440IC can't get spark

Tim_in_IA · Post by **Tim_in_IA** » Tue Mar 31, 2009 12:24 pm

I'm going to check for voltage at the side of the dist terminal when the cap is on to see if it ever goes to 0 or if it stays at -6 or if it stays at 0. That'll tell me what the points are doing inside.

H-D · Post by **H-D** » Tue Mar 31, 2009 5:28 pm

Just for grins, when you test for voltage at the distributor terminal, test for continuity to ground at the point plate with the cap off (naturally) & then also when you press down on the plate. I've seen point plates on distributors with vacuum advance (I know that isn't the case here) flex their grounding lead 'til it broke (within the insulation once) & caused a no start or a major 'dead spot' at a particular load level. Granted, most of these were of the Hop-Sing variety, but you never know what some well-meaning previous owner/mechanic might have done to a fine example of American design & manufacture. Good luck!!! I reckon you're due for some!

jclem40c · Post by **jclem40c** » Tue Mar 31, 2009 8:36 pm

Did you change the cap? Do you have spark if you hold the coil wire 1/4" away from the block (ground)? You state that you lose spark if you put the cap on the distributor. If you have it with the cap off and not with the cap on what about carbon arching? That would be a small carbon trail or possibily a crack (minute) in the cap allowing electricty to follow this trac to ground. This has to be a stupid simple issue that everyone is overlooking. Kinda like Can't see the forest for the trees. If you got spark from the coil wire to ground at 1/4 " and it is crisp and blue in color you will be able to pull the coil wire away slowly and still have it, although the farther away the more yellowish it will become. You should get spark at least 1/2" away from ground. Remember, Infernal combustion engines only need 3 things to function. Spark, fuel & oxygen , the trick is to get them all to come together at the correct time. Go back to square one, breathe deep, and retrace your steps one by one, Slowly. Its gotta work.

CAR · Post by **CAR** » Tue Mar 31, 2009 10:05 pm

When you install the cap you must have somthing that is obstructing the points from operating properly. That is the only thing it can be if you have not hooked the coil wire to the dist. and you lose coil wire spark to ground. Something is not letting the points open and close. You need to make sure you are not pinching the wire to the points or obstructing the points operation in any way. Make sure the points are tightened down good. The rotor and the cap will only come into play when you hook the distributor wire back to the cap. It has to be the points.

I know how frustrating something like this can be, it's like looking for your 9/16 open end wrench and it was stareing at you from the work bench the whole time. You just keep looking past it.

jdemaris · Post by **jdemaris** » Wed Apr 01, 2009 7:58 am

jclem40c wrote: Remember, Infernal combustion engines only need 3 things to function. Spark, fuel & oxygen

Must have compression also, or the other factors amount to nothing.

jclem40c · Post by **jclem40c** » Wed Apr 01, 2009 11:07 am

My oversight, I took compression as a given. Spent 20 years working on lawnmowers and because you spin them over by hand you notice the lack of it right quick.
John

Lu47Dan · Post by **Lu47Dan** » Wed Apr 01, 2009 11:13 am

I know this will sound like a dumb question , but "Do you have the correct distributor cap for the distributor? "
I do not remember if J.D. used several different manufacturers for the distributors on the 440 series or not .
I would suggest that you cut the existing caps top out of it with a wafer wheel (0.045 cutting wheel for a 4-1/2" grinder ) and see if it is pushing against something in the distributor .
I have had electrical problems that were a bear to trace down , broken wires that would test out fine only to go open once they were installed on the equipment again . I had a distributor that would work fine once the cap was off but would quit once the cap was on , that turned out to be the coil to points wire . The wires insulation looked fine and would pass a continuity test with the cap off but failed with the cap on . By cutting the top out of the cap i could see what was happening inside the distributor once the cap was on . I used an old cap I had for it as the new cap was hard to find and expensive to buy . I found out later that there had been a bolt and sleeve through the distributors body originally . This caused a job that should have been a one to two hour job to turn into a three day job .
Keep digging you will eventually get to the bottom of the problem .
JMTC. Dan

Gil · Post by **Gil** » Wed Apr 01, 2009 2:43 pm

Dan, you had the same problem that I mentioned to Tim earlier. I have seen a coil-to-points wire short out where it enters the distributor even when the insulator block looked fine. But I really like your idea of cutting the top off of an old distributor cap so you can peak inside. What a beautifully simple idea

I am going out to the barn now and see if I have an old cap lying around.

Tigerhaze · Post by **Tigerhaze** » Wed Apr 01, 2009 3:55 pm

Gil wrote:Dan, you had the same problem that I mentioned to Tim earlier. I have seen a coil-to-points wire short out where it enters the distributor even when the insulator block looked fine.

I don't kn ow a lot about JD distributors so it may not be applicable, but I have a Ford 8N distributor that had a similar problem. It turned out to be the copper strip connection on the inside of the housing from the through bolt (leading from the insulator from the coil connection on the outside of the distributor) to the points- it had been twisted and had a crack in it. For some reason (probably surface area for electrical contact) you couldn't replace that copper strip with a wire and have it function- I had to order a replacement copper strip to get it to work.

Gil wrote: But I really like your idea of cutting the top off of an old distributor cap so you can peak inside. What a beautifully simple idea I am going out to the barn now and see if I have an old cap lying around.

That is brilliant! I have wondered in the past if I had contact between parts or not and that is a great way to see how the moving parts of the distributor are functioning. Thanks!

jclem40c · Post by **jclem40c** » Wed Apr 01, 2009 9:07 pm

Condenser? A distributor is a distributor is a distributor as the name applies. It distributes spark period. If it( the Spark)comes in to the distributer, the distributor should distribute If it does not, 1, it is not coming into the distributor,2, rotor is not turning (roll pin sheared at base of unit etc,) wires to unit are grounded or broken, condenser bad (?)

Gil · Post by **Gil** » Thu Apr 02, 2009 5:47 am

I agree that the distributor distributes the spark, but it also plays a role in creating it. The spark comes when the coil stores up energy and releases it when the points inside the distributor open and close. A problem can come on the creation portion as well as the distribution portion.

The condenser inside the distributor helps to prevent the points from arcing as I understand it. I would be interested to know what would actually happen if the condenser failed in an open circuit or closed circuit condition. Anyone have any experience on that?

Maynah13 · Post by **Maynah13** » Thu Apr 02, 2009 6:56 am

As an old-timer mechanic, I can answer that one.

The condenser does more than preserve the points, it actually plays a critical part in creating the high voltage spark from the coil. When the points close, a DC current flows through the coil primary, building up a magnetic field. When the points separate, the condenser allows the magnetic field to collapse quickly (acting as a temporary "short"), which causes the induction of high voltage in the coil secondary. If the condenser is open (or removed), you won't get the required high voltage necessary to jump the gap on the plug because the arc across the points dissipates the current into the air too slowly to make the HV pulse. The coil and condenser create an LC oscillator circuit, which is "tuned" to create a high voltage pulse at low frequency.

You can test the condenser with an volt-ohm meter, set on low ohms (200 scale). If it's good, you'll see a slow rise in resistance. Reversing the leads will show a pulse, as the condenser discharges.

Robert

jdemaris · Post by **jdemaris** » Thu Apr 02, 2009 8:00 am

jclem40c wrote:Condenser? A distributor is a distributor is a distributor as the name applies. It distributes spark period. If it( the Spark)comes in to the distributer, the distributor should distribute If it does not, 1, it is not coming into the distributor,2, rotor is not turning (roll pin sheared at base of unit etc,) wires to unit are grounded or broken, condenser bad (?)

No. The word "distributor" in this context is a generic term and connotes a device that has many functions beyond distribution. Some being creating a signal for the coil to create spark when needed, including provisions for timing advance at higher RPMs. Same goes for many other terms used in mechanical technology. Dictionary primary meaning means nothing and context means everything.

jdemaris · Post by **jdemaris** » Thu Apr 02, 2009 8:04 am

Gil wrote:I agree that the distributor distributes the spark, but it also plays a role in creating it. The spark comes when the coil stores up energy and releases it when the points inside the distributor open and close. A problem can come on the creation portion as well as the distribution portion.

The condenser inside the distributor helps to prevent the points from arcing as I understand it. I would be interested to know what would actually happen if the condenser failed in an open circuit or closed circuit condition. Anyone have any experience on that?

Yeah, that's a simple one. A "dead" but not shorted cap can result to a very weak spark in some conditions, along with premature points-wear.

A shorted cap results in no spark at all.

Dead and/or shorted caps in old equipment are very common, mainly because they were wire-in-wax-paper design. New caps are somewhat better with longevity.

A good cap-tester allows you to charge the cap and see how long it holds the charge, along with giving a MFD reading. Usually 1.8 to 3 MFD. Another test is - after charging - hand it to your wife and see if she jumps when the sparks fly from her fingers.

Tim_in_IA · Post by **Tim_in_IA** » Fri Apr 03, 2009 9:30 am

Wow you guys have been busy! This all helps out quite a bit. The weather has been very windy here and some rain so haven't got back to it. Lavoy shipped my new cap out so it should get to me soon. Saturday I should be able to revisit this and do some more of the testing you are recommending. I'll get some pictures and hopefully hear the engine roar.

That is good to know about the condenser collapsing the spark quick. So it still might be in play as an issue but I don't think so since i get a good spark. I should be able to tell if points are opening and closing by watching the voltage on the distributor side terminal go from -6 to 0 to -6. We'll see. I've learned so much from you guys.

Thanks,
-Tim

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