Key switch cranks but grounds the ignition

[75 Bronco Ranger]

Hey guys I am not out of the woods yet. Replaced tumbler cause I lost my key. I can jump the coil and the solenoid and it will fire. Key switch will crank but not fire. Key switch turned to on while running on jumper kills it.

75 bronco w/ 351w and edelbrock dist.

Any easy things to check?

Thanks.

 

[DirtDonk]

This should not be the problem, but might as well disconnect the Brown “I” wire from the starter relay/solenoid.
Also disconnect any radio noise suppressors from the positive side of the coil.
Since you’re disconnecting the easy things, might as well disconnect the brake warning lamp circuit down at the brake H-block.
Neither of these should cause your problem, but it can’t hurt to rule them out and keep them out of the loop.

Since you now have a new key and tumbler, it should also be easy enough to remove the ignition switch from the dash. If you do that, then there is no way for it to ground out any of the circuits. At least not through the switch itself.

If it still has the problem, then I would think the fault is within the ignition switch itself.

I guess my first question should’ve been, are you still running the stock of Dura Spark ignition? Or something else?

 

[75 Bronco Ranger]

This should not be the problem, but might as well disconnect the Brown “I” wire from the starter relay/solenoid.
Also disconnect any radio noise suppressors from the positive side of the coil.
Since you’re disconnecting the easy things, might as well disconnect the brake warning lamp circuit down at the brake H-block.
Neither of these should cause your problem, but it can’t hurt to rule them out and keep them out of the loop.

Since you now have a new key and tumbler, it should also be easy enough to remove the ignition switch from the dash. If you do that, then there is no way for it to ground out any of the circuits. At least not through the switch itself.

If it still has the problem, then I would think the fault is within the ignition switch itself.

I guess my first question should’ve been, are you still running the stock of Dura Spark ignition? Or something else?

Thanks. The new tumbler turns hard. Would something be bound possibly?

 

[75 Bronco Ranger]

Thanks. The new tumbler turns hard. Would something be bound possibly?

Forgot to mention the alternator is dosconnected....would that cause the issue?

 

[75 Bronco Ranger]

Forgot to mention the alternator is dosconnected....would that cause the issue?

Are you one of the VIN gurus on here? Have a parts bronco I am looking at but don't know the year.

 

[DirtDonk]

Among a very few others, Okie’s the VIN man here.

 

[DirtDonk]

Forgot to mention the alternator is dosconnected....would that cause the issue?

Should not make a difference here. But just to be clear, is this all stock wiring? Or has the truck been rewired?

 

[DirtDonk]

And otherwise, why are you running the engine with the alternator disconnected?

 

[DirtDonk]

Thanks. The new tumbler turns hard. Would something be bound possibly?

Yes. The rest of the ignition switch.
Is this a new switch, or an old original?

 

[75 Bronco Ranger]

OK will post the VINs on a new thread.

1.. stock wiring.
2. Long story but the top mounting bolt broke.
3. Original to me ( ~ 30yrs.) ignition switch

 

[75 Bronco Ranger]

I know what your thinking....dumb$%@

Lol.

 

[Oldtimer]

When you turn key switch to RUN, do radio and turn signals work?
Do they work when key switch is in ACC position?

 

[SteveL]

Did you unplug the switch from the harness while working on it? If so make sure the knife blades plugged back together properly. Sometimes if the knife blades miss their female counterparts when you plug em together.