J D 40 will not start

GAS SUPPLY:

When she cranks over is there any smoke or vapor coming out the exhaust??

After you try and start her and immediatley thereafter remove the plugs, are they wet or bone dry??

Are the plugs a sort of gray color or flat black powdery sooty looking or an uneven shinier rough black color????

I guess the fuel is on??

Is there a drain cock at the carbs bottom you can open (with gas turned on) to insure a good stream of gas flows out??? If not, remove the fuel line where it attaches to the carb and insure a good gas stream is there??? If not, remove any glass sediment bowl bottom and with the fuel on see if gas enters to fill the glass bowl??? They can get rust and crud settlled in the tanks botom to fill the inlet pipe or screen preventing fuel flow. Also, be sure it has clean fresh water free gas since shes been sitting a while, even if all the flow tests pass, cuz water or stale gas dont do well.

IGNITION FAILURE Remove the plugs and with the plug wires attached and them up against the tractors frame somewhere to ground their sides, turn the ignition on and crank her over and see if both plugs are firing a good visible blue spark???

You could also remove the coil wire from the distributor (other end still in coil) and crank her over with the ignition on and with the coil wires end 1/8 inch away from the tractors frame and see if she sparks.

Try and see if shes gettign gas and if the plugs are firing and post back. The points could be oxidized or theres a fuel line restriction like at the gas tank to sediment bowl entry or maybe even the carbs needle valve or float could be stuck or corroded or clogged up from sitting. If you drained the gas at the carb and had it shut off above however, the float and needle valve could have been open stuck open, not closed, causing her to flood over.

If shes getting gas, I would inspect the points and clean/polish them if gray oxide coated but otherwise smooth, and check their gap and inspect and clean or replace the plugs and then try the spark tests above first.

John T Nordhoff in Indiana

1) First, I would start with a fresh set of new plugs, as they dont cost all that much and yours could be fouled.

2) With the new plugs and their wires attached, but the sides against the tractors frame ground and ignition on, crank her over and see if both plugs produce a good blue spark. If so, she may be fine, if not, disconenct the coil wire from the distributor (leave attached to coil) and place that end about 1/8 inch from frame and turn her on and cranks her over and see if the coil wire sparks the 1/8 gap to frame. If so but not at the plugs per above, the plug wires may be bad (replace with soild wire core wires, not carbon auto supressor wire) or theres a problem in the distributor cap and/or rotor. Clean and inspect the cap for cracks or carbon paths.

2) If still no spark anywhere: Inspect the points and if gray oxide coated but otherwise smooth and not pitted, clean/polish them but if burned or black or pitted or carboned, replace them gapped at 0.022 and see if she sparks then.

3) If still no spark despite good and proper gapped points: If you have an ohmeter or DC battery powered continuity checker, with the ignition OFF, The points should show an OPEN circuit to the metal of the distributor (ground) when they are open, but a near 0 ohm dead short to ground when closed. If they are permanently shorted out by a bad wire or bad points or spring assembly even when open, she will never run. If they dont show near 0 resistance to ground when closed, she wont run either.

4) Next be sure you have power to the coils high (not to distributor) side when the ignition is turned on. She cant run unless the swith has power and its good, so when all is on theres battery voltage on the coils high side. (Use a test lamp or volt meter) If not, by pass jump around the ignition switch by running a wire from the batterys non grounded post direct down to the coils high side (hot wiring) and see if she fires the plugs and/or starts then. If so but not if switch is on and you remove that wire (ie she runs hot wired but dies if wire is removed) either the switch (it happens) is bad or theres a blown fuse.

5) If theres power getting to the coils high side but still no spark, you can do the step 3 test a little different this way, if you have only a test light but no voltmeter or ohm meter. Turn on the ignition and the coils high side should glow a test lamp. NOW, place the test lamp over on the coils low (to distributor) side and crank the engine over and the light should flash on (points open) and off (points closed) repeatedly. If she dont flash on and off there shes never gonna run, so the points may be bad (not gettign a good ground connection) or the distributor itself dont have a good connection to ground. Try a ground jumper wire to the distributors base plate to insure the points are gettign a good ground and see if the lamp goes off when the points are closed. If so, check the distributor to frame for a good clean grease and rust free contact.

If the lamp never comes on on the coils low side per the tests above, the condensor could be shorted (remove it and see if she works then, if so, it may be bad) or the points assembly or a wire to teh points shorted or the coils primary windign is open.

6) If the points and condensor are good and not shorted out and the lamp flashes on and off on the coils low side as the engine is cranked but she still wotn fire out the coil or the plugs, the coil may be bad.

SUMMARY

I would just try new plugs first and then make sure the coil is gettign power when the ignition is on (by pass the switch to see if its bad) and inspect and change and re gap the points if needed (a common cause of no spark), and clean and inspect the cap and rotor and plug wires, and post back what you find.

Good Luck John T Nordhoff

~On the starting, first thing to suspect on that 40 after sitting idle for a while is oxidized contact points [common]. Clean or replace the points & re-try starting it.

~You might want to pull a plug wire & plug then put the plug back in the wire & lay it on the block, then try cranking it with the ign switch TURNED ON & look for a bluish spark to jump the plug gap [if no spark see below].

~The next thing to suspect is the ign switch for picking up internal resistance from sitting a while [another common failure on the 40].

~The other thing to suspect is the carb internal passages & jets clogged with gum & varnish deposits from sitting without fuel in the carb.

~Start your trouble shooting procedure by opening the carb bottom drain cock & looking for a pencil sized stream of fuel flowing for AT LEAST 30 SECONDS. If you don�t have that you will need to find the restriction & repair it. Start at the tank fitting & work your way to the carb. [could even be a stuck carb float]

~If the fuel flow is ok then use a test light, or volt meter [or even a headlight bulb] & make sure you have over 5.5 volts [or at least power] at the ignition switch side of the ign coil [if not, suspect a blown dash fuse or high resistance in the ign switch]. If you have power at the ign switch side of the coil then suspect oxidized points, open in the wire from the coil to the distributor, or poor distributor ground.

~If you don�t have power at the coil�s ign switch side run a jumper wire from the starter�s big battery stud to the NON distributor side of the coil & try starting it [if it then runs your problem is the ign switch or wiring between the ammeter & the ign coil [goes through a dash fuse & the ignition switch].

~If you have power to the coil & fuel flow out the bottom of the carb & it still doesn�t start your problem could be an internal carb problem or low compression [give it a cranking compression test].

~If the carb is suspected post back & we will talk you through a carb trouble shooting procedure as that 40 carb is a little different than the other 2-cylinder Deere�s & has some little passages in it..