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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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are you sure your tank isn't plugged up. check your fuel filter
 

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Discussion Starter #10
Thanks. Will check/re-check resistances.
The coil was getting hot-hot, not just hot, though seems a more normal temperature now.

Have since tweaked the timing a smidge, and did get it idling nice enough.

Though, after a little bit, it did still idle okay, but when revved would get very shaky and juddery. After a little more, it sounded like it was starting to struggle at idle, so i switched it off. Could this be the coil breaking down as it warms up? Or fuel, as you have suggested.

Filter looks fairly new, but i've not changed it, so will check it out.

Thanks again.
 

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Quick test #2 involves a timing light and a few zip ties.

Attach the timing light to the coil wire. Zip tie the trigger to the "down" position. Run the light out under the back of the hood and zip tie it to the passenger wiper arm so you can see the flashes from the driver's seat.

Take the car for a drive until it acts up. If the flashes from the light remain even and constant as the car dies you have a fuel problem. if the light starts flashing erratically and cuts out along with the car then you have an ignition problem. If you have a coil that is getting very hot, check your resistance between the ignition switch and coil+ and within the coil primary circuit. Many a coil has overheated from bypassing the resistance wire/
 

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Discussion Starter #12
Thanks Woodchuck. Will give that a try.

Coil resistance measures okay. 1.5 ohm primary, 8k ohm secondary.
I have 2 ohm from batt +ve to coil +ve. Maybe a bit high, but think is okay?
 

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Discussion Starter #13
Have tried as you said Woodchuck.
1st time I fired it up since the other day and was missing almost instantly. The timing light was missing also, therefore ignition problem.

I measure 10 volts at the coil +ve post. This didn't seem to fluctuate but maybe multimeter just doesn't pick it up quick enough?
Would this then point back at the coil despite the resistances measuring okay or would you think its elsewhere?

Thanks again.
 

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Discussion Starter #14
Just to expand on the above:
Tried another coil. Still missing.
Tried 12v straight to coil. Still missing.
Added an earth direct from distributor to battery. Still missing.

So, to me it suggests either HT lead, points or condenser.??
All of which are new.

Going to try the electronic ignition again tomorrow to see if it rules them out.

But, are there any suggestions on where to look next please?
 

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There ought to be a little braided ground wire inside the distributor connecting the breaker plate to the case. Might as well make sure that that's in good shape too while you're poking around in there.
 

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Discussion Starter #17
Sorry for my late reply, but thought I'd update you as seems to be okay now.

Seems like it was an iffy coil and bad points, hence swapping out 1 part at a time didnt cure it. Changed the coil and put the electronic ignition back in, and touch wood, has been okay so far.

Many thanks for your help, guys.

Onto the next problem ??
 
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