Solved: ignition switch was cracked but working. ignition wire was shorted in the engine tunnel where previous owner did repair work and had cut the wire leaving it exposed it grounded to the floor pan.

Pretty sure I need a new ignition switch although it bothers me that it went out "suddenly"

I have no voltage at the yellow wire on the starter when I turn the key.

I have no voltage at the large yellow wires on the seatbelt interlock relay with the key in the on position or when I turn the key to start. I disconnected them and plugged them together to bypass the SB interlock relay thing which I thought would eliminate this as a source of any problem. The black wires seem to be tied together but disconnected are those supposed to be grounded? My SB interlock relay is loose and not bolted down. The Black wires have 3.5 volts. Some other wires show negative volts in tiny amounts. Only one wire , a brown wire has 11.5 volts and it is loose, is not connected to anything.

The green and red lights are on the dash and stay on when I turn the key but nothing happens, although all the four relays by the fuse box "click"

The fuel pump fires for a couple seconds when I turn the ignition as well. Most of the lights and signals work on the car.

I suspect the ignition switch is there any way to test it without disassembly?

Any other possible source of this not cranking?

FWIW, when I bought my project car, it had an extra starter button added under the dash. When I eventually got the steering column apart and the ignition switch out, I found it cracked and almost split in half--so it can fail instantly.

I would encourage you to get your eyes on the switch. It is really not that hard or time-consuming to get out.

100% agree. And consider installing a starter solenoid in engine compartment to reduce the extreme electrical load placed on the key ignition switch.

All are poor at best.
We've gone to Porsche for theirs's. No vendor info on the bag.

Just put one in Matt's (914 Rubber) red car.
Time will tell.

Add it to your throw in the glove box kit.

You found a brown wire. A brown wire is typically a ground wire. Look for a small hole on the floor near the interlock assem. Fasten the brown wire to the chassis with a screw. Then, try the key again.

I think that one must go to to the center console guages? It has nearly 12 volts on it.

There is a small brown wire coming out of it that seems to go no where and was thinking that must be ground. Seems like there should be voltage at the solid yellow wire when I turn the key regardless of whether the small brown wire was attached

I took the switch out and looks a little burned inside but not cracked or anything . I think I will just replace it since I have already taken it apart. Lots of built up gunk in the steering column possibly a spilled drink in 1976-1980? lol

a small brass l-shaped piece fell out of the switch assembly

Edit: on closer examination it is cracked

That small piece is a ground for the turn signal/wiper assembly - make sure it goes back in...

Any opinions on which brand to use as a replacement I see Meyle or Vemo

the ignition switch appears to work I have .3volts at the yellow wire on the starter when I crank , the green red lights on dash dim, why is voltage so low? is this a starter problem or low voltage problem?

Install the Ford solenoid hot start fix, link to the instructions below in my signature.

Edit sorry I misread I thought it said 3v...not 0.3v
You should see at least 3 to 9 volts at the yellow wire.

Great idea but my problem is that I have 12v to the fat yellow wire under the seat when cranking, not connected to the fat yellow/red (the is the bypass of the seatbelt interlock). When connected and I crank it, the voltage drops to .8 volts and these wires get smoking hot literally smoke. I never can get even close to 9 volts at the yellow wire at the starting motor, I can only ever get .3v!!

I cannot find anything wrong with transmission ground strap, disconnected wires , shorted wires, or battery ground strap. I do not have an ignition switch problem, my battery is at 12.7 V, fully charged, I have tried two ignition switches I get 12 V at the red wire on it and 12 v when I crank,

Also I took the starter off and verified that both the solenoid and the motor are fine, and work fine together.

Could this be a short in the relay board?

Well, I am screwed now I put a jumper on the relay board from yellow red to yellow and did not hook up the starter and melted a bunch of wires mainly the black wire going from the relay board to the negative distributor . maybe I did not complete the circuit because the starter wasn't hooked up I don't even know now

anyone could offer some good real help to me ... not stuff like bypass with a Ford solenoid kinda stuff or rabbit trail like the brown wire on the seatbelt interlock is a ground... guess that's what I get for going to a forum instead of a professional

Let's see if I got this right. You have 12v at the yellow wire, going into the seatbelt interlock system, when you turn the switch yet when you tie/jump the 2 yellow wires together the voltage drops to <1v and gets extremely hot? If this is correct you have a dead short past this point. To verify connect another wire to that incoming yellow wire and connect the other end to the starter relay. If it still gets hot then your solenoid is shorting and drawing too many amps. Yes, I did see you tested the starter and solenoid.

Thank you that makes sense. I think the short is in the relay board but regardless I will splice in all new wires to the ones I fried , hook up the starter, then give this a whirl

You can bypass the relay board with your new wire to the solenoid. The relay board is merely a junction for this purpose. Hit up Bruce Stone for a refurbished relay board after you prove yours defective.

I am pretty much betting the short is in the relay board thank you I will repost once this is solved for future

Okay I ran a 12 guage wire from the yellow wire under the passenger seat where I had 12 V directly to the solenoid. Now the wires do NOT heat up and the starter clicks hard but does not turn over the engine. I tested the starter when it was off the vehicle and it turns perfect both motor and solenoid were good but is this a sign of a bad starter? The engine turns quite easily by hand when I reach down and grab the fan so I do not think my engine is seized.

Ideas?

Sounds like the low side of the solenoid is closing the contacts. Now you need to verify that you have voltage at the high side to spin the starter motor. If you have voltage, try jumping the starter and see if it turns over. If not it can still be a bad starter even if it spins on the bench. Put it under a load and it may do nothing. Good luck

Thank you

I checked the red wire on the starter solenoid for voltage and there is only .88V , same problem as before , but there is 9.05 Volts at the yellow wire, which indicates that my jumper wire loses 3 volts, maybe because I used 12 guage wire instead of 10 guage ? But regardless the solenoid clicks but does not seem to pass the full voltage to the motor, so is this a bad solenoid? I previously tested the solenoid/motor together, solenoid alone, and motor alone with the starter on the bench, but I never checked the volitage only checked to see if it spin or engaged

I did not have one of the wires to the battery positive hooked up dummy. It is now cranking with my jumper that bypasses the Relay Board. Now I have to find the short between the seatbelt interlock and the starter, I will have to trace it all.