No spark

1986 CADILLAC HEARSE
77,000 MILES • 5.0L • V8 • 2WD • AUTOMATIC
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CMANSON420
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I bought this car it was rough put some money into it it was running but rough. so did a tune up on it but the guy I bought it off of didn't attach the positive terminal on the new alternator properly and it arched out. now I have no lights it will roll over but no spark to the plugs.
Sep 6, 2020 at 11:01 PM
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KASEKENNY
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We need to find out where we have spark and where we do not. So if you have no spark to the plug then we need to find out where we do. So go back to the distributor and see if there is spark coming out of it. If not (assuming it does not) then we need to check the voltage coming from the electronic control module. Also, we need to make sure it is getting 12 volts on the feed from the ignition switch.

Most likely that arc shorted something or popped the 20 amp fuse shown in the diagram.

I attached the wiring diagram. Let me know what the voltage is on each of these and we can go from there. Thanks
Sep 7, 2020 at 9:21 AM
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CMANSON420
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So I pulled the coil out and from ground to bottom center pin on ohms I have a reading 7.94.
Sep 17, 2020 at 4:17 PM
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KASEKENNY
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So if you have almost 8 ohms of resistance then that is an issue. However, let's just run through this test just to confirm that is causing your low voltage but I think you found it.
Sep 17, 2020 at 4:30 PM
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CMANSON420
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I'll check that. thank you so much for your help.
Sep 17, 2020 at 5:04 PM
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CMANSON420
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I also checked every fuse and there good.
Sep 17, 2020 at 5:05 PM
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KASEKENNY
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Okay. If fuses are good then we have to have an issue within that testing. so let us know what you find and we can go from there. Thanks
Sep 18, 2020 at 6:25 PM
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CMANSON420
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It's a Hearse. do you know how to check the back interior lights?
Sep 18, 2020 at 6:54 PM
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KASEKENNY
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I am not sure we have a manual on the Hearse but I am sure we can help figure it out. However, we need to start a new post as we need to keep each one to one topic. The reason is, others will not find the solution to the question on the lights under a topic of No Spark. So let's get a new one started and we can figure something out. Thanks

https://www.2carpros.com/questions/new
Sep 19, 2020 at 7:15 PM
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CMANSON420
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So I just put a different coil in it and still no spark. what's the next step?
Sep 20, 2020 at 4:20 PM
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KASEKENNY
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We need to go to the distributor and check the battery voltage terminal for 12 volts while cranking the engine. Let's do this and go from there.
Sep 20, 2020 at 7:27 PM
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CMANSON420
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Okay, thank you.
Sep 20, 2020 at 9:09 PM
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KASEKENNY
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You are welcome. Keep us updated on what you find and we can go from there.
Sep 21, 2020 at 6:04 PM
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CMANSON420
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How do I do that?
Sep 22, 2020 at 3:18 AM
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KASEKENNY
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You mean how to you check the voltage at the distributor? I attached the wiring diagram. We need to check voltage at this wire (pink) while cranking the engine. You should have 12 volts. Let me know what your voltage is and we can go to the next step.
Sep 22, 2020 at 6:30 PM
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CMANSON420
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Okay, so I took the cover off of the coil igniter put my meter on it and as it's cranking it says 9.20 to 10 volts. I can try putting my coil in it to see.
Sep 23, 2020 at 8:41 PM
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KASEKENNY
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That doesn't point to the coil. That just means we need to check some other things. Next thing is to check the TACH terminal for voltage when the key is on. If it is over 10 volts then we need to check the coil spark output. If it is under 10 volts then the module is the issue.

Just let me know what the voltage is because if it is under 1 volt we need to check some wiring connections.
Sep 24, 2020 at 6:01 PM
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CMANSON420
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How do you check the coil spark output?
Sep 25, 2020 at 12:13 AM
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KASEKENNY
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We need to go to the output to from the coil to the spark plugs and either use a spark tester or pull the coil wire and ground it with a screw driver. The screw driver is not that safe due to it may shock you so I would invest in a spark tester pictured below.
Sep 25, 2020 at 8:56 PM