MEP 701A dies when slave cable disconnected

[Gunwriter]

Question:

A friend has a MEP 701A (MEP 16B) 3kw diesel gen set with the Onan engine.
Battery in it reads about 4 volts.
Putting a slave cable to it, it starts right up and runs very nicely.

However, it dies as soon as you disconnect the slave cable. I did not see anything in
the manual for troubleshooting this. Any advice would be greatly appreciated.

Also how common is it for the convenience receptacles not to work?

thanks!

 

[Ken_86gt]

What voltage is the battery when it is running? Sounds like there is not enough voltage from the gen to keep itself going. Try using good charged batteries to start with .

 

[Gunwriter]

With the slave cable plugged in it is over 24 volts.........as to be expected.
Unplug the slave and it dies abruptly.

My MEP16B runs without a battery....

 

[FormerNewMVGuy]

I have a PU 794 /G (modified mep004) when the batteries on mine dropped below 24 volts the fuel pump doesnt run.... found that out in a major power outage , when my alternator crapped out....

 

[Gunwriter]

Would I be correct in reasoning that the battery charging voltage regulator is likely the culprit?

I will have him test this. If this is bad is there a way to source this part?

 

[Ken_86gt]

With good batteries, or slave cable attached you should have ~24V off. When running it should be slightly higher, 25-27 would sound good to me. If you don't get this higher voltage while running then the charging circuit is not working.

 

[Speddmon]

I believe the MEP-701's have an electrically operated fuel shut-off solenoid (not 100% positive though). If that is true, that is why you are shutting down when you disconnect the slave cable.

Your charging system is not working, therefore there is not enough voltage to hold the solenoid open when you take away the slave cable because the battery is dead.

Fully charge the battery and try it again, and it will probably stay running, but then you need to find out what is wrong with the charging system.

 

[ETN550]

I believe the MEP-701's have an electrically operated fuel shut-off solenoid (not 100% positive though). If that is true, that is why you are shutting down when you disconnect the slave cable.

Your charging system is not working, therefore there is not enough voltage to hold the solenoid open when you take away the slave cable because the battery is dead.

Fully charge the battery and try it again, and it will probably stay running, but then you need to find out what is wrong with the charging system.

Right on. The slave is putting enough voltage on the system to keep the electric controls working. That battery needs to be tossed or the 24vdc charging system could be damaged.

Just temp wire in (2) 12s that are available and get it running on its own. Then put a meter across the pair of 12s and verify 28+ charging volts present. If so all is fine just need a new battery. 4HN is the battery model. Interstate and others have them. I used (2) 12 volt garden tractor batteries in the 016B but they stick out an inch or two so unless you removed the lower acoustic panel they would not fit the 701A. You can look at my threads to see how I made revised battery trays to take the (2) 12s.

Doug

 

[derf]

Battery Warehouse in LA has the correct battery for about $100, shipped dry.
As stated above, check for 28V or so across the battery terminals with the engine running. Remove your dead battery (or just disconnect the + lead) and jump the gen again. If it dies when you disconnect the jump source then it probably isn't making DC charging power. If your battery had a dead cell or short then it could be killing the charging circuit. You can also remove or disable the shutoff solenoid and it will continue to run (it's Diesel) as long as it gets fuel delivery. There is a mechanical lift pump for fuel. If you disable the shutoff solenoid, though, you lose safeguards and have to shut it down manually. It is a good idea to familiarize yourself with the shutdown solenoid and mechanism and know how to shut it down manually, anyway.