Oh Boy! An electrical problem!
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Oh Boy! An electrical problem!
1980 F-250 had no spark...replaced cap rotor condenser wires and plugs still nothing....replaced ignition module and KABOOM she took off and ran like a top for approximately 10 minutes...come back two days later and NO SPARK...so....hopin someone somewhere has a clue because we're scratching our heads and cussing....
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Joined: Jan 2001
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From: Virginia
Take the module and get it tested at the store, most of them can do it. If it's bad, see if they will give you another one.
When you plug the new one in, get a meter and as the engine is running, put one lead on a good ground on the engine block, and the other lead on the + of the coil. If you get 12v or higher, your resistor is missing or some wiring has been done, and you need to turn the truck off and remedy that before you run it very long.
When you plug the new one in, get a meter and as the engine is running, put one lead on a good ground on the engine block, and the other lead on the + of the coil. If you get 12v or higher, your resistor is missing or some wiring has been done, and you need to turn the truck off and remedy that before you run it very long.
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Hi Dave and thanks so much for that suggestion. I will do just that. New question: The resistor you mentioned...where is it located and what do I tell the parts guy that is more specific than, "I need a new resistor." ?? I REALLY appreciate your help this is on my snow plow and winter is comin!
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From: Virginia
Yes, the resistor is made in the harness. See if everything looks original. If not, I bet they wired around it. I have been suggesting people buy the large white resistor for Chrysler products, and it seems to do the job, even though the resistance is just a tad off.
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I had my module tested at Autozone. Failed.
This diagram was posted somewhere else on the board (I forget who scanned it, I'll pull it down if it's not supposed to go here).
The resistor wire is a little fatter and has a squishier insulation and is oftentimes pink or brown/pinkish depending on age. The core is silver in color-not pure copper. Two wires feed into the coil, as one gives it a full 12V when you're cranking the starter.
Just make sure the module gets a full 12V, and the coil between 7 and 9.
This diagram was posted somewhere else on the board (I forget who scanned it, I'll pull it down if it's not supposed to go here).
The resistor wire is a little fatter and has a squishier insulation and is oftentimes pink or brown/pinkish depending on age. The core is silver in color-not pure copper. Two wires feed into the coil, as one gives it a full 12V when you're cranking the starter.
Just make sure the module gets a full 12V, and the coil between 7 and 9.
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resistor wire
Hi guys...sure do appreciate all the helpful info, pictures, diagrams, etc...I am having a hard time finding the resistor wire...can anyone tell me where to look for it? Does it run from the coil to the module...? Or from the module to the distributor....? Thanks again for all the help, this snow plow's gotta run!!!
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pedant
Joined: Jan 2008
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From: EXTREME southwest CT
Follow the coil hot wire back to the plug.
Look on the other side of this plug for a red wire, spliced to the thicker resistor wire coming from the "hot in run" side of the ignition switch.
You will likely have to unwrap some of the harness to find this splice.
Odie has a picture...
Look on the other side of this plug for a red wire, spliced to the thicker resistor wire coming from the "hot in run" side of the ignition switch.
You will likely have to unwrap some of the harness to find this splice.
Odie has a picture...
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coil hot wire
ok that's awesome...now...which is the coil hot wire? and by going, "back to the plug" your're meaning is one of the plugs that hook to the ignition module, is that right? but the wire which needs replacing is running from the ignition switch is that right? thanks for helping this old man get his snow plow running!
pedant
Joined: Jan 2008
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From: EXTREME southwest CT
The coil has two wires.
Red and green.
The green wire is ground and goes to the module (and tach, if you have one)
The red wire is hot and comes from the plug pictured above.
The one with the shrink tube covered splice going to it.
If the resistor wire was open or missing you would only have spark while cranking.
Like Dave Franklin mentioned, get the truck running and then connect a voltmeter to the + terminal of the coil at the 'U' shaped connector.
Test the voltage while running before you think about digging into the harness.
How butchered is the wiring in your plow truck?
Red and green.
The green wire is ground and goes to the module (and tach, if you have one)
The red wire is hot and comes from the plug pictured above.
The one with the shrink tube covered splice going to it.
If the resistor wire was open or missing you would only have spark while cranking.
Like Dave Franklin mentioned, get the truck running and then connect a voltmeter to the + terminal of the coil at the 'U' shaped connector.
Test the voltage while running before you think about digging into the harness.
How butchered is the wiring in your plow truck?
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ok super...the wiring doesn't look butchered up at all to me...I did find the resistor wire YAY!!...if I'm going to replace the resistor wire, do I just cut it off on either end - leave enough to connect to...is that the thing to do? I'm getting a new ignition module and I can run that test for volts going from coil....
Fleet Mechanic
Joined: Mar 2014
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From: Saskatchewan Canada
Test first!
Don't butcher your harness, resistor wires are not a wear item.
Sounds pretty glamorous to say "I've changed the resistor wire", but truth is they almost never fail. Only problems are from people cutting them out.
Don't butcher your harness, resistor wires are not a wear item.
Sounds pretty glamorous to say "I've changed the resistor wire", but truth is they almost never fail. Only problems are from people cutting them out.
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back to the drawing board
I replaced the ignition module and I still have no spark of any kind...refer back to the start of this mess when I replaced this module a week ago and it ran just fine for about 4 times then died and failed to produce any kind of spark...so I don't think its the ignition module and the harness including the resistor wire all seems to be in place...any other ideas would be most welcomed!
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From: Virginia
If you have voltage on the supply to the module, the only thing left is the pickup inside the dist or the coil. I think there is a resistance test you can do on the pickup to see if it's bad. Do a google search and see if you can come up with it. I think some of the guys on here know what it is also. You could try "duraspark ii pickup coil resistance test" or something like that.
There may be a resistance test for the coil also.
There may be a resistance test for the coil also.
pedant
Joined: Jan 2008
Posts: 23,576
Likes: 38
From: EXTREME southwest CT
Unplug the distributor.
Set the meter to ohms.
On the distributor side;
Check the black wire to ground
Should be zero.
(This is the ONLY ground in the system)
Check across the orange and the purple wire.
It should read 400-900 ohms
Set the meter to ohms.
On the distributor side;
Check the black wire to ground
Should be zero.
(This is the ONLY ground in the system)
Check across the orange and the purple wire.
It should read 400-900 ohms