Cummins 160 parked for 10 years. Will it run?

Probably quickest to just back off the adjusters on the injector rockers .........I know there all this B/S about Cummins injectors ,but Ive reset them and the engines run all right.

Check that all valves are free and then achieve decompression on all cylinders by winding in tappet adjuster of exhaust valve for each cylinder. Gardner engines have a lever that does it for you.

If the donk appears seized (wont turn at all either way) i would think some (or all ) pistons could be seized through water ingress  or what ever.         Assuming the box is ok of corse................
Has the clutch been out ???  you havent put a long bolt back in that has maybe jammed the flywheel to the housing ?????
I assume it was running at one stage.........
If an injector or valve was jammed (highly unlikely)    the crank should still have some movement.
Just remember if you decide to take the jeccies out..the large bolts on the rocker gear also hold one side of the head down.
The jeccies dont need that off to come out.
...............Billy................

You can also remove the starter and try (carefully) levering on the ring gear...........if it wont move ,then its time to drop the sump and see if there are any rust stains running down thhe liners.

Unless you are terribly unlucky , there always used to be a hole , about 1 inch dia , in the bottom of the flywheel housing. sitting right under the starter ring gear.   I used to use a screwdriver to turn the donk over, ex amount of teeth,  (forget how many , about 30 odd per set,  when setting the jeccies.                              
              ...................Billy..................

Well I put all the advice given to the test yesterday, I started with BillyP“Has the clutch been out ???  you havent put a long bolt back in that has maybe jammed the flywheel to the housing ?????”The clutch hasn’t been out but the gearbox has… about 5 times!! While I endeavoured to put all the bolts back in the right places, I had a helper the last time I installed it, so couldn’t be sure that got the order right, so yesterday I patiently undid every bolt (not all at once, but every second one) and checked by prying on the starter ring gear as per Billy’s suggestion (..“there always used to be a hole , about 1 inch dia , in the bottom of the flywheel housing. sitting right under the starter ring gear”..) but nothing changed. The engine seemed immovable. Next I looked into John K’s suggestion about stuck injectors and followed his suggestion that it’s “Probably quickest to just back off the adjusters on the injector rockers …”. It was pretty quick too. Firstly I only attacked the three injectors that were tight under the rocker, the other three had a hair’s breadth of fresh air between the rocker and the injector. I marked the position of the adjustable pushrod then backed it off exactly four tuns after undoing the lock nut. This made the rocker quite loose so definitely not applying any compression. Then I tried again levering on the ring gear. At first, I thought maybe it moved a tiny bit, but then I couldn’t get any more out of it. After thinking about it for a while, I realised without an assistant watching to see if something moved, I wasn’t going to pick up on very small movements easily, so I decided I’d try using the starter while filming the ring gear so I could detect if there was any movement. See the result for yourself:  youtube.com/shorts/Jm8xkuCfKqc?feature=share  

I didn’t want to keep cranking as the battery terminals get hot very quickly. I wasn’t sure if the injectors had been the problem or just all the grunting and puffing from me was having some impact. So before getting too excited and burning the starter motor out as well as maybe stuffing up the injector timing, I tightened up the 3 injector rockers I’d loosened and had another go with the starter. See take 2:  youtube.com/shorts/dDSpM6AINXo?feature=share  

Is it my imagination, or did it move a tiny bit more with each attempt?Who knows. After that little bit of positive reinforcement on video, I had a few more goes on the starter, giving it 10 minutes between each burst to avoid over cooking it. It didn’t magical start turning over, but I assumed it moved the crankshaft a couple more degrees, so the pistons might have move a millimetre or 2. Anyway, it was getting late by this stage so a left it at that. Now perhaps some of you will have some more wise words about persisting with the starter, or maybe squirting some WD 40 through the open inlet and exhaust valves, or pulling the sump to check for rusty streaks on the bore before going all out. It’ll probably be a month before I get back to it with all the Christmas and New Year shenanigans about to start.Thanks to JohnK, Mammoth, Billy, Wee-Allis and 180wanabee for the useful suggestions so far.

Its definitely moving ...about 1 tooth of the ring gear for each hit.......mayb some light oil into the cylinders ........you say the clutch  or  flywheel dfinitely not jammed by installing the gearbox............I think my next move would be to check the crank for some endfloat .....the crank should enfloat freely 

Would it be worth trying BilyPs idea with a screwdriver in the hole and see if you can get it to go backwards a bit then forwards again
with the starter like working tight bolt backwards and forwards each time you get a little bit more then a running jump might get it past te tight spot
I’m about to start the same journey with a 46 Ford that has sa in a shed since at least 1980 last redgo sticker 1979
Cheers Bluey

You would have to suspect the last thing you did when a problm occurrs ....and that is fitting the gearbox

JohnK I fear that you could be right. It did take bit of persuasion to get the gearbox to go that last inch, and that could indicate some misalignment that might have damage the input shaft pilot bearing but would that stop the engine from turning over?