Fuel starved Kubota m6800dt

Jackspratt98 · Dec 2, 2015

Kubota m6800dt, 800 hours, starts and runs fine for 5 to 15 minutes just about enough time to deliver one round bale to livestock. Then, power loss occurs with poor to little response to the throttle. Tractor feels like it's on life support, but may suddenly surge somewhat with power (inconsistently, briefly). Shut off the tractor and wait for a while and the process can be repeated. No remarkable smoking, no fluid (coolant or fuel) abnormalities or bubbling, no gauge issues. Changed out fuel filter, now twice. Cleaned my fuel water trap gizmo. The results? Brief improvement with more delay before the problem appears and then returning back to square one. Cracked line downstream from fuel lift pump and pressure seemed ok. Distal to that not sure what to expect for pressure of fuel entering the injector pump or fuel pressure as lines leave the injector pump on the way to the cylinder heads. How to test/what to expect?. Can a defective lift pump cause such erratic behavior? Could it be my injector pump? Diagnostic testing recommendations for this DIYer appreciated. Thanks.

docone · Dec 2, 2015

Check your Air filter and intake hoses, sounds like there is a restriction somewhere. JMHO

Dave

The Fred · Dec 2, 2015

Yes on the lift pump.

Check with a gauge there must be positive pressure not a lot but not negative; I'm not certain of the specs. An old car fuel pressure gauge should work fine. Another test would be that fuel should be returning to the tank from the injector pump also.

If you have an air problem seems like the air filter minder device would be in the red.

Good luck, Fred

5030 · Dec 2, 2015

The shutoff valve (on top of the filter bowl) is clogged with gunk. Disassemble the entire valve and clean it out. Common problem.

Jerry/MT · Dec 2, 2015

Jackspratt98 said:
Kubota m6800dt, 800 hours, starts and runs fine for 5 to 15 minutes just about enough time to deliver one round bail to livestock. Then, power loss occurs with poor to little response to the throttle. Tractor feels like its on life support, but may suddenly surge somewhat with power (inconsistently, briefly). Shut off the tractor and wait for a while and the process can be repeated. No remarkable smoking, no fluid (coolant or fuel) abnormalities or bubbling, no gauge issues. Changed out fuel filter, now twice. Cleaned my fuel water trap gizmo. The results? Brief improvement with more delay before the problem appears and then returning back to square one. Cracked line downstream from fuel lift pump and pressure seemed ok. Distal to that not sure what to expect for pressure of fuel entering the injector pump or fuel pressure as lines leave the injector pump on the way to the cylinder heads. How to test/what to expect?. Can a defective lift pump cause such erratic behavior? Could it be my injector pump? Diagnostic testing recommendations for this DIY appreciated. Thanks.

Rundowns like you are experiencing are generally caused by fuel starvation. The fuel required to move the tractor is greater than the fuel delivery supplied to the pump. So the engine runs down and may stop or not respond to throttle commands.
If you search the archives on this sight you will find this common problem with diesel powered tractors. Most likely your fuel delivery is restricted. The usual culprits are a clogged strainer at the fuel tank outlet, an improperly installed gasket on the fuel filter. a clogged fuel filter, pinched for damaged fuel line, a dirty screen in the lift pump, etc. So start at the tank and make sure the tank out flow is good. Fuel should gush out of the tank bottom outlet like a cow peein' on a flat rock.

Then check the fuel delivery step by step through each component to the injector pump. Make sure the fuel tank vent is not clogged. If it only happens in below freezing temperature, you may have water in the fuel that is freezing on the fuel filter. Using a heat gun carefully thaw the filter out and then open the drain to release the water and fuel. (I had this problem once.) Drain the fuel tank and let the water settle to the bottom and decant it off the fuel or use it to clean parts and refill the tank with clean fuel.

Generally the lift pump either works or it doesn't. My New Holland has a screen in the lift pump that is removable and cleanable and it can be a source of fuel restriction. If yours has this feature , check it out. Some injector pumps have a screen at the inlet fitting. If yours does check it out. Read the owners manual regarding the fuel system operation and understand it and this will go along way in helping you trouble shoot the problem.

Generally speaking, a restricted air filter will cause hard starting and reduced power, not a run down like you are experiencing.

Tx Jim · Dec 2, 2015

5030 said:
The shutoff valve (on top of the filter bowl) is clogged with gunk. Disassemble the entire valve and clean it out. Common problem.

Ditto same thing happened to a M4900 that I owned until I cleaned a tiny white screen in in fuel shut off valve in water separator housing.

5030 · Dec 2, 2015

The reason I mention it, is both my M105 and my M9 had the same issues. Removing and cleaning out the valve (and filter seperator) cures the issue. Blame it on the fuel today, or infrequent use.

I add Powerservice Bio-Kleen to my bulk tank now. It seems to eliminate the issue, haven't had issues in 2 years.

kobboss · Feb 14, 2016

5030 said:
The reason I mention it, is both my M105 and my M9 had the same issues. Removing and cleaning out the valve (and filter seperator) cures the issue. Blame it on the fuel today, or infrequent use.

I add Powerservice Bio-Kleen to my bulk tank now. It seems to eliminate the issue, haven't had issues in 2 years.

hi i have a m105 and it started this, i figured it was just froze up what i found is that i have to pump up the fuel filter and it will start, run for a bit then die out starving for fuel and spin filter off and it has no fuel in it, i cleaned the seperator and put back together and will pump fuel from tank into seperator... but is hard to get fuel up past the lift pump to the filter... help please

jim

banjodunn · Feb 14, 2016

kobboss said:
hi i have a m105 and it started this, i figured it was just froze up what i found is that i have to pump up the fuel filter and it will start, run for a bit then die out starving for fuel and spin filter off and it has no fuel in it, i cleaned the seperator and put back together and will pump fuel from tank into seperator... but is hard to get fuel up past the lift pump to the filter... help please

jim

G'day Jim check your fuel pump for a filter screen in it or on the suction side of it I don't know your model but have found it on other machines sometimes you need to pull the pump aprt to get to them, either that or your pump is on the way out.

Jon