1974 fj 55 only runs in start!

[n2666s]

Wait, if there is power to coil in run then I’m confused

been screwing with this all day; as confused as I am; after cleaning up terminals finally have headlights which started this fiasco; cranked and started ONCE then stopped as it has been doing when key returns to run and now will not crank anymore BUT NO POWER TO THE COIL or resistor on run; it is late and will have to stop for now

 

[LandCrusher'70]

Wait, if there is power to coil in run then I’m confused

Same here...?

 

[LandCrusher'70]

Recheck power at the ignition switch. Verify it STILL IS operating as it supposed to.

 

[samatulich]

Try removing the lock cylnider and turning it clockwise or counterclockwise. When I installed mine, somehow it was “off”. I think the key slot is misaligned with the wiring. Hope that makes sense.

 

[65swb45]

Lou

In 1974, you could also be dealing with an exciter wire issue, to complicate matters. The exciter takes voltage from the starter...WHEN KEY IS IN THE START POSITION...and shunts it to the coil, to help boost the spark.

A fair number of ‘74s no longer have this system operable. But if yours is one of the ones that is, you.

 

[peesalot]

Ok given the last post and your description I would check wires at starter for good connections and check grounds , your comment regarding output voltage at resistor seems to indicate when the exciter circuit is powered it runs, so not enough voltage to coil in run position, check/replace resistor and connections to coil , then to eliminate switch you could tie the main power , the acc, and run together, hit the starter wire with a jumper and see if it runs, if it does the same then it’s the voltage to coil . Again the grounds need to be checked. When finding fuse terminals corroded enough to restrict voltage usually the grounds need attention, they may be fine but it’s worth a quick test light check.

 

[Pin_Head]

I’m not sure what is going on, but if you measure voltages on an open circuit with a volt meter you can get fooled into thinking you have power when you actually have a bad, high resistance connection upstream from where you are measuring. It is best to make sure that the circuit is on and current is flowing or use an old school test probe with an incandescent bulb that has low resistance and “loads” the circuit even if it is not on. If it only glows dim, you have a bad connection upstream.

BTW, these are classic symptoms of a bad ballast resistor, but it could also be a bad wire from the switch to the coil or a bad switch. Hot wire the key side of the ballast resistor to make sure that bypassing the switch makes it run.

 

[Steamer]

As Mark said, if you have that exciter wire, also called "ballast resistor bypass", that will account for it running in the start position when no power is coming to the resistor from the ignition switch.

And if that is so, that would coincide with Pin_Head’s suggestion of a “bad high resistance connection”.
Further evidence of Pin_Heads suggestion would be that at one time you had no power to the resistor (post #5) and another time you did. (post #17)

Pics of starter, ballast resistor, and coil would also help us identify if you have the bypass.

 

[Steamer]

EDIT: Deleted. I posted without thinking clearly.

 

[Pin_Head]

Yes, I read it. It could be an intermittently bad resistor,like when it heats up.
The ignition is one of the few circuits that is not fused. It gets power from the white wire at the starter battery cable and runs to the amp meter, through the map meter and then to the always hot side of the fuse block and then to the switch. It could be a bad connection anywhere from the fue block to the coil.

 

[n2666s]

thanks big for the guidance it is raining but was able to get a few pix as per Steamers recommend ; when tested yesterday ballast had 12 volts in and 9 out to coil then coil had 9 to distributor cap on "run/on'' position then nothing after cranked her and started once will trouble shoot some more tomorrow after get back from work

 

[n2666s]

brief check before work; key in run; full battery power; zero volts at resistor and zero at coil whereas before would get 12 volts in till last cranking will check upstream again
and will try to do more trouble shooting this evening

 

[65swb45]

Lou

Since the lugged terminals of the switch are exposed with the clamshell off, are you checking voltage on the BY wire on the switch in the run position?

 

[LandCrusher'70]

Since the lugged terminals of the switch are exposed with the clamshell off, are you checking voltage on the BY wire on the switch in the run position?

He did that in post #17

Key in run position; power to all terminals except black and white "st" also 12 volts to ballast in and 9 volts out to + side of coil

View attachment 2677014

View attachment 2677016

View attachment 2677017

 

[rkymtnflyfisher]

I just have to say, that Simpson meter is awesome.

 

[n2666s]

I just have to say, that Simpson meter is awesome.

It is OLD school multimeter

 

[n2666s]

Lou

Since the lugged terminals of the switch are exposed with the clamshell off, are you checking voltage on the BY wire on the switch in the run position?

Mark; yes, has 12 volts in on/run so now no power at resistor/coil where as until couple of days ago was getting 12 to key side of coil will get to it again this afternoon

 

[n2666s]

back at it again; multimeter was able to test in on/run again; power to all terminals but none to resistor/coil; then switch in start position 12 volts to black/ white wire BUT no cranking ..............am thinking it has to be between ignition switch and ballast resistor but where

 

[Pin_Head]

Be sure that the points are closed when you read voltage or you will get fooled. Measuring voltages on an open circuit won’t tell you if it is good or not.

 

[n2666s]

am thinking I screwed/shorted something out checking fuses under dash in fuse box to get headlights going, my helper said noticed a "spark" when was pulling fuses, am thinking damaged something and finally failed completely thus 'no cranking" anymore whereas before could crank in start and run hot wired; thanks again P_H; will check voltage and will look at points; if open going to be tough to close w/o starter turning over; wiring diagram I have shows B/W wire going straight from ignition to starter will need to get underneath and check ........ need my assistant to hit starter when check voltage to see if it is getting to starter <LOL> one of my sons "borrowed" my remote starter and can't find it..... need to stop by autozone unless he can find it ....one black yellow wire going to + side of coil from fuse box BUT no power + side of coil??...............something badly screwy
to answer Mark A. going by 1974 FJ 55 wiring diagram the black yellow wire at I.switch connects to fuse box via a blue yellow wire that also powers tailgate relay no connection to "starter circuit" that i can tell