1979 FJ40 no spark issues (I have read all the threads on this issue) What am I missing or failing to check (1 Viewer)

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Good find. That could certainly explain your problems!
I hope. I also found that the battery is supposed to be grounded to the frame. Mine was only grounded to the forward block hook.
I had some West Marine 1 AWG wire left over from my M12000 install on my 80 series so I made new + & - battery cables too. I will use a smaller gauge to ground the battery to the block and body aswell. I also replaced the starter frame ground with a 4AWG gauge bonding strap from @ToyotaMatt. I will add his other frame and body bonding straps too.
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Either you or I may be a little confused. The large black/yellow wire is the ballast resistor. There should be no other ballast resistor.
The small B/Y wire is the power to the igniter. You should check the voltage on this wire during engine cranking.

Yes, I am aware of that ballast wire. It turns into a yellow wire at the green two pin plug by the ignitor. It then connects to the + coil post.

It is one of 3 black yellow wires at the ignitor plugs. The thinner of the two wires in the dual connector is the one you mentioned that needs more than 10v. The third black and yellow stripped wire ends in a bullet connector that connects to the condensor.

My starter only has 3 wires; a red + from battery, a black with yellow striped ground on the bottom 17mm bolt and the black with white stripped spade connector from the ignition switch. There are no other unused connectors in the loom in the vicinity of the starter. I suppose it was removed when the starter was replaced at some point but Aits not needed as you mentioned.

I think you and @pithicus are on to something about checking the wiring. I found the voltage regulator on the firewall plug connected but not snapped in. I also cleaned up the grounds at my fuse box and the individual fuse connections. I suppose it's possible that all the bad or misplaced connections, grounds combined with the "holding on by a thread" fusible link could have been a myriad of issues that culminated in the nonstart issue.
 
If you have a wonky fusible link, that could be the problem.

I guarantee that the B/Y wire at your starter is not a ground wire and is not stock. It could be part of the problem. The starter has a ground strap that is 3/4 inch bare woven wire that goes to the frame. All B/Y wires are engine power. Disconnect it and tape it off.

All Toyota ground wires (and there are very few on FJ40s) are white with a black stripe.

The fuse block is not grounded.
 
The reason I asked about your A/C and emissions is because if you have some cracked / poor solder joints in the emissions control circuit board it could the root of this and other problems. I only posted a portion of the wiring diagram ( sorry ) at that point. This one has the emissions ECU in as well. To bypass the ballast / resistor wire during cranking the start signal goes to the emissions ECU which in turn supplies a full 12V to the coil. That’s why there is no second wire on the starter (BY) solenoid.
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The reason I asked about your A/C and emissions is because if you have some cracked / poor solder joints in the emissions control circuit board it could the root of this and other problems. I only posted a portion of the wiring diagram ( sorry ) at that point. This one has the emissions ECU in as well. To bypass the ballast / resistor wire during cranking the start signal goes to the emissions ECU which in turn supplies a full 12V to the coil. That’s why there is no second wire on the starter (BY) solenoid.View attachment 2279260View attachment 2279260
That was one of my thoughts too. I already resoldered 8 broken solders in the emissions ECU a few years ago. So I pulled it yesterday just to check again. The solders looked good, then I got to thinking about the diode between pins 2 and 1... so I put in my spare Emissions ECU with no changes to the no starting situation.
 
Hey s.carolina , how's progress? Did the fusable link fix solve the problems?
Temporary fusible link complete. Luckily I had some fusible link wire and spade terminals handy. This will suffice for testing until I can obtain one of @Coolerman 's replacement link. All taped up and ready to put the battery back in.
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Hey s.carolina , how's progress? Did the fusable link fix solve the problems?

The short answer is no.

I am still getting the same approx voltages at the pins.

I made new battery cables to include an original style batt - to frame ground and added block and body grounds and cleaned the fuse box terminals.

I jumped the batt + and coil + today and could not get it to start.

I have printed out the electrical schematics and will have to go through all of the wires from the batt to/from ignition switch and to the ignitor and coil.
I did install a new battery tray and hold down as mine were rotted beyond repair.
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If you have a starter button you could jump B+ to the little spade terminal where the black and white wire is on the solenoid to check starter function.

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Electrics gremlins can be a real challenge even on these old trucks.
Thanks for the update.
Tell me about it.

If it doesn’t even turn over, then it is a starter motor/solenoid problem.
The starter turns, the engine just won't light.

If you have a starter button you could jump B+ to the little spade terminal where the black and white wire is on the solenoid to check starter function.
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I picked one of those up awhile back. The starter did work, the engine just would light.

I'll reattack with fresh eyes in the morn.
 
Made some progress on diagnosing. I did a continuity test on all wires going to and from the emissions control box and they all had continuity with their respective origin/termination points. Some wire colors differed from the schematic though.
As per @Coolerman's post on the '78 harness build thread. The pink Yazaki resistor wire should ohm out to 1.2 ohms. This I believe was wired in series with the larger diameter B/Y wire going from the emission controller box to the 2-pin ignitor plug. Anyway, this larger diameter B/Y wire ohmed out 1.2.

Feeling secure that my wiring was good I decided to test voltage at the ignitor plugs during starter cranking;
-Battery was at 12.6 before cranking.
- while cranking;
- the thick B/Y (to coil+) wire was at 11.2v
- the thin B/Y (to ignitor) wire was at 10.6 on the next start attempt
- the Y wire at the single pin plug dropped to 5.9v on the 3rd start attempt.

So after all of this I was convinced that something was not right with my ignitor box. I swapped in a spare and she started right up. It saw the light of day for the first time in months and even drove around the block.

Thanks for all of your trouble shooting advice @Pin_Head @pithicus @ @fjc-man
 
I found this info. Does yours have a inline ballast?
78-80 coils work with an inline ballast resistor wire in the vehicle harness. It's possible to run the 78-80 igniter& coils on full 12V with no ill effects.

Edit, beat me to it, temporary full 12 v.. run a wire from battery + to coil + and crank it over.
[you can remove the 7v ballast wire from coil + when testing]
You guys just saved my weekend. Beer on me!
 

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