8n won't turn over

First time poster, but I've done a lot of reading and searching here and y'all have helped me a bunch already, but now I'm stumped with this 8n.

I was mowing with her a few weeks ago, after an oil change, when she overheated, made a horrible squeak, and stopped. Since then the engine won't turn over but for maybe a quarter turn, unless I take the plugs out. With the plugs out it turns over fine.

So far I've tried
-mmo down the plug holes, let it sit a few days, no change. Repeated this with motor oil, then with mmo again, several rounds of this along with cranking by hand and with the starter with the plugs out
-cranking it with a wrench, turns fine with plugs out, takes some effort but I can turn it with the plugs in too
-dragged it around the yard and up the driveway in gear, she just skidded wherever I took her
-tried to roll start down a steep gravel drive in third gear, nothing but a 20 feet skid mark to show for it
-jacked the backend up, wheels turn freely in opposite directions when it is in gear
-removed the head and oil pan over the weekend expecting to find something broken or stuck everything moves just fine in there and visually seems ok, buttoned her back up and...same thing

It's a 6 volt system. It really acts like it just doesn't have enough Juice to turn the engine, I've been charging the battery between starting attempts and tried to jump it with a 12 volt in my running truck hooked directly to the big post on the starter and a ground, same thing.

Wires are thick, clean bright and tight (as they say)to the starter, the wiring after that isn't great, I have a wiring harness on order, but I'm not sure that's going to fix my issue since it really seems like something mechanical is preventing this thing from turning over freely through the compression stroke.

Anyone have any ideas? I'm not a mechanic, but I would really like to learn more about this and I'm willing to give anything a shot at this point.

Front or side distributor?
75 Tips

Side. Also forgot to mention compression seems good for all cylinders (thumb test)

When you had the pan off, did you remove all the caps? Sounds like you have an insert piling up.

(quoted from post at 19:37:43 10/27/14) When you had the pan off, did you remove all the caps? Sounds like you have an insert piling up.

Click to expand...

No, I didn't remove the caps. I was so convinced that there would be something obviously broken in there that I wasn't sure what to do when everything looked ok. I'll remove the caps next, probably not until the weekend though. Will I be able to see an issue with the inserts when I get the caps off? Or should I just plan on replacing them?

If there is one spinning in the rod, you will need to have the crank removed & ground. If the rods are ok, check the mains too.

When you had the head off, did you try to push on the pistons? Sometimes the cap will come off of the connecting rod and it will bang around on the crank and basically do what you've been describing. If that is the case, the cuprit piston will slide down since its not connected to the crank any longer. Also, you could hit the starter when the head is off to see if all pistons are cycling.

Took everything apart last night. There was 1 rod cap that took a bit of work to get off, the other three came off real easy, this one took some prying and eventually I was able to grab it with a pair of channel locks to get it off. The inserts had turned 90 degrees on this one and the top one was mangled up pretty good.

teddy- can you explain your last post to me? The insert was turned on this one. Is that what you are talking about? Does this mean I need to pull the crank and have it ground? Or would replacing the inserts be my next step?


Poppy- thanks for the suggestions. I did hit the starter when I had the head off. Everything cycled just fine as far as I could tell same as when I hit the starter with the plugs out, it just won't turn when there's compression.

classic spun bearing...

Spun bearing means the crankshaft has to come out and be ground, right? If I just replace the bearing will it just spin again when I fire it up? Sorry, I know these are probably dumb questions, I just want to make sure I understand what I'm doing and why I'm doing it.

i'd be surprised if the crank didn't at least need polishing. then you have to see if the rod survived.

Then you have to deal with the fact of 'why' as in.. why did a rod bearing spin. was it lack of lubrication? if so.. then you need to address the oil pump.. and if it needs replacement.. that's a line bore issue as it's at the front main cap.

May as well go through the whole thing. Then it'll be good for the next 30 years. Sorry for your troubles.

You know, if you didn't want to make a major production of it, you could do some measuring. Ford sold connecting rod bearings that where odd sized. Some of them are just 0.002" and 0.003" oversized, beside the standard, 0.010", 0.020", 0.030", etc. If the crank journal isn't out of round more than 0.001" or scored all up, you might be lucky enough to just put a well selected group of rod and main bearings in.. I do admit it is somewhat of a long shot. Best of luck. :wink:

Make sure you get that rod resized or replaced or it will happen again.