Hi, hoping someone can help me, I have a 1965 Triumph Herald 12/50 saloon positive earth I am currently restoring.
I have temporary wired the ignition system just to start the engine, it turns over but does not fire, on checking the spark at the plug it only sparks when the ignition is turned on and not when the engine is turned, I have followed the wiring diagrams in the Haynes manual but to no avail. needing help/ideas please.
Edited by Webmaster on 26/01/2010 at 23:40
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on checking the spark at the plug it only sparks when the ignition is turned on and not when the engine is turned
Does the system have a ballast wire that increases the voltage to the coil during engine cranking (12 volts or so) but then drops back to 6 or 8 volts when the key is released?
Either that or you've incorrectly wired the ignition system.
I take it the engine will start with a bump start?
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If the Herald is similar to my GT6 (1968) then it will have a 12V coil without ballast resistor. Try wiring the coil directly from the battery if you have it going through the ignition switch at the moment. Is the battery good- does it crank fast enough? Try jump starting?
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If it sparks when turned on is there still 12volts at the coil then cranking. With the points open what is the voltage at the SW side of the coil. I suspect the capacitor has failed/gone open or short cct. Regards Peter
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Sounds like there's a short to ground somewhere on the low-tension side of the ignition circuit, either a chafing wire or (just a thought) is the insulating washer missing where the wire connects to the contact breaker?
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Isn't it good to get to grips with a good old-fashioned problem more of us can understand?
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Now I have woken up...
Is there still 12V going to the coil when the engine is cranked (multimeter or test lamp)?
If so then either a short to ground in wiring around or inside the distributor, faulty points, duff condenser, points not opening, or distributor drive not turning (hope not!).
If no 12V on coil when cranking, have you connected the ignition to an aux terminal on the ignition switch? I did this when fitting an electric petrol pump on the GT6 and it didn't run when the ignition switch was in starting position.
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What history do you know of the car?
A friend had a similar problem when he fitted a six volt coil and ballast resistor 'to get a better spark'.
He omitted to fit a direct feed to the coil, bypassing the ballast resistor, when the starter motor was operated.
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start with the basics again
fuel in tank-
fuel to carburetor
battery turning it over ok and plenty of power.
if you remove a plug are they wet? with petrol?
if you ground the plug against the engine and turn over do you get a spark?
points ok and gap set correctly
TDC lined up OK
just a few thoughts
if all ok can you bump start it?
if not you need to get through the electrics with a fine tooth comb
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he hasnt been back so it probably caught fire :-(
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Assuming fuel delivery is ok and ignition timing is set correctly.
Ignition low tension circuit basics:
Ignition on, test lamp on live side of coil - lamp lit = feed ok
Turn engine over - lamp still lit = cranking feed ok
Move test lamp to distributor side of coil and crank engine - test lamp should flash off and on as points open and close = distributor working
If above is ok, suspect secondary windings in coil (i.e. duff coil) or ignition high tension circuit i.e. distributor cap, rotor arm, leads, plugs, plug caps etc.
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