My 801 with 172 diesel started loosing power and backfiring while mowing with a bush hog. I replaced the fuel and air filters. It would not start acted like a timing problem. I knew the injectors needed rebuilt because of black smoke for the past several months. I had the injector pump and injectors rebuilt. Now it will not start. It will run on starting fluid (which is not good) but still will not fire on diesel fuel. It seems to me to be a timing problem. I've checked the crank and cam timing marks with #1 on TDC all looks good. I keep going back to why did it crap out wile mowing?

I'm at a loss and will welcome any advice on this problem.

If the camshaft broke, I am pretty sure that the engine would have stopped almost instantly.

If it will only start on starting fluid then the compression could be down. Have you done a compression check?

Thanks Sean, the tractor has been starting ok even the day it died. So I had not thought about compression. As soon as I locate my gage I'll check it.

Had you cracked the lines loose at the injectors and made sure you have fuel to them?? It can take a long time and a lot of cranking to get the air out of the system

Roger opened the lines one at a time and fuel spurting out seemed to be about right. Also run it on ether (with great care) long enough to pump out air. I'm still puzzled as to why the power loss and backfiring while mowing when it died. The injector pump rebuild was a waste of money as the tech could not find anything wrong.

Thanks for the reply. it's worth double checking.

I have had a power unit 172 lose a couple teeth off the timing gears and throw the timing off, but you said you changed the injectors so I think you would have noticed a couple bent push rods.

Fritz

Thats a thought, I removed the injectors without pulling out the push rods but I'll check them when I go back in. The timing gears look good. I checked the key on the cam but not the crank, really don't see how a key could be partly sheared.
The tractor was running fine, except for a little black smoke, then it started loosing power and backfiring almost didn't make it back to the barn. So far I haven't gotten inside the engine just the valve cover and timing gear cover. I think the camshaft may have to come out. Ever heard of camshaft breaking or some other disaster happening to it? Also I can turn the engine CCW with a wrench but not reverse. I don't remember if that was the case when I overhauled the engine about 20 years ago.

Thanks