Kohler 7.3 ECD Intermittent Shutdown; UU UF Error Code

[PSNI]

Happy Independence Day all!

I'm having intermittent issues where the gennie shuts down after several minutes and will not start again until it cools down; i.e. the next day.

I can run it for 1/2 an hour but after shutting it down it will not start. Sometimes it shuts down itself and will not start with UU error code.

When I do start it the next day, it will take 2-3 tries before it starts (each with UU error code) and then start and run.

For this reason, I suspect a fuel issue and don't believe the code.

I have:

1. Changed spark plugs, wires and tested resistance on ignition coil leads (all good)
2. Changed fuel filter and remote fuel filter
3. Bled air from fuel line from bleed valve
4. Confirmed fuel pump is working. When bleeding fuel line the pump is pumping.
5. Oil level is good
6. Fuel is new and tank is full.

The Service Manual advises to check wires and test resistance on SCR module. I opened up the control panel housing. The wires all look good and I'm about to test that resistance when I feel up to squeezing into the tight space to reach it.

I have not inspected the fuel injector....not sure what I would observe. I've considered replacing it but the fact the it starts the next day is steering me clear of accusing the injector.

I've contacted the local gennie service people to make an appointment but they are a little busy right now.

Any thought?

Thanks in advance.

 

[fwebster]

The UU error code indicates low voltage; the UF error code indicates low frequency. Having both at the same time probably indicates low fuel pressure but could be an electrical problem as well since the engine isn't running at full speed.
Given all that you have already tried, it may be time to call a Kohler dealer/technician with Kohler experience for help.

Not a lot of. help, I know, but it's all I got!

 

[Christian Mckenzie]

Any update on this? Having the same issue. I’ve spent weeks trying different things.

 

[PSNI]

Yes. Apologies for not reporting back sooner.

I finally hired a mechanic who diagnosed a faulty high pressure fuel pump. The pump would lose pressure after the engine heated up. The way to diagnose (which I did not do) is to place a pressure gauge on the schrader valve and determine if the pressure is to spec. It should be at 45psi.

I had him replace the both fuel pumps and the fuel injector as well.