Greetings to all. I'm new to the forum, and the proud owner of a old beater 1982 Hitachi OH82 trackhoe that, while having some sort of problem most of the time, I've been lucky enough to be able to keep running on my 'farm'. I'm not an experienced heavy equipment operator, and don't know much about the functionality of hydrualic systems, but am a motivated and eager student. The machine has been running reliably until recently when it developed a progressive loss of power when under load. When I say 'load', I mean simply moving the machine or moving the arm or bucket. It doesn't have to be actually digging. When started, she will run fine, and will function normally for the first 5-10 minutes. As the controls are operated, the engine begins to progressively bog down each time any hydraulic controls are moved...no matter which contols and including the cab swing or tracks. If the controls continue to be exercised, the engine will eventually bog to the point that it dies. If the controls are halted, the engine slowly perks back up, runs a little rough to the ear, and if left alone will, over the next couple of minutes, slowly smooth out and will again be able to operate normally for a few minutes before beginning to bog down again with the same behavior. The failure is progressive, in that it bogs a little at first...and will begin to return to normal power level as soon as the load is removed from the hydraulics, however if the load is not removed or is initiated again, the bogging progresses until either the load is removed or the engine actually dies. I have replaced the fuel filter and disassembled the water catcher bowl to eliminate water in the fuel as a possible problem, with no change in the behavior. Similar posts here have noted the possiblity of a screen in the banjo fittings for the fuel/water filters, but I find none on my machine. The fuel appears clear and clean. Thanks in advance for any assistance.
Sounds very much like a Fuel issue Do you have a good flow of fuel ... Over the years dirt will have entered the tank It could be stuck in any elbow/banjo fitting could be dirt in the tank Remove lines and try and blow air back through them I think the banjo fitting with the screen could be the inlet fitting onto the injection pump Good luck
I've also heard stories of a "floater" in the fuel tank. The engine runs okay until the chunk of debris floats over to the fuel pickup and obstructs flow. Shut the engine off and the floater drifts away from the pickup.
Thank you for your responses. Earlier I found a small amount of gunk in the fuel filter or water bowls, but began discounting a possible contamination issue when the machine would run fine for 10 minutes, then falter, then run again. I was motivated to look elsewhere when I determined that the failure mode seems unrelated to the engine speed. I came to this conclusion because the engine will run fine, even at full power. It is not until the hydraulics are actuated that the engine stall occurs. I'll blow the fuel lines and report back.
There should be a strainer in the banjo fitting on the lift/prime pump. If that is clean then remove the pump and disassemble, you will see 2 white nylon valves which over time get pitted and don't seal. These can be cleaned up with some very fine sand paper but is best to replace if possible. Gees that takes me back
Is it possible that a banjo fitting would have a screen in it but you couldn't tell that it did from a casual inspection without removing it? In researching the problem here, I found several descriptions of behavior similar to my machine, and one had a picture of a banjo with an integral screen. It was obvious from looking at the fitting without disassembly that is was not a standard banjo. I looked throughout the fuel line plumbing, with particular attention to the fittings at the water trap and the fuel filter, as well as the inlet to the fuel injection pump, but see no fittings that look like they could contain a screen. I also note that the suggested repair for these other more modern machines seemed to be related to some form of hydraulic control valves. I admit that the suggested tests for these machines were a little beyond me. Presumably my machine has a much simpler design due to age, with no computer or advanced diagnostic assistance. I've waited to read a few more posts here before disassembling the fuel lines for a reverse blow hoping to dislodge debris because once I get air in the fuel lines its a real pain to get the machine running again. Most recently, after using the lift/prime pump to refill the lines, filter, and trap, I've had to resort to a ton of starting fluid to assist the machine in priming the fuel lines before the machine will start. I did note that when using the lift/prime pump I see what seems like a lot of air bubbles in the transparant overflow line from the lift/prime pump output. Even after pumping for what seems like a long time, the bubbles don't seem to go away. I wondered if the lift/prime pump was working properly, so I removed the fuel filter globe to verify that it was getting filled, and it seemed to be full. The overflow from the lift/prime pump is located at the very top of the fuel filter globe. Does it seem like it could be a fuel delivery issue if I can run the machine at full throttle, with no hydraulic load, and the engine runs fine? If the answer to this question is YES, it could still be fuel delivery, then I'll pull and blow all the way to the fuel tank.
How might one determine if I have a good flow of fuel? If this would be a fuel pressure test gage I can get one to find out.
The very first connection where the fuel line comes from the tank, usually connected to the transfer pump right under the priming pump, the banjo bolt looks exactly like all the others but has a tiny nylon screen threaded into the internal bore of the banjo bolt. Mitsubishi was famous for this but as I recall the Isuzu and some other Japanese diesels had the same setup. Check them all just for giggles, I have found more than one in a system. When priming are you opening the bleeders on the injection pump? They will be the hex head bolts that also have a screwdriver slot in them, usually one at each end.
The banjo fittings look the same but the one I'm taking about is on the line from the tank. Bleeding shouldn't be a problem as all you have to do is crack the bleed screw on the injector pump. Back flushing the system is not a good idea is it gets the crap on the wrong side of the filter.
Hi all. I went through all of the banjo fittings and no screens are present. Surprising as this is, there doesn't seem to be a fuel transfer pump. I confirmed what the assembly diagram shows, that the line from the screen at the bottom of the tank runs directly to the inlet of the water trap bowl. The outlet of the water trap runs to the inlet of the fuel filter bowl, and the outlet of the fuel filter bowl runs directly to the fuel injection pump on the engine. The only other line running to the fuel tank is the fuel return line from the injector array. I see no bleed ports on the injection pump, except for a slotted tap on each of the injector feeds, probably for individual bleeding of the injectors themselves. My take on the prime/lift pump bleed has always been that the bleed is accomplished by opening an easily accessable bleed bolt with a clear overflow line attached located at the top of the fuel filter bowl. Whenever I've needed to prime and bleed, I've just opened that bolt and pumped until I got clean fuel running overboard through the clear drain line. This has worked to remove air/water from the line in the past. According to the assembly diagram, there is not a transfer pump in the tank either. I suspect that the injection pump may function as a fuel transfer pump as well. Keep in mind that this is a 36 year old machine. I'd still like to know if it makes sense that this is a fuel problem when the engine will run fine at full throttle. Thanks.
Are the inlet to pump lines/ hoses collapsing internally or sucking air from deterioration ? FI pumps get cranky if theres air commin in
x1. If I remember correctly the prime pump should be mounted on the side of the injector pump. it has a round handle which you unscrew. When the handle then pops up it's ready for use. If as you say there is no primer can you post some pic's of your setup.
PROBLEM SOLVED. Tones: there is a manual primer pump located as you describe, but there is no transfer pump, i.e. no seperate fuel pump. Perphaps I'm using the wrong termonology due to my inexperience. I expected a seperate fuel pump, but it must generate the suction from the injection pump. I went through the fuel lines from tank to injector looking for leaks, and as I was beginning to remove the primer pump to check it out, I discovered a banjo fitting covered with gunk that I had missed. Lo and behold it contained the famous integral screen which was nearly completely clogged. Ipso facto off we go...a little cleaning and VAROOM the pumpkin (shes orange) lives again! THANKS to all who helped.
Yep just a terminology thing, there isn't any transfer pump. Glad she's a goer
GOOD TO HEAR !! diesels are a simple critter.. suck, squish, bang, blow, at the right time come to think of it all IC engines are that way.. LOL