Ignition coil gets no power
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Registered User
Joined: Jun 2024
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From: California
Ignition coil gets no power
Truck suddenly won't start anymore.
I replaced plugs and plug wires 4 months prior to this. Battery is 1 year young. It turns over, but no voltage at the coil.
I checked the fuses .. other than the "stop lamp fuse" all seem to be ok.
Truck was running, I made a stop of less than a minute (engine off). Did not restart since then.
A friend said something about "interlock fuse" which supposedly is NOT in the 2 fuse places known to me.
Is this a real thing?
Any suggestions?
I replaced plugs and plug wires 4 months prior to this. Battery is 1 year young. It turns over, but no voltage at the coil.
I checked the fuses .. other than the "stop lamp fuse" all seem to be ok.
Truck was running, I made a stop of less than a minute (engine off). Did not restart since then.
A friend said something about "interlock fuse" which supposedly is NOT in the 2 fuse places known to me.
Is this a real thing?
Any suggestions?
Administrator
Joined: Apr 2010
Posts: 87,366
Likes: 4,209
From: Clayton MI
Never heard of an interlock fuse.....
Does the coil get power at initial key on? (It will only see power for about 3 seconds, so, two people is pretty much a requirement to test....) After that, the PCM needs to see the engine turning to power it again. If you get the initial 3 seconds, but, nothing thereafter, could be a bad crank sensor, or pcm......
What year is your truck? Engine? Trans?
Does the coil get power at initial key on? (It will only see power for about 3 seconds, so, two people is pretty much a requirement to test....) After that, the PCM needs to see the engine turning to power it again. If you get the initial 3 seconds, but, nothing thereafter, could be a bad crank sensor, or pcm......
What year is your truck? Engine? Trans?
Thread Starter
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Registered User
Joined: Jun 2024
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From: California
No power to coil
I actually had a mobile mechanic look at it with me.. I turned the key and he checked the voltage. There was none.
The guy who mentioned "interlocking fuse" is a different guy, not the mechanic.
It's a 2001 RAM 1500 Gasoline engine, Magnum V8, I think 5.2L. Automatic transmission.
The guy who mentioned "interlocking fuse" is a different guy, not the mechanic.
It's a 2001 RAM 1500 Gasoline engine, Magnum V8, I think 5.2L. Automatic transmission.
Last edited by ptiemann; Jun 9, 2024 at 06:19 PM.
Administrator
Joined: Apr 2010
Posts: 87,366
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From: Clayton MI
Download the service manual for your truck from here. Wiring diagrams are in section 8w.
That said, the ASD relay, which is what supplies power to the coil, and injectors.... is in the Power distribution center, under the hood. Pull the relay, and glance at the bottom, terminals should be labeled. You want to verify you have power at pin 30, at all times, and at pin 85, when the ignition is on. If those check out, swap it with the horn relay, see what happens.
That said, the ASD relay, which is what supplies power to the coil, and injectors.... is in the Power distribution center, under the hood. Pull the relay, and glance at the bottom, terminals should be labeled. You want to verify you have power at pin 30, at all times, and at pin 85, when the ignition is on. If those check out, swap it with the horn relay, see what happens.
Champion
Joined: Sep 2012
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From: Central VA
Did you try scanning the PCM for any codes with an OBD2 code reader? If so, what pending or stored codes are displayed?
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Administrator
Joined: Apr 2010
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From: Clayton MI
We don't even know if his vehicle IS OBDII......
Grand Champion
Joined: Feb 2015
Posts: 7,435
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Not to mention the lac of punctuation and capitalization and you can throw in grammar also. None of us here are English teachers but come on now. Oh, And i forgot to mention posting on a year old thread instead of starting your own. And everybody here has a crystal ball to know details so there is no need to post them. 
