Still missing....

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Model T Ford Forum: Forum 2012: Still missing....
Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Statham on Sunday, August 19, 2012 - 02:00 pm:

I've gapped the plugs to .30, changed the timer, cleaned the carb, checked the compression and checked the air pressure in the tires but I can't seem to get the miss out of my engine!

Originally I had a problem with #3 - I seem to have solved that but now #4 won't fire. Switched plugs and coils - still #4. If I short the commutator wire to the rad support rod - it seems to be ok. I took the nuts, wire and insulator off, cleaned everything and tightened it all back up again but no luck.

Any ideas??

Thanks,
Jeff


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, August 19, 2012 - 02:37 pm:

Carbon tracks in the coilbox wood??
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson-Nicholasville, Kentucky on Sunday, August 19, 2012 - 02:39 pm:

You only have to troubleshoot and locate that problem once in your life and you will never forget it.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Craig Anderson, central Wisconsin on Sunday, August 19, 2012 - 03:43 pm:

No kidding Ron!
It's pretty hard to beat the School of Hard Knocks.
It's the best education you can get.......not very pleasant but one sure remembers....... :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Statham on Sunday, August 19, 2012 - 03:50 pm:

I took the coil box apart last week and coated it with an epoxy. Sanded it smooth and put it all back together and no change.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel D. Chicoine, MD, Pierre, SD on Sunday, August 19, 2012 - 03:52 pm:

Get one of John Regan's coil box rebuild kits and neither you or your grandchildren will ever have to worry about shorts there again.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Garnet on Sunday, August 19, 2012 - 04:29 pm:

Jeff, are you saying you grounded the commutator wire for #4 on the support rod? If so, then that coil will be firing continuously which is not good - it will probably start leaking tar if left operating like this very long. If your engine runs better then you have a problem with that particular wire OR terminal on the commutator. By permanently grounding it you are bypassing the commutator. You should be able to find this problem quickly with a voltmeter (and the engine off).

First, be careful that your meter leads won't be caught in the fan blades, the fanbelt or the pulleys - Safety First.

With the ignition switch OFF connect the positive lead of your voltmeter to a constant source of B+ or the positive side of your battery. Connect the negative lead to the commutator terminal on the coilbox for #4. Crank the engine over by hand and see if you get an indication on your meter of 6 volts or whatever your battery voltage is. Every time the camshaft brings the commutator contact or brush past the #4 terminal your voltmeter should show 6 volts as the timer is supplying the ground connection to the meter which otherwise isn't there. The rest of the time there should be no voltage reading. If you get a good reading then the problem is with the coilbox, the coil, or how the coil fits in it.

If you are not getting a reading then you have a problem back towards the commutator. #4 coil should be connected to the lower right commutator terminal when viewed from the front of the car. Connect your negative meter lead there and crank the engine over by hand again. Again, you should see battery voltage every time the commutator contact comes around. If you get a good reading every time #4 comes around then your problem is with the wiring between the commutator and the coilbox. If you aren't getting a reading then there is something up with the commutator or the terminal is covered with corrosion. It's all just a logical approach.

In real life on large circuits, your fastest troubleshooting method is to cut the circuit in half with your testing process and then go back or forward to the next halfway test point. In the case of our Model T's, the entire circuit is very small so you can find the problem in a minute or two:

(commutator brush or contact) - (commutator contact segment and its terminal) - ( wiring harness) - (coilbox terminal) - (coil)

Rather than just troubleshooting one particular problem with the ignition chain though, start at one end cleaning and tightening connections and put in a new harness if the old one is ratty.

Regards,
Garnet


Top of pagePrevious messageNext messageBottom of page Link to this message  By john kuehn on Sunday, August 19, 2012 - 04:38 pm:

Do you have original wiring, battery cables or have you replaced any or all of them?
I replaced the original battery to starter cable on my 1919 roadster years ago after fighting a battery drain problem. I know that may not sound like anything like that would cause a miss but after 90+ years original wiring and cables get a little less conductive than when everything was new. Thats only my opinion but somtimes things can be less obvious when they are covered up by insulation.
Just a thought.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Sunday, August 19, 2012 - 05:37 pm:

If when you ground the #4 coil ground to the engine, radiator rod or similar, you get good spark at #4 plug that coil should be OK. My guess is your coil contacts in the coil box are not making good contact, particularly on #3 and #4. With the engine running, a good clean plug in #4, remove the coil box lid and push the #4 coil down and forward. If this solves your problem then shim the coil box with cardboard.

You might also pull the coils and bend the contacts out just a little. If you have repro coil box contacts, this could be your problem. Solve this by buying a junk coil box with the original contacts and replace yours.

Do things systematically and when nothing seems to work, quit for the day and try a fresh approach tomorrow.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Jeff Statham on Monday, August 20, 2012 - 10:31 pm:

Thanks for some great ideas folks! I'm heading out camping for a couple of days...with the modern car :-( but I'll try some of these when I get back.


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