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Discussion Starter #1
Hi.
So, I've been having intermittent engine cuts out, but would fire straight up again after.
Recently it's been harder to start and keep running that I haven't dared drive anywhere.
Have set timing, new distributor, plugs, leads and coil.
Latest addition was electronic ignition and after that was running okay with just the very occasional slight miss. Came to it a week later and it was more misses than fires.
Put the points back in, no change. Reset the timing (was a couple degrees out) and did fire, but missing a bit still. My thinking was maybe bad distributor earth and adjusting the timing just scratched the contact faces a bit cleaner.
Anyway, still not very good, so have got the multimeter on it.

I'm more familiar with diesels than petrol, but I'm pretty sure these readings aren't good.

Can anyone shed some light on next steps and where to look please.

Voltage readings between the earth cable and the earth Post of battery:

Ign off. 0.7 micro amp draw. 10v then drops to 4v.

Ign on. 12.7v. Also have 12.7v at coil.

Acc position. 12.7v. Also have 12.7v at coil.

Voltage reg disconnected, Ign on. 12.7v.

Then, with earth cable reconnected to battery:
Ign on. Battery reads 12.3v. And only 3.6v at coil.

The battery itself is new and when isolated is 12.7v.

So, low coil voltage probably my problem. Any suggestions on where to go next?

Many thanks in advance.

1966 289 Auto :)
 

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This is a schematic for a 69, but yours is essentially the same. The problem is in that path across the bottom. Check the battery ground (far left), check for 12v coming out of the ignition switch, through the tach if you have one, and to the resistor wire. The resistor will lower the voltage to the coil. You mentioned adding an electronic ignition so something in the circuit here has changed. Don't forget to check the engine ground to chassis (at the far right). The upper path through the starter solenoid gives 12v to the coil around the resistor wire for starting only.
 

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My guess is something is amiss with the power going to the coil/electronic ignition. Have a jumper wire ready and hooked up to +12v, start the car and wait for it to start missing and such, then connect that jumper wire to the positive side of the ignition coil. If it smooths out then your problem lies somewhere upstream of the +12v coil supply wire connection. If it continues running rough then your problem is elsewhere.
 

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Hi.
So, I've been having intermittent engine cuts out, but would fire straight up again after.
Recently it's been harder to start and keep running that I haven't dared drive anywhere.
Have set timing, new distributor, plugs, leads and coil.
Latest addition was electronic ignition and after that was running okay with just the very occasional slight miss. Came to it a week later and it was more misses than fires.
Put the points back in, no change. Reset the timing (was a couple degrees out) and did fire, but missing a bit still. My thinking was maybe bad distributor earth and adjusting the timing just scratched the contact faces a bit cleaner.
Anyway, still not very good, so have got the multimeter on it.

I'm more familiar with diesels than petrol, but I'm pretty sure these readings aren't good.

Can anyone shed some light on next steps and where to look please.

Voltage readings between the earth cable and the earth Post of battery:

Ign off. 0.7 micro amp draw. 10v then drops to 4v.

Ign on. 12.7v. Also have 12.7v at coil.

Acc position. 12.7v. Also have 12.7v at coil.

Voltage reg disconnected, Ign on. 12.7v.

Then, with earth cable reconnected to battery:
Ign on. Battery reads 12.3v. And only 3.6v at coil.

The battery itself is new and when isolated is 12.7v.

So, low coil voltage probably my problem. Any suggestions on where to go next?

Many thanks in advance.

1966 289 Auto :)



" My thinking was maybe bad distributor earth and adjusting the timing just scratched the contact faces a bit cleaner"

Its definitely possible it happened that way. Car running volt meter attached to battery negative and the other to the dist housing you should see less than a quarter a volt.. Next pop the cap off and attach your lead to the points plate and crank the engine. The spec should be same as the cable test. .5 or less

"Voltage readings between the earth cable and the earth Post of battery:
Ign off. 0.7 micro amp draw. 10v then drops to 4v."

Your choice of using mA to read for an issue statically really wont bear much fruit for battery cable testing. Using volts and turning auto ranging off if you have it and moving the decimal over. Engine cranking you should be at .5 or so

"Then, with earth cable reconnected to battery:
Ign on. Battery reads 12.3v. And only 3.6v at coil"

I would suspect you may have accidentally attached your meter leads positive battery term to positive coil. It makes more sense if you subtract the 3.6 volts you read from the 12.3. You would get 8.7 volts on the coil positive. Otherwise your engine would never run on 3.6 volts..Unless your intermittent fault happened at that moment. Which if it did you needed to jump on it to discover the issue.
Hi.
So, I've been having intermittent engine cuts out, but would fire straight up again after.
Recently it's been harder to start and keep running that I haven't dared drive anywhere.
Have set timing, new distributor, plugs, leads and coil.
Latest addition was electronic ignition and after that was running okay with just the very occasional slight miss. Came to it a week later and it was more misses than fires.
Put the points back in, no change. Reset the timing (was a couple degrees out) and did fire, but missing a bit still. My thinking was maybe bad distributor earth and adjusting the timing just scratched the contact faces a bit cleaner.
Anyway, still not very good, so have got the multimeter on it.

I'm more familiar with diesels than petrol, but I'm pretty sure these readings aren't good.

Can anyone shed some light on next steps and where to look please.

Voltage readings between the earth cable and the earth Post of battery:

Ign off. 0.7 micro amp draw. 10v then drops to 4v.

Ign on. 12.7v. Also have 12.7v at coil.

Acc position. 12.7v. Also have 12.7v at coil.

Voltage reg disconnected, Ign on. 12.7v.

Then, with earth cable reconnected to battery:
Ign on. Battery reads 12.3v. And only 3.6v at coil.

The battery itself is new and when isolated is 12.7v.

So, low coil voltage probably my problem. Any suggestions on where to go next?

Many thanks in advance.

1966 289 Auto :)

" My thinking was maybe bad distributor earth and adjusting the timing just scratched the contact faces a bit cleaner"

Its definitely possible it happened that way. Car running volt meter attached to battery negative and the other to the dist housing you should see less than a quarter a volt.. Next pop the cap off and attach your lead to the points plate and crank the engine. The spec should be same as the cable test. .5 or less

"Voltage readings between the earth cable and the earth Post of battery:
Ign off. 0.7 micro amp draw. 10v then drops to 4v."

Your choice of using mA to read for an issue statically really wont bear much fruit for battery cable testing. Using volts and turning auto ranging off if you have it and moving the decimal over. Engine cranking you should be at .5 or so

"Then, with earth cable reconnected to battery:
Ign on. Battery reads 12.3v. And only 3.6v at coil"

I would suspect you may have accidentally attached your meter leads positive battery term to positive coil. It makes more sense if you subtract the 3.6 volts you read from the 12.3. You would get 8.7 volts on the coil positive. Otherwise your engine would never run on 3.6 volts..Unless your intermittent fault happened at that moment. Which if it did you needed to jump on it to discover the issue.
 

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You might want to consider purchasing a cheap 12v buzzer, toss some alligator clips on the end, and hook one lead to ground and the other to the "hot" side of the points (place a piece of paper or boxboard between the contacts) turn the key "ON" and start wiggling wires. When the buzzer starts "skipping" you probably found your issue.
 

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Discussion Starter #6
Thanks for the replies, all.

Have tried a couple other bits, such as jumping from battery straight to coil, but no difference. Put the timing light on the coil output HT lead, and no sparks whatsoever.

Reset points gap, etc. Checked cable fitment, etc. No change.

Put my old coil back in, and fired straight up. Had the very very occasional slight miss, but that might have been because it was fairly cold, and i need to adjust the carb a bit more. But seems promising.

Reason i took the old coil out was because it was getting very hot, so figured some issue with it.
(Though, thinking back, i had a bad battery before, and dont think the voltage reg was working 100% right, so this may have had an effect in causing it to get hotter than usual? Though, the voltage reg was under charging, not over charging, so probably not a high voltage issue, unless there were spikes that were upsetting it).

Anyway, looks like the MSD coil is not creating a spark.

Do coils just go bad? Would there be something frying it? It's not been on there very long. Resistances seem to measure okay of the coil, so not sure why it's not creating a spark...

Any thoughts welcomed, please.
 

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One way Coils can be hurt is by having the primary switching circuit grounded for 20 30 minutes with the key on eng off but it will hurt the points as well.. As a note I have never condemned a coil because it felt hot either. Your new coil appears to be a defect too. Its been my experience also through dyno sessions with NA engines HiPo coil changes make no difference on the bottom line either. In general HiPo coils under a hood can be more like engine jewelry like a nic nac on a coffee table.
 

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Grab your ohmmeter and check the coil. Primary resistance should be +/- 1.5 ohms. (RED on +, BLK on -). Secondary should be 7-15kOhm (RED on +, BLK on high tension tower).
 
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