Farmall 400 Ignition Problem

pmarkel · Oct 18, 2016

Updating my post from a week or so ago about the Farmall 400 that will not start. I had rebuilt the carb after suspecting that was the problem but after receiving advice from members of this forum, I was redirected to the ignition. I have since purchased a multimeter and tested for current at the alternator, coil, and distributor. The tractor cranks so I know the starter is working fine and a 12v reading is present at the top terminal of the alternator, both terminals of the coil, and on the terminal on the distributor. The only place where there is not a 12v reading is on one end of the resistor bolted onto the alternator (one end reads about 2 and the other end, which is wired to the coil reads 12). I have checked for spark at the coil by grounding it to the block but I do not see or hear spark when the engine is cranked. A look inside the distributor reveals a little corrosion on the rotor which I cleaned, but no real red flags as far as I can tell. I welcome all advice as I'm a bit of a novice with these things. Thank you for your input.

Peter Markel

rvirgil_KS · Oct 18, 2016

"a 12v reading is present at the top terminal of the alternator, both terminals of the coil, and on the terminal on the distributor"

Check your reading at the wire from coil to side of distributor. Should be 12 volts with points open. With points closed it should go to zero. If it does not go to zero the points, even though closed and properly gapped, are not making contact. Clean points contacts

pmarkel · Oct 18, 2016

Your suggesting the point gap might be incorrect? I was actually going to check that tonight or tmrw morning (at a quick glance they looked pretty far apart and they're supposed to be .020 i think). When I bought the tractor it ran fine and I never did anything with the points, which the previous owner changed in June. Can the point gap change over time?

rustred · Oct 18, 2016

yes it can change... as the lobe on the points wear from use it causes the point gap to decrease. there used to be a small tube of grease that came with points to lube the cam to lessen wear. never see that grease anymore. just use a tooth pick and apply a small amount to the cam. it dont matter what gap the points are set to the engine will still run, as long as the points are opening. but there is a spec..020 to follow for performance. must make sure the point contacts are clean.

John T · Oct 19, 2016

Try my ignition testing procedure

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

John T
John Ts Ignition test

khouse6 · Oct 19, 2016

i had a coil wire that burned to such an extent that tractor would not start. check the ignition wiring

pmarkel · Oct 19, 2016

(quoted from post at 04:48:11 10/19/16) Try my ignition testing procedure

http://www.ytmag.com/cgi-bin/viewit.cgi?bd=farmall&th=5745

John T
John Ts Ignition test

hanks for the link, very informative.

Farmall 400 Ignition Problem

pmarkel

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rvirgil_KS

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pmarkel

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rustred

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John T

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khouse6

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pmarkel

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