Engine shuts off after about 1 hour

[Val V]

Wow, this is a massive body of work on this topic. Sorry, i didnt search for it before i posted. Still, what would cause tach to barely move now?

[ndutton]

Sorry, I thought the main question was coil temperature.

Regarding the tachometer, right now it could be any number of things:

• Is it driven off the coil, alternator or a dedicated tach drive (old school)?
• How is it supposed to be driven?
• If coil driven type, is it connected to the "-" coil post?
• Connections good?
• Maybe the tach has expired.
• Is there a 4-6-8 cylinder switch on the back?

Too many unknowns for a meaningful response. Pictures? Existing wiring diagram?

[Val V]

[*]If coil driven type, is it connected to the "-" coil post?

Yes it is driven by coil. It is connected to "-" and to "+" and to the ground. This hasnt changed but after this new coil i put on its barely registering any rpms.

Val

[ndutton]

Well then, since its performance changed immediately after replacing the coil which included removing and reconnecting all the wires . . . . . time to double and triple check those connections and positions. I mean, if it worked before the coil change and not after, the timing is pretty incriminating.

[tenders]

In my experience tachometers are quite sensitive to corrosion on the contacts. Take some fine sandpaper and shine up everything going to the tach and she might spring back to life.

[Val V]

Well then, since its performance changed immediately after replacing the coil which included removing and reconnecting all the wires . . . . . time to double and triple check those connections and positions. I mean, if it worked before the coil change and not after, the timing is pretty incriminating.

I am not on the boat now to check but should i maybe try verifying voltage by the tach and/or between + and - of the coil? I dont know if it supposed to read 12v or thereabout

[ndutton]

I am not on the boat now to check but should i maybe try verifying voltage by the tach and/or between + and - of the coil? I dont know if it supposed to read 12v or thereabout

No, no. The "-" coil terminal is NOT a solid negative. If you measure voltage between it and the "+" terminal it will be jumping all over the place. The "-" terminal is a switched negative at a frequency of 2X RPM. It turns the coil on and off.

I have every confidence the coil and EI (the source of the switching) are working fine because the engine is running. The culprit I think is the quality of signal the tach is receiving either by poor connection or a simple wiring issue.

I'll add this: I'd forget about the tachometer until the new EI ignition system is dialed in re: system amperage/volts/ohms. It's way more important right now.

[Val V]

Results and a question

Just wanted to report to the community my results. Installed 50 watt 1.5 ohm resistor. Engine starts right away and after 15 minutes coil is now hovering around 100F (35-40 degree drop from before the resistor install). Voltage at the coil to the block now reads 10.7 v.

Resistor on the other hand is around 170-180F. Hard to get precise reading with IR but few times temp showed over 200. Tom's FAQ says it is expected to be around 165F. So time will tell if this temp will kill the resistor.

So now to the question: I've been reading a lot on this forum how coil overheating coult be caused by high voltage and installing a resistor mitigates the risk of burn out. But I was curious how much coil heat could be attributed to the spark plug wires and/or spark plugs themselves? Wouldn’t coil get hotter and hotter if all the voltage it builds up cannot be adequately dumped out? Maybe coil gurus could chime in on this.

As always, thank you so very much for the time!

Val

[ndutton]

Resistor on the other hand is around 170-180F. Hard to get precise reading with IR but few times temp showed over 200. Tom's FAQ says it is expected to be around 165F. So time will tell if this temp will kill the resistor.

It depends on the resistor. If you used an automotive type designed for ignition use, the kind with the ceramic body, there's a reason it's ceramic. It should be just fine. Excessive resistor heat is an indication of excessive amperage and should be addressed however.

I've been reading a lot on this forum how coil overheating could be caused by high voltage and installing a resistor mitigates the risk of burn out.

Coil overheating is a result of amperage which is a function of voltage and resistance. It's often generalized around here as voltage only but that's not entirely accurate. I could provide an example of two systems with the exact same voltage where one is guaranteed to cook the coil and the other isn't.

But I was curious how much coil heat could be attributed to the spark plug wires and/or spark plugs themselves? Wouldn’t coil get hotter and hotter if all the voltage it builds up cannot be adequately dumped out? Maybe coil gurus could chime in on this.

You have hit on the theory that started me off on the coil/EI studies, a theory I never tested to conclusion. The idea I wanted to test was whether a slightly greater plug gap (although still functioning) would require a more complete coil dump and therefore a cooler coil. I was planning on coil temp measurements with different plug gaps but in following where other testing and research led, I got distracted.

[Val V]

Neil,

Pertronix suggests to have .040-.045 gap with the flamethrower. I did that on mine and coil temp was around 135-145. I didnt test before/after just went with the redommended settings as part of the install steps. I can continue testing this theory if this would be of use for the community. However, i dont have high end 8mm+ wires. Mine are only a year old which i bought at a local marine shop for A4. They are indeed perfectly sized in length but not as beefy as some i've seen.

Is it possible to test amperage with my multimeter? Mine only allowed for upto 10amp. If i put it inline between ign and coil would it be too much for the meter during cranking/running?

Val

[ndutton]

I can continue testing this theory [plug gap variation and its effect on coil heat] if this would be of use for the community.

I'd be interested but I can't speak for others. I might be the only one.

However, i don't have high end 8mm+ wires. Mine are only a year old which i bought at a local marine shop for A4. They are indeed perfectly sized in length but not as beefy as some I've seen.

Beefy in terms of outside diameter? That may be due to insulation so perhaps not an accurate comparison.

Is it possible to test amperage with my multimeter? Mine only allowed for up to 10amp. If I put it inline between ign and coil would it be too much for the meter during cranking/running?

Your multimeter's amperage is sufficient for our ignition (~4 amps) but I have a minor concern about a loss of voltage due to the typically small size of the tester leads. All the ignition power will be going through the meter and its leads during the test.

As for what Pertronix suggests, my opinion is some days chicken, some days feathers.