MEP-002a Troubles and Diagnostics

[aheilmann68]

I accicentally won two lots of 2 -002a's on a M103 trailer out of DE last week. Loaded them up and got them home no problem the hours were 351, 451 on one trailer and 351, 1 on the other with the latter trailer having better looking generators. All of the units had Mfd dates of 1982/3 and all fluids were flushed on the units and the fuel lines to the tank disconnected.
I started with my two good units namely the 1 hour one first. I believe that this one is a true one hour unit as there is no overhaul tag on this (or any unit) and the problem I found was that the governor shock type linkage's plastic ball joint clip had split and would slide when pulled. I put a hose clamp on it to lock the plastic on and it has not been a problem since. I have load tested it to 5kw for a half hour and there appears to be an issue with the breaker.

1)After running for 15 minutes the breaker drops out and opens up so I reset it and it will run another 15 minutes and repeat the same issue. Has me stumped but this one is not my priority at the moment.

Unit #2 with 351 hours just needed fluids and runs like a top with no issues in a hour load test at 5kw.

Unit #3 with 451 hours was found with a stuck IP and a broken bowtie clip in the IP. I took it all apart and rebuilt if after getting parts from AMBAC ( call them the nice lady took more than 1/2 off the price compared to their online catalog and it was a A+ experience). So I put the IP back in and time it 180 deg out, curse a bit and then reinstall it with the correct timing and it starts right up and runs like a top. On a side note the fuel tank had built up crud as well as the fuel system so the tank was cleaned and the usual system flush and filter exchange. The fuel line on both units #3 & #4 from the check valve to the IP were shot and basically was just the spring to I made up a new one from soft copper and flared the ends.
Now onto the real problems for #3, the unit does not make power. I spent all weekend working on the unit tracing everything, manually flashing fields and trouble shooting the unit with some success and some failure and here is what I found. Right off the bat the speed switch was off as it pulled the starter in constantly so that was fixed in order to manually flash the field. Once running the manual field flash going back to start did nothing so I started to look at why and tried applying 12V to TB5-6? iirc, its listed in the tm, and had no success. Went onto looing at the diodes and I found that one diode had the solder joint fail, reattached it and retried the 12V to the point. SUCCESS, we were making power as long as I had 12V energizing that connection for the field. As I kept digging, I found that the rectifier bridge A4 was giving me a problem on for the field flashing and when I would ring it out it was ringing on almost every terminal which I verified in the good unit that it should not be. Took the board off and low and behold a solder bridge failed and melted, installed new jumper wires and verified that the components to what I believe are ok and put it back in the unit. I know the voltage regulator is fine since I took it out and put it in my running unit and had zero issues. Now I go to start the thing and the + line from my slave cable that is loose decided it wanted to go to ground so it wiped out my DC side. My real question is that the unit will try to start and will run but the fuel pumps will not. The glow plug relays pull in, dash lights work, start solenoid all work but the fuel pumps do not come on line I will mention that the DC breaker on the dash did not trip and is operating as normal. I disconnected the power supply to the fuel pumps and rung the wire out and am finding that it goes to ground before going to the pump. Any one have any ideas where to look before I ring every wire out?

2) DC circuit is shorting out before powering the pumps but the unit will try to start it just is not getting fuel. The unit also when it ran after being shorted, had the voltage meter indicating overcharging at one time and ran normal the other time with the fuel pumps working.

Unit #4 had the same IP issue so it was removed and rebuilt but when it was put back in it would not start up. I was getting fuel up to the injectors but it does not look like the fuel was going through the injectors into the engine. To me it looks like the injectors either were to popping or the pump was not developing enough pressure. I had all of the injectors apart on the two units and cleaned them up with the exception of the actual spring in the injector as I cannot figure out how to get it apart the cap comes off but does not bring the body with it to get down to the springs. I wonder if crud and algea got into the injectors.

3) injectors will not pop, either the pump is not making full pressure or the injectors are gummed at the springs

On a side note, units #3 and #4 o the fuel side were terrible!! Algea had taken over and I had deposits everywhere in the fuel system. Brake cleaner was needed to clean the IP's and get the parts to even move. Both of the on/off slides in the IP were seized due to being gummed up and luckily did not break any other components other than the bow tie. If you have diesel that sits, make sure you treat it. I always treat my fuel for bacteria as well as lubrication with this ULSD being rougher on older equipment but lets not talk about that debate.

Any help on these questions would be wonderful

 

[aheilmann68]

I did some additional probing of the DC side of things and I am perplexed as to why the fuel pumps will not run. I have verified that I have voltage to the pumps but am having a similar issue to what a few people have had. If one pump is plugged in the voltage goes down to 2-4V but when all pumps are removed I have 24V. When I go to start the unit I get 24V to the pumps (all pumps are disconnected) then as the unit begins to start, voltage goes to zero then begins to creep back up after the starter inrush is complete. The voltage only rises to 18V. I have tried disconnecting the emf suppressors, swapped a pump from a working unit still with no luck. They all ring out as 18-20 ohms at the pump. I am wondering if I have a short elsewhere or something. I've disconnected the DCVR with no luck probed the master switch and just cannot find anything. When I turn the master switch on when I have batteries supplying the unit the voltage gage goes negative, to the left which leads me to believe a short only thing is i'm kind of stumped as to where since the unit does a normal start order just less the fuel pumps.

 

[Harleyd315]

Did you clean/check all the ground straps/connections?

 

[aheilmann68]

That just occurred to me to check again but when I was ringing everything out the pumps all had to ground paths to the main frame since I did most of my probing to ground. I did find that the line that goes to the DCVR from the control box for a time was ringing as going to ground. I disconnected the plug by the fuel cut off solenoid and tested there with no findings and reconnected and my issue went away. That however did not solve anything and I even tried to get the pumps to run with the DCVR disconnected.

 

[Harleyd315]

I also have a couple of good injectors if you want to borrow them to check your other unit

 

[aheilmann68]

I have 2 units that are running fine so im lucky enough that I have a few references to use but thank you

 

[gimpyrobb]

I have IP parts. Let me know when your ready to fix them.

 

[aheilmann68]

IPs are fine just need to trouble shoot one unit. The wiring on #3 is my priority now

 

[aheilmann68]

Ok so im still stumped. I have voltage at the pumps and when you turn the switch to either purge setting you can feel the pump "thud" like the solenoid coil becomes active and the field is created but nothing happens. I took one pump apart to look at how its made and all these are are a solenoid with check valves and operate like a hand pump for inflating things. Im trying to figure out what causes the field to either stop or pulse on the pumps and create the up and down motion. When any/all pumps are hooked up my voltmeter goes negative to the left but with no pumps hooked up it operates normally. I have tried using what I believe to be is a good pump (one from a running unit) but it will not work. I have good grounds and continuity to the pumps and back to the master switch. I did notice that when i disconnect all pumps and put a voltage meter from one of the leads to ground, i get 24 V in the purge and run positions then when I go to start it, the voltage drops out (starter is the larger load) but then the voltage slowly comes back (10 seconds) and builds from 3V to 18V which has me puzzled. I am going to run the same test on my know good unit. Could K1/A1 be an issues as the wiring diagram shows some functions of start utilizing that.

 

[Isaac-1]

This sounds to me like you have a marginal connection somewhere, might be in the relay. It probably shows voltage fine to the meter, when when you start drawing amps through it, then it gets hot, resistance goes up and voltage drops off. This is just a guess, but seems to fit the facts.

Ike

 

[aheilmann68]

I am almost thinking that. Im still trying to figure out how the electro magnetic field pulses in the fuel pump or how it creates a reciprocation of the piston. I wonder if it is just the spring rate of the large spring at the bottom of the stroke exceeds the force from the coil and thus pumps. Is there a source for the A1/K1 relay? I think I will take that whole board off the wall and inspect the back since my A4 looked fine but had burned out wires on the back.

 

[Triple Jim]

The pumps are a big solenoid, with the iron slug being the piston. The connection to the solenoid is normally closed, and when the piston moves, a switch opens, and a spring returns the piston. The pump's output is during the spring return stroke, so the output pressure is determined by that spring. If the pump flow is blocked, the spring moves the piston only as fast as fuel leaks around it, so the pump runs slowly. When flow is allowed, the spring can return the piston quickly, so the pump runs at higher speed.

 

[aheilmann68]

Triple Jim, Thank you for confirming that I was thinking of a similar process after I opened the piston of one up. I think it is a wiring issue that I am having that causes a 24V reading when disconnected then an apparent short when connected to a pump. If it was not for a presumed working pump that did not operate when swapped in then I would think its the pumps. It did go from a negative ground system to a positive ground system for a few seconds. My real puzzlement is why after a few start ups in this shorted, no pump condition, did it start up with pumps and no short for one occurrence and then continue back to no pumps. I guess I will look into testing K1/A1 as that is the only thing that I can find that has any sort of diode or flow control device on it in the starting circuit. Any other ideas are greatly appreciated.

 

[aheilmann68]

Well it's always the simple things that come back to bite you. Grounding issues back to the battery was the reason for the no pump condition. My A4 board has Cr1 and Cr4 Fried at the least. Does anyone know the specifics for these diodes otherwise I'll have to dig for it.thanks

 

[Triple Jim]

I'm sure you can use any of the 1N400x series diodes (x=1,2,3,4, etc). Personally I think I'd drill the holes if necessary, and use 1N5408 diodes, rated for 3A at 1000V. They're dirt cheap and would be unlikely to blow again.

 

[aheilmann68]

Triple jim, thanks I think I should be able to get some tomorrow and see if I can get the field to flash

 

[aheilmann68]

Well #3 is on line, the two diodes on A4 were replaced with the diodes that triple jim suggested and she fired right over making power. Moving onto #4 tomorrow with the ip and injector issues

 

[aheilmann68]

#4 is running fine and making power. Had to make some Adjustments to the governor to bring the unit up to speed but other than that it looks like it just needed a longer preheat time to light of.
Overall I got all 4 running and working handing a 5 kw load with easy, now to bring my load up to 8kw and test there. Thanks to everyone who helped out and offered advice.

 

[Smallblockfuelie]

Is this the diode?

 

[aheilmann68]

That is one of the field diodes but not the one I was referring to. If you need that just look up field flash diode and you should have success getting the pn