901D shutting off

showcrop

Well-known Member
My 901D is shutting it self off, when sitting idling. It will run for hours at higher RPMs and at load. When sitting idling I have noticed that the RPMs will drift up and down a little now and then, once it starts to do this, if I don't touch it it will stop. If I give it a little throttle it may come out of it. After it quits, it may restart or it may not. It seems to do better if I give it a few minutes. it was rebuilt three years ago. I repeat: it runs for hours at higher RPMs and under load.
 
Sounds like the metering valve may be sticking. When throttle is brought down to idle speed quickly from wide open does the engine under run idle speed and/or die? When the valve first starts to stick the engine will hesitate to speed up too.
 

I have seen this with fuel delivery problem where air is getting in system or leaks on delivery line as well as pump problems. faster rpms and pump is able to overcome problem. check for full fuel flow and change filters, drain water traps.
 

It quit again and doesn't want to restart. It is turning over very quickly but only occasionally fires. Usually no white smoke. I tried throttling down abruptly from full RPMs but it didn't go below idle. It doesn't hesitate at all to speed up. If it were a sticking metering valve is it difficult to get at to free up? Or perhaps give it some power service treatment?
 
(quoted from post at 15:18:09 06/24/15) I don't think you have a sticking metering valve if it accelerates fine. I'm wondering if it's getting air at the inlet now..

with a full tank of fuel above, If there was an air suction leak, wouldn't it be leaking fuel when not running?
 
Yes, I'd think it would leak. I've seen inlet hoses break down inside and cause flow issues. Might take it off and look through it since it's short. Also possible the blades in the vane pump are worn enough that at lower speeds the pressure is down low enough to cause trouble. Depends which end cap the pump has which blades should be used. At higher speeds worn blades may work OK to keep the pressure high enough to keep the plungers charged.
 
Diesel fuel is a mixture of lots of different long chain hydrocarbon molecules. Air molecules are mostly Nitrogen (N2) and oxygen (O2), which are much smaller than long chain hydrocarbons, and can go through holes that are too small for the long chain hydrocarbon molecules to fit through.

A latex balloon filled with helium will deflate in a couple of days because the helium molecules can easily pass through the pores in the latex, but a balloon filled with regular air will take much longer to deflate because of the larger molecules of N2 and O2 in regular air. Same principal applies to small leaks in a diesel system that can allow air in but not allow fuel out easily, especially on the suction side of the system, as that side is never under pressure that would push the fuel out, but when it's running it is under suction, which will suck air in through even the smallest openings.
 

Well you guys were right about it sucking air at the intake. At least I am optimistic that it is cured. I broke it where the rubber line goes into the pump head and put some new thread sealer there. Where the line comes out of the filter housing it had not been tight since I owned the tractor, about twelve years. It never moved because the rubber line had it under tension. But I got 3/4 of another turn on it there. So then I went and raked and baled my hay and when I got done I left it idling for 45 minutes at 450 RPMs while I ate lunch. It was still running when I got back so it looks like it is cured. Thanks.
 

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