I have a 4LE1 Isuzu engine in a generator. It will run as smooth as silk and then start to miss. Sometimes fairly bad , some times hardly noticeable. I have bled fuel lines, no change. It has new injectors in it about 20 hours ago. I replace the electric fuel supply pump, put new fuel lines on, used a different source of fuel, bypassed the original fuel filter with a new one, still no change . Will run for about 20 minutes and start to miss. shut it off, restart runs like a top, then will start to miss. I am still thinking fuel because if it was a straight mechanical issue would it not miss all the time? Any thoughts Cheers
Check the valve lash, maybe a hair tight on one?
:iagree What he said. Check the valves. If ones of thems a little tight once it warms up its probably not seating properly.
The valves were reset before I acquired this unit so your thought on the valve settings sound suspicious to me. If I shut it down and immediately restart it and it runs smooth does that still make sense?
Just something to check, things that are borderline can be intermittent. Could be in the injector pump. If it has banjo fittings in the fuel system pull each bolt one at a time and check for material blocking the holes and also look for a tiny strainer screen in the center of the hollow bolt. More common on Mitsubishis but you never know.
Thanks for the input. I will let it cool down and will check both ideas.
Well I finally got to pulling this apart so I could get the valve cover off. Valve lash was good on all cylinders. Checked fuel system again. Still misses on and off. I am starting to think the PFR fuel pumps. Could 1 be starting to fail? It now runs good then will miss, then clean itself up and run smooth. I can now crack an injector line when it misses and it will clean up and run smooth. Such an intermittent thing it is hard to diagnose. It is a lot easier to work on now that I have the lid of it. Any Thoughts.
Might be getting a tiny bit of air somewhere? Grasping at straws....
Was the reason for the new injectors because of the miss? If it is starving for fuel, once it runs crappy, shut it off and pull the filter, if it is not full of fuel you have an obstruction somewhere. We had an old Komatsu that had some debris in the tank, and sometimes required a gentle blast of air back through the fuel line to clear it. We always meant to fix it... then it was sold. Sadly lots of things could be the culprit.
Is it possible to fit some clear fuel lines on it as a temporary measure to see if there's any air bubbles? Possibly help the diagnosis. It does sound like its drawing air from somewhere. As it enters the pump, it starts to miss fire, then when you crack an injector you purge the air and it runs fine again.
Is it missing on the same cylinder .Could it be a faulty injector ?
My history also points to air (put clear hose like mentioned) and sticking injector(s), isolate witch cylinders are affected> Could try heavy dose of atf, see what that does.
If you have a diafram lift pump, good place to look for air.
Hello all, I saw this post from 2015. I am trying to contact Bardon to see if he resolved the issue. I am having the identical issue. Appreciate the help!
They had many of these units in a rental company I worked for years ago. There was a problem with the governor sticking from what I recall. Positive air into the fuel tank entry with a blow gun at 1 PSI will help to determine if it is a fuel quantity issue. Make a ball from rags to help block opening. It will usually show you any loose connections or leaking hoses as a leak. If it leaks fuel it can suck air. Simon C
Just finished figuring out a John Deere Gen Set that was missing all of a sudden, had air in fuel filter. I have to remind myself that even if it does not leak fuel out, it can still suck air in slowly, especially at a certain vibration. I used a new suction line out of a big fuel tank with separate return tank. Ran flawlessly. Try a separate tank with new fuel to eliminate lines, with new filters. Simon c
I had one a bit larger in the shop recently, I could tell from trying to prime it was sucking a lot of air as well as some fuel. I rigged up an arrangement to pressurize the incoming fuel line with 5 psi air and just started going over everything with soapy water. I found leaks galore and after fixing them all, it ran much better. Previous "mechanics" had put it back together with obviously defective seal washers as well as other nonsense.