I just bought this machine Sunday April 6th 2025. I’m hoping to be able to go through it and bring it back to a serviceable condition to reliably work around our property. I have looked through multiple other posts to narrow down some of the issues, however I’m not having a ton of luck. I have a laundry list of issues, and I want to just work through them one at a time. First thing is it runs great, however like others, some movements load up the motor up to stall. I have read multiple posts regarding electronics, however these seem to be on EX100-2 and above. This is definitely a EX100-1. I don’t see the dreaded angle sensor on the pump at all.. I don’t seem to have a computer behind the seat that I know of, and none of the gauges or lights work on the right console. My questions are many, but where should I even start here. I will probably start replacing switches as they are all stuck in one position or another. Is there anything I should avoid to start out with?
Have you tried the fuel filters??
Last night I did some preliminary testing and it appeared to blow heavier smoke when it loads up. Not a ton, but noticeable. I will change the fuel filters tonight and retry. Also I believe I read there is a screen on one of the banjo bolts to check as well.
my 50d did the same thing changed the fuel filter problem gone.
An air filter hopefully is not expensive and can cause problems.
Sump the tank before you mess with the fuel filters. That is where the crap lives. You could change out filters just to re-load them with gunk. If you pull the plug and open the valve and nothing comes out, there's your sign. You may have to rod some crap out of it to get it to flow. After that is running clean fuel, work your way up. Somebody posted about a parts 100 they bought to work on thier 120. Might be a good contact to make, not implying you need big parts but if you ever did
Finally got around to working on it today. I drained the liquid that was in the fuel tank. I am reluctant to call it fuel.. I sloshed the tank as clean as possible. I then removed the banjo bolt thinking there would be a screen, but no screen in any banjo bolt I found. This worries me as any debris went to the lift pump for sure. I changed the fuel filter, and added an inline filter under the tank. The old filter had a ton of junk in it. It still does the same thing losing power. My next step may be setting up an electric pump from the tank to the filter housing to see if the lift pump is working good enough to supply. I don’t know if there is a way to take apart the lift pump for cleaning, but I could try that also. Other news, there are zero electrical items plugged in. It appears that everything has been disconnected. I guess I’m not sure how everything works, but I want to get it to run correctly before I tackle those obstacles. Judging how nasty everything has been so far, could the hydraulic filter cause this issue? Or is this more than likely fuel related. When it lugs down, it definitely changes exhaust smoke, but it does not roll coal by any means..
your electrical system is more of a read and report system, not a read and control. That's why just about everything is unplugged and it doesn't matter. that's an older machine - like mid 80s; you won't have a computer. You'll have a tach source from the alternator, temp and pressure sensors for various items. It's possible you could have some solenoids for control of auxiliary hydraulics, you'd have to look for that, but i'm sure it would be rather obvious. As to the engine - that model is commonly (always?) supplied with an Isuze 4BD1, and IMHO Isuzu makes some fantastic diesel engines. I don't know anything in particular about this model, but there's guy on these forums who's really good with the pumps. @thepumpguysc is his handle - you may want to reach out to him before you tear into you injection pump. How many hours are on this rig?
By the way, if this was my project, I'd not be running in much if it's sat for years. I know the desire - but i'd have changed the engine oil and filter, and the hydraulic oil and all 3 or 4 of it's filters before I went nuts running it to see what it did. Then I'd change out the drive finals oil. THEN I'd play around with it. You could be cycling milky fluid in there and not knowing it. Just changing all the filters and fluids is a major first step. After I did that, I'd take off the cab, the the seat, the floor shields, etc. Dig into the unit. clean out all the gunk in the main body of it. see what the rodents have done. see what kind of lack of maintenance has gone on. this isn't going to be a weekend project. It took me 3-4 months to fully go through my 50 sized mini. you have a good sized machine there. it's going to need good care.
@Pont463 , how are you set up for operator/ service manuals ?
I apologize for not explaining better. I did change the oil and filter, and I simply blew out the air filter. The radiator has been checked and was verified full and in good condition. I also checked the hydraulic fluid for moisture before restarting the machine. I did not however change the hydraulic filter yet as it is ordered. The only obvious issue was the rotary gearbox was considerably low of gear oil. I topped that off as well. Though I don’t know the history of the machine, it has plenty of hours. The hour meter shows 2600 or so and I assume it’s 12600 as non of that is connected anymore. Oddly the pedals, seat, and controls look more like 2600 hours, but nearly every window is gone. And dents around the cab area. I’m not trying to “operate” the machine except for diagnostics at this point. No digging or driving. I do have the operators manual with schematics, and there definitely is a computer, however apparently it is for the hydraulic operations not engine related. There are a couple idle related servos to kick down when not moving. It doesn’t appear that these has touched the throttle linkage, so I am ruling them out. I also still need to change the pilot filter as it is separate. I definitely won’t tear into the injection pump. That is way out of my wheelhouse. I do think this is fuel related but hopefully not the injection pump.
I have an operator manual so far.. I definitely need service manual
@LACHAU posted a link to a EX100-1 service manual in the thread below ,see post #9. . HeavyEquipmentForums
Thank you so much!!.. I will be diving into this today.
Latest update.. I removed all fuel pipes, cleaned everything up.. no change. Removed the lift pump and cleaned it. Reassembled and no change. Now I’ve broken one of the hard lines from the filter housing to the injection pump. I will have to order one of those. I can’t seem to locate my electric fuel pump, so I will have to order one of those as well. Then I can bypass the lift pump and try direct filtered fuel to the injection pump.
Ok.. I’m at a loss.. this acts as a fuel issue, but now I’m not sure. I bypassed the mechanical lift pump and connected an electric fuel pump to the filter housing. Same thing. The machine has no power and bogs under any load. I then bypassed the filter housing and connected the electric pump directly to the injection pump. Still the same issue. I don’t have experience with Isuzu engines, however any other diesel I’ve had or worked on will start “fueling” under load. (Black smoke) .. this does not do that. What am I missing here? Is there something wrong with the injection pump? Or injectors?.. I did break each injector line while running and noticed a definite change for each one, so I’m confident they are at least doing something. This thing runs like a sewing machine until you put any load on it. I have the manual, however all the troubleshooting says to put it into certain modes. With the electronics unhooked, I have no way to do that. If anyone has a direction or advise I would greatly appreciate it.
New theory. I read some previous posts from another member that had a similar issue. He never said if it was fixed, but it got me thinking too. The swash plate on my machine is operated from the solenoid on my pilot system from what I can tell. That solenoid is not electrically connected to anything. I believe it is just an on off solenoid. Is it open or closed the wrong way? Could this thing be open all the time and sending pilot pressure to the swash plate loading the pump? Or the other way not allowing pressure to it? My machine doesn’t have an angle sensor like others, so I don’t think I can monitor it. How much pressure should go there? When?
Engine running at full throttle, the throttle lever hits the high idle stop on the injection pump ? The way you describe the machines poor performance sounds like the injection pump is the issue. Post a pic of the injection pump and the info tag and @thepumpguysc may be able to suggest other checks that may have been missed.
The hydraulic pump flow is commanded by the flow sense valve signals sent from the main control valve. As the hydraulic system pressure increases towards maximum the regulators on the back of the pump start to de-swash the pump to ensure the engine is not pulled down excessively (approx 150-200 rpm from high idle) . The solenoid valve I believe you are referring to only allows the pump angle to increase approx 10% above normal for faster dig function speeds when in “P” mode only. You have no electrics working so the machine operates at the mechanical settings I mentioned above. If the machine is able , time how long it takes to travel 65 feet (20 meters) at full travel lever movement, engine at full throttle. Spec is approx 16 seconds. See screenshot below. .
Correction, since you have no working electrics to acheive “high speed“ travel , I expect the travel speed would be at least 10% higher than spec.
I just came home quick and tried the travel test. With the throttle wide open against the stop, it takes off fast.. then the motor bogs down and it goes to a crawl. If I don’t let off the travel, it will die out. If I lift the boom up, and just swing the dipper, it bogs the motor down and kills it. It doesn’t matter up or down. God forbid I try two operations at once. I took a picture of the pump.. I also took some quick video of what it does, but not sure how to load those.
Upload the video to utube and then post the utube link here.
Bogging Hitachi Try this link I uploaded to youtube
Bogging Hitachi engine side This is looking at the engine when it Bogs down. I see a very light bit of smoke, but not much. This is with the electric fuel pump force feeding the system.
The best view is against the back drop of the shop door, there is definitely no smoke as the engine is dying. Injection pump issue.
Ok.. are there any tests I can do before I pull the trigger on a new one?
@thepumpguysc may be interested in rebuilding the pump.
I think I would clean out the banjo bolt with the screen in it BEFORE doing anything else.. The bb is the one below the hand primer on the supply pump. I just watched the video.. U say u were running an electric fuel pump.. how did u plumb it.??
I removed the fuel lines, and the white screen I see on every other machine was missing. I removed nearly every fuel feed line to verify they were clean and open. I first bypassed the lift pump with an electric pump to the filter housing. Same bogging. I then bypassed the filter housing and sent electric pump direct to the injection pump. Same result. I tried it feeding from the factory fuel tank, as well as a secondary boat tank with fresh fuel.
Well damn.. it sounds like you covered your bases.!!! Just make sure the throttle is touching the stop screw..
Is there a chance this could just be injectors? I should probably buy them first and try before the big ticket item.
all the injectors behaving uniformly and poorly seems unlikely. I never did pull the injectors on mine (albeit half the size Isuzu 4LE1). Mine also has a distinctly different and much easier to work on set of 4 injector pumps. Regardless, @thepumpguysc is probably the best on the forums to help you through problems with your injector pump. you'd be well advised to ask him for some pointers to determine if it is or is not the pump itself at fault. might be there's something you can test? I don't know.
I’d pull the injectors and crank the engine over to see what’s going on before I pulled the pump and sent it out. I bought a cheap injector bench tester that showed I had leaking, plugged and the wrong pressure on all the nozzles. You can measure the amount of fuel thats coming out of them too. Crank it over it a few times and take the average. It won’t be perfect but it will get you in the ballpark. It’s a good time to compression test the engine with the injectors out too.
Today I thought I would try something different. I believe the fuel screw is the one under the 17mm cap on the rear of the pump. I removed the cap and it looked to me that the fuel screw was way out. From past experience, I thought I would try to turn the screw in and see what happens. Nothing changed. From my perspective, it should have really started to fuel up, but didn’t. I turned it in 4 full turns with no change. Shouldn’t this make an obvious difference??
Hy, was just looking at hydraulic issues on the forum and came across your post... Its been a long time i don´t walk around excavators, but back in the day when they were around, that simptoms in your machine is hardly related to the engine alone, as the hydraulic relief system has to be able to destroke the pump for a certain amount of RPM. And usually keeps doing that and does not alow the engine to die.... and the consequence is poor hydraulic speeds or break force. 1-clearly that thing need to be checked on that side, (looking to your video the stick travel is too fast, indicating the system is not compensating) 2-The engine beeing that used might be just that! used, and it does not have to smoke hard actually they are not set to smoke much, i hardly belive u have a fuel pump problem. 3- In excavators when its not obvious, usually one start my measuring travel times of actuators, in your case u have a obvious problem, no need to time the actuators. U got to lay your hands on the description HYD of system. U´ve mention pilot filter, if your machine has pilot operated valves that alone is another can of worms. Hydraulics is never a easy task for common beeing, it takes time and a lot of study to get there. I would start by the HYD pump destroke system, specially the RPM compensator/governor. good luck
Only just found this thread. To me this machine doesn't look like a series 1 but much newer. Series 1 has only 1 hydraulic pump, series 3 has 2 pumps mounted beside each other and driven off a gearbox. If what I've written is correct then the fix will be very different. Can you confirm.
Back at it I guess.. I have now replaced the entire fuel system. New line from the tank. New lift pump, new injection pump, new injectors. Guess what.. same problem. I did a compression test and all cylinders are 440ish. All good and within about 7psi of each other. Now it smokes under load. Fuel smoke heavy when I try to move different functions. I now have to believe this is a hydraulic problem for sure. There is only one pump, so I do believe it’s a series 1. I don’t know where to start here. I changed the hydraulic filter and fluid, but that hasn’t done anything. There has to be a relief that is stuck somewhere. Or the pilot system is defective somehow. Any info on this would be good. The repair costs are starting to add up relatively quickly with what I’ve done so far. I will try anything at this point as I need this thing to work.
It appears that it only has a single pump. I can get a picture if that helps. I am totally lost here.
did you read what @Mquinista stated about the destroke? He's right about how fast that stick moves. His statement: ". I would start by the HYD pump destroke system, specially the RPM compensator/governor." holds value. See what's going on there.
@Pont463 ,A picture of the hydraulic pump would be good.
Here is a couple pictures of the pump itself.
well, the good news is there's a LOT of links for Uchida (now part of Rexroth) pumps - just loads of rebuild kits. I've never attempted to rebuild one of these... not sure that's what's needed or anything, it's just nice to see the A8V appears to be a very common series.
What am I looking for, for the RPM destroke gov valve thing.. is this a pump function, or on the main valve bank?
A quick search shows that there's an association with Rexroth, probably made under licence. Heres a schematic of the guts but can't find anything about the valving on the pump. Google Image Result for https://seimthydraulics.com/wp-content/uploads/2019/05/A8V55ESBR.png Before guessing a pressure and flow test is the best course of action That second photo tells a tale that someone has been into the pump in it past life so who the heck can determine exactly what has/is been going on without a tear down. I'm thinking the valve body on the top of the pump may be a problem. Again testing can give the answers.
Claude.AI states this: