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No spark

Tiny
CMANSON420
  • MEMBER
  • 1986 CADILLAC HEARSE
  • 5.0L
  • V8
  • 2WD
  • AUTOMATIC
  • 77,000 MILES
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.
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Sunday, September 6th, 2020 AT 11:01 PM

18 Replies

Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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
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Monday, September 7th, 2020 AT 9:21 AM
Tiny
CMANSON420
  • MEMBER
  • 10 POSTS
So I pulled the coil out and from ground to bottom center pin on ohms I have a reading 7.94.
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Thursday, September 17th, 2020 AT 4:17 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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.
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Thursday, September 17th, 2020 AT 4:30 PM
Tiny
CMANSON420
  • MEMBER
  • 10 POSTS
I'll check that. Thank you so much for your help.
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Thursday, September 17th, 2020 AT 5:04 PM
Tiny
CMANSON420
  • MEMBER
  • 10 POSTS
I also checked every fuse and there good.
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Thursday, September 17th, 2020 AT 5:05 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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
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Friday, September 18th, 2020 AT 6:25 PM
Tiny
CMANSON420
  • MEMBER
  • 10 POSTS
It's a Hearse. Do you know how to check the back interior lights?
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Friday, September 18th, 2020 AT 6:54 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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
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Saturday, September 19th, 2020 AT 7:15 PM
Tiny
CMANSON420
  • MEMBER
  • 10 POSTS
So I just put a different coil in it and still no spark. What's the next step?
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Sunday, September 20th, 2020 AT 4:20 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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.
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Sunday, September 20th, 2020 AT 7:27 PM
Tiny
CMANSON420
  • MEMBER
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Okay, thank you.
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Sunday, September 20th, 2020 AT 9:09 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
You are welcome. Keep us updated on what you find and we can go from there.
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Monday, September 21st, 2020 AT 6:04 PM
Tiny
CMANSON420
  • MEMBER
  • 10 POSTS
How do I do that?
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Tuesday, September 22nd, 2020 AT 3:18 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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.
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Tuesday, September 22nd, 2020 AT 6:30 PM
Tiny
CMANSON420
  • MEMBER
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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.
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Wednesday, September 23rd, 2020 AT 8:41 PM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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.
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Thursday, September 24th, 2020 AT 6:01 PM
Tiny
CMANSON420
  • MEMBER
  • 10 POSTS
How do you check the coil spark output?
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Friday, September 25th, 2020 AT 12:13 AM
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
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.
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Friday, September 25th, 2020 AT 8:56 PM

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