MEP-804A Shutdown on Under Voltage, now won’t start

[Jdj211]

Hello, I just got an MEP-804A and after giving it a once over, I started it up. It ran for about 60 seconds before it shut down. The “under voltage” light was lit. I turned the master switch to the off position, then back to prime & run, then hit the button to test/reset the fault lamps. When I try to start it again, it will crank but won’t start. I did put in about 3 gallons of fresh diesel prior to starting it, and the gauge is reporting about 1/4 tank. While it was running it was under no load and the AC contractor was not closed.

I searched for under voltage in the TM’s and only found a basic procedure to verify battery voltage. The batteries are both brand new and fully charged. I’m reading 25.1VDC across them. Is there somewhere else in the control panel I should verify this?

I’m thinking perhaps the under voltage was more of a symptom than a cause of my issue. My uneducated best assumption is that the engine isn’t getting fuel for some reason. I am not a mechanic so I wanted to check with the experts before I make things worse.

My next thought was to see if somehow there is air in the fuel lines but I’m not exactly sure how to verify or correct that. I’m sure it’s in the manuals, and I am searching through them currently.

 

[Guyfang]

After reseting it, when you try to start it, is the under volt light still on?

 

[Jdj211]

After reseting it, when you try to start it, is the under volt light still on?

No it is not.

 

[Guyfang]

Is any light on?

 

[Jdj211]

Is any light on?

No fault lights when I turn the switch to prime & run or start. All fault lights come on when the test/reset button is pressed. The panel lights work. The AC contractor light comes on when tested.

 

[Guyfang]

Unplug the fault indicator and try and start it.

 

[Jdj211]

Unplug the fault indicator and try and start it.

I disconnected this plug on the back of the fault indicator board and it still didn’t start.

 

[Guyfang]

Apply 24 VDC to the electric actuator.


Take the J10/P10 apart. apply 24 VDC to J10 pins. Hold it there, you should hear/feel it click. Hold it there, have someone else turn the set over. If it starts and starts to run up, remove the 24 VDC from J10.

 

[Jdj211]

Apply 24 VDC to the electric actuator.
View attachment 926209

Take the J10/P10 apart. apply 24 VDC to J10 pins. Hold it there, you should hear/feel it click. Hold it there, have someone else turn the set over. If it starts and starts to run up, remove the 24 VDC from J10.

Forgive the basic question, but I am still getting used to reading the schematics. Do you mean apply the 24VDC to the pins connected directly to the actuator (marked blue in my picture)? I was thinking that was P10. I’m not sure how to determine polarity for the wires A6-1 and A6-2. I’d rather not break something with the guess and check method.

 

[Jdj211]

I opened the cap (green in my picture) per suggestion from the guy I bought it from. It looked dry in there so I figured I wasn’t getting fuel. He suggested turned the engine over to see if I can see the rod move in there. I hit the dead crank and nothing moved. But I’m thinking maybe he meant turn the master switch to start, so I’m not sure the rod should have moved on a dead crank.

I opened the bleeder screw (red in my picture) and pumped the primer to get fuel into the injection pump. At first no fuel, then after a few presses I had fuel coming out. With the screw still cracked I hit the dead crank and fuel came out.

At this point I was going to try starting it again thinking maybe I bled the air out of the fuel lines. But I noticed the panel lights wouldn’t come on, and no fault lights when hitting the test. Needless to say it wouldn’t crank from the master switch. I verified 24.6VDC at the batteries. I need to check the schematics to see where that battery voltage should be coming in the control panel.

 

[Jdj211]

I opened the cap (green in my picture) per suggestion from the guy I bought it from. It looked dry in there so I figured I wasn’t getting fuel. He suggested turned the engine over to see if I can see the rod move in there. I hit the dead crank and nothing moved. But I’m thinking maybe he meant turn the master switch to start, so I’m not sure the rod should have moved on a dead crank.

I opened the bleeder screw (red in my picture) and pumped the primer to get fuel into the injection pump. At first no fuel, then after a few presses I had fuel coming out. With the screw still cracked I hit the dead crank and fuel came out.

At this point I was going to try starting it again thinking maybe I bled the air out of the fuel lines. But I noticed the panel lights wouldn’t come on, and no fault lights when hitting the test. Needless to say it wouldn’t crank from the master switch. I verified 24.6VDC at the batteries. I need to check the schematics to see where that battery voltage should be coming in the control panel.

UPDATE: The heat must have been getting to me yesterday. I had mistakenly left the dead crank switch in the off position. That was why I had no DC power at the control panel.

I tried starting the unit and it actually got some fuel and ran for about 15 seconds before shutting down again.

I will try applying 24VDC directly to the actuator when I have someone else to crank the unit with me.

 

[Jdj211]

Apply 24 VDC to the electric actuator.
View attachment 926209

Take the J10/P10 apart. apply 24 VDC to J10 pins. Hold it there, you should hear/feel it click. Hold it there, have someone else turn the set over. If it starts and starts to run up, remove the 24 VDC from J10.

When applying 24VDC to the A6 pins I heard a click. And again when removing power. I opened the large hex plug view port and did the same test. I have as able to see the shaft move.

I also verified the other side of the plug was sending 24VDC when turning the master switch to start.

After some more searching on here I found that the MPU can be problematic. I saw that the resistance should be 900-1200ohms. Mine was reading 800. When cranking the unit, I got 5.5VAC.

I pulled the unit found it had a lot of debris on it. After cleaning it and reinstalling I was getting 1.8-2.2VAC. I saw in another post to aim for 3VAC. No matter where I adjusted the MPU, it would never get about 2.2VAC, almost always less than 2VAC. It is still reading 800ohm across the leads and at the control panel. They are only $20 so I ordered a replacement. I figure it doesn’t hurt to have an extra on hand anyway.

 

[Jdj211]

When applying 24VDC to the A6 pins I heard a click. And again when removing power. I opened the large hex plug view port and did the same test. I have as able to see the shaft move.

I also verified the other side of the plug was sending 24VDC when turning the master switch to start.

After some more searching on here I found that the MPU can be problematic. I saw that the resistance should be 900-1200ohms. Mine was reading 800. When cranking the unit, I got 5.5VAC.

I pulled the unit found it had a lot of debris on it. After cleaning it and reinstalling I was getting 1.8-2.2VAC. I saw in another post to aim for 3VAC. No matter where I adjusted the MPU, it would never get about 2.2VAC, almost always less than 2VAC. It is still reading 800ohm across the leads and at the control panel. They are only $20 so I ordered a replacement. I figure it doesn’t hurt to have an extra on hand anyway.

I’ve tried 2 different MPU’s and both are only 300-330 ohms. They only put out 1.6VAC maximum. I found some posts on here that said a MSP6729 would work but both I got aren’t doing it. Any suggestions on where to get one that is in spec with the original?

 

[Guyfang]

All of the following NSN's and Part Numbers are good for your set:

6695-01-581-1306
6695-01-367-9723
6695-01-372-2583
2815-01-499-1057

96-23734
MSP6735
1500-2501
771721011800
8009291Q00
DT 17200-001-000
DYNT-17200-1

I would look them up in the net.

 

[Jdj211]

I was able to get the unit running again. I got another new MPU (nearly 6x the cost of the $20 options floating around the bay), and this one was in spec. Just north of 900 ohms across the leads and I was able to get it set around 2.7VAC when cranking.

Next issue was the fuel. I opened the valve on the bottom of the water separator. A watery mix of diesel and tiny gelled up chunks came out. I tried the priming pump to bleed out the air but it wasn’t pulling any fuel up the hose. So I replaced the hose between the tank and priming pump, and that did the trick.

Next more minor issue. The unit shuts down when I turn to the prime and run aux. fuel position. It would be great to hook up to a large tank and not have to pour 5 gallon cans all the time. We are 3 days into a power outage (thank you Hurricane Beryl and our crappy infrastructure) with probably 3 more days until power is restored. I’ve quickly learned that the auxiliary hook up is much more of a convenience than I could have anticipated. It would be great if anyone could point out typical points of failure here or go-to places to start looking while I take some time to read through the TM’s.

Thank you all for your assistance so far!

 

[Guyfang]

Next more minor issue. The unit shuts down when I turn to the prime and run aux. fuel position.

How soon? Tell us the whole story. Not just it shuts off. Fault lights?

 

[Jdj211]

Next more minor issue. The unit shuts down when I turn to the prime and run aux. fuel position.

How soon? Tell us the whole story. Not just it shuts off. Fault lights?

No fault lights. When I turn from prime and run to the prime and run aux fuel it immediately shuts down as if I had turned to the off position.
When turning from off to prime and run aux, I do hear the pump kick on. So when going from off state to aux, it appears to be functioning correctly. But when in a running state, it shuts off.

 

[Guyfang]

Show me a picture of S1, and maybe you need to look at the wires to S1.

 

[Jdj211]

Show me a picture of S1, and maybe you need to look at the wires to S1.

None of the wires were obviously loose or damaged. I’ll take a more thorough look tomorrow and disconnect/reconnect to ensure good contact.

 

[SCSG-G4]

How full is your primary fuel tank? Aux fuel pump should only start running when your primary is down to 1/4 tank, and shut off when it gets to 3/4 tank. Is the aux line clear and hooked up properly at both ends?