Farmall 400 oil pressure drop, will not start

pmarkel

Member
Working on my Farmall 400 again, rewired it enough to start it again but it was over-revving. After some inspection, I hadn't gotten the governor to carb throttle shaft in the right groove. Fixed that and started it the other day, ran ok for 45 seconds or so. Started it this morning to test out a new alternator. Ran ok for 10 seconds and then I noticed a large drop in oil pressure. I shut it off right away. On subsequent attempts to crank it the starter makes a terrible grinding noise and does not turn the engine over. Took the starter over to the guy who repairs them for me, he tested it and found nothing wrong. Seems to me there are new burrs/grinds on the starter gear that weren't there before. Engine can be turned at the fan yet but it feels awful tight at the ring gear when I stuck a long screw driver in there and attempted to turn it over by hand. How much trouble am I in for? Thanks,

Pete
 
The ring gear is 'munched' Split the tractor and replace the ringear.you don't even need to remove the flywheel. Tap the ring off, slowly working around the flywheel, Hang or lay the new ring close while you heat it.It does not have to be cherry red. Then quickly grab with pliars,vise grips,etc and place onto flywheel. Tap it home. Let cool and slide the tractor back together.
 
The only reason I can think of that the engine would turn easily in the front, but be hard to turn in the back, is a broken crankshaft. That may also explain the sudden problem with the starter, because depending on where the crank broke, the flywheel may not be sitting where it belongs.

First thing I would do is drain the oil and pull the oil pan. All you can do is start opening things up and looking for problems. If there's nothing obvious on the surface, you have to dig deeper even if it means tearing the engine completely down.
 
I agree. Though the diagnosis is a bit tough. If the crank broke (maybe from over reving) at the #3-4 end, the flywheel may be hanging crooked enough to cause the starter drive
to fail to engage the ring gear teeth. Jim
 
Just a quick comment here when turning the engine that have the old style TA behind them make sure you are turning the engine in the normal direction of rotation. If the TA is in good shape you are unable to turn the engine backwards. (unless the TA lever is pulled back).
 
Thanks for the tip. When I pulled the TA back I could turn the flywheel over real easy. Now to the starting issue: I talked to the starter guy again last night and he said there was one more thing it could be. Took it in this morning and when he unbolted the gear reduction he found a woodruff key had sheared inside so that tested on a table the starter would spin but under the load of turning over the engine it just sat there. He patched it up for me and I put it back in and started her up. Sounded fine but didn't have oil pressure right away. Let 10-20 seconds go by and pressure built up and stayed at around 65 pounds. Mechanic said pressure could have dropped due to clogged oil filter or sump. Previous owner said fluids were fresh when I bought it July of 16. I like to change my fluids regularly on my other tractors but could scarcely keep this one running long enough to get it warmed up and drain it. Will do this week and see what I find. Thanks,

Pete
 
i dont know if your aware, but the oil pres. does not just jump up as soon as the engine is started. takes a bit for the oil to follow that tiny line. in cold weather it is slow.
where you actually looking at the guage when you said the oil pressure dropped? cause if you just started the tractor for 10 seconds the oil pressure did not have time to register on the guage.
 
actually i got this mixed up with the 560 and 660 engines they are really slow with that tiny line. i know i have to wait and watch. these engines are not that bad as the line is bigger. just something to think about.
 
(quoted from post at 17:10:38 02/22/18) I was watching at the time but I had also backed the tractor down to low throttle so I wonder whether that would have contributed. To be honest I am not very used to this particular tractor and it's quirks. My deeres have very high pressure upon start up in cold weather and drop off to medium once the oil warms up
 

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