Ignition Amp Woes
Discussion
Imagine a month after a 12k service, car singing and dancing for a few hundred miles, the car suddenly cuts out at a junction and has no spark...
So yep, definite failure of the ignition amp, OEM Lucas, suspect original to the car ('96), 81,000km (52~k miles). Cool. Bought a new one from a main dealer although without any sort of Lucas badge on it. Car fires right up. Excellent I thought. I give it a few revs, and it sounds well. I start packing my tools away, and it suddenly cuts out, just like at the junction.
Being close to a generic auto part shop, I got a compatible replacement - a CAMBIARE VE520236 - and sure enough, the car fires up and sounds healthy for a few minutes, then flat out cuts out. Again, no spark from the king lead, never mind the plugs.
Just done a continuity test of the wiring on the remote mount kit and that seems fine, I replaced the ground strap under precaution but seems healthy enough.
First car with a distributor so please bear with me.... Is there a possibility of something in the distributor causing these sudden ignition amp failures? I know they're not Lucas replacements but it seems absolutely bizarre that 3 ignition amps have failed with exactly the same failure mode within 24 hours?
tested immobiliser to be ok
So yep, definite failure of the ignition amp, OEM Lucas, suspect original to the car ('96), 81,000km (52~k miles). Cool. Bought a new one from a main dealer although without any sort of Lucas badge on it. Car fires right up. Excellent I thought. I give it a few revs, and it sounds well. I start packing my tools away, and it suddenly cuts out, just like at the junction.
Being close to a generic auto part shop, I got a compatible replacement - a CAMBIARE VE520236 - and sure enough, the car fires up and sounds healthy for a few minutes, then flat out cuts out. Again, no spark from the king lead, never mind the plugs.
Just done a continuity test of the wiring on the remote mount kit and that seems fine, I replaced the ground strap under precaution but seems healthy enough.
First car with a distributor so please bear with me.... Is there a possibility of something in the distributor causing these sudden ignition amp failures? I know they're not Lucas replacements but it seems absolutely bizarre that 3 ignition amps have failed with exactly the same failure mode within 24 hours?
tested immobiliser to be ok
They are known for being poor quality these days but should last longer than that.
if the coil is correct then I’d be checking for a poor connection somewhere leading to it overheating, the wiring here is a real mess.
If you have mounted it using the heat sink paste then you can’t do much more, I believe the plate it’s mounted on needs to have a good ground too for correct operation.
if the coil is correct then I’d be checking for a poor connection somewhere leading to it overheating, the wiring here is a real mess.
If you have mounted it using the heat sink paste then you can’t do much more, I believe the plate it’s mounted on needs to have a good ground too for correct operation.
Wiring seems to be ok when I play monkey with a meter, but the ignition amps are definitely toast having battery voltage solidly through the trigger side when tested on a bench. I have just ordered a replacement cap, rotor arm and Lucas amp from Powerspark hopefully to come Tuesday to try and revive the car with, with a view to finding some Lucas bits to keep in my touring bag. Looking through the service history since the car was imported in 2018, haven't seen any of the above replaced and it just seemed to be plugs on my 12,000. Hoping it's something silly like worn rotor arm or dirty cap causing excessive stress on the amp. I don't have a feeler gauge to test, not sure what the specs are and my Chim is still at my friend's house. I think they were tested fine in 2017 according to the Japanese service history but that's the last I've read of it - no clear evidence it was replaced.
Coil: I have tested 2. The car had one on already, not sure what it was but seemed to work, didn't bother looking. Could be original? Replaced it with a Bosch one for good measure anyway, acquired from the dealer.
So in short, let's see how long it lasts with a distributor cap, rotor arm, Lucas amp and some fresh land rover HT leads. Should I replace the ceramic socks or are they fine to reuse (I don't have plug extenders thank goodness)?
Coil: I have tested 2. The car had one on already, not sure what it was but seemed to work, didn't bother looking. Could be original? Replaced it with a Bosch one for good measure anyway, acquired from the dealer.
So in short, let's see how long it lasts with a distributor cap, rotor arm, Lucas amp and some fresh land rover HT leads. Should I replace the ceramic socks or are they fine to reuse (I don't have plug extenders thank goodness)?
Edited by geordiepingu on Saturday 24th April 14:15
The secondary HT circuits will affect the primary ringing voltage the amp sees - I know for sure low resistance in the HT lines causes the voltage to go up in the primary as Ive blown up things trying copper HT leads, but I've also been told an open circuit secondary has the same effect as the HT voltages rise to a much higher level that also spikes the primary. Shorts in the amp semiconductors are likely to be an overvoltage ringing spike breaking down the semiconductor junction, or possibly over current in the coil primary.
Penelope Stopit said:
No, nothing in the dizzy will blow the amp
As you know, short on wiring or wrong coil voltage will
Thank you for the sanity check. Your post prompted me to play monkey with the ignition amp unplugged, and sure enough the ground from the coil has a decent amount of resistance on it. In other words, cool seems to have been grounding through the ignition amp. No wonder it’s been blowing them. Thanks for the prompt of me to not be a moron!As you know, short on wiring or wrong coil voltage will
blitzracing said:
The secondary HT circuits will affect the primary ringing voltage the amp sees - I know for sure low resistance in the HT lines causes the voltage to go up in the primary as Ive blown up things trying copper HT leads, but I've also been told an open circuit secondary has the same effect as the HT voltages rise to a much higher level that also spikes the primary. Shorts in the amp semiconductors are likely to be an overvoltage ringing spike breaking down the semiconductor junction, or possibly over current in the coil primary.
So it would still be wise to replace the cap and rotor anyway if they are original? The problem is that most of the caps and rotors etc around are complete junk these days, even the stuff branded as original Lucas.
The stuff I had from power spark was no different.
The distributor doctor is supposed to be ok for rotors, not sure if they sell caps.
I have 2 original Lucas resistors here your welcome to foc, one measures 6.9 k and the other 7.3 k.
Pm me if you want them although I doubt they are your problem as one is for the Rev counter and the other to stop ecu spikes (from memory)
The stuff I had from power spark was no different.
The distributor doctor is supposed to be ok for rotors, not sure if they sell caps.
I have 2 original Lucas resistors here your welcome to foc, one measures 6.9 k and the other 7.3 k.
Pm me if you want them although I doubt they are your problem as one is for the Rev counter and the other to stop ecu spikes (from memory)
Belle427 said:
The problem is that most of the caps and rotors etc around are complete junk these days, even the stuff branded as original Lucas.
The stuff I had from power spark was no different.
The distributor doctor is supposed to be ok for rotors, not sure if they sell caps.
I have 2 original Lucas resistors here your welcome to foc, one measures 6.9 k and the other 7.3 k.
Pm me if you want them although I doubt they are your problem as one is for the Rev counter and the other to stop ecu spikes (from memory)
Thank you kindly for the offer - but keep them for someone who really needs them in that case - tacho and ECU still work The stuff I had from power spark was no different.
The distributor doctor is supposed to be ok for rotors, not sure if they sell caps.
I have 2 original Lucas resistors here your welcome to foc, one measures 6.9 k and the other 7.3 k.
Pm me if you want them although I doubt they are your problem as one is for the Rev counter and the other to stop ecu spikes (from memory)
Will keep that in mind and probably keep the cap and rotor on for now. I'd like to think that if it was really bad the dealer would have noticed and replaced. Hopefully a 1k ohm ground is the real smoking gun here.
is this the 3.9i running the 14CUX EFI? If so, I had a similar issue (although not repeatedly) with that engine in my Defender not so long ago. I ended up replacing everything except the distributor itself (coil, arm, cap, leads, amp) but specifically I also replaced all of the low-tension wiring, including new crimps, and then it ran again. I suspect there was a break or other fault/bad connection in the LT wires themselves.
geordiepingu said:
Penelope Stopit said:
No, nothing in the dizzy will blow the amp
As you know, short on wiring or wrong coil voltage will
Thank you for the sanity check. Your post prompted me to play monkey with the ignition amp unplugged, and sure enough the ground from the coil has a decent amount of resistance on it. In other words, cool seems to have been grounding through the ignition amp. No wonder it’s been blowing them. Thanks for the prompt of me to not be a moron!As you know, short on wiring or wrong coil voltage will
geordiepingu said:
Hopefully a 1k ohm ground is the real smoking gun here.
With the ignition coil disconnectedIf you're seeing that the amplifier to coil negative switching cable is down to ground (1K Ohm), this is a problem but it won't cause the amplifier to blow
The amplifier to coil negative switching cable would have to be shorting to positive to blow the amplifier
Sanity check- disconnect the -ve of the coil and do the ground check. There are three connections to the coil as even through there are two coils inside with 4 connections, so the secondary and primary are joined at one end and fed to the negative side of the coil, so your 1k resistance could (?) be through the HT coil back into the ignition circuit. Easier to do the tests with all wires disconnected. This diagram is points, but you can substitute this with the amp.
Edited by blitzracing on Sunday 25th April 10:50
That’s what I did, completely disconnected the LT side and did a continuity check. Ground is fubar. Strap to plenum for now awaiting for a new amp. Radio is isolated by a separate suppressor so not too concerned, would rather not disturb the entire loom until I have the rest of my standalone system ready
Fixed all of the connectors and gave them a clean, repaired the wiring and replaced the cap and rotor. Sure enough the cap and rotor seemed to be in a miserable state - lots of corrosion on the terminals, definitely original Lucas items. Right now I've got the cheap Powerspark replacements on with Land Rover leads, I'll endeavour to get hold of a cap and rotor from Dr Distributor.
Car was a bit spluttery and found #5 a bit fouled, Cat overheat light kept flickering and the fuel trims from the odd bank on my built in rovergauge were ridiculous. Cleaned it and it was singing. Going to replace the plugs anyway as a precautionary and replace some of the ceramic socks, but looking great so far! 8 plugs for £13 online, not bad at all. I'm aware there are tricks to recover plugs but at £13 for new plugs, why would you cheap out?
Back in my garage now and certainly elated for it. Thanks all for your help.
P.S @Blitz/Mark, I do follow the theory that the resistance on the HT side from worn/corroded cap and rotor arm contributed to this. I'll try and remember to post pictures but they looked past their best to me. More reason for me to get around to finishing my standalone loom and converting over to fully sequential ignition and injection... but maybe that's a next summer problem. Thanks again for your RoverGauge cable - came in handy for identifying the missing plug!
Car was a bit spluttery and found #5 a bit fouled, Cat overheat light kept flickering and the fuel trims from the odd bank on my built in rovergauge were ridiculous. Cleaned it and it was singing. Going to replace the plugs anyway as a precautionary and replace some of the ceramic socks, but looking great so far! 8 plugs for £13 online, not bad at all. I'm aware there are tricks to recover plugs but at £13 for new plugs, why would you cheap out?
Back in my garage now and certainly elated for it. Thanks all for your help.
P.S @Blitz/Mark, I do follow the theory that the resistance on the HT side from worn/corroded cap and rotor arm contributed to this. I'll try and remember to post pictures but they looked past their best to me. More reason for me to get around to finishing my standalone loom and converting over to fully sequential ignition and injection... but maybe that's a next summer problem. Thanks again for your RoverGauge cable - came in handy for identifying the missing plug!
Belle427 said:
The problem is that most of the caps and rotors etc around are complete junk these days, even the stuff branded as original Lucas.
The stuff I had from power spark was no different.
The distributor doctor is supposed to be ok for rotors, not sure if they sell caps.
I have 2 original Lucas resistors here your welcome to foc, one measures 6.9 k and the other 7.3 k.
Pm me if you want them although I doubt they are your problem as one is for the Rev counter and the other to stop ecu spikes (from memory)
Could you please let me know if those resistors are meant to be both the same value for the Chimaera? Mine are both a corroded mess, have the same part number (RD953066) and measure ~6.8 kOhm. The stuff I had from power spark was no different.
The distributor doctor is supposed to be ok for rotors, not sure if they sell caps.
I have 2 original Lucas resistors here your welcome to foc, one measures 6.9 k and the other 7.3 k.
Pm me if you want them although I doubt they are your problem as one is for the Rev counter and the other to stop ecu spikes (from memory)
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