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Ford NAA Coil Check
|Don Hildebrand||I'm trying to get a friend's 1953 Ford Jubilee tractor started and can get no spark to the plugs.
I have used a Craftsman Miltimeter to check continuities and voltages in the distributor and ignition system and have yet found nothing wrong.
On pulling the distributor to coil wire out of the top of the disributor and holding it 1/4 inch from "ground" while cranking the engine with the ignition "on", I get no spark.
Is this indicative of a bad coil?
I was told that the tractor had not run for over 3 years. It is obvious that there has been little maintenance on the tractor and what changes have been made are of the "baling wire" variety.
The electrical system has been converted to a 12 volt alternator system years ago.
I have a Ford Jubilee wiring diagram that I just copied off the internet today.
I'm an amatuer mechanic and don't know any way to test a coil.
Am hoping for some good advice.
|Bob G||With the key on, position the points so that they are open. then hold coil to dist wire like you did and use a screw driver to bridge the gap at the points. You should get fire from the coil wire. if not check for valtage at the wire going to the coil. should be battery voltage. if present check terminal going to points, should also be battery voltage with the points open.
If yu get fire this way then the points may be bad not making contact. Hope i did not confuse you too much!
|Don Hildebrand||Bob G.,
I will do what you suggested tomorrow.
I have 12.5 volts at the terminals where it should be.The point gap measures .025 inches.
I slid paper thru the points to clean them.
Watching the points while cranking the engine, the operation appears "normal".
If I can't identify the points as the problem, does that indicate a bad coil?
Thanks for your reply.
|Bob g||If yu can get spark by jumping the points then the coilis good. no spark would be a bad coil. these round coils are pretty much bullet proff, but yours couldd be bad.
|Don Hildebrand||Bob G.,
This morning, under my shade tree,I resumed the search for fire at the plugs.
I rechecked for 12 volts into the coil, which had been there previously, and now measured less than 4 volts (and fluctuated).The 4 ohm resistor got too hot to touch in a couple minutes.
I removed the resistor from the circuit and connected the ignition switch wire to the coil input terminal.
Then, with the switch "on", I performed the "coil wire to ground" test you suggested.
I got "spark" from the coil wire when held 1/4" from engine ground. I then cranked the engine while holding the coil wire and got normal spark that the plugs should see.
I then connected the #4 spark plug wire to an external plug with a 3/16" gap and got a yellow spark thru the gap when cranking.
I had previously disassembled and cleaned the carb and lines and verified there was gas in the carb float bowl.
Then I attempted to start the engine for a few short cranks with no success.Tried once with starter fluid into the air cleaner with the same rsult.
I am not optomistic about getting this tractor to start without major engine work.
When cranked, the engine exhibits very little compression and ,seems to me, to spin too freely.
I plan to put a tablespoon of ATF into each of the cylinders and let it sit for a day to see if I can get more compression for starting.This was suggested in one of the Forum Archive comments.
Then I will go from there.
The owner of this tractor dabbles in old vehicles and old old machinery,buying low and selling for a profit.I doubt if he wants to sink money into it but in my opinion, this 1953 NAA, with good tires and no missing parts may not be ready for salvage, and then again it may be.Hard to tell at this point.
Thanks for your help.You saved me from buying a new coil for testing.
|BOb G||I would do a compression check. may be aable to rent a gauge from a local autoparts store.
If you have a 6 volt coil I would not run it without the resistor should yu get it running. 12 volt coil does not require a resistor.
|Don Hildebrand||Thanks Bob G..
I do have a compression tester and measured the compression this morning.
#s 1,2, and 3 have equal 78 psi compression.
#4 cyl. has no compression. Probably a stuck valve.
I will let you know how I come out.
|Jim Loveridge||Now that you've got spark at the plugs, double check the firing order. Who knows how many other folks have messed with this tractor? It's 1-2-4-3 in case you don't already know. But if it's a 6 volt coil don't keep the key on for very long with the resistor by-passed or you will be buying a new coil. Also, not all 12 volt coils have internal resistors. Strange that you had 12 volts at the coil at one time and then it was down to 4 another time. Makes me think that there are bad connections in the circuit or the ignition switch may be at fault.
|Don Hildebrand||Bob & Jim:
After freeing up the throttle linkage this afternoon, the Jubilee started. I ran it for about 10 minutes stationary. Did not let the RPM go much above 1200 because the water pump and fan shaft have wobble.Needs a new water pump.
The alternator system showed 30 amps charge.
Oil pressure was 50 psi on the guage.
The #4 cylinder kicked in, off and on, after running for a few minutes. Sounded like it was hitting on all 4 when I shut it down.
A reason for the voltage discrepancy may be that
the wiring was not correct. someone apparently worked on the tractor previously trying to get it to run and jazzed it all up. For example, the fuel line connection at the sediment bowl was connected to the "blind" port instead of the outlet port.
The ignition wire from the toggle switch (key switch was bypassed and wires were hanging loose)
was connected to the distributor terminal.The faulty resistor may have also been part of the errant reading.Then again, I am prone to goof more often than I like to admit.
But, because I got lucky,with the help from the Forum, on an 8N and Jubilee, my friend who owns the tractors will consider me an ezpert.
Thanks again for your help,
|Bob G||The compression reading you got are pretty low. I would fill the cylinders with AFT and let her set for a week or so. might free up the rings.
good to heqr you got it running!
|Jim Loveridge||Ditto what Bob said. Thanks for the up-date.
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