360LA Intermittent Issue

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CoolDave

CoolDave

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Got a little bit of a weird intermittent issue, I’ll try keep it concise, looking for ideas before I go chasing it down..

Motor is a 360, sitting in a ‘73 D100 with the auto behind it.

The issue I have (today) is that the truck will not kick over. It cranks strong and I have fuel to the carb and squirting in the barrels with the throttle. I had this issue when I brought the truck home, some times it would just sit and crank and some times it would fire up, which led me to..

I have replaced the distributor, wires, plugs, ballast resistor, coil, ignition module, starter solenoid and neutral safety switch. I have verified my timing and idle settings. A few weeks back I went out there to start it up and with three slow pumps of the gas it fired off almost instantly. Today, nothing. It’s also had a weird intermittent issue where the idle some times would get a mild miss to it and then some times it was smooth like a sewing machine.

Are there any weird little known things about these trucks/motors I should look into before I go literally chasing down every wire to verify condition and connection?
 
Loose wire going from engine bay into the firewall junction block bulkhead.

Screenshot_20240313-231314_Gallery.jpg


'76 D100 pictured here ^


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Have you actually done any diagnostic at all?
 
George Jets said:
Loose wire going from engine bay into the firewall junction block bulkhead.

View attachment 1716221178

'76 D100 pictured here ^


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Good starting point, I’ll inspect those.

RustyRatRod said:
Have you actually done any diagnostic at all?
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Not specific to this issue, no. It’s been so intermittent and random, I did one day start looking with a meter and sure enough, the second I turned that thing on the truck kicked over. That’s why I was asking if there was any weird little commonly known things that come up.

hotrod swinger said:
Looks like a multimeter is in order.
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It’s at work, need to remember to grab it and bring it home!
 
This sounds a lot like an anecdote about a melted harness @67Dart273 has shared on this site. If I can find it I’ll link it.

Groinded ignition circuit.
 
hotrod swinger said:
This sounds a lot like an anecdote about a melted harness @67Dart273 has shared on this site. If I can find it I’ll link it.

Groinded ignition circuit.
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That would be great.

a-bodyguy said:
Your in good hands
Bad ground my guess
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I feel like it’s probably a poor connection or ground somewhere too.

I have also already found and repaired a bad connection at the electric choke baseplate where it would occasionally short and cause a stall. I’m sure there’s going to be something similar I stumble upon.
 
Next time it does it, have a test light ready and see what it has on the + side of the coil.
 
Update as of this afternoon..

Voltage at the coil is good in run and start, voltage to the ignition module is good, continuity in the wiring to the coil/distributor checks out also. I found some minor corrosion buildup on one contact of the ignition module that runs out the distributor pickup so I cleaned that off too.

After all that I had the same issue but it sounded more like it wanted to fire so I threw in the cheap backup module I had on the bench, fired first time. So maybe I just need to put in the effort of finding a good reliable unit before I go any further!
 
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