1970 Road Runner won't crank using key

[Norv]

OK, so my 70 road runner won't crank using the key. Sometimes it would when I shift the gears back and forth from park to neutral (automatic transmission) but now it only works once in a blue moon. I tried by-passing the neutral safety switch, but that doesn't seem to be the problem. I can turn the key on and start it by touching the two points on the starter relay switch in the engine bay. Do you think it could be the ignition lock cylinder on the steering column needs to be replaced or the actual starter switch in the column? Or could it be something else? Thanks in advance.

 

[BeepBeepRR]

Check your neutral safety switch wire on the starter solenoid also check the neutral safety switch plug on the transmission.

 

[Don Frelier]

I agree the initial symptons sure sounded like a neutral safety switch.
How did you bypass it?
Which two points are you jumping at the relay?
Because it could be the relay.
I've never had an ignition switch problem on any of my cars (although it seems like quite a few people do for some reason)

 

[Ron H]

Yeah sure sounds like the N-switch. Did you try to start it in N not just P? Other deal could be the lever linkage. Does it feel sloppy?

 

[Fran Blacker]

Once I had the plug on the steering column burn because of a poor connection. It was only 1 wire, the plastic plug was white. Saw the brown burned on the white plug. Just cut the wires and wound ends together to get home.

 

[Billccm]

I like to trouble shoot this by measuring continuity to the starter relay from 12V and from the starter relay to ground.

Take an ohmeter on the low scale and in Park and Neutral backprobe the yellow wire at your starter relay. It should read very low ohms (less than 40 ohms).

If you measure good continuity then your neutral safety switch and linkage adjustment are good. If you measure high ohms try contact cleaner in the neutral safety switch plug, or check linkage bushings and adjustment.

Next is continuity from battery to relay. Remove the positive battery cable. Place the ohmeter lead on the positive cable. Place the other lead backprobed to the yellow wire. Crank the key to the start position. You should measure low ohms in the range of 10 or so. If you measure high ohms then contact clean the bulkhead, ignition switch plug, and maybe even flood the switch itself with cleaner.


Let me know what you find.

 

[Norv]

I agree the initial symptons sure sounded like a neutral safety switch.
How did you bypass it?
Which two points are you jumping at the relay?
Because it could be the relay.
I've never had an ignition switch problem on any of my cars (although it seems like quite a few people do for some reason)

This is how I crank it using the starter relay switch:

 

[Norv]

Yeah sure sounds like the N-switch. Did you try to start it in N not just P? Other deal could be the lever linkage. Does it feel sloppy?

I don't know if the linkage is sloppy. I've never had a problem shifting while driving.

 

[Don Frelier]

Your

This is how I crank it using the starter relay switch:

View attachment 1316014

Close but red to yellow would pull in the relay you are going battery to starter Bendix. Try red to yellow and see if anything happens. If not you need a new starter relay

 

[1 Wild R/T]

Sounds like the starter relay but could be the yellow wire from the start lug of the ignition sw

 

[Photon440]

Sometimes their is weird stuff happening in the electrical circuits. Probably not your problem, but my car wouldn't start unless the heater fan motor was running. Turn it off and no cranking. I thought it was a good anti-theft idea.

 

[Norv]

Your

Close but red to yellow would pull in the relay you are going battery to starter Bendix. Try red to yellow and see if anything happens. If not you need a new starter relay

I don't know what your talking about. When I touch those two points on the starter relay I show in the picture, it cranks the car and it starts (just as if I'm turning the key).

 

[Don Frelier]

I don't know what your talking about. When I touch those two points on the starter relay I show in the picture, it cranks the car and it starts (just as if I'm turning the key).

I'll try again.
You are not using the relay to energize the starter you are bypassing it.
Put 12volts on the terminal where the yellow wire connects as that is the terminal the ignition switch powers. If it starts you have an ignition problem. If not you need a new relay.

 

[WileERobby]

Have you tried this ?

 

[eldubb440]

I had once swapped out a perfectly normal looking starter relay......... I opened it up, and all that came out of it were flakes of rust

 

[Norv]

Have you tried this ? View attachment 1318111

Yes, I just converted to a crank handle. Works perfect.

 

[WileERobby]

Yes, I just converted to a crank handle. Works perfect.

See ?!?! Ingenius ! You're not as dumb as I look.

 

[Norv]

Thanks for all the help. I changed the starter relay switch and that was the problem (not sure if the old one was the original). Cranks like a charm now!

 

[Dan yates]

OK, so my 70 road runner won't crank using the key. Sometimes it would when I shift the gears back and forth from park to neutral (automatic transmission) but now it only works once in a blue moon. I tried by-passing the neutral safety switch, but that doesn't seem to be the problem. I can turn the key on and start it by touching the two points on the starter relay switch in the engine bay. Do you think it could be the ignition lock cylinder on the steering column needs to be replaced or the actual starter switch in the column? Or could it be something else? Thanks in advance.

I had the same problem dam near drove me crazy turned out to be loose relay to the fire wall caused by trailering 300 miles