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MEP-803A, AUX fuel pump won't work

Guyfang

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Howdy folks! I have started this thread for Jeff, to get him started out on the right foot. I will walk him through how to do it a bit later.

I am new to the forum. I have an MEP 803 which works fine, EXCEPT the aux fuel pump won't run. I have followed the above suggestions, it still doesn't pump. I have replaced the aux fuel pump, also a new float switch which shuts the gen down when the bottom float is down, THIS part work.s, BUT with the bottom float up, the gen runs fine, and if I move the upper float down, there is 21.5 volts delivered to the pump. Apparently the aux pump needs at least 24 volts to run. I am doing these tests with the tank full and with the float switch outside the gen plugged into the appropriate connector. I don't believe that should matter, since the bottom float tells the electronics the tank is not empty and the upper float tells the electronics in its down position that the tank needs the aux pump to run. I have studied the wiring diagram and schematic for hours and I was Navy Electrician so I know up to a point how to read the schematics. I get lost in the complexity of the relays interactions, and the fault indicator module, since the fault indication module seems to be involved when the aux pump should run. There are NO warning lamps except when I make the low fuel float at the bottom position, then the fault lamp no fuel comes on. Also the connectors with the screw bottoms in the rear panel, do I screw them out with the twisty idem at the bottom of the plug, or do I simply rotate the twists screw then a quarter or half turn then pull up. I don't want to assume I am disconnecting the jacks right and mess them up. So I don't pull them too hard. I want to see if all that is going on is a loose connection, or high resistance connection, or a bad relay, or module. I need pin out readings on what voltages to read on S1, and the relays to trouble shoot this. I have and have read the manuals, not enough info on this specific problem. Any ideas would be much appreciated !! Thanks, Jeff
 

fa35jsf

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Fuel pump module. It is the little box on the right lower side of the unit, looking at the fuel tank. Try unplugging it and jumpering pins 1&3. If aux pump turns on, then it’s the transistor inside that burned up.

Technically this part is considered a consumable and non-repairable part. But it is actually very easy to fix. You just need to purchase a mje800G transistor and solder it in.


Sent from my iPhone using Tapatalk
 

jmenende

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Fuel pump module. It is the little box on the right lower side of the unit, looking at the fuel tank. Try unplugging it and jumpering pins 1&3. If aux pump turns on, then it’s the transistor inside that burned up.

Technically this part is considered a consumable and non-repairable part. But it is actually very easy to fix. You just need to purchase a mje800G transistor and solder it in.


Sent from my iPhone using Tapatalk
My problem is that the aux pump is only getting 23.6v and will not start. I have tested it with 24v and it works. Im gettimg similar voltage at the relay too. The main pump works fine and units runs. Any suggestions?
 

Ray70

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I would definitely say the module as well. The issue is not that you only have 23.xV , the pump will definitely still run on 23V but if you put a load on that 23v line you will find it drops to probably around 6V, which will not run the pump.
It's the module causing you to not have voltage once you add the load of the pump onto the 24v line.
In fact, I have a bad module on the shelf and will take the transistor info from above and try to turn it into a spare module!
 

jmenende

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I would definitely say the module as well. The issue is not that you only have 23.xV , the pump will definitely still run on 23V but if you put a load on that 23v line you will find it drops to probably around 6V, which will not run the pump.
It's the module causing you to not have voltage once you add the load of the pump onto the 24v line.
In fact, I have a bad module on the shelf and will take the transistor info from above and try to turn it into a spare module!
Looks like I have two of these modules that are bad. Im gonna ask klopp if he repairs them.
 

Guyfang

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Another thought. If your ground is not good, what happens when you turn on something. Voltage appears good, or close to right, before turning it on. But when the circuit is turned on, voltage/amps head to the basement. Nothing works.
 
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