Ford NH 1920 compact tractor with 4-cylinder Shibaura N844 diesel engine, has always started and run smoothly, but just recently began running a little rough, like one cylinder is occasionally missing. Hoped it was just bad fuel or moisture in the sediment bowl, so I cleaned the bowl and drained out the fuel tank, put Seafoam in the sediment bowl and new fuel in the tank. Starts fine and idles fine, but as it warms up it begins missing, and get worse the longer it runs. It is worst around 1500-2000 rpm; at wide-open (2500 rpm) it doesn't seem to be missing as much, but isn't running perfectly smooth either. I tried loosening the injector compression nuts one by one, bleeding each line, but that didn't seem to change anything. The engine isn't misfiring on every revolution, so that operation didn't indicate whether one injector was causing the problem. My question is whether this sounds like a faulty injector, or something else? If it's an injector problem I will try to get a new set and replace them all at once - they don't look that expensive, the tractor has been cheap to run for many years, and I can't imagine life without it now. But I'd like to know if there is more I can do to diagnose the problem.
Have you checked the valve adjustment ??
No, not yet. Would that be consistent with the symptoms? It puzzles me that it starts easily and idles fine, then starts missing as the rpms go up.
You stated as it warms up it starts missing sure would make me check valve clearance
OK thanks, will give that a try.
I was hoping to get a set of injectors so I could replace those as well, but can't seem to find any that math the original equipment. These have leak-off lines and look completely different from the ones I see offered online for the Shibaura N844. Anyone know the original part number?
Contact @thepumpguysc , he may be able to help/guide you. He was helpful to me, Thanks again @thepumpguysc
That could be injectors or pump timing.. The timing is with shims UNDER the inj pump mounting flange..& unless your have experience checking the timing u should get help.. If u want, u can contact me thru this site and start a conversation.. just click on my screen name..
The shiabaru n844 is also a perkins 404c22 I believe, I just rebuilt one that blew a head gasket at the pushrod cavity and was getting harder to start until one day it wouldn't start at all. Looked like a lot of blowby but ended up just being the head gasket but we were that far into it so we went through it
Today we checked the valve lash and everything seems fine. Wondering is maybe it just hadn't been run hard and hot enough in a while - this tractor sees mostly light work - I put the rototiller on and tilled for about two hours, after partly blocking the radiator screen, to get the engine nice and warm. It got a little better after warming up, but still runs rough at 1200-2000 rpm. Still a bit mystified by the fact that it starts easily and runs smoothly at idle, only getting rough when revved up a little. It also will run pretty well wide-open, though maybe not quite perfectly smooth. It doesn't seem to smoke much, even when running rough - there is a little blue smoke when it's really rough, but while I was tilling it didn't seem to be smoking at all.
I finally got the injectors out - they weren't stuck too bad. They look awful, covered with carbon, can't even see the nozzle orifice; I'm surprised it ran at all. Sending them off tomorrow to see if they can be restored.
Got the rebuilt injectors back and installed, bled the lines, started up and ran the engine. Still misses at around 1500 rpms. Super frustrated now. When I saw how bad those injectors looked I was sure that was the problem, but apparently not. I checked and there is no "blowback" coming out of the crankcase vent. Turning the fan by hand it feels like good compression. If it's fuel pump timing that's going to be a tricky job. I can't figure out why that would go haywire though, is there something that wears down that could cause the pump timing to go bad? Up until this spring, this tractor has always run really well.
Problem solved! A friend who is a diesel mechanic came out and diagnosed it - the coughing was not accompanied by smoke, indicating it was "starved for fuel" - probably caused by gum buildup in the inlet ports of the injection pump. This engine does not have a low-pressure fuel supply, it's just gravity flow and the injector pump is above the bottom of the fuel tank, so it's sucking diesel. Any little restriction on the inlet side will result in insufficient fuel flow to support higher rpm. Solution: install an inline low-pressure fuel supply pump. Easy-peasy and now it runs like a top again!