Ignition system issue

[Sisujoel]

My '70 F100 has been slow to turn over the last few times I've driven it. Last night it left me stranded on the shoulder so I spent the day trying to figure out why. I had the battery tested (good charge), replaced the alternator and voltage regulator, the starter (which was bad) and the starter solenoid. Still no luck. My brother-in-law was able to start the truck by shorting the starter solenoid and once started the truck runs fine.

What else could be the problem? Ignition switch? The one in the truck looks like the original. I came across a similar issue posted in another Ford truck forum and a fusible link between the voltage regulator and the alternator was mentioned. I couldn't find where the link was according a '68-'72 Ford truck wiring diagram.

Thanks in advance for possible solutions...

[Nitekruizer]

You haven't mentioned it, but if you haven't checked your timing, you could check to see if it's advanced too much. My 351 has a habit of becoming too advanced over time. Retarding it, even temporarily will help start a hot engine. You could check and clean the connections, to the starter motor, all grounds too.

[Sisujoel]

Thanks Nitekruizer. I haven't checked the timing so thanks for suggesting it.

[Craigerf100]

this happen to me in 2 different trucks. since the battery has checked out. id check the ground cable on the battery and the to the starter solenoid as well as all the connections to the solenoid. an easy way to do this get a hold of another solenoid that u know works. or a new one. and completely install in place of your old one. (tighten the wires down and screw it tight to the inner fender). I guarantee its the soleloiod. but you never know with these old trucks.

[Sisujoel]

The starter solenoid was the first thing they told me to check at the local Ford dealership. That was after I had had replaced the alternator, voltage regulator and starter. "but you never know with these old trucks" is certainly the case esp. when it's electrical in nature!

[sargentrs]

Don't be surprised if the "new" solenoid is also bad. I've installed 3 new one's before finding a good one right out of the box.

[Sisujoel]

I will definitely dbl check the new solenoid.

[Craigerf100]

I will definitely dbl check the new solenoid.

keep us updated with what u find out

[Craigerf100]

Don't be surprised if the "new" solenoid is also bad. I've installed 3 new one's before finding a good one right out of the box.

yep, ive had a many "new" parts work as well as the part I replaced that did not work at all

[Sisujoel]

So I still haven't resolved my ignition issue. I've replaced the starter solenoid twice. Still having to "jump" start the solenoid with a screw driver.

Here's another symptom: my alternator dash light and the brake warning light have not worked since the problem started. Possible wiring issue at the ignition switch?

[cep62]

If you can jump the solenoid , thats not the problem .
No power getting to the small terminal is the problem.

Do you have an automatic trans? if so there should be a neutral safety switch ,that might be misaligned or broken.
If you have one you can bypass it , but be carefull it will start in gear.

Otherwise you'll have to get behind the ign switch with a test light and trace some wires.

[basketcase0302]

cep62 » Sat Nov 05, 2016 7:51 pm

If you can jump the solenoid , thats not the problem .
No power getting to the small terminal is the problem.
Do you have an automatic trans? if so there should be a neutral safety switch ,that might be misaligned or broken.
If you have one you can bypass it , but be carefull it will start in gear.
Otherwise you'll have to get behind the ign switch with a test light and trace some wires.

Umm...correct me if I'm wrong but I've never seen a neutral safety switch in our bump era trucks?
Follow wire #32 to #32A that gets power directly from the ignition switch, (that should be the fusible link-they are known to burn out over the years).
But cep62 is right about tracing the wire back as you have no power to hold the solenoid in.

[cep62]

Umm...correct me if I'm wrong but I've never seen a neutral safety switch in our bump era trucks?

Neither have I , But I never owned an automatic.
I just assumed autos would have one. ??

[m9452p]

The neutral safety switch is on the steering column for the automatics, just below the mounting bracket for the dash. It won't start unless its in Park or Neutral of course, and it is also the switch for the backup lights. Its held on by two sheet metal screws, and the mounting holes for the switch itself are slotted to adjust it. If the screws loosen from vibes the switch won't make contact with the pin on the shift tube and the starter will not crank. My has come loose a couple of times, till I discovered the PO had taped it on!.
The switch and the small lever on the tube are depicted in the automatic steering column diagram. Just about middle far right of the diagram, part number 7A247.

[Ranchero50]

Umm...correct me if I'm wrong but I've never seen a neutral safety switch in our bump era trucks?

Neither have I , But I never owned an automatic.
I just assumed autos would have one. ??

There's a four wire plug under the dash. Auto's use all four (2 for reverse, 2 for NSS). On the manuals, the NSS wires are jumpered out completing the circuit.