S V6 Won't Fire, No Spark
Discussion
tvrgit said:
Next question: do the wipers work? Or the indicators? Or the heater motor? Or anything that is only supposed to work with "ignition on"? If they all work, but still no volts to coil, then you have a problem specifically in the coil wiring.
Don't forget to check the Ignition Fuse as well. See also ... HERE
I have mentioned this on here before, those fuse diagrams in the "bible" are very misleading.
The circuit/s that each fuse feeds is labelled above each fuse.
It is easy to unwittingly think the labels refer to the fuse immediately above and not the correct one spaced away below.
Take heed!
The circuit/s that each fuse feeds is labelled above each fuse.
It is easy to unwittingly think the labels refer to the fuse immediately above and not the correct one spaced away below.
Take heed!
Edited by glenrobbo on Tuesday 10th January 20:42
tvrgit said:
I can't see the bit on the wiring diagram that says "just here is a bright yellow connector block that carries more current than it was ever designed to do and will (not might, but will) eventually burn out. Symptoms- car cranks over but won't start, but no other ignition switch controlled circuits will work either."
Yes there may be a variety of reasons for no supply to the coil - but on these particular cars, that yellow connector is the most likely culprit and should be checked and eliminated first. Most owners have already changed or removed that connection for exactly this reason.
If the OP reports back "yellow connector ok, still no supply to coil but wipers etc work" then I agree, its wiring diagram time.
But if one test can identify what is likely to be a 90% probability problem, that's simple to check, go for that first, no?
That good old yellow connector, guess you mean the one on the ignition switch loom, or dribbled over the steering column cowl like mine. I'm re-wiring and routing all the heavy stuff through relays. There's a good reason for banks of the dam things in modern cars.Yes there may be a variety of reasons for no supply to the coil - but on these particular cars, that yellow connector is the most likely culprit and should be checked and eliminated first. Most owners have already changed or removed that connection for exactly this reason.
If the OP reports back "yellow connector ok, still no supply to coil but wipers etc work" then I agree, its wiring diagram time.
But if one test can identify what is likely to be a 90% probability problem, that's simple to check, go for that first, no?
Just a quick update.
I can confirm that all my interior bits work when the ignition is on, including wipers etc. Also checked and the coil does seem to be earth through the casing. Check yellow connector and that seemed fine. The random red wire appears to run under the dash and split to feed the gauge lights...? (Really weird, that one. I'm going to have to run some checks on that as I can't see how my interior lights are run off the bleeding coil...!).
Semi gave up after that as I was distracted by fitting a new brake servo. Still, I'm spending a few hours with her on Saturday, so I'll run through fuses and other connections to see if I can nail down the source.
Cheers for the help so far.
I can confirm that all my interior bits work when the ignition is on, including wipers etc. Also checked and the coil does seem to be earth through the casing. Check yellow connector and that seemed fine. The random red wire appears to run under the dash and split to feed the gauge lights...? (Really weird, that one. I'm going to have to run some checks on that as I can't see how my interior lights are run off the bleeding coil...!).
Semi gave up after that as I was distracted by fitting a new brake servo. Still, I'm spending a few hours with her on Saturday, so I'll run through fuses and other connections to see if I can nail down the source.
Cheers for the help so far.
Definitely no supply to coil? (I.e. Meter -ve direct to battery earth, +ve to coil +ve terminal, ignition on?)
Then you do now need to follow the wiring diagram!
Remember some gauges (not the instrument lights, the gauge itself) and warning lights have an ignition -switched feed, and earth through the sensor - possibly a gauge or two have stopped working at some point and rather than try to unravel the electric spaghetti that TVR used as a wiring loom, a previous owner has run that red wire direct from the coil knowing that's only live with ignition on. Not neat but not unheard of.
I think your on the right lines now, if there's no feed to the coil - track where that red wire goes by all means, but also follow through the connections in the circuit diagram to find where along the line it goes dead.
Then you do now need to follow the wiring diagram!
Remember some gauges (not the instrument lights, the gauge itself) and warning lights have an ignition -switched feed, and earth through the sensor - possibly a gauge or two have stopped working at some point and rather than try to unravel the electric spaghetti that TVR used as a wiring loom, a previous owner has run that red wire direct from the coil knowing that's only live with ignition on. Not neat but not unheard of.
I think your on the right lines now, if there's no feed to the coil - track where that red wire goes by all means, but also follow through the connections in the circuit diagram to find where along the line it goes dead.
The Beaver King said:
.... the coil does seem to be earth through the casing.....
If you have mounted the coil on the bulkhead it will need a separate earth to the chassis, or other known good earth point.The Beaver King said:
.... Check yellow connector and that seemed fine. ....
Have you pulled the connector apart and looked at the inside? These things can look OK on the outside but on the inside look like this...
tvrgit said:
Definitely no supply to coil?
Still not clear to me from the "update"?The Beaver King said:
The random red wire appears to run under the dash and split to feed the gauge lights...? (Really weird, that one. I'm going to have to run some checks on that as I can't see how my interior lights are run off the bleeding coil...!).
Not that weird, TVR used two ballast resistors as a way to dim the instrument lights, someone may have mistaken these as actually being part of the ignition circuit?v8s4me said:
If you have mounted the coil on the bulkhead it will need a separate earth to the chassis, or other known good earth point.
Mine doesn't... 
phillpot said:
tvrgit said:
Definitely no supply to coil?
Still not clear to me from the "update"?phillpot said:
The Beaver King said:
The random red wire appears to run under the dash and split to feed the gauge lights...? (Really weird, that one. I'm going to have to run some checks on that as I can't see how my interior lights are run off the bleeding coil...!).
Not that weird, TVR used two ballast resistors as a way to dim the instrument lights, someone may have mistaken these as actually being part of the ignition circuit?phillpot said:
v8s4me said:
If you have mounted the coil on the bulkhead it will need a separate earth to the chassis, or other known good earth point.
Mine doesn't... 
tvrgit said:
phillpot said:
tvrgit said:
Definitely no supply to coil?
Still not clear to me from the "update"?EDit cos I screwed up the quotes.
Ok, so for my two penny's worth.
Some coils need grounding from the body some don't . I don't understand why either, but I learnt this over a very long weekend changing a coil on a mini back in the eighties. So if your coil is mounted on bulkhead and your ,"New" coil is of the type that needs grounding, then u immediately have an issue.
Secondly, do you have an imobiliser. My s had one, that went duff one day and required removing to get power to the coil.
Third, back in the bad old days when I drove Ford's and every sod was out stealing them, one of the tricks to stop it happening was to run a "insert colour here" wire from the coil to a hidden switch inside the car.
This could still be in place but may have a broken connection.
Some coils need grounding from the body some don't . I don't understand why either, but I learnt this over a very long weekend changing a coil on a mini back in the eighties. So if your coil is mounted on bulkhead and your ,"New" coil is of the type that needs grounding, then u immediately have an issue.
Secondly, do you have an imobiliser. My s had one, that went duff one day and required removing to get power to the coil.
Third, back in the bad old days when I drove Ford's and every sod was out stealing them, one of the tricks to stop it happening was to run a "insert colour here" wire from the coil to a hidden switch inside the car.
This could still be in place but may have a broken connection.
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