1977 F-150 Ignition

Tiny
77F150
  • MEMBER
  • 1977 FORD F-150
  • V8
  • 4WD
  • MANUAL
1977 F150. Died during normal operation. Seemed to be an ignition issue, so I replaced every component fo the ignition system (except wiring harnesses) but still am not getting spark. I have tested and I am getting power to every portion of the ignition system I can think of.
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Sunday, February 6th, 2011 AT 7:05 PM

14 Replies

Tiny
WRENCHTECH
  • EXPERT
Why don't you list the parts you have thrown at it.
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Sunday, February 6th, 2011 AT 7:38 PM
Tiny
77F150
  • MEMBER
Distributor, rotor, cap, plugs, wires, ignition control module (brain box), ignition coil
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Sunday, February 6th, 2011 AT 7:48 PM
Tiny
WRENCHTECH
  • EXPERT
Did you ever check to see if the ignition module and the coil were receiving power input?
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Sunday, February 6th, 2011 AT 7:54 PM
Tiny
77F150
  • MEMBER
Yes. Every part of the ignition system is receiving power. I am currently checking my timing.
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Sunday, February 6th, 2011 AT 8:11 PM
Tiny
WRENCHTECH
  • EXPERT
There seems to be some conflict to what you are saying. If you have verified all you say you did, verified that the distributor is turning, you would have spark.
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Sunday, February 6th, 2011 AT 8:57 PM
Tiny
77F150
  • MEMBER
Hence my dilemna. I just checked my timing. It was a little off, but I corrected it and still no spark.
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Sunday, February 6th, 2011 AT 9:16 PM
Tiny
WRENCHTECH
  • EXPERT
I suggest you go back and check it all again. You had to have missed something.
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Sunday, February 6th, 2011 AT 9:19 PM
Tiny
77F150
  • MEMBER
Yeah. Done that a time or two. Replace the ignitioni coil and module both twice, now.
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Sunday, February 6th, 2011 AT 9:25 PM
Tiny
77F150
  • MEMBER
This morning, I started from scratch. Power to ICM, check. Power at both legs of the coil, check. Rotor turns when engine cranked and in proper position at cylinder #1 TDC, check, Starter relay, check. Continuity inside ignition swtich, check. All fuses power on both sides, check. Plugs properly gapped, check. Plug wires in correct timing sequence, check. Engine compression, check. Spark through any plug wires, negative.
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Sunday, February 6th, 2011 AT 9:28 PM
Tiny
WRENCHTECH
  • EXPERT
See if you're getting ground pulse at the (-) side of the coil when cranking.
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+1
Sunday, February 6th, 2011 AT 9:31 PM
Tiny
77F150
  • MEMBER
Stays constant on both sides when cranking. Bad coil, again?
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Sunday, February 6th, 2011 AT 9:39 PM
Tiny
WRENCHTECH
  • EXPERT
No, that means it's not getting the signal to fire which comes from the ignition module which gets it's reference signal from the coil pick up in the distributor. Could be either of those, any of the related wiring or the power supplies to them.
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Sunday, February 6th, 2011 AT 9:42 PM
Tiny
77F150
  • MEMBER
Ok, I know I'm good on power supplies, and I'm going to play the dangerous assumption card and figure the compnents themselves are good, since they are both brand new, and I have no idea how to trace the wires through the harnesses and looms and what not.
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Sunday, February 6th, 2011 AT 9:47 PM
Tiny
77F150
  • MEMBER
The biggest issue is that this is a 1977 that has had ALOT of shade tree mechanics do a "this will work for now" type electrical fix, so there are litterally hundreds of extraneous wires that do God only knows what. Some aren't even connected, but not sure which of those should be and which should just be torn out.
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Sunday, February 6th, 2011 AT 10:04 PM

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