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No Spark - Trying To Fire The Resto Project

 
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Old 02-06-2019, 01:18 PM
Superblue400
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No Spark - Trying To Fire The Resto Project

So, I'm trrying to start the 79 F250 Custom 400 I've been working on for 2 1/3 years. I'm getting power to the red wire at the coil with key on, but not getting anything (flashing or constant test light) at the green wire on the coil when cranking. It has a NOS Motorcraft Ignition module, and a reman dist unit (actually - it looked Chinesium new). I tested the green wire that goes to the coil at the connector to the module on the fenderwell - when you first crank it, the test light lights up bright for just a second, then it does nothing. Anyone encounter this before?
 
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Old 02-06-2019, 02:22 PM
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Have you verified the distributor rotor is turning?
 
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Old 02-06-2019, 03:16 PM
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Yes it is.
 
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Old 02-06-2019, 05:57 PM
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Does the ignition module have power? I tried to hotwire my "new" 77 a few days ago b/c the key was lost. I had power to the coil, but if the ignition module isn't supplied power it will not fire. Learned that the hard way, after pulling my hair out for a couple minutes.
 
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Old 02-08-2019, 06:52 PM
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I would check the pick up coil in the distributor. I got a new one that only lasted a short while and a replacement that was open.

Disconnect the connector at the distributor. Testing the connector that goes into the distributor, make sure the black wire (ground) has little to no resistance (0 ohms) to ground.

Check the resistance between the two other wires that go into the distributor. This tests for an open pickup coil. Should have around 400-800 ohms.

Then check each of those leads to ground. Should be in excess of 70,000 ohms. This tests for a shorted pickup coil.

Also make sure the connections are tight at all of the plastic connectors (one at distributor and two at the module) including the one on back of the ignition switch. The retaining ears and plastic become brittle over time and crack and break causing poor connections.
 
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Old 02-09-2019, 10:33 AM
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I think it's also common for the connector on the coil itself to make a poor connection. When I bought my truck the PO had the connector taped on in a "special' way. I was like..you know you can buy new connectors, right?
 
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Old 02-09-2019, 12:53 PM
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Green? Red? Is this all factory wiring, or have some (or all) been replaced?
Are there stripes/traces on each wire? If so, what color are they?

Yes to checking the magnetic pickup at the connector. And make sure that the Black wire (might be Black w/white stripe?) shows a good ground connection between the distributor, then the distributor body and engine block, and ignition module. The module is bolted down, correct?
Is this the original ignition control module? Or if not, is it an original replacement? Should have a blue colored "grommet" for all '79's I believe, but you would no normally have been able to match up the connectors if it was wrong anyway.
In the module's 2-wire connector the Red wire should have a full 12v with the key ON. The White wire should have 12v when the key is in START. Having both is not critical to getting a spark, but at least one of them must have 12v with the key in RUN/ON position.

Good luck!

Paul
 
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Old 02-10-2019, 03:59 PM
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Thank you to all for your help. I will try testing everything tomorrow. I have a distributor and module out of the 79 Bronco I bought I will also try swapping - that truck was running when I parked it a month ago.
 
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Old 02-11-2019, 05:20 PM
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Originally Posted by 1TonBasecamp View Post
Green? Red? Is this all factory wiring, or have some (or all) been replaced?
Are there stripes/traces on each wire? If so, what color are they?

Yes to checking the magnetic pickup at the connector. And make sure that the Black wire (might be Black w/white stripe?) shows a good ground connection between the distributor, then the distributor body and engine block, and ignition module. The module is bolted down, correct?
Is this the original ignition control module? Or if not, is it an original replacement? Should have a blue colored "grommet" for all '79's I believe, but you would no normally have been able to match up the connectors if it was wrong anyway.
In the module's 2-wire connector the Red wire should have a full 12v with the key ON. The White wire should have 12v when the key is in START. Having both is not critical to getting a spark, but at least one of them must have 12v with the key in RUN/ON position.

Good luck!



Paul
Paul, am getting 12V at the white wire, but nothing on the red wire in any key position.
 
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Old 02-11-2019, 05:49 PM
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Reach under the dash and hold firm pressure on the ignition switch connector, pushing it tight towards the ignition switch for a positive connection and try starting the engine WHILE you hold it in this manner.
 
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Old 02-19-2019, 11:22 PM
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Any luck Superblue?

Originally Posted by Superblue400 View Post
Paul, am getting 12V at the white wire, but nothing on the red wire in any key position.
When you get power on the White wire, is it only with the key in START, or anytime the key switch is ON?
While my own personal vehicle worked with power to the White wire only with the key ON, yours may not for some reason. In my case I had power anytime the key was in the ON position and that was enough to run the engine even with no power to the Red wire.
But they may not all work that way.

Again though, is this a re-wired truck, or all original wiring?

Paul
 

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