No Spark. Help please
Discussion
I posted this in the MG section but looks like it is one of the least read forums on here!
Basically I would like to get things sorted/ ordered this w/e and I'm after some advise. I unfortunately left my ignition on when testing other ignition components and being distracted by tasks which were not the task at hand. This has resulted in failed ignition components.
I have a Lucas sport coil, Mallory Unilite distributor and a Jaguar Ballast resistor.
I immediately replaced the coil with a spare. I then did the coil test of connecting the red multimeter lead to ignition side of coil and black lead to earth. I had a reading of 7.1v. I assume my ballast resistor is okay as if it was fried it would surely be reading 0 or 12v? (My MGB has a V8 conversion so requires a ballast resistor).
Then, I did the test demonstrated here
https://www.youtube.com/watch?v=PSiw4thM21k.
Which is:
Remove both the distributor cap and rotor, then turn the ignition ON but DO NOT START car.
Now connect your Red voltmeter wire to the NEGATIVE terminal (-) on the coil, by attaching the Red lead wire clip from voltmeter to the (-) terminal.
Next attach your Black voltmeter wire to an engine ground on a good ground source. We suggest a manifold, or header bolt. Most anywhere on the engine is good.
Now the voltage should read about 11 to 12 volts at this point. Remember to turn the key on for this reading! 12 volts must be present on your voltmeter.
Next, place a credit card down into the distributor, blocking the 2 photo optic eyes on top the module facing each other on the top. With eyes blocked, the volts should drop way down below 2 volts or less. This drop is a must! If the voltage drops down to anything under 2 volts, then the module is good and ready to use. If the voltage does NOT drop, the module will need to be replaced.
This damage could have been caused by many things, such as: power surge from an alternator, high resistance spark plugs and plug wires, improper ground wires, if someone has given you a jump, if you have given someone a jump, or battery chargers, which can also damage ignition modules. If voltage always stays below 2 volts and never increases up to 11-12 volts, then the module has been spiked by high voltage and needs to be replaced.
I had a consistent reading of 1.14 with the optic eyes clear and obscured. I did not see a 12v reading.
I conclude that the Mallory Unllite module is fudged. Is this likely to be the correct diagnosis?
Basically I would like to get things sorted/ ordered this w/e and I'm after some advise. I unfortunately left my ignition on when testing other ignition components and being distracted by tasks which were not the task at hand. This has resulted in failed ignition components.
I have a Lucas sport coil, Mallory Unilite distributor and a Jaguar Ballast resistor.
I immediately replaced the coil with a spare. I then did the coil test of connecting the red multimeter lead to ignition side of coil and black lead to earth. I had a reading of 7.1v. I assume my ballast resistor is okay as if it was fried it would surely be reading 0 or 12v? (My MGB has a V8 conversion so requires a ballast resistor).
Then, I did the test demonstrated here
https://www.youtube.com/watch?v=PSiw4thM21k.
Which is:
Remove both the distributor cap and rotor, then turn the ignition ON but DO NOT START car.
Now connect your Red voltmeter wire to the NEGATIVE terminal (-) on the coil, by attaching the Red lead wire clip from voltmeter to the (-) terminal.
Next attach your Black voltmeter wire to an engine ground on a good ground source. We suggest a manifold, or header bolt. Most anywhere on the engine is good.
Now the voltage should read about 11 to 12 volts at this point. Remember to turn the key on for this reading! 12 volts must be present on your voltmeter.
Next, place a credit card down into the distributor, blocking the 2 photo optic eyes on top the module facing each other on the top. With eyes blocked, the volts should drop way down below 2 volts or less. This drop is a must! If the voltage drops down to anything under 2 volts, then the module is good and ready to use. If the voltage does NOT drop, the module will need to be replaced.
This damage could have been caused by many things, such as: power surge from an alternator, high resistance spark plugs and plug wires, improper ground wires, if someone has given you a jump, if you have given someone a jump, or battery chargers, which can also damage ignition modules. If voltage always stays below 2 volts and never increases up to 11-12 volts, then the module has been spiked by high voltage and needs to be replaced.
I had a consistent reading of 1.14 with the optic eyes clear and obscured. I did not see a 12v reading.
I conclude that the Mallory Unllite module is fudged. Is this likely to be the correct diagnosis?
Then
lucebayjack said:
If voltage always stays below 2 volts and never increases up to 11-12 volts, then the module has been spiked by high voltage and needs to be replaced.
I had a consistent reading of 1.14 with the optic eyes clear and obscured. I did not see a 12v reading.
seems fairly conclusive to me.I had a consistent reading of 1.14 with the optic eyes clear and obscured. I did not see a 12v reading.
TooMany2cvs said:
The only thing that determines whether you need a ballast or not is the coil. If it's a ballastless coil, you don't need it - and you're feeding the coil half the voltage it's expecting, as a result.
This. Plus, if the V8 conversion retained the original wiring there's a ballast wire [resistor] built into the wiring loom...which may mean you could be running with two ballasts :. if still fitted, it would be wise to remove this wire and run with a new coil, either ballast or without. The only other point is that depending upon the coil type you may get tachometer flicker if running without a ballast.Is the V8 conversion a 3.5 carb one or a 3.9/4.0/4.2/4.6 EFi conversion?
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