I tried turning the relays around(K1 through K4) But it still won't run. I only had a problem with the control breaker tripping the one time, but thought that might be an indication that something else tripped because it happened right before I had the issue with it not running.
I took the fuel line off of the injector and there was no fuel in the line. There is no fuel in the filter either. There appears to be a fuel pump below the fuel filter mounted to the bottom frame rail. It only has one wire going to it I am assuming it is 24V + and it is grounded through the body of the pump. Is there a inline fuse or another breaker I should check ?
In that case you have an MEP-016E not "B". The "E" has the Yanmar engine which was a retrofit from the "B" with the Onan engine. They did not change the nameplate so it probably does say "B". The Yanmar has the red compression release on top of the head the Onan does not. It also has the pull start rope. In the case of the Yanmar there is no mechanical fuel pump. The pump below the filter is the primary pump from the on board tank through the filter to the injection pump. This pump should run all the time provided the float switches and relays in the tank are saying there is enough fuel in the tank. The other Aux pump is down by the fuel tank on the opposite side. The two pumps are identical. Try unplugging the primary pump under the filter, check its incoming connector for 24vdc with your meter with the switch on. If it does have the 24vdc on it then try switching out the pumps. Coincidentally, I had one of these pumps bad on an "E" and it was a brand new pump. Those pumps are available new around $90 - $120 and used around $50. Generally, they are not known to give trouble.
If you do not have 24vdc to the pump with the switch on then the problem is either the fuel level switch system or the pump feed.
Regarding the relays you can identify the pump relay in the control panel and you can feel the individual relays moving and hear them clicking if they get power. So if that relay is moving I would assume it is good. And you can interchange any of the relays for testing as they are all the same. Also, as noted before you can flip them over for a new set of contacts within a relay.
The float system is easy to check. With the tank empty or nearly so (easy to siphon out or drain on bottom) the lower float can be moved up and down with the switch on. This is the low fuel shut off float. Again, the relay can be felt and heard when the float position changes. The float switches are magnetic sealed reed switches and are very reliable. Sometines the float may be stuck if the gunk in the tank has caused it to be glued to the shaft. But there is a lot of clearance on the shaft and it is easily freed up.
The top float controls the other Aux pump down low on the right side. With the switch in the Aux fuel position cycling that float will cause the Aux pump and Aux relay to turn on and off.
It is not uncommon for the pumps to be stuck from sitting but since you have been running this is not too likely. However, they are easily serviced and cleaned up. (Always recommended) The bottom end caps unscrew and there is a filter screen and then a wire snap ring affair which when released allows the only moving part to come out. careful it is spring loaded! It is nothing but a solenoid plunger with some check valves in it. The plunger needs to move freely and the screen needs to be free of varnish. The pump can be bench tested by putting 24vdc to the one wire and grounding the body. It should pulse loudly with no fuel in it on the bench. My defective one quivered or vibrated only a little before it quit all together. The Aux pump is the one that usually is gummed up from sitting. Get it working and you will note how they pulse and the noise they make.
So first check that the pump relay is clicking and feel free to swap relays around. If okay then verify 24vdc at the main pump under the filter. If the relay is not getting power then the problem is between the master switch and the relay board. (Unlikely as the master switch controls all of the board at once)
When you do get the pump running open the bleed thumbscrew on top of the filter housing to let air out then close it.
If all this works as it should then the problem will may return later. If the round 24vdc breaker was bad or weak it would shutdown all functions.
See if any of this info helps you and report your findings or if you need more info. I have completely torn into these things many many times it is just a matter of isolating the components and systems until the problem is found. It never seems to be anything major.
