MEP804A Overspeed Trip

My son and I are working on an MEP804A with the Isuzu diesel. When we got the unit a few weeks back, it would not start. Starter would spin the motor but not fire. After several hours of troubleshooting, we found that the fuel suction hose had tiny hairline cracks and was letting air in. Long story short, it took forever to get all the air out of the system. Then we found that there was water everywhere in the fuel system. I drained around 5 gallon of water. We filled the tank with new fresh fuel and went back to starting it. The unit finally started. Then after the engine stopped "shuttering" and wanted to run smooth, the thing would start and immediately rev wide open then get an overspeed warning light come on the control panel. This happens every time within 2 seconds of starting. I found a manual on here for this unit that was a -24 level that had some good troubleshooting info. My son adjusted on the governor control as stated in the manual for a while but no luck. He finally got to speak with a sargeant in a unit that actually works on generators. He told my son he would need a -34 level manual. I have not been able to find a manual ending in -34. My son is in the Va National Guard. His MOS is Heavy Equipment mechanic and I am a civilian mechanic. We are really beating our heads trying to figure this one out. Is that manual available on here? Any help you can give will be greatly appreciated.

Your son needs to talk to someone who knows generators. There is no -34. The -24 is it. Try taking the electric Actuator off and seeing if the linkage is hooked up right.

Is the mag pickup (MPU) adjusted properly and providing 2-3 volts AC across GC terminals 16 & 17 when dead cranking the engine?

According to the info below the DC voltage across GC terminals 9 & 10 may give a clue. This is the voltage sent to the actuator to control engine RPM.
When initially cranking the engine the voltage there should be 16 - 17 volts DC. This is setting the actuator to a nominal starting position.
Once the engine has started the voltage there should drop to 7-8 volts for no load running. This is setting the actuator to a nominal no load position.
20 - 21 volts indicates the GC is not receiving the MPU signal and the GC is compensating by going to max output.

Guyfang said:

Your son needs to talk to someone who knows generators. There is no -34. The -24 is it. Try taking the electric Actuator off and seeing if the linkage is hooked up right.

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My son said he had never heard of a -34 manual as well. He is going to try to talk with one of the actual generator mechanics. We will take the actuator off and check everything. We know that the actuator is working but you are right the linkage could have a problem. Thank you so much for your reply.

kloppk said:

Is the mag pickup (MPU) adjusted properly and providing 2-3 volts AC across GC terminals 16 & 17 when dead cranking the engine?

According to the info below the DC voltage across GC terminals 9 & 10 may give a clue. This is the voltage sent to the actuator to control engine RPM.
When initially cranking the engine the voltage there should be 16 - 17 volts DC. This is setting the actuator to a nominal starting position.
Once the engine has started the voltage there should drop to 7-8 volts for no load running. This is setting the actuator to a nominal no load position.
20 - 21 volts indicates the GC is not receiving the MPU signal and the GC is compensating by going to max output.

View attachment 941169

Click to expand...

We will check this voltage. Thank you for the reply.

Often, someone can not get the set to start. They think that the Actuator is the problem. So it gets removed. Then incorrectly installed. Has anyone ever seen this set run right?

More often its the MPU, as Kurt highlighted in his message.

The actuator is the issue if you performed the adjustments in the homemade drawing in an earlier post following the manual passages it referenced. On the A5 you may have to turn the freq counterclockwise a couple turns. From scratch turn it counterclockwise until it clicks. Now turn it clockwise 10-12 turns. This s only a starting point and usually the engine is running well below frequency if everything is working. The overspeed setting is on the right. You may have to turn up the overspeed so you can actually adjust things to within reason. NOTE THE PICTURE OF THE OTHER SETTINGS. When I drew this up in the early 2000s from the white book I pictured it as it should be. Please set yours accordingly. Good start point and usually works well. Get the manual from this forum and start reading. You can use a screwdriver (no fingers) and after pulling the big top plug, inj pump and don't drop it, you can work things by hand and you can look into the Actuator to fuel rack connection to see if the pin is in the square hole as the manual says to have. Don't start the gen while your doing this. The finger spring keeps the rack on the pump side of the actuator rod hole and assists to eliminate motorboating of the engine due to slop in this connection. If you manage to remove the actuator, pull it out and see if it snaps back to full shut off. If you have no response at the hand made diagram shows, you have issues with the A5 or Actuator. Let everyone know how it goes.