Hello Everyone, Fuel issues with our Hitachi EX120. Not running out of fuel. This happens at 2/3 tank. Summary: Engine began to bog down under load (fuel gauge 1/2 tank). Cleaned dirty banjo bolt filter and replaced fuel filter. Prime pump took a long time but finally got it to bleed and it ran great again for a week or so. Fuel tank looked 'ok', some sediment but no water or sludge. A week later, bogged down under load (2/3 tank) . Blew air back through the tank feed line to ensure no blockage and checked the filters again which this time looked ok but then noticed the original hand prime pump wouldn't prime at all but seemed to be just pumping air . Ok, figured it's old and maybe the diaphram is going bad, so replaced the original lift pump with a Boursin brand lift pump (3 nuts holding it were an unpleasant job for sure) and also added a clear inline filter from the tank to catch any sediment before the banjo filter. New Boursin pump seemed to prime well the first time used and the machine ran really strong for only 2 days. Bogged down under load (just barely under 1/2 tank). Uuuhhhgg. Inline filter from the tank was dirty with sediment and flow restricted. Removed and cleaned it, reinstalled and fuel was flowing strong again. Removed and thoroughly cleaned water separator; filled it with diesel then went to prime; Now the new Boursing prime pump seems to be pumping air just as the old one did...? Checked for air leaks but nothing that I can see or hear. What am I missing?? I figure the hand prime pump ' pulls ' fuel from the tank, through the water separator (which is full) and into itself but 'pump all day', I'm just not getting anything that feels like fuel coming through or at the bleed bolt. If there's air in the fuel line anywhere Before the lift pump isn't that what the hand prime pulls through? Did I get a bad 'new' lift pump? Seems somewhat unlikely considering the symptoms are exactly the same of each pump; old & new. Frustrated but resolved to start at the beginning. 1. Drained and removed the fuel tank from machine and thoroughly cleaned it out. Definitely No sediment now. 2. Replacing fuel feed line and return line. That's where I'm at. Tank is out but I'm hesitant to reinstall if going to an electric lift pump based on your advice. At this point then, do I simply reinstall the tank with new lines, fill with fuel and try again with the manual pump? Should I keep the inline filter from the tank? Tank is definitly clean, but figured meh, would it hurt? Ran great for 2 days with it installed. I think no; but figured to ask anyway. Do I replace the 'new' pump or can anyone offer advice as to why the lift pump won't prime. Pretty sure it's something simple but that I just don't have the skill or knowledge to recognize the problem. Bottom line: Someone suggested and after having done a bit of research, I'm considering simply removing the manual lift pump altogether and going electric as others seem to have had good results. With that in mind and based on answers to the previous questions; what advice about going electric would you have and which pump? The Facet brand electric fuel pumps are often used but I'm not exactly sure which PSI for the EX120; 4 or 6 lbs? What do ya'll think about this? Many Thanks to you for any help, E
About $10 will get you a kit for the lift pump. About 30 minutes of your time to install.
I'm not 100% sure about the injection pump u have.. but it sounds like a Bosch DGK 301 is all u need.?? OR a DGK 301H which comes w/ a new hand primer.. IF your going w/ an electric pump, based on my assumptions, it needs to be capable of pumping 25+ psi.. to overcome the overflow valve.. THATS PROBABLY what your over-looking..?? The ovflo vlv is located on the return fuel side of the inj. pump.. its prob. a banjo bolt style valve.. IT MUST hold 25-30 psi of fuel before it opens.. Otherwise, the fuel gallery wont have enough fuel to supply the pumping plungers.. Good luck.
Get rid of the clear inline filter. Don't guess, take the fuel system apart to see where there's fuel and where there's air. The priming pump will not "make" air, if it's sucking air, then there's a leak and a blockage in most cases. Blowing back through lines sometimes works, sometimes doesn't work, and sometimes works for ten minutes. If you're suspicious of the fuel lines, take them apart and blow through them one at a time, look through the fittings. wait, you said you have a water separator? most of them are removed because they're plastic and hard to get not to leak... I like them, because they'll catch a ton of water and crap if they have the screen in them (that I think they came with) and keep that ridiculous little screen in the banjo bolt from plugging up. Any rubber suction line is suspect of leaking air. Pumpguy is talking about why you're bogging, I'm talking about why you're sucking air and not priming. Hey pumpguy, what's the story on the bosch VA pumps from the TD8 thread? are they bad news or just a little sensitive? and how to tell the difference? HeavyEquipmentForums
If the valve under the h. primer is sticking IN the HP, that would cause the air symptoms.. the valve cant seal on its seat.. same w/ the other side. & if the overflow was broken or weak, that would cause the hp to just keep pumping w/o getting hard too. I take it, that's what your seeing?? the HP isn't getting hard.. U mentioned that there was debris in the banjo bolt.. its not uncommon for that debris to make its way up in the body & valves.. I would take the HP & other side out & make sure the stems on the plastic valves slides freely in & out of its "hole".. & check the ovflow vlv. Cant u pressurize the tank & get the fuel to the supply pump?? U might just see where your sucking air.?? loose connection, bad oring, split line..
Good day Which dash of 120 are we talking of ? Do you have a engine designation ? Kind regards Uffex
Thank you Tones.
Thank you Pumpguy, I still have the original pump and will consider the rebuild kit that you and Tones suggest. E
Hi Delmer, Ok, I'll lose the inline filter and get the new lines installed. Yes, the water separator (WS) is the original plastic part. I didn't consider it a problem because the engine ran good when fuel was flowing well. Maybe it's time for a new WS too or should I simply bypass it and solve by reduction? Would I run the tank fuel feed line directly to the bottom of the lift pump? Thank you, E
Hi Pumpguy, Both. The hand pump is not actually moving fuel and it's not getting hard either. It did the first time after it was installed last week but 2 days later no lift, flow or hardening. This new lift pump has only run with the inline tank filter and banjo bolt filter installed so it's very unlikely that any debris would cause a valve seal to become damaged. We did pressurize the tank for prime after the second bogging and before the new pump was installed. Bad o-rings.... yeah, that's a possiblity, they're old and a couple of them are sketchy at best. OK, will replace those too. Pressurize the tank after installing with new lines sounds like a good plan to find a leak. Didn't think of that but makes sense. Will do. Question: Does the fuel tank actually become slightly pressurized as it runs by the return line? Thank you again, E
Hi Uffex, It's the Hitachi EX120-3; Isuzu 4DB1T which runs really well when fed. Thank you, E
Good day A point worth checking is if air has free passage into the tank, if a vacuum forms you may have the symptoms you are describing. Kind regards Uffex
Opps missed
Im sure the EX series run an Isuzu engine which has a Denso fuel system. The plastic valves in the lift pump are prone to pitting
I skipped most of the replies, more then likely its a fuel line getting old and hard, try just tightening a few hose clamps first. Them Isuzu's are pretty solid design, but the fuel lines are kinda iffy, I also put a larger fuel filter on mine and the problem more or less went away, I think I had an algea problem at one time so several of the original small filters got plugged quick, the biocide stuff is also really hard on fuel lines... a competent parts guy can cross referance filter numbers with the same threads and seal size.
The way I always diagnosed that type of problem is> 1> check out & rebuild the supply pump.. 2> install a psi gauge to the inlet on the pump & check the pop off value of the overflow valve.. Rig up a short hose & run the supply pump inlet from an old 1 gal. oil jug & run the return line in the same jug.. simply because the pump returns more fuel than it uses.. THEN, run a short line FROM the supply pump, directly to the PUMP INLET,.. That way its not running thru any filters.. Work the HP to get fuel up to the inlet & start the machine.. look at the psi gauge for the overflow & hope its staying around the 25-30 psi mark.. THEN start replacing your lines 1x1 w/ the machines lines to find the machines problem areas.. U can move your jug back further down the line if things are good w/ your rig.. BTW> u can check for leaks by watching that psi gauge.. it should hold some pressure w/ the engine off..
Hi Uffex, Yeah, that makes sense. I imagine the tank is venting from the cap. Do you know if this is the case on the EX120. I'll check it out. Thanks again, E
Thank you for this too.
Tones, The original pump I'd imagine could be bad, but the new one too with the same symptoms? I'll disassemble the old hand pump and diagnose. E
Hi Northman, Agreed, the engine runs great when fed properly and I have 25' of new fuel line that will replace the tank feed and return. E
Hi Pumpguy, I understand your method of parts reduction to determine the problem but can't really visualize the process described. What type of psi gauge & how to connect? Are you saying just plumb in a Harbor Freight psi gauge with barbed fittings and fuel hose type of arrangement? I'd need a couple of banjo bolt hose connectors too, correct? Where's the 'pop off valve'? I almost understand this next section, but not fully. "Rig up a short hose & run the supply pump inlet from an old 1 gal. oil jug & run the return line in the same jug.. simply because the pump returns more fuel than it uses.. THEN, run a short line FROM the supply pump, directly to the PUMP INLET, .. That way its not running thru any filters.. Work the HP to get fuel up to the inlet & start the machine.. look at the psi gauge for the overflow & hope its staying around the 25-30 psi mark.." Are you talking about creating a circuit through the same pump or from the lift pump through the injector pump to the return? Hmm, struggling to grasp this... I realize getting into technical details through forum posts can be trying and appreciate your help. Please don't exhaust too much time with my problem and I'll re-read a few more times. Thank you again, E
Yes, like Delmer said, get rid of the clear inline filter. If you bought it at an automotive parts store, or anywhere for that matter, it's likely a gasoline filter. They do not like diesel. And try bypassing the water separator first, they get old and, well Delmer said it best.
Hi Everyone, (My work schedule only allows me to deal with this in short increments of time during the weekends and I truly appreciate all of your input) I'm taking that most feel there's a leak somewhere or this new Hand Pump is defective. Simplest answer is most likely the actual solution. Currently : Cleaned the tank out and have 25' of new Gates 3/8 fuel line to replace feed and return. No in-line filter. Question: On the fuel tank there are two electrical parts. On the bottom there's a 'fuel tank level switch ' and on the backside (below the return tube) there's a ' tank float '. Can someone explain the difference? I assume the tank float is for the console fuel gauge, but what's the level switch for? (O wait, is that to shut off fuel before running it dry?) From there, I'll simply go through the connections 1x1 and where needed replace sealing washers. Question(s): Would anyone know what the actual size of the sealing washers are for this system? Can I replace with solid copper Also, if replacing the Water Separator, would anyone know where to get a replacement for this week? Amazon doesn't seem to have a direct replacement and Ebay vendors availability is mid-September from overseas. No biggie as I'll bypass it if needed for the time being. At which point, trying the hand pump again should say alot about system integrity and depending on that result applying a little air pressure to the tank as you've suggested seems like a wise plan to detect leaks. Question: I've heard that applying air pressure to the fuel system can cause issues at the injector pump, is this correct? What should I be cautious of? Rebuilding the hand pump seems reasonable, but it is brand new..? Replacing the lift pump is no joy as the two bottom 10mm nuts are in a tight spot and really tough to see nevermind wrench from the top of the engine bay. I'm certainly open to listening to a better means of accessing them directly. The machine isn't running so swinging the cab isnt' an option to offer easier access from below. Thank you all again, E
Good day I believe your priming pump has two check valves if either become lodge in the open position it will prevent the pump from operating. You could install a simple oil pressure switch wired to a LED for sure that would show up any pressure loss, maybe have one in your shop. Kind regards Uffex
Came across this may be of help Kind regards Uffex
Thank you Uffex, It looks nearly identical to the part I have. Good schematic. Thanks again E
Those lift pumps are a copy of a Bosh. The plastic valves maybe the same, TPG could confirm.
its a task for sure... I'm lazy/busy so I just cut the end off and tightened the clamp some more...
What I was saying was.. Run a short hose to the INLET on the supply pump..& get your fuel from an old 1 gal oil jug.. THEN run another hose from the OUTLET on the sp pump UP TO the INLET on the INJ. PUMP. Then, run your return fuel into the same old oil jug.. That may be easier said than done.. as I have a wealth of barbed banjo fittings & hose. The overflow valve will be on the fuel return.. it'll either be a spring loaded banjo bolt or a fitting that screws into the inj. pump housing.. the fuel return/out in usually on the gov. end of the pump & the in is on the drive end of the pump.
Welp, the problem is known and the machine is running well again and will continue to. The culprit... Delmer nailed it... the Water Separator. It's original, plastic, and when bypassed, the lift pump worked fine. Anyone have advice for a replacement WS? OEM or is there a better solution; like leave it out and install a dual purpose fuel filter / water separator cartridge? At the same time, in power washing the fuel tank I must have compromised a bottom tank support rail weld, because now the tank is weeping from below. Not bad, but certainly. It's always something huh; but a problem I beleive a 'tank sealer' will fix up. I'll drain it again and deal with it this weekend or next. Anyone have advice for a good tank sealer? Many thanks again, E
Was it one of these before? https://www.jdgfarmworks.com/1132008410-water-seperator-assembly/
Hi Birken V, Close. Mine has both in & out connectors on the same side, but yeah nearly identical. There's a couple on ebay but figured if a dual purpose cartridge would work, it's just one less part to go wrong. Thank you, E
We have a lot of those out and about that do not leak so just replacing it with the proper new one and getting going might be the smartest and easiest thing to do. Custom modifications always have a way of coming back to bite....
I just went through this exact same problem, all the same symptoms that you are having, found the fuel feed line inside the tank had hole in it half way down, would run good till the fuel level in the tank dropped down to the level of the holes in the feed lune then it would lose prime and primer pump would not work. Try running a line into a can of fuel and eliminate the tank,if the primer pump works fine it will tell you that you have a supply from tank problem. it worked for me and I got that advice right here.
Hi All, Current status: Drained & removed the tank again to discover weeping area. it was coming from behind one of the tank support rails. Used grinder to cut welds and remove the tank support rail only to discover a lot of rust between the rail & tank. Used grinder to clean rust and found small hole where the rust on the bottom of the tank had let go. After grinding and cleaning, hole is 1/4" round. What are my options? Metal is thin and welding will blow through. Braze a patch? TIG? Epoxy fix? Looked for a replacement tank but no go. Thank you, E
Got it fixed! Met a local welder who came to evalutae and ended up tanking the tank home with him, MIG'd in a patch and the same for the support rail. Wet tested and all is looking dry. Will clean it out again and reinstall tomorrow and hopefully up and running by noon. Thank you all again for the help and support! Cheers, E
THAT'LL save a few bucks on the ol' fuel bill.. Isnt it amazing the **** we find wrong when we're looking.??
True that, and when we're Not looking too... Progress, progress... Stop... Fix, progres, stop fix...
Egetebee some bigger Hitachi machines have a banjo fitting near injection pump one has a screen in it I would check it ...its fine mesh cone type screen …….you've had trash in other fitting this one is catching the rest ..Glad you are up and running hatz off
Those banjo bolt filters have ruined many of mechanics.!! The pump takes a LOT of time to pull & then fighting traffic, just to slam it on my front counter.. & scream, "O/H this SOB".. Only to be lead by the hand to my work bench, where I gingerly removed the clogged banjo bolt & hand it to the mechanic for his inspection.. which in-turn they bellowed, "Well I'll be a SOB"!!!!! {Lol}
Truecountry & Pump Guy, Yeah, I had TWO of them! I knew of the one at the fuel feed line banjo to the water separator and then discovered the second on the bottom of the lift pump from the water separator. Both are clean now and the machine is running like a champ, albeit the water separator is on my work bench but should have a replacement coming in the next week or so. Fuel tank is clean as a whistle, lines are new and fuel is double filtered so I've got a little time. Thanks for thinking of me, E
I dont miss much and always willing to learn I will ask questions even stupid ones ...the clogged banjo fitting I saw I was letting my tech do the job while I was working on another machine and was watching him get more and more pissed getting to the point boss was going to order a injection pump ..I said nope let me finish and have a look I went to first fitting in line supply side on water fuel separator asked u check this yes I had flow from tank from hose ok did you check fitting no I had fuel ……………...removed banjo fitting and half of a grass hoppers body was in it …...how did it get there I dont know ..ive found knotted rags in tanks to a clay dirt ball and heard of latex gloves fingers I guess being pinched off in hoses...**** will Happen and Think out side the Box ….Air fuel and compression ...its simple to a point