Help troubleshoot running rough on battery

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Model T Ford Forum: Forum 2017: Help troubleshoot running rough on battery
Top of pagePrevious messageNext messageBottom of page Link to this message  By David Kriegel Mishawaka Indiana on Friday, May 12, 2017 - 04:51 pm:

Well new starter installed, new coils, gapped plugs new plug wires
'

Starts quickly on battery at high starter rpms ( not sluggish) Same speed starter will not start on magneto

Car runs rough on battery trying different spark advancements

Switch over to magneto the engine is SMOOTH and PuRRRS

Any idea on how to smooth it out on battery? It is amazing how rpms pick up on magneto with the carb still set at around 900 rpm jumps to 1400?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Friday, May 12, 2017 - 05:40 pm:

Why would you ever want to run on battery if your mag works well? They were built to run on mag. The coils are properly set up to work at their best on mag and while they can be adjusted to run fairly well on battery you would be compromising performance on mag by doing so. Start on battery and switch to mag immediately.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Kriegel Mishawaka Indiana on Friday, May 12, 2017 - 06:07 pm:

Val my point is this. I like my cars tuned well. My other T's run well on battery and mag So again my question is why? Low voltage from the battery? No Puzzeled


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Zibell, Huntsville, AL on Friday, May 12, 2017 - 06:22 pm:

It was how the coils were adjusted. Car should be run on magneto as the coil points will last longer on AC current than DC current from what I've been told. Have you tested your magneto output? There are many posts on the form to tell you how to do that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kevin Fielding "Ewe-taw" on Friday, May 12, 2017 - 06:42 pm:

David,
You are on the right track, I would guess low voltage as well. If the truck starts fine your battery maybe fully charged but it isn't making it to the coil box.
I would look for good grounds from the frame to the firewall to the coil box. Then I would check and make sure you are getting full voltage at the coil box. I would be highly suspect of the key switch dropping your voltage.
I had a similar problem with the truck and took a bit to figure it out.
Good luck,
Kevin


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Friday, May 12, 2017 - 06:44 pm:

Swap a set of coils from a car that runs good on both and see if it stays the same or runs better.
Some coils run better on Mag, some run fine on both and some run better on battery.
Some of the coils made in the 50's and 60's seem to run better on battery.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Friday, May 12, 2017 - 06:49 pm:

I'm thinking low battery voltage to the coils too. The points will last longer on the mags AC current but they should not run as poorly as you state on the battery especially if it runs so well on mag. Regardless of how they were set up, hopefully with an approved tester such as an HCCT , their performance should not vary to the extent you describe. Battle voltage to the coils would have to be quite low to cause this but something's going on when you switch over. Check it out with a voltmeter and let us know the result as this seems to be the most likely problem.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Kriegel Mishawaka Indiana on Friday, May 12, 2017 - 09:12 pm:

Kevin and Charlie THANKS the key switch and wiring is old. Also lights not working. I will replace the wiring harness and switch to both hopefully fix this problem and prevent others !


Top of pagePrevious messageNext messageBottom of page Link to this message  By Tim Eckensviller - Thunder Bay, ON on Saturday, May 13, 2017 - 08:06 am:

Since the key switch and wiring are old, does it have an old ammeter too? My car was giving me all sorts of trouble until I figured out the ammeter was intermittently grounding itself. Had I managed to make it run long enough to get to the switch I bet it would have run wonderfully on mag like that.


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