phil Dean Posted February 5 Report Share Posted February 5 I used my tr4a last Thursday did about 20 miles in it. Came to it this morning to start it and it wont start. Last time this happened I had flooded it Cleaned the plugs, and it fired up straight away from cold. This time nothing plenty of petrol but no spark at the plugs. Yes the garage is cold but I have a heater on under the sump, maybe thought a bit of damp. so sprayed with WD 40 the plug leads look newish. and don't know how old the plugs are. How do you check the coil it also has Lumination electronic ignition on it is there a way of checking this. Help please Phil. Quote Link to post Share on other sites
RobH Posted February 5 Report Share Posted February 5 It's more difficult with electronic ignition but..... First check that there is supply voltage on the ignition coil + terminal when the ignition is on. Check both LT connections are secure Disconnect the 'king' HT lead from the centre of the dizzy cap. Connect a spare sparkplug to the end of the lead and rest the body on the engine metalwork so it is earthed and you can see the gap. Turn the ignition on and crank the engine. If there is a spark, the Lumenition and coil are OK and the problem may be the rotor arm or the dizzy cap. If there is no spark then leave the King lead and spark plug connected and disconnect the Lumenition brown (violet?) lead from the coil ' - ' terminal. Connect a short wire instead. Turn on the ignition and watch the spark plug while you dab the end of the new wire on and off a good earth point. If there is a spark, the coil is probably OK and the Lumenition or connections to it are faulty. If there is no spark the coil may be duff. Quote Link to post Share on other sites
phil Dean Posted February 5 Author Report Share Posted February 5 As usual thanks Rob will try as recommended Phil Quote Link to post Share on other sites
AndyR100 Posted February 5 Report Share Posted February 5 Page 2 and 3 has the fault-finding info for Lumenition Optronic https://www.merlinmotorsport.co.uk/files/transfer/technical/doc/optronicinst.pdf …… Andy Quote Link to post Share on other sites
phil Dean Posted February 5 Author Report Share Posted February 5 (edited) Thanks Andy will save a copy of that, but weirdly it started I checked the supply on the ignition +terminal. it was 11.9 volts the battery was reading 12.5 volts. took the king HT lead of and used plug from cylinder 4 lovely spark so much so that it nearly started on 3 cylinders.Put plug and lead back and it fired up first time. Obviously this is good news but slightly worrying. When it wouldn't start this morning I checked and there was definitely no spark. Could it be that under very cold condition the coil breaks down. !!!!! Maybe showing signs of it coming to the end of its life. Took it for a drive its pulling like a good Un, no misfire or hesitation. anybody maybe got ideas on this one.Could it be a coil breaking down which under cold conditions starts to act up. But I have started it under colder conditions than today a few weeks ago. The only difference being I have a tube heater under the sump which is set by its own thermostat and last night I turned it off to use the socket for something else and forgot to turn it back on could it just be damp. Phil. Edited February 5 by phil Dean Quote Link to post Share on other sites
RobH Posted February 5 Report Share Posted February 5 Something you disturbed when making the voltage checks? It has been known for wires to fracture inside the insulation, close to spade terminals. Happens over time where wires are unsupported and can wiggle due to vibration or engine movement. The ends make intermittent contact and moving the wires slightly can seem to cure things. I would check the leads to the coil connections for that. Quote Link to post Share on other sites
phil Dean Posted February 5 Author Report Share Posted February 5 ok Rob will have a look in the morning. Quote Link to post Share on other sites
TR Rob Posted February 5 Report Share Posted February 5 5 hours ago, RobH said: Something you disturbed when making the voltage checks? It has been known for wires to fracture inside the insulation, close to spade terminals. Happens over time where wires are unsupported and can wiggle due to vibration or engine movement. The ends make intermittent contact and moving the wires slightly can seem to cure things. I would check the leads to the coil connections for that. +1 Quote Link to post Share on other sites
AndyR100 Posted February 5 Report Share Posted February 5 The 3-pin connector from the PMA to the optical switch is a common failure-point of the Lumenition wiring, probably worth checking while you are at it. .…… Andy Quote Link to post Share on other sites
Z320 Posted February 6 Report Share Posted February 6 13 hours ago, RobH said: Something you disturbed when making the voltage checks? It has been known for wires to fracture inside the insulation, close to spade terminals. Happens over time where wires are unsupported and can wiggle due to vibration or engine movement. The ends make intermittent contact and moving the wires slightly can seem to cure things. I would check the leads to the coil connections for that. Once this was the case on my 4A Quote Link to post Share on other sites
phil Dean Posted February 6 Author Report Share Posted February 6 PMA !!! Quote Link to post Share on other sites
AndyR100 Posted February 6 Report Share Posted February 6 1 hour ago, phil Dean said: PMA !!! The Lumenition optronic system has a silver finned box with wires going into and out of it - called a PMA50 - the P stands for Power, the M stands for Module - I don’t know what the A stands for! In the Lumenition instructions and parts book it is usually referred to as the PMA. if you follow the wires back from the optical switch in the distributor you will come across a 3-pin connector plug. Apologies if my earlier post upset you. …….. Andy Quote Link to post Share on other sites
phil Dean Posted February 6 Author Report Share Posted February 6 thanks Andy it didn't upset me, I didn't know what PMA was. Thanks for the clarification. Phil. Quote Link to post Share on other sites
RobH Posted February 6 Report Share Posted February 6 Useless fact - A in this context usually stands for 'assembly'. Quote Link to post Share on other sites
AndyR100 Posted February 6 Report Share Posted February 6 1 hour ago, RobH said: Useless fact - A in this context usually stands for 'assembly'. Thanks Rob - I love to extend my knowledge of (almost) worthless info …….. Andy Quote Link to post Share on other sites
phil Dean Posted February 6 Author Report Share Posted February 6 I have checked every thing in terms of loose connections etc which I have found none. is there anything I can check with my multi meter Car fired up no problem this morning but I would still wouldn't mind trying to find the issue. Phil. Quote Link to post Share on other sites
keith1948 Posted February 6 Report Share Posted February 6 Hello Phil Trying to find an intermittent fault when it isn't causing any problems is a bit of a wild goose chase. Wait until you actually have the fault again and then look for the cause. Unless the fault is glaringly obvious you could spend a long time looking for it. If you want to use a multimeter then check for high resistance across connectors and cables but if the fault isn't present when you do it then you won't find it. (if you follow my logic). Keith Quote Link to post Share on other sites
phil Dean Posted February 6 Author Report Share Posted February 6 I think if it happens again I will try one wire at once moving it about then try restarting the car, if the car doesnt start I will move onto the next wire its the only basic logic I can come up with. Phil Quote Link to post Share on other sites
RobH Posted February 6 Report Share Posted February 6 (edited) Yes you can use your meter Phil. Disconnect one end of the wire. Clip the meter to both ends of the wire you want to test and set it to the ohms range. Wiggle and tug gently on the connectors and watch for changes - it helps if your meter has a continuity 'beep' function as then you can just listen for breaks in the tone. Every self-respecting wireman has a battery powered continuity 'beeper' just for this sort of use. This is the one I have. Home-made using a 3-cell AA battery box and a piezo buzzer glued on. Dead cheap, nice and loud. Edited February 6 by RobH Quote Link to post Share on other sites
phil Dean Posted February 6 Author Report Share Posted February 6 thanks Rob will try this. Quote Link to post Share on other sites
Andy303 Posted February 6 Report Share Posted February 6 On 2/5/2024 at 11:30 AM, RobH said: Something you disturbed when making the voltage checks? It has been known for wires to fracture inside the insulation, close to spade terminals. Happens over time where wires are unsupported and can wiggle due to vibration or engine movement. The ends make intermittent contact and moving the wires slightly can seem to cure things. I would check the leads to the coil connections for that. This exact thing happened to me many years ago on a Land Rover Series IIA. The wire going into the terminal on the dizzy looked perfect but it was broken on the inside and invisible. The engine would cutout on an intermittent basis. Simple to fix once identified. If all else fails you could go back to points, using a good quality condenser and red rotor from here: https://www.distributordoctor.com/ Quote Link to post Share on other sites
TR Rob Posted February 6 Report Share Posted February 6 1 hour ago, Andy303 said: This exact thing happened to me many years ago on a Land Rover Series IIA. The wire going into the terminal on the dizzy looked perfect but it was broken on the inside and invisible. The engine would cutout on an intermittent basis. Simple to fix once identified. If all else fails you could go back to points, using a good quality condenser and red rotor from here: https://www.distributordoctor.com/ Had a similar intermittent fault on my TR3A , installed electronic ignition which meant disturbing the wires on the coil/distributor, until then no problems . After installation had problems starting and also cutting out. Turned out to be the internal wires of the white power wire to the distributor had fractured inside the insulation, just after the connector . It had been supporting itself for 63years and possibly me disturbing it was the last straw! Remedy was to slightly shorten wire and add new connector…..problem solved! Quote Link to post Share on other sites
phil Dean Posted February 6 Author Report Share Posted February 6 I keep looking at the white power wire it looks stretched like somebody has already cut it back once. Will be my first port of call if it happens again. Phil Quote Link to post Share on other sites
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