Farmall A, I'm stumped, won't fire

First off thanks to everyone who has replied
to my previous posts.

Can't get this 39 farmall to fire. Below is
what I have done and checked. Whats my next
step? Could I have messed up the timing the
first time I took the magneto apart? Would I
even be getting spark if so? Would that
even keep it from running?

Have spark at all 4 plugs (could it be too
weak? I don't know how bright it should be,
did replace condenser)
Have compression
Have gas to the cylinders (plugs wet with
gas after cranking for a while)


Thanks in advance for your help!
 
A thready light blue or yellowish spark will not light the fire. It needs to be able to jump a quarter inch with a crisp medium blue snap. If the spark meets that test it should make the engine run. Firing order:1342 with #1 at the radiator. Looking at the cap from the back the order is:
2-1
4-3
The internal rotor drive gear must be in time (marks on teeth) to assure the pointing of the rotor to the correct terminal to the correct plug.
.013" is the gap set on the high point of the distributor cam. The impulse coupling must work (a crisp snap as the tractor is cranked or rotated with the starter) No impulse coupling snap. no spark. Timing is at TDC. when the coupling trips. If all else fails, put a distributor and coil on it from another Farmall and hot wire it to the battery to get it running. when you knoe it runs, the repair will be easier. Jim
 
check the rotor if it lines up with the tower when the impulse trips make sure #1piston is on compression, You can be off 180. 39 A does it still have the slide sw on the mag
 
IF the plugs are wet, it may be flooded. Heat them with a torch to burn off the fowling. & try again. Rotor should be timed on the C mark if you had that apart.
 
Sounds like I do have too weak of a spark (altho that might not be my only problem). How can I get a better spark out of the magneto? Anything I should clean/replace?
 
If the gap is correct and points are clean, and the rotor is timed, the condenser could be failing, or the magnet could be weak. the magnet should attract a screw driver with aggressive pull. Jim
 
By rotor timed do you just mean the gears lined up properly? Is there anything to what some guys say about getting "HOTTER" spark plugs? Would replacing the coil do anything?
 
The coil is built into the mag top. If it is making a spark, it is likely OK. Not guaranteed to be, but starting spark voltage is not as high as running or full power. Jim
 
if you have spark it will fire I have seen all colors and they do start and run but spark needs be in time. You mite want to remove all plugs now hook up #1 plug ground it near the hole. Using the starter with finger in the hole watch for spark when #1 hits compression that way you know everything is in time and it will start and run if there is gas.
 
They do flood easily - I agree with others, dry to plugs and start again - this time no choke.

I'm a fan of starting fluid at times like this. It's helpful in finding the problem. If it starts firing on the starting fluid, you'll either be up and running, or if you get nothing at all, you know something's up beyond flooding - probably timing, or open valves.

Another thing you can try is make some timing marks with chalk. If you're pulling plugs anyways, that's a good time to do it. Make sure you've got cylinder 1 (front) on the COMPRESSION stroke - not exhaust (remember there are two top dead centers - many forget). and match mark that position on your pully and engine somewhere - doesn't have to be fancy.

Then you can use a timing light to see where it's actually firing. You may be surprise.

It can be easy to get those mags set to fire like half a step before they hit the tower - my memory's very fuzzy on that and I can't remember exactly why that is but I remember doing it myself. So you end up firing NEAR the pin which give you a weak spark. Somebody help me out here! what am I talking about? I can't remember. :)


Another kind of obvious thing to check is that the wires are in the right order, but also in the right order of rotation - don't assume you did it right.
 
Can check or change the coil. When our A died once, a 7 mile tug didn't do anything(drove it to where it died, no trailer available) Poked at everything that we could without pulling the mag apart. Eventually we took it off so we could check the coil(couldn't get at cap screws with on) and other parts. Turns out the coil was warped about a 1/2 inch shorter then a new one. Now it runs great.
 
Those tractors only want a QUICK burp of choke.

Make sure you have a good blue spark on each plug that will jump a 1/4", I put a screwdriver in the wire and hold it about that far from the block.
 
pull starting the tractor is a possibility (assumes you and one other are safety oriented and iknow the procedure. No over speeding the engine, use 3rd gear and stay near 3 or 4 mph. Have good signals between puller and pullee. The brakes work well or this is not an option. Keep the chain tight at all times.
If it starts with the pulling effort, it may be the impulse coupling. The mag will not produce enough voltage at cranking speeds to fire plugs unless the impulse coupling is snapping correctly, but if pulled, the speed is enough. Jim
 
(quoted from post at 14:37:37 01/31/16) Boy I can barely get 1/8 inch spark with a screwdriver and it's yellowish. What else should I be checking?
see you replaced the condenser but what about the points? How are the contact faces?
 

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