Trying to resurrect a 77 4.9L I6. I've got several problems and need you guys to keep me straight. Original motor was V-8, PO put in an I6 a long time ago, but there are wiring hacks because of it.

1) The wiring is/was crap. I've pulled out all the PO's non-stock add-ins. Replaced both battery cables. Got a solid ground connection to the block (didn't have one before in the original setup). Contacts from starter switch to starter are cleaned and tight. Starter appears to be OK.

2) About every 3rd time I turn the key it'll turn over. Felt like the starter switch /solenoid might be bad, it was rusty and ugly. Pulled a nice pretty one from the junkyard and swapped it out. I'm pretty confident this new one is good.

3) Still only turns over about every 3rd time I turn the key. Yesterday I turned the key and it started to turn over -- released the key and it kept turning over. Pulled the battery wire to shut it down. Now I figure I've got a bad ignition switch. Pull the ignition switch out to test it (haven't tested it yet).

4) I reconnected the battery to ensure that removing the switch had cleared the fault. Guess what? Connected the battery and it started to turn over without the switch.

OK guys, what's the logical thing to do next???

 

Ignition switch is most likely not your problem. A brand new solenoid should be pretty cheap, I would start by replacing that and then take it from there. I've had this problem before after having a starter rebuilt. Turns out it was a bad starter solenoid.

 

When you say "Connected the battery and it started to turn over without the switch," do you mean without the ignition key turned at all? If it's turning over, power is getting to the solenoid. Are you sure the ignition swich is wired properly?

 

Yeah, the "new" junkyard switch/solenoid is dead-shorted to on. Put the old switch back in and ordered a new motorcraft switch. Set the timing with a dowel in number one and used a bar to turn the crank. It wasn't even close. Had to pull the distributor and turn it a quarter turn. Got it in the neighborhood of right. Hold the choke and pull the throttle and it cranks. First time in 8 years.

Got a ton of work to do on carb and vacuum, but doggone it, it'll run.

I'm getting this old truck stuff in my blood and I like it.

 

ok man heres some things that might help u first thing unhook the fuel line from the tank at the pump because i can tell u from experience the tank is trash any time these trks set they build up w rust n u dont want that goin in ur carb,take n tap the top of ur solienoid w a wrech the contacts are stuck it happens all the time when they set or u crank on them for a long time,make sure its on a compresion stroke when u set the dist,dump some gas in the carb n fill the bowl theres a tube in the top of the carb that u can pore gas into to fill the carb it will probaly take a lil bit but it should fire up, make sure u ck n c if its firing hope this helps u get it started i just picked one up that had been sitting for 12 yrs it took us about an hour to get it runnin but we drove it up on the trlr n took it home

 

Got a new motor craft starter solenoid? Can I possibly have gotten three bad in a row??? Same failure, this one shows as shorted? Or am I blowing them up?

Did pull the carb apart and clean it. It was loaded with crap and the diaphragm was stuck hard.

Why can't I get a starter to behave?

 

When it starts turning over on its own: what happens if you pull the wire from the ignition switch off of the solenoid (so that it only has the battery and starter cables attached)? Does it stop cranking?

 

Nope. Have to pull the battery. Put the battery back and starter engages. Has to be a bad switch, right? A, I blowing them up somehow?

 

If I pull the little "S" and "I" wires and just leave the battery connection and the connection to the starter, it will still turn over. This is the third solenoid I've tried. The odds of three in a row being bad is pretty slim. Am I doing something to burn them out?

 

Quit buying the cheapo parts store items that say "Made in China".
I dunno how they can consistantly screw up something as simple as these things, but they do.......

 

This 3rd one is the full-on Motorcraft part.

 

Wiring Diagrams pictures from trucks photos on webshots

clicky the link for wiring diagrams. from harness to charging system

 

Is the solenoid getting a good ground connection? They bolt on using sheet metal screws. If the screws are rusty, or the holes a bit wallowed out, it won't ground well, which can cause it to weld itself together inside.
If there is nothing attached to the "S" terminal, and the starter spins when the battery is connected, it is the solenoid itself.

Also, it wouldn't hurt to pull the starter and have it tested. If the starter is pulling way too many amps, it can also cause the contacts inside the solenoid to weld themselves together from the heat of the current draw.
While you're at it, check the connection on the engine for the ground cable. A poor quality connection on the ground can also cause the solenoid to get too hot internally.

 

GREAT suggestions. I was going to say, get the starter load tested!

 

Stuck a good fluke ammeter on the line to the starter. Inrush was 300a, continuous was 150a. With a battery voltage at 11.25V, that's 1687 watts. That's pretty close to the nominal 1.5kw for the part. I think the starter is good.

I'm pretty sure that I've got an ignition cylinder that is bad. Still have wiring that I suspect is fouled up.