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Massey Harris & Massey Ferguson Tractors Discussion Forum
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Weak spark from new distributor

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George in Spoka

10-05-2005 21:02:50




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I just installed a complete and new distributer in my 1955 TO-35 with a Z134 engine. I get a wonderful thick white spark from the wire going into the distributor but I only get a weak thin red spark coming out of the distributor (paper clip test).

I first thought poor ground but I cleaned everything and still no go. Is there some trick to installing a new distributor? Do I need to oil something?

Thanks.

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Jerry/MT

10-07-2005 13:39:37




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 Re: Weak spark from new distributor in reply to George in Spokane, 10-05-2005 21:02:50  
Your spark should have a bluish tinge to it. Are you sure about the oint gap? I'm presuming that you are using copper wire core spark plug wires. Make sure that the wire from the coil to the cap has the brass tips conected properly and is shoved all the way into the distributor cap and the coil. Make sure that rotor metal clip that touches the carbon button on the cap is bent up to make good contact with the button. Make sure all you copper core plug wires have the brass tips connected properly and that they are all pressed down completely in the distributor cap.

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michael lamothe

10-07-2005 09:14:06




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 Re: Weak spark from new distributor in reply to George in Spokane, 10-05-2005 21:02:50  

Is the cap too deep for the shaft that hold the rotor?



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John T

10-06-2005 07:10:49




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 Re: Weak spark from new distributor in reply to George in Spokane, 10-05-2005 21:02:50  
George, Do you mean you get a good high voltage spark out of the coil wire when you remove it from the distributor cap and place its bare end near the engine or frame etc., (and turn engine over) but a poor spark from any plug wires leading out of the distributor cap or what????? ?????

If so, I would suspect a faulty rotor tip or faulty distributor cap like a crack or carbon trace or oil or moisture (but its new right???) or else a bad plug wire.

Or are you talking about the lil coil primary wire that connects to the distributor (and then internally to the points n condensor). When the points are closed and assuming they and the wiring is good and the coil is good and energized you would get a spark when thats connected to the lil distributor side terminal and then the coil would fire when that circuit is opened.

Of course, the distributor has to have a good frame ground to the engine cuz thats where the points gets its ground.

Lemme know

John T, retired electrical engineer in Indiana

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George in Spokane

10-06-2005 21:10:52




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 Re: Weak spark from new distributor in reply to John T, 10-06-2005 07:10:49  
>George, Do you mean you get a good high voltage spark out of the coil wire when you remove it from the distributor cap and place its bare end near the engine or frame etc., (and turn engine over) but a poor spark from any plug wires leading out of the distributor cap?

Yes.

>If so, I would suspect a faulty rotor tip or faulty distributor cap like a crack or carbon trace or oil or moisture (but its new right???) or else a bad plug wire.

I thought the same but it's all brand new. Wait a minute, the fog is lifting...I ordered the original distributor (clip on cap) which is 6 Volt.

I have switched everything else to 12 volts but I assumed that a 6V distributor was the same as a 12V one. Should I have used a different condensor? Is there such a thing as a universal 12V condensor that I can get at an autoparts store?

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John T

10-07-2005 05:47:36




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 Re: Weak spark from new distributor in reply to George in Spokane, 10-06-2005 21:10:52  
George, the distributors ought to be the same, thats just a hunk of iron to turn the rotor and mount the parts etc.

Unless it were DRASTICALLY oversized (which I very seriously doubt) even the wrong condensor shouldnt prevent a spark. If the condensor were bad/shorted, totally removing it will let her spark, but not quite as well plus the points will burn up much quicker.

I have to run, going to an auction but will post my standard troubleshooting procedure for no spark and check back later. This is wayyyyy y more then you need but it saves me time. Let me know what you find.

TROUBLESHOOTING A BATTERY POWERED EXTERNAL COIL TYPE IGNITION SYSTEM:

PRELIMINARY CHECKS:

(A) To see if it happens to be a cap n rotor problem and to see if at least the coil is firing, remove the coil wire from the distributor (leave coil end intact) and place its bare end to within 1/8 inch from tractor iron, turn her on n crank her over, and see if she jumps that gap with a good visible blue spark????? If so but the plug wire ends (from wire end to 1/8 inch to frame) or the plugs themselves don�t fire, its a cap n rotor or plug wire problem. If the coil wire isnt even sparking, see below.

(B) Next open the cap and see that the points are gapped correct and indeed opening and closing as the engine is cranked and the distributor shaft rotates and MAKE SURE THEY ARE NOT BURNED OR PITTED OR CARBONED UP BADLY !!!!! !!!!! If so, running a point file between them to clean them up might make her run again HOWEVER that�s only a temporary cure, so if that cleaning makes her spark, INSTALL N GAP NEW POINTS. In the event they appear good but only gray oxide coated, non abrasively clean/buff/polish them using say a dollar bill or shop cloth etc. and see what happens.

MORE TROUBLESHOOTING IF ALL THE ABOVE STILL FAILS TO MAKE HER SPARK

1) THE VERY FIRST THING YOU GOTTA HAVE is voltage to be present on the coils high supply (NOT to distributor) terminal when you turn the Ignition switch ON. If not she cant ever fire, but in the event the ignition switch or circuit/wire down to the coil or any Ballast Resistor is bad or open, you can HOT WIRE it by jumping a hot ungrounded battery voltage source to the coils high input supply (NOT to distributor) side n see if she runs then???? If she fires hot wired, you could have a bad ignition switch ((That can happen, when Ignition is on, the switches IGN terminal must turn hot)),,,,, ,or an open Ballast (if it has one) or a bad/open wire from switch to coil.

If the switch is good, if you turn the ignition switch on and place a test lamp on the coils high (NOT to distributor) terminal SHE MUST LIGHT UP. If not again, look for an open Ballast Resistor (if it has one, it should read around 1.25 to 2 ohms across its terminals) or bad/open wires from the switches IGN output down to the Ballast (if it has one) and distributor.

2a) When the Ignition switch is turned on, voltage should appear on the coils high input side. That would be 6 volts on a straight 6 volt system or 12 volts on a 12 volt non external ballasted system, or around 6 volts on a 12 volt system that used a 6 volt coil plus an external Ballast Resistor and the coil is good and the points are closed and they and ALL wiring is good.

2b) To insure the coils low voltage primary winding is not bad/open, use an ohmmeter and measure its DC resistance between its lil + and -terminals. If its an open circuit (no continuity) its bad/open and will NOT work. It should measure around 1.25 to 2 ohms or so if its a 6 volt coil and maybe 2.5 to 3.5 if its a 12 volt internally ballasted coil. NOTE CAUTION have all leads and any voltage source attached to the coil for this simple primary winding continuity test. 3) Next, place your voltmeter or test lamp over on the coils other low to distributor terminal side, turn her on and crank the engine over.

4) A test lamp there should flash ON (when points are open) and OFF (when points are closed) as the engine is cranked slowly.

5a) If the lamp never comes on there, the coils primary is bad/open,,,,, ,,,,or the points are never opening,,,,, ,,,or theres a shorted/bad condensor (remove its lead to points and see if lamp comes on, if so, bad shorted condensor or its wiring),,,,, ,,or the points wire is shorted,,,,, ,,or the distributors side pass thru stud is grounded (use ohm meter to test that),,,,, ,,,or the points may have a shorted spring.

5b) If the lamp never goes off as engines cranked, the points are not closing or are bad,,,,, ,,or the wire or circuit is missing from the distributor to the points,,,,,or the distributors not well grounded to the tractor.

She cant fire the coil unless its low side is getting a conductive ground return path via closed points and then the circuit is open when the points open.

Be sure the condensor or its wiring is NOT shorted out and see if the lite comes on (when points open) with the condensor disconnected. If removing the condensor makes her spark, replace the condensor.

SUMMARY

Be sure the points are closing fully and open on high cam and ARE NOT BURNED OR PITTED OR CARBONED UP BADLY,,,,, ,theres voltage present on distributors high side at all times when ignitions on (or its a bad switch or open ballast or bad wiring to col),,,,, ,voltage on coils low side flashes on and off as distributor is cranked,,,,, ,,,condensors not bad/shorted,,,,, ,,no shorts in wires to points and no shorts in pass thru side out distributor stud,,,,, ,,coil has continuituy.

You may luck out n just need a new set of points. If the coil wire fires (see above) and the plug wire ends to 1/8 from frame but NOT the plugs, they are baddddd ddddd . Check them BOTH.

Good Luck n God Bless, post back any questions and your findings and any questions.

John T Nordhoff in Indiana, retired electrical engineer who usually lurks over on the Mother Deere boards versus over here on the �dark side�.

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Jerry/MT

10-08-2005 12:10:34




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 Re: Weak spark from new distributor in reply to John T, 10-07-2005 05:47:36  
John, in 4) where you say "A test lamp should go ON when the points are open...." shouldn't that be when the points are closed as that is when the primary circuit is closed to ground through the closed points? Then the light should be OFF when the points are opened.



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John T

10-08-2005 20:39:05




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 Re: Weak spark from new distributor in reply to Jerry/MT, 10-08-2005 12:10:34  
I stand on what I said. The light should flash ON when the points are open and go OFF when they are closed. Think aobut it, when they are closed that electrical point id dead grounded cuz the points closing takes it there i.e. NO LIGHT cuz the points are basically shortign out any voltage to lite the lamp. When the points are open theres voltage present and the lite comes on if the switch is good n working and the coils primary is good.

Perhaps you misunderstood or I mis explained where the test lamp is attached and measures voltage??? The test lamp measures voltage from frame ground to wherever you stick its other tip probe.

Anyway thanks for your question n discussion, maybe we had a "failure to communicate" like in the old movie Cool Hand Luke lol

take care, John T

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Jerry/MT

10-09-2005 13:25:42




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 Re: Weak spark from new distributor in reply to John T, 10-08-2005 20:39:05  
Thanks for the explanation, John. Guess the lamp resistance is real high relative to the point resistance so there is little or no current supplied to the lamp. Thanks again for the explanation. Guess I would have checked the coil by putting the lamp across the coil primary connections and then watched for the lamp to go on and off when the points closed and opened respectively.



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George in Spokane

10-08-2005 20:27:09




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 Re: Weak spark from new distributor in reply to Jerry/MT, 10-08-2005 12:10:34  
Thanks for all the advice guys but no go.
Using a different condensor, using no condensor, bending up the rotor metal, pushing in the wire connectors in the cap, checking everything else still results in a weak spark.

If I wasn't bald I would be pulling out my hair!

I think I'm going to have to find a mechanic to come over. I can't believe I'm being stopped by what should be such a simple problem.

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