View Full Version : 4JH3TE dies at idle RPM problems

11-08-2007, 10:24 PM
"Help! I have a Yanmar 4JH3-TE; 1997 but only 70 hours. Ran perfectly until a big trip in July; after 6 hours hard running it died when returned to idle; starting up would only get to 1800RPM,then after 5-10 minutes suddenly would get full power and happily go all day, only to die again whenever idled. Mechanic recommended diesel fuel conditioner at high concentration; tried without success; eventually pulled injector pump and had it rebuilt (all except hydraulic head); problems persisted on re-installation. Found a similar engine with a cracked block; installed its injector pump; worked fine on first trial, then identical problem. Swapped out inejctors; no improvement. Mechanic suggested fuel might be bad; today spent 4 hours discarding fuel, cleaning tanks (indeed dirty with gel-like layer on bottom), replaced dual Racor 10-micron primaries and yanmar secondary filters, flushed with brand-new diesel from busy gas station, primed lines to injectors.... ran motor directly from jerry-jug of fresh diesel; same problem. Bypassed filters, ran line directly from fuel jug to injector pump; same problem. I am stumped!!!! Any suggestions?"

Axel Brill
06-02-2008, 10:35 PM
have the same problem with my 4jh3-hte.
did you find a solution already?"

06-02-2008, 11:44 PM
"Yes, finally. Problem was the gummed-up injector pump. Biodiesel blend sitting for months had gummed everything up; stupidly I'd installed the rebuilt and then replacement injector pumps before changing out fuel/hoses etc and deep-cleaning fuel system. Ended up having original injector pump rebuilt again, though never needed it; while waiting for rebuild I disconnected fuel and injector lines from replacement pump and ran a few ounces of straight acetone through injector pump by turning it over with the starter (acetone had proved to rapidly dissolve the fuel-gum in the tank and lines); collected acetone in a jar. Followed this by Stanadyne, Marvel mystery oil and then clean diesel; finally reconnected everything and the engine has been trouble-free ever since.
Bottom line:
1) avoid biodiesel, especially if it's gonna sit
2) clean the entire fuel system, replace hoses etc before rebuilding the injector pump.
3) if bad fuel was the problem, consider running a solvent and fuel conditioner through the pump (but not into the engine) before resorting to rebuild.
Hope this helps you avoid my costly and stupid mistakes."

05-04-2009, 07:35 PM
"Biodiesel will clean out all gunk in your fuel tanks and lines when you first put it in your tanks, which most likely accounts for the sludge you found in your system.
Additionally, biodiesel corrodes rubber hoses, which may account for the deposits in the injector pump. Biodiesel, when operated in a clean fuel system is as clean and gunk free as regular diesel.

If you are planning to start using biodiesel consider doing some research here: http://www.biodieselnow.com/ ("") and others."