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 Post subject: no power to coil
PostPosted: Sat Mar 06, 2010 12:40 pm 
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1 BBL (New)

Joined: Sat Mar 06, 2010 12:23 pm
Posts: 2
Car Model:
1986 Dodge D150 Sl6 4 on the floor.

ok here's where the problem started. i changed my distributor without setting TDC and so i had to do it the hard way. somehwere down the line i lost spark.. i've replaced the coil and the ignition control module (icm) i have a hot? wire that goes from the icm to the resistor and a + wire from the coil to the resistor then the - from the coil is grounded. my issue is im getting power when the icm is unplugged i have power to the resistor but when i plug it in i have no power i've had this truck for 8 months and it has ran with no prior electrical issues. maybe some wiring is wrong idk but this is how it is currently wired and how it was wired when it ran, to the best of my knowledge.

please help any word of advice will be much oblidged


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 Post subject:
PostPosted: Mon Mar 08, 2010 1:17 pm 
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Turbo Slant 6

Joined: Fri Sep 09, 2005 9:51 am
Posts: 855
Car Model:
You probably have a poor connection (high resistance) before the ballast; when you attach a small load (test light, multimeter) drawing a few mA you see power, when you attach a big load (~8 A) you see none.

If turn signals, lights, etc. are OK w/ ignition on, check the connection at the connector right at the steering column for a fried connection, then the bulkhead. There's no substitute for good schematics when troubleshooting. Good luck!


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 Post subject:
PostPosted: Mon Mar 08, 2010 2:04 pm 
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1 BBL (New)

Joined: Sat Mar 06, 2010 12:23 pm
Posts: 2
Car Model:
well ive done some research and i keep coming up with i need the 4 prong icm and not the two prong i found a complete rewiring diagram for the ignition system im going to give the a shot in hopes for the best.

oh and i was reading 12+ volts on hot wire going to the resistor when the icm was unplugged.


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 Post subject:
PostPosted: Mon Mar 08, 2010 2:29 pm 
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Turbo Slant 6

Joined: Fri Sep 09, 2005 9:51 am
Posts: 855
Car Model:
You wrote:

"i have a hot? wire that goes from the icm to the resistor and a
+ wire from the coil to the resistor then the - from the coil is grounded. "

If I read your statement correctly, ICM->resistor->coil->ground; then there could be no voltage present with the ICM unplugged.
I suggest you doublecheck your connections.


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 Post subject:
PostPosted: Tue Mar 09, 2010 7:18 am 
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Turbo Slant 6

Joined: Fri Sep 09, 2005 9:51 am
Posts: 855
Car Model:
I don't have a 1986 D150 factory service manual (FSM), sorry, so I don't know which system it uses.

I consulted my 1987 FSM (the nearest year schematics I have); all the car models used a spark control module (SCM); +12V ign power went to the (+) coil via a DG/BK or DB wire; the (-) coil went to the SCM via a BK/YL wire to a 10(?) pin connector. The SCM I took apart had an internal resistor; no external resistor is shown in the schematics.

If you truck uses the older "traditional" electronic ignition (2-pin inductive pickup distributor, pentagonal ignition module connector), one pin on the module and one end of the ballast resistor ought to go to +12V ign, the other end of the ballast to the (+) coil , the (-) coil to the ignition module. During cranking, +12V is directly connected to the (+) coil.

The ground for the ignition module is through the case; the module pulls the (-) coil down to ~0.7V when on and engine not turning. You ought to see 6-8V at the (+)coil at the same time.

I've seen those 5pin connectors go bad and make intermittent connection, and a temporary fix by stuffing some aluminum foil into the hole. Also, if the coil is hooked up backwards it will run poorly.

In neither design is (-) coil connected directly to ground; offhand, I think that would only make sense for some kind of aftermarket capacitive discharge system.


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