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I use a Stag Automatic as my daily driver ( I need the rear seats for Grand-Children)and for over 3 years perfect, the other day at a set of Traffic lights Ignition cuts totally, no warning lights but the HeadLights work, Starter Motor works but zero ignition, after a few minutes it comes back...Outside lane of Motorway 80mph..same again, this is getting serious ..seriously dangerous I mean..
I fiddle with the ignition switch and it works all day, then after a 10 mile run off it goes again.
It didn't work last night after I freewheeled onto the drive ..but did this AM
I'm thinking WW2 gremlins are at work!

Sounds more like WW2 wiring at the plug socket, have had similar experinece with a Triumph 2.5 and turned out to be the ignition switch itself.

I have had similar experiences with a points type ignition when the condensor was faulty.

Coils can also act in this manner.

Basically they work cold but cut out after they warm up. Once they stop they cool off and start the cycle over again.

Edward Hamer
Petaluma CA

Again, it stopped working but after a rest recovered...I lose some of the warning lights ie the ones that come on when the ignition is switched prior to engaging the starter motor, that is the oil and ignition lights, my thoughts are that I have a fault within the ignition switch, the reason why it should be intermittent is eluding me at present.
I really need to find the exact cause though but its so difficult as it can rectify itself pretty quickly...ho hum..

What is on your key ring?

My daughter had this problem with a Honda Prelude.

She was running an architectural office. They had a large number of blueprint safes, each with a key. She had about 15 of these, the office keys, car keys, & home keys all on a large key ring.

The Prelude started cutting out when going around roundabouts. It would immediately restart once stopped & park was selected.

It turned out the barrel of the ignition switch was a bit worn, & the weight of the keys swinging to the left was moving it far enough to break the contact. Being an auto the thing had to have neutral or park selected to restore ignition power.

Hasbeen

Stag/TR8 Ignition switches usually fail on the starter engage portion of the switch. You could try moving the key slightly next time it cuts out before the car stops moving.

Alternative you could run a hot wire from the battery to the coil and see if it stays running. Be careful though as if the switch cuts out all the power will be running through the bypass wire so you want to keep the switched power load to a minimum.

Edward Hamer
Petaluma CA

Hi,

When the electronic OPUS distributor on my 7V8 died whilst driving, the loss of power was immediately accompanied by the rev counter dying, though still in gear. A common issue with the Opus.

Did your rev counter do the same? Is your distributor on the original points or electronic?

I had the ignition switch issue not working the starter motor earlier this year. S and S sourced me a replacement.

Adam

Thanks for the help so far, when the problem occurs I lose the radio the indicators and the warning lights, when it last worked 2 days ago I noticed that the Voltage meter was very low just before cutout and I recall this on previous occasions, I did change the alternator back in November and I know that there is a direct connection to the ignition from the alternator could any of the connections be shorting that would cause this effect, I would have thought that a dead alternator would just cease to function rather than cause an ignition failure?

Could be a poor connection or cracked wire that's just about ok until the car warms up and conductivity is lost?

I've lost count of the number of connector blocks, spade connections and earthing points on my 40 year old wedge that have been coated with green grunge or worn loose.

If the voltage/battery had dropped low enough to not allow the ignition to function it would not have enough power to energize the starter.

Have you tried running a direct power wire from the battery to the coil yet?

Edward Hamer
Petaluma CA

I haven't..its the fact that I have clearly lost all the functions that normally apply to the white wire from the ignition..no warning lights, fan motor, indicators, ignition, that is flummoxing me to be honest as I say if this was a Motorcycle that the killswitch was on or the sidestand was down its almost as if I have an immobiliser fitted?

If that is the case it could be the actual ignition switch. Fortunately, if you have a UK spec TR7, the switch is the same as a Spitfire so it is readily available and inexpensive. The US type is almost impossible to find and expensive when you do.

It can be changed out fairly easily by removing the steering column cover. There are two very small screws that connect the electrical part to the key/column lock. After that it is just the connector under the dash.

Edward Hamer
Petaluma CA

thanks for the reply, yes,i swapped the switch..but no luck so far

Right then...been outside had yet another check all to no avail, however in my changing the fuses...again...I accidentally bridges Battery control to Ignition control...everything came on...please explain and is there a fix that might get me mobile given these circumstances?

Bridging the battery to the switch by passes the ignition switch and associated wiring.

Have you checked the clamp on connection on the positive battery cable? It should be fairly close to the positive battery terminal end of the cable. It will have several brown wires and is the source for almost all the power in the car except the started motor. I would check the overall condition and look for corrosion and loose fitting terminal ends.

The Roadster Factory here in the USA sells new battery cables with the power tap installed if yours is no good.

Edward Hamer
Petaluma CA