Ignition Problems /Ignition Switch

[svenedin]

I have recently had a spate of ignition problems which I tend to regard as not a coincidence but which might be very bad luck.

I have never had a series of ignition problems before but of course I have had occasional faults over the years.

The one change in the car, which may be significant, is that before the ignition problems started I installed a USB charging socket. This I did by running a green wire from the fused side of the fusebox to supply a maximum 5A USB charging socket (not a cigarette lighter socket but a dedicated USB socket).

The first breakdown I already wrote about. This was on the M4 and the coil failed. The coil tested with a much higher primary resistance than the 3 ohms that it should be and was extremely hot. I changed the coil to a spare and was back on my way. Some people may have thought that was the end of it but being me, I was suspicious that the actual fault had not been rectified. I was right about that......Then no troubles for several weeks until we broke down on a roundabout in Saint Malo, France. Very embarrassing and awkward and with the bonnet up trying to fix the car a seagull relieved itself in a massive way all over me and the car (which had the top down so it went all over the interior). Again the coil was very hot but it was 35 C that day (and for many day afterwards). I changed the coil for a spare and the car ran but not very well. The engine was sluggish and didn't accelerate well. I then decided that perhaps the electronic ignition had been damaged in some way by the first coil developing a high resistance and that this might have led to the second coil overheating. I had tested the coil earth which was faultless and the ignition module earth which was also fine (in a positive earth car with electronic ignition the + terminal of the coil is connected to earth). However, the voltage at the - coil terminal with the engine running was too low at about 10 volts whereas the voltage at the ignition white wire was a healthy 12 volts. So on that basis I reverted to points and ditched the electronic ignition. That worked acceptably but the car still didn't feel right. I thought this might be a timing issue and borrowed a strobe (having tinkered with the timing without a strobe using the advance until it pinks and then retard a bit in stages until it stops pinking under load) but it made no difference. Then on the way home from the port at Portsmouth the car suddenly started to misfire (yet again) and died. I suspected the condenser and changed it and the car started immediately and we drove another 100 miles without issues.

On my return home I decided I must get to the bottom of the problem. It is all very well to say maybe I should have tested this or tested that but the priority is to get the car going as fast as possible when broken down. There is never a good place to break down it seems. I had a check of various things. Distributor rotor, cap, HT leads, all electrical connections to coil and the low tension to distributor. Measured voltages and resistances. It all seemed OK and so I thought I'll warm up the car and then I'll check the timing. Engine ran fine. I stopped the engine so that I could connect the strobe and hey presto it would not start. Lights came up on the speedo but it would not start. Cranked fast and normally. Fuel pump working fine. I used my spark plug testers and a very weak spark then no spark at all. Hmm. There was power to the coil but not enough. Finally I decided that it must be the ignition switch and I changed it for a new one and the car started immediately with much brighter speedo lights evident.

So, I have come to the conclusion that the ancient ignition switch was just about working but when I added my USB charging socket to the load on the switch it couldn't cope with it and caused all manner of problems which seemed unconnected. If an electronic ignition system gets a varying voltage from the ignition it can damage it permanently or cause an excessive coil dwell time that overheats and destroys coils.

I have left the USB socket disconnected for now but intend to wire up up via a relay so that there is minimal load on the new ignition switch. Any thoughts on this? Should I have used a relay from the very start?

Stephen

[mobylette]

I imagine you can now test the old ignition switch for high resistance etc, or perhaps dismantle it to examine the contacts.

[myoldjalopy]

"Finally I decided that it must be the ignition switch and I changed it for a new one and the car started immediately with much brighter speedo lights evident."
Or, possibly, the wire connections to the old switch were not good? But resolving the problem by swapping over switches does at least suggest the switch was at fault.Certainly the ignition switch would not be most people's first thought when encountering ignition troubles on the road! It will be interesting to see the results of testing/examining the old switch,as 'mobylette' suggests.

[svenedin]

I imagine you can now test the old ignition switch for high resistance etc, or perhaps dismantle it to examine the contacts.

Absolutely. The answer to that is that in the "run" position (off/run/start) the resistance between terminals 2 and 3 is between 2 and 5 Ohms depending on on how the key is jiggled. This is far, far too much. This is the resistance cold. In use, the switch would have heated up with that resistance and then the resistance would have been even higher. The barrel is very worn and sloppy. It would have jiggled around with vibration as the car was moving causing a variable resistance. That would have caused a randomly varying voltage to the electronic ignition on a background of a voltage that was persistently too low. This I hypothesise caused the electronic ignition to malfunction giving a coil dwell that was too long and cooked the coil. When I switched "back to basics" the points system was much more tolerant but the spark was still too weak and so the car ran but didn't feel right. The condenser blowing on the way home may have been random bad luck.

For comparison, the new switch has a resistance of effectively zero ohms (the resistance is too negligible for my meter to measure it) in the run position!! Bit of a difference.

It's nice that everything fits together and I am absolutely positive that the ignition switch was the real fault. One symptom I didn't mention is that the car ran perfectly if it was stone cold but after 5 minutes drive it didn't feel good. This must have been the switch heating up due to the resistance.

Stephen

[svenedin]

So now the question is, with the ignition problems diagnosed and remedied, is it OK to put 5 amps through the ignition switch for my USB charger or should I go ahead with my plan and fit a relay for it? I found a nice little relay that has an integrated fuse. The supplied fuse is too high a rating but I can easily change it to a 7.5 or 10 amp fuse.

This one: https://www.autoelectricsupplies.co.uk/ ... -and-break

Stephen

[svenedin]

Here's the worn out old switch. You can even see the wear where the key goes in. It's the original switch for the car, week 9, 1969

The modern replacement 47SA switches have a slightly different design of barrel that means they cannot be re-keyed for an FS series key. A bit annoying as it means one key for the doors and another for the ignition. I am going to try to source a new old stock original but for now at least the car is reliable again and I am not in fear of it suddenly cutting out.

Stephen

IMG_3438.jpeg (894.59 KiB) Viewed 9344193 times

IMG_3439.jpeg (984.86 KiB) Viewed 9344193 times

[mobylette]

As these USB sockets draw a small current even with nothing plugged in, I would run a fused connection direct from the fuse box via a dedicated on/off switch. That way you save overloading the ignition switch and can isolate the socket when not in use.

[svenedin]

As these USB sockets draw a small current even with nothing plugged in, I would run a fused connection direct from the fuse box via a dedicated on/off switch. That way you save overloading the ignition switch and can isolate the socket when not in use.

That's an idea. I ran a green wire from the fused side of the fusebox with an additional, lower rated fuse in the new wire to the USB socket. That does go through the ignition switch of course. For a relay I would use that same green wire I have already run as one of the wires to the relay coil and a purple wire would be the feed for the USB socket so that it does not go through the ignition switch. Your idea is a good one as no relay is needed, it doesn't go through the ignition switch and with its own on/off switch it could also be used with the ignition off if fed by a purple wire (always on). Would have to remember to turn it off though as it would be a drain on the battery. We did actually find there were times when we would have liked to have charged stuff when the ignition was off.

Stephen

[Andmurph]

This is the way I did it on both the pickup and the Midget. It is very easy to leave it switched on though as the switch is hidden.
I also run a separate switched purple wire back to the bed of the pickup so that we can plug in the fridge when travelling to events.

[svenedin]

Just a few observations and things I have learned from this spate of ignition problems. When the spark is weak, the engine can idle quite well but it has trouble accelerating under load. With no change to the fuel mixture from previously running perfectly, a poor spark gives an exhaust that smells of petrol at idle from incomplete combustion. These observations will help me next time as they do not require any special equipment.

It's also worth considering that ignition switch problems like this can affect both ignition system and fuel pump so you could have no spark and no fuel at the same time but it didn't affect the fuel pump in my case.


Stephen

[mobylette]

Would be interesting to see the guts/contacts of the old switch.

[Bill_qaz]

Stephen my usb has a small led to show its powered. If you power via a switch for non ignition use you could easily wire an led to remind you to switch it off if leaving for a period of time.

I use it as an indicator/ reminder for master switch on or off

[svenedin]

Stephen my usb has a small led to show its powered. If you power via a switch for non ignition use you could easily wire an led to remind you to switch it off if leaving for a period of time.

I use it as an indicator/ reminder for master switch on or off

Good idea.

Stephen

[svenedin]

Ok, decisions decisions.

I ordered and now have a suitable relay but I'm waiting for a switch to arrive. Two switches actually as I might fit a concealed coil cut out. Unrelated but whilst I have the access I am also going to install a clicker for the indicators as I found I had a tendency to leave the indicators on by accident in France which is a bit dangerous.

I have to decide whether to use an ignition on via relay supply to the USB charger or an ignition independent power supply via a switch. It is quite handy to be able to charge stuff without the ignition on e.g at a car show, while waiting in queues like we recently had at ferry ports etc. As we all know you can't just tun the ignition on without starting for an extended period or you'll burn out the coil. However, there is another way. An ignition operated relay combined with a coil and fuel pump security cut off switch. In the rare circumstances where I want to charge stuff without the engine running, use the fuel pump+coil isolator switch to turn power off to coil and pump and then the ignition can be left on as long as wanted.

Stephen

[Andmurph]

I’m surprised you are mulling this idea Steven.
In all the years you have owned and driven Xavier you have been conditioned to drive a car with care, not leave the ignition on, not leaving it in gear with the clutch pedal down whilst waiting at lights and so on. You have also in recent years tried to resist the temptation to customise and kept things original.

I would have thought a discrete hidden switch to turn on the auxiliary socket while queuing or at a show would br in keeping with the rest of your car.

Just my observation, I may be wrong.

Cheers

Andrew

[Bill_qaz]

Ok, decisions decisions.

I ordered and now have a suitable relay but I'm waiting for a switch to arrive. Two switches actually as I might fit a concealed coil cut out. Unrelated but whilst I have the access I am also going to install a clicker for the indicators as I found I had a tendency to leave the indicators on by accident in France which is a bit dangerous.

I have to decide whether to use an ignition on via relay supply to the USB charger or an ignition independent power supply via a switch. It is quite handy to be able to charge stuff without the ignition on e.g at a car show, while waiting in queues like we recently had at ferry ports etc. As we all know you can't just tun the ignition on without starting for an extended period or you'll burn out the coil. However, there is another way. An ignition operated relay combined with a coil and fuel pump security cut off switch. In the rare circumstances where I want to charge stuff without the engine running, use the fuel pump+coil isolator switch to turn power off to coil and pump and then the ignition can be left on as long as wanted.

Stephen

Overcomplicated IMHO. Just leave it standard as far as ign/pump etc etc.
Run your fused feed via a switch to the usb with either warning light or use an illuminated switch. Less to check if you do have further issues.
But as always your car your way

[svenedin]

Ok, decisions decisions.

I ordered and now have a suitable relay but I'm waiting for a switch to arrive. Two switches actually as I might fit a concealed coil cut out. Unrelated but whilst I have the access I am also going to install a clicker for the indicators as I found I had a tendency to leave the indicators on by accident in France which is a bit dangerous.

I have to decide whether to use an ignition on via relay supply to the USB charger or an ignition independent power supply via a switch. It is quite handy to be able to charge stuff without the ignition on e.g at a car show, while waiting in queues like we recently had at ferry ports etc. As we all know you can't just tun the ignition on without starting for an extended period or you'll burn out the coil. However, there is another way. An ignition operated relay combined with a coil and fuel pump security cut off switch. In the rare circumstances where I want to charge stuff without the engine running, use the fuel pump+coil isolator switch to turn power off to coil and pump and then the ignition can be left on as long as wanted.

Stephen

Overcomplicated IMHO. Just leave it standard as far as ign/pump etc etc.
Run your fused feed via a switch to the usb with either warning light or use an illuminated switch. Less to check if you do have further issues.
But as always your car your way

You're right. Simple is always best. I have a phone holder that lights up when it is switched on so I won't forget to switch it off (he says overconfidently )

Stephen

[svenedin]

Ignition all fixed now and back to the Lumenition Optronic, which I rate very highly, after an emergency dalliance back on points. Always keep the parts to convert back to points in the car (low tension connector, points, condenser). They weigh next to nothing, would fit in a matchbox and points will get you home when electronic ignition can't cope with a poor electrical supply.

These ignition switch problem must have been going on for quite some time. The engine now idles so beautifully and quietly that out on a test drive I thought I'd stalled it several times.

Stephen

[svenedin]

I've decided to go with the suggestions to wire the USB socket with a permanent live feed (purple), via a suitable in-line fuse and a toggle switch hidden under the dashboard. As ever I am very loathe to drill holes anywhere, whether seen or unseen but having the means to power a phone/GPS is just too useful especially when I am driving solo without a navigator. I am waiting for a Lucas SPB200 65SA toggle switch which even though it can't be seen matches the others. Unfortunately, I will have to drop the parcel shelf to drill the hole which is a job I dislike. Dropping the shelf is easy but refitting it can be annoying. Then there is no additional load on the new ignition switch. I spoke to Martin Jay (Distributor Doctor) he said the old switches rarely fail but the new ones are not very reliable. Club spares are on the case to find me an original FS series switch which I can get re-keyed so the whole car uses only one key. The modern switches have a slightly changed design so they cannot be modified to accept the original key.

I hadn't planned to go to the National because it is a long way and I'd have to go on my own but now there is an incentive because the club want to do another presentation of the Ian Portsmouth prize which "Xavier" won on Minors on Tour 2026 (best car on tour). Therefore, I need to sort this USB socket out and the gearbox rear main seal leak.

Stephen

[svenedin]

All done. Here is my very discreet switch to the USB socket.

If it did get left on it's no really big deal. The drain with nothing charging is tiny but it would eventually flatten the battery (assuming a 50 mA drain it would take 50 days to completely drain a 60 amp hour battery).

Stephen

IMG_3451.jpeg (3.59 MiB) Viewed 9341840 times