Mep 804a won’t start

[C pope]

Generator won’t start. It’s a fuel shut off problem. Tracked it down . The fuel shut off is not getting any voltage sent to it. I jumped power to it and generator cranks right up. Anyone know witch component controls the voltage to the fuel shut off?

 

[robertsears1]

I am 99% sure you have a magnetic pickup problem. Search mpu. Have you ever seen this run correctly? You can get a piece of funk on the end of the magnet that will all of a sudden not let the fuel flow since it doesn’t realize the engine is turning. If you crank and don’t start to see puffs of white smoke from the exhaust in a few seconds, probably the MPU. The logic tree in the T.O/T.M. under ‘fails to start’ should have checking the MPU right after verifying the unit has fuel but it is farther down the list.
Robert

 

[C pope]

I am 99% sure you have a magnetic pickup problem. Search mpu. Have you ever seen this run correctly? You can get a piece of funk on the end of the magnet that will all of a sudden not let the fuel flow since it doesn’t realize the engine is turning. If you crank and don’t start to see puffs of white smoke from the exhaust in a few seconds, probably the MPU. The logic tree in the T.O/F.M. under ‘fails to start’ should have checking the MPU right after verifying the unit has fuel but it is farther down the list.
Robert

 

[C pope]

Yes it did run correctly. Have had it since 2016. Two weeks ago I was using it and it shut down. Went out to check and it had an over heat light. Started checking and found belt was loose. Got it back tight . Went to start it and nothing. Shot a little starting fluid at her and she stumbled over. Next I fueled it up. Then I checked to see if fuel was getting thru the filters by using the primer pump. ( it was) so my next thought was fuel actuator. Pulled it off and put power to it and it worked. Next I used my finger to push the rod inside of fuel injection pump and cranked her over and she started. Then I put a meter on the wires that power actuator and cranked it and got no voltage. Next I put actuator back on and put power to it and she started up.( no control of the rpm. It wants to run wide open)
Thanks in advance for any and all help!

checked this mo

 

[robertsears1]

Install the mpu until it bottoms out, then back out 1.5 turns and tighten down. Crank with the dead crank switch and measure VAC from the wires on the disconnected mpu. You should see maybe 2 or a little more. Screw it in a RCH and check again (1/8 turn). You want to get up toward 2.8 vac but do not grind the end of the mpu off or you will have to get another. It that works, put the switch in normal, reconnect the mpu and see what happens. You may need help holding the voltmeter wires and cranking. Never use ether on these units since it has a glowplug.

Robert

 

[C pope]

Install the mpu until it bottoms out, then back out 1.5 turns and tighten down. Crank with the dead crank switch and measure VAC from the wires on the disconnected mpu. You should see maybe 2 or a little more. Screw it in a RCH and check again (1/8 turn). You want to get up toward 2.8 vac but do not grind the end of the mpu off or you will have to get another. It that works, put the switch in normal, reconnect the mpu and see what happens. You may need help holding the voltmeter wires and cranking. Never use ether on these units since it has a glowplug.

Robert

Finally got to it and I only got .33 volts. That was at 1.5 turns out when I turned it in more I got less. Do you think the MPU is bad?

 

[robertsears1]

Make sure you are measuring AC volts. I think the Ohms should be around 700-900. I bought a mpu from ebay, search MSP6729, 3/8-24, $20.34. I tried to find the test procedure but couldn’t, perhaps someone can chime in where to find it.

Robert

 

[Guyfang]

First, pull it out, inspect, clean, reinstall and adjust properly. READ THE TM. Or risk buying another MPU.

TM 9-6115-643-24. Page, (PDF reader) 366.

 

[robertsears1]

Guy, hope you had a pleasant Memorial Day. The last photo with the yellow bucket on the right side is C Pope’s MPU. He said after reinstalling it 1.5 turns out, he’s only getting 0.33 volts ( I told him to make sure it’s VAC).

 

[Guyfang]

Robert, Was a nice smooth day. Rain, but not all day. Had Grandson #1 over. That was a full time job!


If thats all he is getting, then he needs to screw it in, a tad at a time, until he gets to 2.5-3 volts. But first, do what I wrote in message #8.

 

[Sgt Mo]

Robert, Was a nice smooth day. Rain, but not all day. Had Grandson #1 over. That was a full time job!


If thats all he is getting, then he needs to screw it in, a tad at a time, until he gets to 2.5-3 volts. But first, do what I wrote in message #8.

Hey guys just wanted to add some info that I did not see here but this post just helped me get my mep804a running. My generator has been starting great since I bought it for the last two weeks on weak batteries. After charging the batteries for two or three days it cranked over better than ever but would not even try to start. I checked for power on the fuel solenoid on the injection pump no voltage dc but I did notice the meter would flicker like it was going to read then go back to zero. After reading this post I went back out to measure the mpu (magnetic pickup) and it was reading 3.5v ac cranking over with the dead crank switch. I turned out the mpu till I got 2.9v ac, didn’t take much 1/8 of a turn or less, and it started right up no hesitation. Apparently you can have to many volts on mpu. Right now she’s out there purring away the way she’s meant to.

 

[hawk-aggie]

Yes it did run correctly. Have had it since 2016. Two weeks ago I was using it and it shut down. Went out to check and it had an over heat light. Started checking and found belt was loose. Got it back tight . Went to start it and nothing. Shot a little starting fluid at her and she stumbled over. Next I fueled it up. Then I checked to see if fuel was getting thru the filters by using the primer pump. ( it was) so my next thought was fuel actuator. Pulled it off and put power to it and it worked. Next I used my finger to push the rod inside of fuel injection pump and cranked her over and she started. Then I put a meter on the wires that power actuator and cranked it and got no voltage. Next I put actuator back on and put power to it and she started up.( no control of the rpm. It wants to run wide open)
Thanks in advance for any and all help!

checked this moView attachment 800727

I'm a little late to the party, but I have a question. Did servicing and adjusting the MPU fix your generator's "run away" issue?

 

[Guyfang]

Mr Pope has not been in the forum since his last post.