804B shuts down

[MikeCas]

We have an MEP 804B that runs unattended to power a deep well pump for livestock water. Lately we have found it shut down with no indicator lights to tell us what the trouble is. The batteries are usually dead unless we catch it soon after shut down. I suspect the fuel transfer pump stays on and that is the load that drains the batteries. The one time we did find the shutdown indicator light on it was for under voltage. This thing is in a remote location and it is a real nuisance to have take batteries up there to jump start it. It always starts fine and runs great until you drive out of sight. Does anyone have a clue as to what is causing the shut downs?

 

[Guyfang]

I assume you are running in the Aux fuel mode? If so, the fuel pump can not run the battery down, unless your fuel tank switch/Float is bad, The system works like this. The set runs, and when the set tank is low, the float triggers the replenish function. The AUX fuel pump comes on, fills the tank and then the Float switch senses full tank, and shuts the Aux fuel pump off. Are you sure the set batteries are good? Are you sure the alternator output to the batteries is good? This sent needs a good steady 24 volts to run right. You have no idea how long it runs in between outages?

 

[Guyfang]

More questions.
Do you use a solar battery charger/maintainer?

You wrote that it starts fine and runs great after jumping it of. By starts fine, do you mean in less that 20-30 seconds after you turn S1, (start switch) to the start position? Of does it take 60 seconds, (or longer) of cranking to get it started?

Look in the fuel tank the next time it happens. Is it full? And I mean LOOK, not at the gage, but into the tank. And while you are looking in there, do you see a bunch of junk and trash floating around. Use a flashlight.

When is the last time you changed the fuel filter AND the filter that is screwed into the Aux Fuel pump.

 

[MikeCas]

Thanks for the replies. Sorry to be so long responding. We don't use a solar battery charger. We haven't had to in the past and usually the batteries stay charged unless the generator is shut down for an extended time with the switch on. The battery charging circuit breaker was tripped once but the ammeter shows a good charge rate on startup and gradually drops as it should as the batteries charge. If we happen to check it soon after shut down it starts on it's own. I have not looked in the tank for trash.

I don't think we are running in AUX mode, at least not intentionally. I hear something running that sounds like an electric fuel pump when I turn the switch on that I always thought was a fuel transfer pump. I don't run the generator on a regular basis myself. I just have to go try to figure out what is going wrong when it doesn't start up an run normally which is usually not very often. The last time I had to jump it, it cranked for a long time (40-60 seconds) before it started, then it died for a few seconds and finally caught and spooled up like always. It acted like it had been fuel-starved and I suspected that was what killed it and why there was no trouble light to explain the shutdown. I just jumped to the fuel pump conclusion without thinking about the fuel filters being the most likely cause. This generator gets fueled from 5 gallon cans hauled up there in a Gator. I think our guy is careful with the fuel but I am not sure. I will check the filters next. I suspect that is our problem.

Do these generators have a fuel transfer pump that supplies the injector pump? That's the way our diesel pickups work and I assumed these would be the same. If they don't, what do I hear when I turn on the switch and what runs the batteries down if the machine is shut down for 12-24 hours with the switch on?

 

[Guyfang]

The only Electric fuel pump, is the one for the AUX mode.



The Auxiliary Fuel System consists of an external fuel supply, fuel filter, piping, a 24 VDC auxiliary fuel pump and
a fuel level float switch. When the MASTER SWITCH is set on PRIME & RUN AUX FUEL it actuates the auxiliary
fuel pump and transfers fuel from the external fuel supply to the generator set fuel tank. The fuel level float switch
shuts off the auxiliary fuel pump when the generator set fuel tank is full and reactivates the pump as the level
drops. The FUEL LEVEL indicator indicates fuel level of generator set fuel tank from (E) empty to (F) full in
quarter tank increments.


When you turn it on. Do you put the S1, (Start Switch/Master Switch) in the Prime & Run position? Or the Prime & Run AUX Fuel Position?

 

[MikeCas]

I am pretty sure we always use the prime & run position. I do hear something that sounds like an electric fuel pump running when I turn S1 to Prime & Run. Maybe we have something messed up that causes the aux pump to come on. We have never connected an auxiliary tank. I haven't been able to check out the fuel supply and the filters. I plan to get up there tomorrow and I will post what I find. Thanks again for the help.

 

[MikeCas]

I finally had a chance to go back to the generator last night. There was just a trickle of fuel from the second filter going to the injector pump. We changed the fuel filter/water separator and increased the fuel flow by several times. The unit started faster and runs fine now. Thanks for all the help.

 

[2Pbfeet]

I finally had a chance to go back to the generator last night. There was just a trickle of fuel from the second filter going to the injector pump. We changed the fuel filter/water separator and increased the fuel flow by several times. The unit started faster and runs fine now. Thanks for all the help.

Congratulations on fixing the issue!
If you have fuel quality issues at the site, you might consider using a Racor style filter unit with a clear bowl. If you have concerns about pressure loss across the filter, I would go up a size or two, which also gives the filter more capacity.

All the best,

2Pbfeet

 

[Guyfang]

Might want to check the water separator/filter again in 3-4 weeks. If its got water and trash in it, run the set till it stops for no fuel. Elevate the front end of the set, and drain out whats left in the fuel tank. The petcock in in the back of the set. Flush the tank with some fuel or other liquid. Refill and change/clean the water separator/filter. Or you will start having the problem again. Check your fuel supply. Its where the problem came from.

 

[2Pbfeet]

@Guyfang What about the fuel tank cap? Does it have an air vent in it that might be picking up water?

All the best,

2Pbfeet

 

[Guyfang]

It has a vent. But there is no way water gets in it. The cap gasket maybe. Take your gen set cap off and turn it over. See the little handle? in the closed position, it lets no air in. Forget to open it, and your set will not run long, and you will wonder why the fuel tank looks like a pretzel.

But 99.99% of the time, its simply dirty fuel being put in the set. In El Paso, we had dirt and water problem, or better said, sand and water. Lots of sand in the air and fuel point had old tanks. Fuel absorbs water. In Germany, we had water and trash problems, VERY badly. The fuel came from an old Wehrmacht fuel point. We simply changed filters at 50 hour, instead of 100. If the problem happens again, you need to look at where your fuel comes from, and how YOU store it.