Changed Coil & wont start, no spark ! 74 3500

DamianZ28

DamianZ28

Active Member
Hi all, car had new coil I fitted a while ago but wasn't running great so I refitted the old one to see if any different but no change, left it on as it turned out to be carb issues. So thought I'd refit the new coil for peace of mind as the old one is 'very old' indeed, as precaution I took photos of the wiring connections , swapped it all over, all back as it was but now will not start, no spark at all, cannot figure out for the life of me why it suddenly has no spark, have not touched any other wiring at all, car ran literally before this as I moved it out of the garage to work in the sun! Checked & rechecked all the connections, fuse is ok, it has new plug leads too!. I don't have a metre so cannot check any power so to speak, refitted the old coil but still no go, removed one plug, pushed the lead back on & held it against a bare metal patch in the engine bay to earth it but no spark whilst cranking the engine over... any ideas most welcome ! so bloody annoying as I want to cruze in the sun to get to the 500 mile running in!. cheers Damian.
 
First thoughts are:

[1] New coil is a dud, had premature failure.
[2] Something in the loom broke when handled during the replacement.

I would start systematically. Unfortnately you'll need to beg/borrow/buy/steal a multimeter. Measure ohms between the two low tension terminals on the coil (Make sure wires are disconnected to get a true reading). It should measure between 1.5 ohms (Ballasted) and 3.0 ohms (Non-Ballasted)
depending on whether you have a ballasted or non-ballasted system. If that comes out of range its most likely the coil is bad. As an aside I would measure the old coil to see which was fitted before, a coil for a ballasted system on non ballasted system will cook itself pretty quickly. (My figures are for a 4 cylinder car, please correct me if I have the ohm values off)

Next test would be for power getting to the coil. Rotate engine until contacts are closed, turn on ignition but dont try and start it, then using the voltmeter measure voltage across the low tension wires that should be connected to the coil. You should see between 9v (ballasted) and 12v (non-ballasted). If not you have a wiring issue.

Hope that helps you some. I would say get a multimeter, they're pretty cheap and essential for keeping our cars running.
 
Hi sdibbers, many thanks for your help, much appreciated sir. I have fitted a Accuspark electronic ignition kit so no points, also dont think my car has the ballasted version as its late 1973 ending in suffix D seriel number but l could be wrong!. How would l check? I'll borrow a meter and check out the coil and wiring, hopefully it's an easy fix. Cheers again
 
They are all ballasted coils. difference is the later cars have the ballast built into the wire so you can't see it. Normally there are two input wires to the coil one for starting and one for running. The starting wire comes from the starter motor and is 12V. you can check if that wire is working by connecting a light bulb between it and earth then cranking the engine. It should come on. You can try the same trick with the other wire but be aware with the lower voltage it will be dim.

Make sure the point plate still has its little earth wire attached firmly
 
Hi all, tested coil and power to it and there is just under 12v at the end of the lead which goes into the disty. I did a tiny bit of welding on the interior gear box tunnel but have just realised l completely forgot to disconnect the battery . I wonder if l have fried the Accuspark ignition module? However it did start after l finished welding but not after changing coils.
 

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I swapped coils from a Lucas to some local red thing that since went into the bin, without noticing the length of the connector to the distributor was longer. So the plug was not even contacting the coil despite everything looking quite wonderful from the outside. That wasted a lot of time…..
 
To make a crude meter;- take a low wattage, 12v, bulb and wire to each connection on the bulb, one to chassis or body metal work, and metal probe, (old small screwdriver,) probe onto where you are looking for power, and if OK the bulb lights.
Cride, robust and cheap, you can keep his in your on-board tool-kit use a filamen bulb, not LED so no need to worry about polarity
 
Aha. I have a new battery, new coil, new dissy cap, ht leads, new plugs, points and a terrible spark. On the box the Coil was sent in, Geoff from Wins, I presume, wrote: "Ballast GCC - 111v". What does this mean? I'm terrible with electrics!
 
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That will be the part number.

The plate the points are on moves, there is a small, normally braid, wire running between the moving plate and its check it's still there and if so tug on it to ensure you have decent connection. Bad connection there will cause what you describe.

M
 
mikecoombs said:
That will be the part number.

The plate the points are on moves, there is a small, normally braid, wire running between the moving plate and its check it's still there and if so tug on it to ensure you have decent connection. Bad connection there will cause what you describe.

M
Click to expand...
Thanks Mike, every day is a school day!
 
She lives, life in the ole dog yet, new powerspark electronic ignition kit with rotar arm , reset the timing which was oddly way out. So purrs nicely but stll could do with carbs sorting as still has its moments, hasn't helped that l stupidly snapped the small screw (with the small spring) that holds the jet adjustment mechanism inside the float chamber and no idea on how to get the remaining broken thread out..yeèey, probably now need a good 2nd hand carb body, so although its running its still up n down on the right carb, all good fun. Possibly though l maybe able to purchase an excellent 2nd hand chevy 305ci small block V8 of 89 vintage, almost the same size as the rover motor but 5.2ltrs & much more room to play with in terms of upgrades
 
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