Mep 803 with problems shutting down

[Guyfang]

This is where I should say to you, "Read the manuals!"

But, being a nice, harmless old man, I will tell you. Take off the rear, top of the set. Remember, the control panel end of a gen set is ALWAYS the rear. You have to remove the control panel cover, (door) at the same time. In the space behind the control cube, above the K-1 relay, you will find the TB-4. TB stands for Terminal Board. If you take a gander at almost any part in the control panel, as well as the rest of the set, you will often find that someone printed things next to the parts. Next to every TB on the set, should be the TB number, like TB-4. Next to the relays should the relay numbers, for example, K-1 or K-16. And so on. Helps when you have to start looking for things and are not familiar with the set. Hint, Try not to drop the nuts into the control panel when removing the top cover. Hint, always disconnect the negative side of the batteries when doing work on the control panel, if you are not familiar with where is "hot", DC voltage, and where is not. Even with all switches off, and the emergency stop pushed in, there is 24 volts present in the control cube, and behind it. Some people find it a PITA to remove the clamp, and then hook it back up to troubleshoot. Burn up the wire harness once, and you might change your mind about that. It was an nice refreshing chore to replace the control cube wire harness one night in Vilseck, just before the unit deployed. And no, your not dumb. But do get the books and read them.

 

[Triton]

Did some more checking today, The CR-5 diode is there and is mounted per the TM. I removed it and checked the current flow, it flows one way and not the other. While I was checking diodes I checked the diodes behind the flip up panel, I didn't take those off but they did test ok. I guess I will start checking the fuel solenoid wire back to their locations.

 

[Triton]

Still having same issue this 803 it won't shut off by the master switch. Here is what I have done so far!
Printed large schematics so I can see them
Located a lot of the components on the schematics and labeled them
Labeled some of the components on the unit that were not labeled so I could identify them (still don't know what J7 or P8 means)
I traced the wires for the fuel solenoid, Starter solenoid, and fuel pump they seem to check out and be in the right place
Checked the master switch several more time for correct voltage and operation, I think it's good
Checked the fuel solenoid with the single white wire to the starter solenoid disconnected, when I turn the master switch on the fuel solenoid pulls back, when I turn the master switch off the fuel solenoid releases, there is 24 volts on the pull and hold
With the start solenoid wire connected the fuel solenoid pulls back, when I switch the master switch off it does nothing and there is 24 volts on the hold wire
I have switched the relays to all different positions and nothing changed, I do see them working as the master switch is moved
Any ideas on what to try next?

 

[Daybreak]

Howdy,
It sounds similar to another member here which had troubles with the S-1 start switch. At some point in time, somebody replaced the S-1. But, they did not get all the pieces back in place. A few of the wires then have jumpers over to another screw. Anyway, he ended up disconnecting all the wires. He then put them all back and made the missing jumpers. Its in a thread here somewhere.

 

[Triton]

I checked out the switch and it has some connections that have 2 connections for the same number pin (3), this unit does not have the blue plastic switch, my other 803 has the plastic blue switch. I'll try to compare the wires on that switch

 

[Guyfang]

Triton,

J and P are canon plug, or other types of plugs. The ends. For instance, P-14 is the plug on the fuel cut off solenoid. The corresponding end on the branched wire harness is J-14. Just keep in mind that the plugs on the branched wire harness are ALWAYS a J.

Another tip. Any wire number that starts with 100, is a ground wire. Pin 3, on P-14 has a wire number of 100D, hence, its a ground.

 

[Triton]

Did some more checking today, the S-1 master switch is wired correctly, I checked all the wiring numbers and pins for the switch. Checked the wiring diagram from the fuel solenoid to both fuel pumps and to the relay, that all was right. Checked the 4 K relays they seem to be switching correctly, Since I take the wire to the starter solenoid off and the fuel solenoid and fuel pump shut off I checked to see if there was any voltage on the start solenoid wire, there was none. I checked the solenoid connection for the start solenoid to see if there was voltage back feeding the start wire and there was none. Unit still will not shut down!

 

[Kvl00ej]

Hello all,
Newby alert, I just joined today and I already wished I would have joined earlier before I started bidding n a Mep-803a. First I want to say how great this site is and I hope I haven't hi-jacked this post that's not my intent. But if someone could help me I'm just wondering how far I should take an 803a that has 12hrs on a rebuild from letterkenny? Thanks in advance and Semper Fi

 

[CT-Mike]

Hello all,
Newby alert, I just joined today and I already wished I would have joined earlier before I started bidding n a Mep-803a. First I want to say how great this site is and I hope I haven't hi-jacked this post that's not my intent. But if someone could help me I'm just wondering how far I should take an 803a that has 12hrs on a rebuild from letterkenny? Thanks in advance and Semper Fi

Best to start your own thread, but I paid $3,800 after all fees and taxes for mine with 16 hours after Letterkenny total rebuild.

 

[Guyfang]

I second the motion for CT-Mike. Just keep in mind, the hour meter is not written in stone.

Break.

Triton.

When you say "Checked the 4 K relays and they seem to be switching correctly", Just how did you test them? Or just eyeball them? I possible, get someone to help you in this endeavor. They can start and stop the set, while you do voltage checks.

Can you read what wire on the starter you took off?

 

[Triton]

The wire on the starter that I removed is 113 B, I take that off so the engine won't start, I take it off so I can check the circuits. When I go to the master switch and turn it to prime run the fuel pump start some relays click, when I turn it to start the fuel solenoid moves back just as it does when it starts. When I turn the switch to off everything shuts off and the fuel solenoid releases, this doesn't happen with 113b connected

I check those relays for the capture wire in the wrong place, I checked for loose wires, I switched them around multiple times to different sockets, I didn't mix them up with the s14 switch. All of them will get power through the switching of the master switch and voltage does switch to the other side of the relay

 

[Triton]

I also notice when the engine is running the hertz gauge works but the volts do not, when I hold the master switch to start and hold it for a few seconds the volt gauge shows voltage but when I release it to run it stops, hz is still at 60

 

[Guyfang]

Start the set normally. Hold the S-1 up to get the fields to flash. When you have AC voltage on the meter, (Still holding S-1 up!!), then turn S-7, (battle short) on. Let S-1 return to the run position. Do any of the fault light come on?

 

[Triton]

Just tried that 2 times to be sure, had no fault lights come on!

 

[Triton]

Very interesting thing happened today, I purchased a kill-a-watt meter today and plugged it into the convenience receptacle and the voltage meter show 240 volts the kill-a-watt meter show 120 volts 60hz. Tried to shut the engine off and no luck. I pulled the fuel solenoid connector to shut the engine off and tried it again, got voltage on the gauge and at the lugs. Still won't shut off!

 

[Triton]

Doing some more testing and the voltage at the lugs is off. Still trying to trace back the wiring so far everything seems to be correct, does one of the relays lose power from the S1 switch and that's what releases the fuel solenoid?

 

[Triton]

Tried another experiment today, I pulled the wire 137N from the master switch S-1 pin 3, it did not shut off the engine. I'll try pin 7 tomarrow

 

[DieselAddict]

Based on all you've done so far I'm wondering if you have a problem with the starter solenoid.

I'm working to get the schematic cleaned up so its easier to understand. Let me finish that up and things should be a lot more clear.

 

[Triton]

Thanks DieselAddict, I have the schematics blown up and marked to make them easier to locate components, I had to blow up the diagnostic port pic today so I can check voltages through that connector. Doesn't look that will help my problem though!

 

[Guyfang]

The wire to pin 7 is for excitation voltage. If you took of the wire to pin 3, and it didn't stop, you need to see why. Somehow, the run circuit is staying energised. Tell, me, did you measure from wire 137N to ground when it was removed? When removed, it should be without voltage. If it had voltage present, we need to find out from where.

When it's hooked up right, (S-1) with the engine running, and you turn S-1 off, do all the relays go back to the non energised position?