My engine speed slows down from partial or full throttle without letting up the throttle. It also sometimes speeds back up after a few seconds. So basically the engine speed is fluctuating on it's own. Is it starving for fuel?
That's the first thing I would check, the fuel system. I would start by replacing the fuel filter(s).
Anything rubber or plastic on that fuel system. Pay attention to the gaskets on the fuel filter when you replace them, make sure you take out the same gasket that you put back in, easier if it's the stanadyne glass box filter. Rubber hose between tank and lift pump? check it for cracks, if it has crimped on ends and special fittings, you can grind off the ferrule and reuse the fittings with hose clamps, they'll just pull off faster if you snag them on a branch. Check JDparts to see if there's a screen in the tank, those like to plug up and collapse, you can pull the screen, clean it, put a spring inside so it doesn't collapse. Clean the tank even. You do drain the water out of the tank every time you start it, right? That's what the petcok is there for.
Thanks so much for your reply! I replaced the filter, (square glass type), tried to keep fuel in it but much of it leaked out while I was installing the bracket. The engine started but stopped after about 30 seconds. I presume I need to bleed the system now? I am not very familiar with diesel engines and do not know where to even begin. I found the petcock I am supposed to open to bleed out water, I will use it from now on!!!
That’s a classic symptom of a run away engine.. where the flex ring has deteriorated to the point that it’s hitting metal to metal & about to sheer the rivet pins.. Check the aforementioned parts.. if none of those solve your problems, get ready to pull the pump..
Now I am totally confused??? Run away Engine? It simply stopped running after I changed out the filter?
The rpm fluctuations are a classic sign of a dirty filter, air in the system or a run away.. Remove ALL the fittings on the top cover.. Loosen all the steel lines coming from the pump, AT THE INJECTORS.. Move the throttle to WIDE OPEN @ crank the engine till fuel spits out of the loosened lines n tighten.. It should start now.. Once started, ease the throttle back to idle n start assembling the fittings on the top cover 1x1.. n wait for it to shut off.. If it never shuts off n your surging is gone, good..
Listen to Thepumpguy. But first, find the transfer pump with a lever hanging under it on the side of the engine, pump that lever to bleed the air out of the filter with the top hex head plug on the filter base, then close the filter once there's no more air. Keep pumping until there's no more air coming out of the injection pump, might have to crank it for a couple seconds between hand pumping. If there's any or dirt in the filter, drain it out with the bottom hex head plug on the filter base, finger tight is enough with those plugs, or very gentle with the wrench, they're AL I believe.
Sorry for my lack of knowledge but, what is the top cover you are referring to?
He is talking about the top cover of your injection pump. ]
Thanks guys, I will work on it tomorrow and let you know how I make out. It is raining this afternoon, I could possibly melt!!!
The fittings you want to remove are attached to the return line to the fuel tank from the injection pump. On the top of the injection pump is a cover that is screwed/bolted to the main body of the pump. On top of that cover are some fittings with a fuel line going back to the tank, right? take that fuel line loose, then unscrew all the fittings so you're looking directly into the pump. If you start it like that, it will make a mess. Check inside the fittings, is there a check ball? is it plugged with "mouse turds"? Is it wide open with no check ball? You can bleed the system and start it without messing with the fuel return fittings. But if they're plugged up already, I suppose it wouldn't bleed very well, and would bleed very well with that fitting removed. If it starts and runs smooth, don't worry about it until it starts "hunting" or surging again.
I finally got back to it, needed my sons help remiving the hoid for better access. I opened the bleed petcock at the filter and let it fill with fuel. I then cranked the engine to build pressure and bled the air at the outlet of the injector. I then began bleeding at the injectors and the engine fired up and purred like a kitten. The power is great now and does not surge. You guys are great!!! I really appreciate the help!!
Glad to hear it.. If it starts hunting, always change the filters & blow back thru the feed line 1st..& if it continues, watch out for a run-away..