No Spark from Coil: Ignition Issues

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GarnerFJ40

GarnerFJ40

10 Year 15 Year
Joined
Mar 10, 2007
Threads
199
Messages
4,508
Location
Garner, NC
All,

I've finally reached my wit's end on not having spark on my 1974 FJ40. Long story short, ran fine and parked it for a 6 month work assignment and came back to it not wanting to start. I've played around with it here and there a few hours at a time, changing some things here and there, but the past 2 weeks I've been hitting it hard every weekend. Here's the details:

1974 FJ40 with the F1.5 engine, ignition coil with external resistor (no ignitor), and I moved to the GR starter before this all started (years) happening with no issues. Usually on a 5amp battery charger between starting "campaigns".

Here's what I've either replaced or bypassed to rule out components:
  • New voltage regulator (PO had a non-LC VR with additional connectors but ran with it for years) removed it and utilized the original socket
  • New Alternator (old one is still good (replaced in early 2000's when I got the truck, but if I'm changing stuff up I'll throw a new one in)
  • bypassed the ammeter (gauge cluster removed, clamped white and white/blue wire together)
  • used a donor steering column for the ignition switch check
  • used a donor fuse block (fuses look good in both blocks)
  • new points installed (gapped at 0.018)
  • 2 new condensors (did have to add a new plastic washer to the external - terminal, thought for sure that was my issue) have more and passed resistance check
  • have used multiple coils in troubleshooting (new and used (internal and externally resisted)) have verified multiple to be within tolerances at some point in troubleshooting (I'll probably re-verify again on 22MAR2026)
  • added a secondary ground to the coil bracket (have both sizes of coils so use the proper size bracket for each) bracket location on passenger fender well
  • new rotor (old one looked fine though)
Here's the items I've checked
  • verified voltages across multiple connections (fuse block, guage cluster, coil itself)
  • used the test light scenario when cranking (I do get blinking lights as points open and close, and of depending upon where the points stop when turning off the switch, open and closed points with on and off light settings) and this is on an internally resisted coil
  • Current Wiring: solid black wire from - coil to distributor terminal, black with yellow and black with white to the + side of the coil, internally resisted coil. Original wiring: external resisted coil with a ballast resistor, black and yellow going to one side of the resistor, then to the + coil, black and white on + side also
  • tried sparking the HT wire off the key on scenario, and grounding the - side of the coil momentarily (no spark) (Have not tried with it cranking)
  • randomly have interchanged the main HT coil wire based on length
Things I haven't checked
  • Mainly secondary ignition items becuase I'm failing the coil spark
    • cap (looks OK no residue or arching signs, haven't switched as light test checked out OK) have one ready
    • wires (have a new set ready)
    • plugs (have a set ready)
  • grounds at the battery, distributor, starter, voltage regulator (all seem fine, starter works, test light scenario works, other items on fuse block working)
I'm really trying to not change too many things at once becuase I really want to know the root cause, and not just change a bunch of things out and it work and not know. I'm really stumped at the coil not sparking even when pulled off the distributor and near the engine block, after changing multiple items out with no change in the end result. I've checked the primary and secondary resistance (at some point in the process) on all the coils (and condensors), but will do again if this continues or someone reading this has an idea. Reading on the forums, the coils don't go bad very often, and I have access to 6 or so for troubleshooting.

Anyone reading this have any ideas, or similar situation to add? I've see a few posts where the wires were mixed up from the + and - side of the coil, the plastic terminals were missing or broken upon inspection, no grounding from the coil bracket,etc.

Thanks in Advance!!!
 
Does your distributor cap have aluminum contacts on the inside. Yes - lightly scrape them with a pocket knife blade (small blade on a swiss army knife "climber". A hair line crack can act as a conductor and short out the spark.

How old are the spark wires? The contacts on either ends of the wires could be bad under the boots. Clean/inspect plus the contacts on the cap outside.

Run a points file threw the points if they are new - some have a coating that acts like an insulator. Old ones could be corroded enough on the contacts to be insulated.
 
igotta40 said:
Run a wire from the (-) coil terminal to the terminal on the side of the distributor and see if it starts.
Click to expand...
Made a jumper wire and tried starting a few times, no fire up. I'm going to leave it for now though becuase at least I know it's a undamaged straight wire!
 
charliemeyer007 said:
Does your distributor cap have aluminum contacts on the inside. Yes - lightly scrape them with a pocket knife blade (small blade on a swiss army knife "climber". A hair line crack can act as a conductor and short out the spark.

How old are the spark wires? The contacts on either ends of the wires could be bad under the boots. Clean/inspect plus the contacts on the cap outside.

Run a points file threw the points if they are new - some have a coating that acts like an insulator. Old ones could be corroded enough on the contacts to be insulated.
Click to expand...
Yes, at least 2 of them have the aluminum contacts, so I'll give them a little scrape/file and see if I can get some good fresh metal.

Pulled the # 6 and #5 wires, one was nice and corroded at the plug end. So, I think I'm going to go ahead and change out the plugs and put on new wires today.
 
New plugs, a little oily on the electrodes, but they got replaced. New NGK wires, made sure they "popped" into place. New rotor, scraped the main terminal anyway. No change. Did blow in some starting fluid into cylinder 5 just to see if I could get a cylinder to ignite (no dice) as I need to prime the fuel up to the carb again. Today I noticed I didn't have any gas in the window with all the starting...

I'm going to go out tonight and see if I can get some spark from some of the wires, with a little help from my 15yo.

New Thoughts?
 
Did u try 12v from battery to coil? … temporarily to see if you get spark?

If your carb bowl is emptying and not filling … that’s an issue
 
I've tried it before, but not recently. I'll give it a try tonight.

I assumed it was mostly due to evaporation. It's parked in the sun and the air cleaner assembly is disconnected. I'm going to change out the fuel filters (yeah PO put a second on), blow the lines down, and then prime with either my hand bulb, or brake bleeder.
 
As a fellow “doing too many things at once” guy, solve each one individually. Usually, I’d focus on making sure you can get fuel visible in the sight bowl, first (because I think that’s easier), however, I’d now do that 2nd now. I would go ahead and fix the grounds from the battery.

I went down a heck of a rabbit hole over the last year because my grounds were insufficient and ended up frying some wiring using the ground from the alternator to the VR to start my engine. New battery cables would have saved me literally thousands of dollars (but I wouldn’t have a sniper, so it’s not all bad).
 
Yeah, I plan on troubleshooting the fuel later, as I've had fuel in the bowl more recently than I've had spark.

Nadeem, I took your advice and just took a set of jumper cables and attached the two leads to random sections of the block and attached them to the frame, just in case I didn't have the best ground. No change...

But, I didn't get a chance to have my helper crank the engine while I checked for spark, so I'm hoping on that tonight.
 
Unhook the wire that comes from the key to your distributor at your distributor, then get a test light from battery pos to that terminal. Spin the engine over and check that the light flashes on and off. If it stays on there is a problem with the terminal insulation somewhere
 
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