Engine is a 70s 460 with dura spark and C6

Truck idles fine, revs fine in Park or Neutral, but when putting it into any other gear it stalls. I can keep it from stalling if I switch it back quick enough. I drove the combination in the truck it came out of it and it worked just fine.

Issues I know about:
Neutral switch needs replacing because I can start it in any gear.
Vacuum line is smaller than what it was (I went off what it was supposed to be and found the fittings to require a larger line)

What I've changed or added because it was missing:
All the vacuum lines
C6 Vacuum modulator
C6 kickdown cable
Brake booster (new to my truck but his had one)
Added the wiper line to the engine (opened a closed port that was available)
Transmission radiator cooler


I checked for vacuum leaks with some WD-40, didn't have any carb cleaner handy. Electric choke is wired to the alternator, the engine starts up, idles and runs without issue.
I *may* have put it through the gears with low fluid before adding on the driveshaft while running, but I can't remember. Might have just had the thought.
Truck has rolled back about 2 feet down a sloped driveway to test the brakes after the driveshaft was attached. Moved easily and freely.
I did try to start it in different gears and while in drive it starts to turn over but won't catch and didn't lurch forward (up hill) when I tired without the brake (had tire wedges keeping me from rolling back).

The transmission and engine where separated when I got them, I believe I put everything back correctly and made sure the torque converter was seated but it's my first time with an automatic transmission. Fluids were not completely drained but I did add about 5.5 quarts to get it back up after everything (including the extra for the cooler).

Vacuum leak? Stuck torque converter ? Minions?

Any idea what to test for or check for? It's almost there...

Thanks

 

Do you have a tachometer on the truck , what rpm's does the engine idle at ?

 

No tach, I did try to rev it up a little bit and put it into gear but same problem. Only revved it maybe 1k more at most as I didn't want to go flying if it worked.

 

It might be an internal pressure problem, just a thought on my part..

 

Mine did the same thing inadvertently and I finally discovered that I had one spark plug wire that was actually coming loose. New wires and no problem.

 

Ok, swapped in a larger vacuum line for the transmission and did a quick spark plug wire check. No change.

it doesn't stall once its out into gear, it starts to stall the second I try. I never actually get it into gear before it stalls.

Also I tried revving the engine higher and shifting and no change.

Nothing moves at all. No lurch it just stalls out but I can keep it from stopping if I put it back into park real quick.


I'm at a loss. Granted the parts where separated and put back together and it's been over a year since they drove but I can't think if what could have changed to keep it from working.

would the duraspark system have anything to do with it? Like I said the engine is a champ in park or neutral.

Could an air bubble or something work it's way in if I ran something before I should have? Did I miss a step in assembly? Something need to be bleed?

There is no grind or any sound other than the engine running. Nothing sounds out of place, just stalls like the fuel got cut off.

I guess I could try to raise the rear end up, even though I'm on a slope and see if I spray it with starter fluid if it runs in gear then. Guess the duraspark could control that, I dont know enough on it. Would make sense since I can get it to turn over but not catch it I try to start it in gear. But it doesnt explain that the truck didn't lurch when I did.

If it's just fuel shouldn't it had moved somewhat as I tried to start it? Slope or no slope, as reverse was the same.

I'm starting to get why the Flinstones used their feet lol.

thanks

 

It sounds electrical to me. If it was fuel I think it would slowly cut out or sputter.

I had this happen to me and it turned out to be something in the distributor was grounding out when the car was put into gear. You could also disconnect the NS switch (you said it wasn't working?). Maybe its wired wrong?

 

I re-read this:
Truck idles fine, revs fine in Park or Neutral, but when putting it into any other gear it stalls. I can keep it from stalling if I switch it back quick enough. I drove the combination in the truck it came out of it and it worked just fine.

The more I think about it, the more I think the NS switch is wired wrong. Disconnect the cables from the switch and connect them together. See what happens.

 

That's a good point, it doesn't slowly cut out or sputter and the the amount of gas I give it doesn't effect anything. It doesn't act mechanical but like it's loosing spark... like a **** being turned down.

I'll start with the NS switch tomorrow. My [loose] understanding with it is it was basically a mechanical switch that only had 2 spots in it's movement where it would allow the engine to crank, but if I have something backwards or it's got a problem, who knows. Maybe I have the crank wire wired as the running wire and vice versa, but I was pretty careful with it... but if it worked when I turned the key I wouldn't have a need to look into it farther.I vaguely remember a couple wires on it being folded over and taped on the NS switch by the PO.

I do hope that's it because the Duraspark was a massive pain to find how it should actually be wired up, like 4 different wiring diagrams for the same version out there. And it's possible I have an old harness on one half of the connection because the colors where reversed when I plugged it in (instead of red to red and white to white it's red to white and white to red. I caught this when wiring it back up and went off the color from the CPU side and not the connection, but if for some reason they changed it over time as a quick fix...? It only connects one way.) They're for the ignition at the starter solenoid and the coil. I've found no diagram or mention of these two ever being swapped, which is why I think I just have a mis-match of parts and connectors, considering how easy they seem to break.


Also need to find out where my coolant is going. Seems low when I check it, might have my ratio too far off though and it's boiling/evaporating. Has a new cap though.

 

I was going to suggest you ask the question over to the driveline specific forum but it sounds like you have the problem figured out as electrical. Perhaps that is why you found the neutral safety switch wires taped up. I would never suggest anyone bypass the NSW but these trucks had none when they were designed and built.
https://www.ford-trucks.com/forums/forum69/

 

It was the neutral safety switch.

I bi-passed it since it wasn't working anyways (I'll put it back when I get a new one). Still need to bleed my brakes, it wanted to go as I was holding them, which is why I left the tire wedges in. Used up all the gas I had in it, I'll add some more this next week and bleed the brakes and it *should* drive again.

Just need to be certain it stops first, that engine makes a tremendous amount of low end torque. I miss a clutch pedal.


Thanks for the help everyone!

 

It must be wired incorrectly for it to cut the ignition , it should be in the starter circuit and not the ignition circuit .

 

That's great! Make sure you re-route the wires from the run circuit to the starter circuit when you replace the switch.