pickmaster Andy Lowe Posted February 28, 2015 Share Posted February 28, 2015 Quote Link to comment Share on other sites More sharing options...
Terry Everall Posted February 28, 2015 Share Posted February 28, 2015 Note that the main feed from the BATTETY to the Cut Off switch is +ve and not -ve Quote Link to comment Share on other sites More sharing options...
Quinten Posted February 28, 2015 Author Share Posted February 28, 2015 At no point have I said that I have a FIA cut off switch. I don't. I have a battery cut off switch, which rightly or wrongly has been on the car since well before I bought it and has always been perfectly adequate in isolating the electrics. The above is a representation of the ignition/start/alternator circuit. The reason I have left out the headlight/fan/horn wiring is because they are all very straightforward driven by independent relays of which I am 99% convinced they are of no influence. The starter and alternator are connected to each other by 2 thick red wires, and the starter is connected directly to the battery by a very thick red cable. There are then two thinner red wires going to the two fuse boxes (6 fuses), so they are always 'hot'. I've already explained the battery cut-off switch, so won't repeat that. The ignition barrel switches a relay, and the accessory position and starter position are both unused and not connected to anything. To start the car I am using a (Savage) switch. The starter switch drives again a relay. The alternator tell tale wire (aka the excite/ignitor wire?) is connected to the battery warning light on a Lighting Looms Light6/Bright6 dash panel. Mine didn't come with internal wiring diagram, hence the big ? in the 'cloud' on the diagram. Looking at the current installation version (seems newer as all the wiring colours are different) it may well have the correct diode/resistors on the PCB, but I can't tell as the whole PCB is covered in this black glossy paint (it's not paint, but I have also no idea what the correct name is). The panel takes 12V from the ignition bus and also connects to ground. The fuel pump and ignition coil positive are driven by a relay which is active when the ignition is on. Looks all very reasonable? There is one thing I am absolutely not sure off, and that is the speedo wiring. I've connected it in the same way as it was before I replaced the dash, using a 3 core wiring plug which has a red (connected to 12V), a black (connected to ground), and a silver (speedo signal) wire. When you switch the key to ignition, it does a test sweep (which I expect), but when you start the engine it does another sweep. I have no idea if this is to be expected, nor do I know (or have traced) where the red and black wire go to on the other end of the 3 core wire. Quote Link to comment Share on other sites More sharing options...
TableLeg Posted February 28, 2015 Share Posted February 28, 2015 Looking at your diagram and taking the simplest approach, without power to the fuel pump/coil relay the engine can't run. Can you test this relay is ok? check it engages and disengages with the ignition switch on? Quote Link to comment Share on other sites More sharing options...
Quinten Posted February 28, 2015 Author Share Posted February 28, 2015 Looking at your diagram and taking the simplest approach, without power to the fuel pump/coil relay the engine can't run. Can you test this relay is ok? check it engages and disengages with the ignition switch on? Yes, that relay works, as the fuel pump will run when I turn the key to ignition, and stop if I turn the key to off. Quote Link to comment Share on other sites More sharing options...
TableLeg Posted February 28, 2015 Share Posted February 28, 2015 Ok, but turns on with ignition, stays on with engine running but then fails to disengage when you turn the ignition off? When you switch the ignition off it should break the +12v supply to the ignition/coil relay cutting the pump and the ignition spark. Quote Link to comment Share on other sites More sharing options...
Quinten Posted February 28, 2015 Author Share Posted February 28, 2015 Ok, but turns on with ignition, stays on with engine running but then fails to disengage when you turn the ignition off? No and yes. When I had the engine running for a short time, I was able to switch it off again using the key as normal. It stopped the fuel pump just as expected. When the engine was running for a bit longer, the key no longer switched the engine off, nor did it seem to kill any electrics (as I could for instance still use the fan override switch). So it seems something is backfeeding into the ignition circuit, and the only thing I can think off is the Light6/Bright6 panel... Quote Link to comment Share on other sites More sharing options...
TableLeg Posted February 28, 2015 Share Posted February 28, 2015 How about the ignition switch itself? Is it old or in need of cleaning? You could check it by bypassing it with a wire direct to the battery and see if connecting it, starting and running the engine for the time when it usually won't stop with the switch and then disconnect your temporary wire and see if that kills it. Maybe the contacts in the switch have been a bit cooked and are shorting due to a high current between them. Quote Link to comment Share on other sites More sharing options...
Quinten Posted February 28, 2015 Author Share Posted February 28, 2015 How about the ignition switch itself? Is it old or in need of cleaning? You could check it by bypassing it with a wire direct to the battery and see if connecting it, starting and running the engine for the time when it usually won't stop with the switch and then disconnect your temporary wire and see if that kills it. Maybe the contacts in the switch have been a bit cooked and are shorting due to a high current between them. It's certainly old. Not sure if there is anything to clean on, but I can not rule it out 100% that it is no longer working correctly. I'll put this on the list of things to try Quote Link to comment Share on other sites More sharing options...
TableLeg Posted February 28, 2015 Share Posted February 28, 2015 Some switches can be dismantled and the contacts cleaned. Good luck. I hope you find the issue. 1 Quote Link to comment Share on other sites More sharing options...
darve Posted February 28, 2015 Share Posted February 28, 2015 Looking at your wiring diagram, the 12v bus rail must be live to allow the engine to run on (to close the coil and fuel pump relay) From the diagram this can only happen if the relay controlled by the ignition switch is closed or if you're getting a 12v feed back from the alternator. I would think you only need a small current back feed to close the fuel pump/coil relay To determine which, with the engine running on and ignition switch off: a) check continuity across the relay which is controlled by the ignition switch. If the switch/relay is working you shouldn't have continuity (Between the feed and output pins) b) measure the voltage on the line from the alternator. If you have 12v and the ignition switch controlled relay is open, this is where the 12v is coming from. Rather than measuring the voltage, you could disconnect this cable and see if that kills the engine. If a) then it's the relay or ignition switch If b) then maybe the alternator (sorry don't know anything about alternators really). Perhaps a diode could be fitted in line to allow 12v from the bus to ignite the alternator but 12v can go back up the line Hope this helps I could be talking rubbish Quote Link to comment Share on other sites More sharing options...
darve Posted February 28, 2015 Share Posted February 28, 2015 Sorry where I referred to the "excite" cable I meant the one that goes from your bus rail to your bright 6 panel. And when I said feed back from the alternator, this is via the bright 6 box Quote Link to comment Share on other sites More sharing options...
Kit Car Electronics Posted March 1, 2015 Share Posted March 1, 2015 Hi Q, the Bright6 schematic shows an alternator protection resistor in parallel with the led and diodes. Depending on the coil resistance of your fuel pump relay, that will keep a voltage drop across the coil that could be enough to keep the relay on. You could either swap the fuel pump relay for one with a lower coil resistance, or add a resistor in parallel to it. If you measure the voltage across the coil when its running on, plus measure the coil resistance (remove the relay for that check) then I can suggest a resistor rating and value. Unless there's another explanation but I can't see one from your helpful diagram. Quote Link to comment Share on other sites More sharing options...
Kit Car Electronics Posted March 1, 2015 Share Posted March 1, 2015 It might be easier for you to just put the fuel pump relay coil in parallel with the ignition relay coil- then it would definitely turn off with ignition barrel switch? Quote Link to comment Share on other sites More sharing options...
Quinten Posted March 1, 2015 Author Share Posted March 1, 2015 Cheers darve and R7WSC (we should have a first name field on the little profile thing ) for the explanations. I think I would have come to the same conclusion; either the ignition switch or the backfeed from the Bright6. My gut feeling says its the last one... Testing the theories as soon as I get dressed Just a thought, but if it is the Bright6, a simple diode on the 12V feeding the Bright6 to restrict current flowing the other way would be sufficient right? Quote Link to comment Share on other sites More sharing options...
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