John Deere PowerTech 6068 hard start

[RafikiRW]

Here at Rafiki Rwanda we have a 120KVA generator powered by a John Deere PowerTech 6068T. A few weeks back it began not starting properly. The Autostart would engage and the motor would start for about 1 second then stop with an indication of Underspeed. After a bit of investigation, I discovered that re-priming the fuel system would enable the motor to start. Since then I have taken apart all the fuel lines on the tank side of the filter and fixed a couple of potential air leak problems. However, the problem persists and I'm now way out of my range of experience. My latest idea involves replacing the fuel supply pump as there may be a problem with the inlet check valve.

With no test equipment or qualified diesel mechanic in sight does anyone have any ideas of what I should look at?

Thanks,
Mike
Rafiki Foundation Rwanda

 

[GregD1]

If it starts in auto start then quits as you say, it will set a fault. It should be able to clear it out. You may well have a trnsfer fuel pump issue as you say it will run once primed. Try using a 5 gallon can of CLEAN fuel and eliminate the hose and fttings to the tank. I would also loosen the inlet line to the pump, manually engage the starter and see how much fuel you get, or don`t get.
Hope that may be of help.

 

[03hdrk]

Did this problem get fixed?

 

[RafikiRW]

No, it hasn't. I have a new fuel pump which should arrive next week. Hopefully the check valve is bad in the old one and that will fix the problem.

 

[03hdrk]

If the controller does not detect engine speed then it will shut down - at least on most generators. If there are no RPM detected or the RPM are below a certain number... Usually if the gen starts and runs it will use frequency to shut down on low or high RPMs. If the engine starts just long enough for the controller to see that there are no RPM's then shuts down, the problem is likely related to the control system - speed sensor(usually at the flywheel), Controller (maybe not reading the sensor), Wiring problem, etc.
If it has a rpm on the controller screen, see if it is showing anything during start and when it shuts down.

If all that checks out, keep looking at the fuel system. As mentioned, if it has a lift(supply) pump take the line loose somewhere in the system between the lift pump and the injection pump, crank on the engine and see if the lift pump is pumping. If not, check all hoses and fittings for clogs. I had one just last week have a clog in a banjo bolt at the filter housing that caused the problem you describe.

Don't mess with any of the steel lines from the injection pump to the rail or from the rail to the injectors (I think this is a common rail engine).

More info on the make and model of the generator would be helpfuel. If it is a Magnum, call the number on the name plate- they are normally really good with tech support.

 

[RafikiRW]

Thanks for the new items to check out. Thank God for Google - I had to look up banjo bolt to find out what it was! I'm 99% positive it's a fuel issue as now the lift pump is beginning to leak a small amount. I'll wait until the new parts arrive from the U.S. and see how it goes. Mike

 

[03hdrk]

If it has a lift pump that is mounted to the block, make sure that your engine oil is not contaminated with fuel. The pump is likely a diaphragm style pump. If the rubber diaphragm breaks it can cause fuel to go into the engine oil. High oil level, thin oil that smell like fuel, low oil pressure can all be symptoms of this.

 

[bunkclimber]

sounds like you may have to readjust start (crank) time to be longer, I'd say three second starter crank time is a good place to start..currently at 1second the bendix drive is probably just getting engaged before fault

The Autostart would engage and the motor would start for about 1 second then stop with an indication of Underspeed.