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Tractor Talk Discussion Forum

O/T 71 or 72 ignition problems

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Gary in TX

02-13-2008 14:39:36




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I have purchased a 71 or 72 C/40 Chevrolet Dump/Grain Truck. Put points/condenser/rotor and cap on today as well as a coil. I can't get fire to the plugs.
Any ideas, I know it can't be much. I want to do the work myself to save teh labor. i'm not a master mechanic by any means but not a dunce by any means either. Looking for any and all help. I'm getting 12 volts to the coil on both sides, 12 volts to the points and condenser, just can't get anything out too the plugs.
Don't make sense to me?????
Thanks in advance

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Gary in TX

02-14-2008 05:55:56




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
Thanks for all the great information guys, its been a long time since I dealt with point ingnition on a truck or car, never did deal with a point ign. on a V-8 either. My bet is from what I've read is that its in the points or coil wire. I will tinker with it some more afterwhile. I did get 12 volts to both sides of the coil each time I checked. You can't hardly see in there to do any checking on the poing setting but I do have a dwell meter out in the shop. I bet ya she will crank today. Keep the information coming guys.
Thanks!
Gary

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ericlb

02-14-2008 04:07:50




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
most common things are 1 points not closing, check as described below, 2 wires from points or condensor touching ground somewhere in the distributor, 3 metal tang on top of rotor not touching nipple in the top center of the cap[ my jubilee got me that way yesterday] 4 bad new parts, post back with what you find please



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RusselAZ

02-13-2008 20:47:51




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
Your points aren't closing. The chances are tiny of your engine stopping with the cam holding your points open so you have that 12 volts on both sides of the coil. when the points close it should be 0 volts on the negative side.



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noncompos

02-13-2008 20:29:33




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
Were rotor and cap exact replacements?? If rotor arm short may leave too much air gap between rotor arm and plugwire contact inside dist cap; check cap carefully for cracks (they get banged around in shipping and stocking). Check cap contacts inside and in outside plug wire connections to make sure no preservative coating or anything could be preventing passage of spark. Assuming truck ran before you did your work, try replacing old parts one at a time to see if it runs.
Good luck.

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2x4

02-13-2008 17:29:02




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
sometimes the wire thru the bottom of the distributer will wear thru the insulation & short out against the plate.



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leroy in ne

02-13-2008 16:31:28




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
oil film on points? run adollar bill thru them to clean. wire from coil to points shorted or broken? wire connection at points tight and not shorted to advance plate? just a few things to look at you may have forgotten to check. also point gap , as i remember these are the delco unipoints adjustable with an allen wrench and can be a little touchy to adjust, with dwell meter recommended for final adjustment

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Old Ford Mechanic

02-13-2008 16:30:50




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
Gary stick another coil wire on that baby and see what you got.And also this,you have made sure the distributor is rotating? A sheared distributor gear roll pin is a possibility.



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Bob

02-13-2008 15:05:44




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
Connect a 12-Volt test light between the points side of the coil, then turn on the ignition.

If the points are "open", the test light should light.

If the points are "closed", the test light should NOT light.

Then crank the engine. The light should flash as the points open and close.

Post back with the results of those simple tests!



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old

02-13-2008 14:58:55




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 14:39:36  
Points maybe bad/dirty. Cap or rotor could also be bad. Any one or all of them can cause that problem. I would replace the points condenser cap and rotor and then go from there. Never hurts to do a full tune up any how



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GAry in TX

02-13-2008 15:05:55




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 Re: O/T 71 or 72 ignition problems in reply to old, 02-13-2008 14:58:55  
As per my first post, I have allready changed the points/condenser/cap/ rotor and coil.



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old

02-13-2008 15:12:24




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 Re: O/T 71 or 72 ignition problems in reply to GAry in TX, 02-13-2008 15:05:55  
You may have a bad new condenser, not uncommon now days. Or you could also have a bad set of plug wires. The wire from the coil to the cap if bad will stop the spark before it gets to the cap



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Gary in TX

02-13-2008 15:23:39




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 Re: O/T 71 or 72 ignition problems in reply to old, 02-13-2008 15:12:24  
Thanks, I have thought that the new parts might be bad as well as I have done quite a bit of lawn mower service many moons ago. Saw that quite often in spark plugs and cheap ign. sets.
Will keep on plugging, I knwo it has to be something simple.



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504-2

02-13-2008 18:15:18




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 Re: O/T 71 or 72 ignition problems in reply to Gary in TX, 02-13-2008 15:23:39  
make sure you have fire from the coil,could be a bad coil wire.



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