Cough, cough

[billwill]

Here's a typical INCORRECT diagram that I found on the internet for wiring a ballast coil circuit:



Whoever drew it up did not realise that there would be a spurious current flow through the ballast resistor and then through the activating-coil of the starter relay to ground. Depending on the value of the ballast resistor it might actually be enough to pull in the starter relay causing the starter motor to run all the time.

[billwill]

Here's a diagram that I found that is correct, the normal feed to the ignition coil is through the ballast resistor, but when the starter solenoid is operated there is a direct feed bypassing the ballast resistor.



It's not completely easy to understand due to the attempt to make it seem simpler by drawing pretty pictures of the components instead of one which shows the internal connections, especially in this case the starter solenoid.

[Chancer]

The first diagram will also result in a significant drop in the ballasted voltage to the coil, if it is also used to power an ignition module then you really are asking for trouble.

[Craven]

Extra contact on ballast type solenoid short circuits the ballast resistor in start mode.

starter-sol.jpg (19.15 KiB) Viewed 842 times

[Robbie693]

Don?t know if new wiring harnesses have the anti theft switch included, if they are sold as a direct replacement they should have. A quick phone call to the supplier should get you the answer.
Unless you have lots of electrical problems or want to replace your dashboard, personally I wouldn?t consider replacing the dash and front wiring harnesses just for this problem. The bullet connectors are on the left behind the glove box if you are on a rhd car, they should be tight to get apart and will probably look a bit discoloured and grey when you get them apart. They can be cleaned with fine abrasive paper and if the connector blocks are corroded or don?t hold the wires in tightly then replace them, try to get good quality replacement connectors as some on sale are apparently poor quality, I?ve bought some recently which were advertised as genuine Lucas and they seem fine.
Replacing a wiring harness sounds simple but is a time consuming job if you do it right, even when you have the dash out on the bench, and a new harness beside it, it can be a daunting task to swop every thing over, secure it in place and replace the dash and all the trim you have disturbed. If it is a problem with the wire and not the ignition switch or bullet connectors, I?d be tempted to loosen the dash and lean it back in situ to give access to run a new wire from the ignition switch via the tachometer and out through one of the bulkhead grommets on the right hand side to the coil as this would be the shortest simplest route and could be made to look neat and almost out of sight with a bit of careful route planning. Even doing this will need you to drop the steering column, disconnect the bonnet catch, choke cable, eyeball vent pipes and more, unless others have found another way for this?

Oh no - I wasn't contemplating replacing the loom, I only asked because mine has had a new loom in the past and I wondered if there was a connection in there somewhere that would have been where the original anti-theft switch would have been. Sorry I wasn't clear. You have given me further pointers though, for which I am grateful, they will help a lot and I need all the help I can get!

Cheers

Robbie

[Spyder fan]

Just a bit of light relief here, all these electrical diagrams remind me of the idiots flow chart




I still suspect a fuelling rather than electrical problem here. Dellortos have a rubber O ring rather than a metallic washer beneath the pump jets, these are susceptible to being eroded by the ethanol thats present in normal pump fuel these days. A carb rebuild gasket set is a good investment and the process of stripping, cleaning and rebuilding is quite satisfying.

[Robbie693]

Thanks Alan, a set of O rings and fibre washers for the pump jets have arrived so that will be my next experiment!

Robbie