Coil problems

Hi everyone,

As some of you may remember, i've been on here a few times trying to find answers to the engine problem my 2.5 petrol 90 has.

Quick recap, when she started to get warm after going 20miles or more she would start to act like she was running out of fuel and losing power, if i slowed down she'd be fine for a bit then, like groundhog day, it'd all start again.

After help from some kind people on here, help from a mate, and after replacing, (pause for deep breath), the coil, HT leads, plugs, rotor arm, points, condenser, fuel pump, all the fuel lines, fuel filter, ripped out the old knackard SU carb and inlet manifold and refitted a new Weber with new manifold; have had the carb set up fully and been told by garage that after test run, of 15 miles, the coil had got hot enough to burn the mechanic.

Turns out that the coil might be drawing to much power and overheating and all i should need is to do is fit a 'buffer' resistor, or fix it if it's knackard.

Does anyone know if i should have one and where it could be in the engine bay, so i can see if it needs replacing.

Or if i don't have one, can someone tell me which one i need and where to fit it; or at least let me know somewhere i can find the information i need to fix the coil.

Last, possibly stupid, question... would fitting the coil for a 3.5 V8 work or solve the problem?

Thanks all, Jim.

The V8s use a " Ballast " resistor its seperate from the coil ( 2" long square block of bakerlite with the resistor inside it normally bolted right next to the coil ) , this will drop the power to the coil to around 7v , the only prob you'll have if you do fit one is bad starting , v8 starters had a jumper wire from the starter motor back up to the coil bypassing the resistor so it gives battery voltage to the coil under cranking m so it gives the coil a boost of power .

As for yours I cant remember for the life of me if the petrols had a ballast on them ?????

Don't know specificaly about the landy 2.5pterol engine bay layout, but a company called Luminition make uprated ignition systems for older coil and points based ignition systems. I have one sitted to my BL A series engine and it makes so much difference to reliability and overall smothness of the engine.

More notably for you they make uprated 12V ignition coils that does not need a resistor. I have not put one this engine as I had no need for it and the optronic igniton system (sits inside the distributor where the points shoudl be and connects to a small ECU box) keeps the coil at a nice temp.

If you can't find a LR coil to fit, they them as I'm sure they will make one to fir yours. I know they have a system for the BL V8.

Ignition coils are TRANSFORMERS (auto-transformers actually) with two coils of wire, one of a few turns of fat wire that carries the 12 volts (or whatever) and one of hundreds of turns of very thin wire that makes the high voltage for the sparks.

Sometimes the thin wire will break after a while. Usually, when the coil is COLD the two ends of the broken wire touch, and it works. Then the coil wams up and it all expands, and the two ends of wire at the break separate and start sparking across the gap. At this stage you begin to notice the engine running a bit roughly. But you keep going, and the coil gets hotter and the gap widens, and eventually the engine stops.

You turn off the ignition, the coil cools down, the gap closes, and the car drives away as if there was never a damned thing wrong with it - until the coil heats up again.

I once had this happen with a Lucas (Prince of Darkness) coil. I eventually tracked it down to the coil, which I opened up and unwound, and inside I found the burned and broken wire. I fitted a Bosch coil after that.

CharlesY

Sorry this seems like an old thread now. I have just sold my 2.5 petrol 90 becuase of this same problem and I had had enough after changing everything I could think of bother electrical and fuel. The guy I sold it to fitted a ballast resistor and it has been fine since. I am not sure why it worked fine for me for three years then started playing up but it drove me mad. Everytime I went out I expected it to stall which it always did after 7 miles!

PinkTequila said:

Sorry this seems like an old thread now. I have just sold my 2.5 petrol 90 becuase of this same problem and I had had enough after changing everything I could think of bother electrical and fuel. The guy I sold it to fitted a ballast resistor and it has been fine since. I am not sure why it worked fine for me for three years then started playing up but it drove me mad. Everytime I went out I expected it to stall which it always did after 7 miles!

Click to expand...

Probably because as I explained earlier, there is a broken connection in the coil windings somewhere. When the coil is COLD the ends of the break are joined and make contact, so the thing works. When it heats up and EXPANDS, the ends of the break separate, arc for a bit (poor running engine now) and then it stops.

As soon as it stops the current stops flowing, and it cools down.

Go back to the start.

CharlesY