whether there is any obviously blown component to suggest overloading
Danger Will Robinson....
I wouldn't chop one open as the components inside usually use beryllium based compounds as part of the heat sink and this stuff is nasty. Perfectly safe in its package but a real H&S issue if the package is opened up.
If it's not a broken wire as Deeeeen suggests (Hi Deeeen, must do that Cotswold run again sometime), then it could either be too much current and overheating (as some bright spark above suggested), or a voltage spike (which could cause a bright spark - poor attempt at a joke)which could be killing an electronic component. It may be that the high tension voltage is tracking from the coil central lead to the coil -ve, or it could be getting onto the -ve by inductance, for example if one of the HT leads is routed close to the -ve. You would see this if you attached a scope to the -ve (and earth of course). You may even be able to see this as a dull blue flashing if you look closely while the engine is running on a very dark night.
Just a thought. Hope you find the problem soon.
Steve
Just a thought. Hope you find the problem soon.
Steve
I replaced mine a few weeks ago and getting hold of a Lucas one was quite tricky as Lucas have stopped trading 
Managed to find one at an old skool car auto parts place though, but it was definatly old stock, having a build date of 1999 on it
it all seems to be working fine though, and as has been said don't forget the heat sink paste, mine came with some in the box 
Managed to find one at an old skool car auto parts place though, but it was definatly old stock, having a build date of 1999 on it
it all seems to be working fine though, and as has been said don't forget the heat sink paste, mine came with some in the box Blimey, what can I say! I'm speaking to the "respected specialist" tomorrow so hopefully the brute will be up and running again soon - To answer a couple of the queries, yes I've used the heat greasy stuff and the coil was replaced by the garage which got it running again and then it conked so the amplifier was replaced.
My gut feeling (and it ain;t the morning after a madras feeling) is that is could be the lead to the amplifier that goes through the metal plate - It's a 2 point connector from memory so me thinks I'll get one of those if they seem to perish!!!! Pennies are running low!!!!! Thanks again me ol' muckers and I'll be sure to keep you all posted!!!!
My gut feeling (and it ain;t the morning after a madras feeling) is that is could be the lead to the amplifier that goes through the metal plate - It's a 2 point connector from memory so me thinks I'll get one of those if they seem to perish!!!! Pennies are running low!!!!! Thanks again me ol' muckers and I'll be sure to keep you all posted!!!!
Hurrah,
After what seems an eternity, got the beast back the other day and all seems well. Was tracked down to a dodgy connectin on the coil which fed the ecu to tell to to open the injectors ready for the next spark. Apparently, the ecu wasn't reeiving a return signal so engine fueling shut down!!! So....sounds a bit unlikely but it's working again!!!!!!
After what seems an eternity, got the beast back the other day and all seems well. Was tracked down to a dodgy connectin on the coil which fed the ecu to tell to to open the injectors ready for the next spark. Apparently, the ecu wasn't reeiving a return signal so engine fueling shut down!!! So....sounds a bit unlikely but it's working again!!!!!!
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