MEP002A just stopped running

[rustystud]

Vent on underside of Fuel Tank cap set to open?

The fuel system would not work for 3 to 4 hours with the vent closed.
You need to think about what a diesel engine needs to run and then go from there. First a diesel needs three things, 1st fuel, 2nd air, 3rd compression (heat) . So since the engine was running fine for over 3 hours we can eliminate air and compression. That just leaves fuel. Since the engine didn't run rough or stumble for a while but "suddenly" shut down that means the fuel was cut off. If it was bad filters it would still run just badly. If it was the fuel pumps then they would not still be working (unless they got jammed or gummed up) . I still would check the fuel return to the tank for proper flow. So it must be something that can cut-off fuel flow immediately. That leaves the engine sensor switches (air temp and oil pressure) injection pump and actuator, and the inline "one-way" flow control valve . If we have full returning to the tank then the one-way valve is OK.
So the first thing I would do is check the return line. If no fuel returning to the tank then I would crack a line at the last fuel filter. Unless the filters just decided to go to crap there should be fuel there. If you have fuel coming out there then the one-way check-valve is stuck. If you have fuel at the tank return, then I would check the injection pump and actuator. A wire could have come loose from the solenoid shutting down fuel. If the actuator works and is pulling off like it should then we will have to regroup and look at further causes. Meaning it then could be the injection pump itself, but before we jump to that these other things need to be checked first.

 

[Light in the Dark]

@doghead... will be checking the pump screens next. It was dark as I walked by and knew I had enough light to turn a switch only

 

[Light in the Dark]

Ok, so the pump screens were clean. I opened up all three canisters, and all looked fine. I did replace the second in line filter, so both are new now. I cracked the lines after the third canister, where it turns up into a 90*... and set the normal prime, and after 30 seconds I got fuel. Buttoned it up, and gave it a test fire... SUCCESS.

I proceeded to pat myself on the back on a quick fix, and let it run for 15 minutes. While testing for fuel pressure, I just let it pour back into the 5 gal aux tank I pulled from last time. I set the knob to prime + aux, and let is refill the day tank again.

I flip the breaker and put the house on, and proceed to load the clothes dryer and give it ****. It seems to be working fine under load (about 80% listed on gauge). It runs for about 10 minutes, and I get the silly notion to change the starting knob away from prime + aux back to regular prime + run... she goes 10 seconds and up and dies on me again. I am now getting the same conditions I started with... will run very strongly with the knob being held after starting... and dies once I let go (will run 5-10 seconds... haven't held it longer than that after its been running).

So I cracked the line at the same point again (just before the T and it goes into the IP)... set to prime + run and she is pumping fuel fine. So might my starting switch be faulty, and when I changed inputs, it says no bueno?

Thanks all.

 

[Chainbreaker]

It runs for about 10 minutes, and I get the silly notion to change the starting knob away from prime + aux back to regular prime + run... she goes 10 seconds and up and dies on me again.

I am now getting the same conditions I started with... will run very strongly with the knob being held after starting... and dies once I let go (will run 5-10 seconds... haven't held it longer than that after its been running).

1. Switching from "Prime, Run, Aux" (switch pins 11, 13, 17) to "Prime Run" (switch pins 11,13) normally does not make any difference since pins 11, 13 are common and are only pins necessary to keep unit running. Pin 17 contact is what engages the Aux pump relay. However, not knowing the internals of that switch perhaps its possible the contacts for pins 11,13 are intermittent when physically placed in the "Prime Run" position if those contacts are worn...?

2. What is oil pressure reading when you let go of the start switch when it dies? I think it is likely that you have a faulty oil pressure switch assuming you are able to maintain good oil pressure when running.

Assuming you have good oil pressure, I would jumper across the pins of the oil pressure switch and see if that makes a difference. The oil pressure switch (S5 on schematic) is pretty easy to find and easy to replace.

 

[jamawieb]

It would really help if you let us know if the fuel cut off solenoid is engaged or not. As stated earlier, when starting the unit it bypasses the oil pressure switch and temperature switch. When you release the start switch, if the switches are not reading correctly or not functioning the unit will shut down immediately.

 

[Light in the Dark]

When holding the start switch, the oil pegs at 50... and once I let go, stays at 50 while the motor is shutting down. The gauge settled out at 30 when I just tested it (didnt reset to 0 when off).

 

[Guyfang]

LITD,

If the S4, (Low Oil Pressure switch) was bad, how come the set ran for 15 min in Aux fuel position?

Try to simulate the same thing you had before. Start and run in Aux fuel position. If it runs in the Aux position, then turn it to the normal run position. What happens? If your oil pressure gage is up high enough to run the set, If the set runs in Aux for 15 min, and stops when you turn it to normal run position, then you need to look at S1, first. You can jump the S4 later if you want, but if the set runs in Aux, then it will run in normal run position. Your S-1 sounds fishy to me.

 

[Chainbreaker]

OK, so you have proper oil pressure and it continues to run when held in "START" position AND continues to run when switched to "PRIME RUN AUX". So it always stops when in the "PRIME RUN" position? If so, that would seem to indicate S1 Master Switch is the likely culprit. I would open the control box front panel and look at S1 and verify that all the terminal screws are tight and there are no broken terminal lugs on the wiring harness attached to switch.

 

[rustystud]

OK, so you have proper oil pressure and it continues to run when held in "START" position AND continues to run when switched to "PRIME RUN AUX". So it always stops when in the "PRIME RUN" position? If so, that would seem to indicate S1 Master Switch is the likely culprit. I would open the control box front panel and look at S1 and verify that all the terminal screws are tight and there are no broken terminal lugs on the wiring harness attached to switch.

Yes, loose wires can cause this.

 

[Light in the Dark]

@Chainbreaker: It was running fine in PRIME RUN AUX for 15 minutes, then I switched and it won't stay running in either.

 

[rustystud]

@Chainbreaker: It was running fine in PRIME RUN AUX for 15 minutes, then I switched and it won't stay running in either.

Check the S1 switch. You could have loose wires. We once had a bus that would run great until you went over some railroad tracks then it would try and apply the brakes (ABS system) . We worked on that bus for weeks and could not find the problem. Then one of the older mechanics went into the rear control panel and using his screwdriver started tightening the "buss bar" screws until he came to a loose one. After tightening that one we took the bus out again and it was fine. Loose wires can cause tremendous problems, and can be extremely difficult to find due to their intermittent nature.
You came here seeking our advice, and many of us have given you this same advice. Take it or not, your decision.

 

[Light in the Dark]

I will be checking that switch. I don't think I indicated otherwise. Just a little dark at 0530 to do so. Thanks all the same.

 

[doghead]

I've had to replace the rotary switch once. It was doing something similar. Sometimes it worked, sometimes it didn't.

I bought a used(guaranteed) switch from Delk's.

 

[Light in the Dark]

I found two NOS on eBay... one of which I made an offer on. Figure it can't hurt to have one as a backup, in case it is just a loose connection (the set is 35 years old, even without the reset 10 years ago).

 

[Chainbreaker]

@Chainbreaker: It was running fine in PRIME RUN AUX for 15 minutes, then I switched and it won't stay running in either.

OK, so now the only repeatable pattern is that your unit will ALWAYS RUN as long as you hold master switch in the start position, either at initial start up or a hot restart? Correct?

1. I would still recommend jumpering past the oil pressure switch it's so easy to do and would eliminate it as a possibility. Like you said your unit is 35 years old. No telling if the oil pressure switch has ever been replaced or not...I would think they would have during a RESET but you never know 100%. Even if they had, the switch would now be 10 yrs old. The switch could be an intermittent switch...one that works when oil pressure is higher (cold) and loses switch actuation pressure when unit has been running for a while (oil is hot and running at lower pressure). There could be some gunk up in the switch orifice restricting pressure making it act intermittent.

2. If that does not resolve the issue the next thing to eliminate as a shutdown possibility would be the Overtemp switch. If I recall correctly, you need to remove the muffler shroud to access it. Then jumper past it to eliminate it as the culprit.

3. Have you put a screwdriver to the screws on the S1 Master Switch and made sure all the lugs are tight and intact? These units are subject to a lot of vibration which can loosen and even crack terminal lugs over time. The shank of the lug can still be attached to a wire but broken loose from the other half of the spade/eye and just touching it, causing an intermittent connection. You have to look very closely to notice if any are cracked/broken. While your inside it would not be a bad idea to go over all the TB's (terminal block screw connections) to insure none are loose/cracked. Caution: I always remove a battery lead when poking around inside the control box with tools.

Ordering a replacement Master Switch is a good idea. If the above two switches (oil & temp) are not causing your shutdown it very well could be the Master Switch internals.

 

[DieselAddict]

3. Have you put a screwdriver to the screws on the S1 Master Switch and made sure all the lugs are tight and intact? These units are subject to a lot of vibration which can loosen and even crack terminal lugs over time. The shank of the lug can still be attached to a wire but broken loose from the other half of the spade/eye and just touching it, causing an intermittent connection. You have to look very closely to notice if any are cracked/broken. While your inside it would not be a bad idea to go over all the TB's (terminal block screw connections) to insure none are loose/cracked. Caution: I always remove a battery lead when poking around inside the control box with tools.

In addition I like to give the wires a gentle tug at the crimped terminals to check for bad crimps. I have chased my tail a number of times to find the problem in a bad crimp connector.

 

[Light in the Dark]

Yes, that is correct Chainbreaker.... holding master in start position.

1.) I will locate this in the TM and figure out how to do this.

2.) We'll hold on that for now.

3.) I went over S1 earlier, and all screws were tight and all wires appeared to be firmly in their lugs. I did notice that there was (1) screw missing though (and no wire with it or loose). Are there supposed to be any threaded provisions on these switches that aren't utilized in these machines?

Due for 6-8" of snow tonight, and freezing rain. Really wish this was operational as thats the perfect cocktail for an outage here. At least I have an 803A in the garage that I know is good.

 

[Light in the Dark]

I haven't opened the PDF of the TM yet tonight... but is the oil pressure switch the item in the block near where the oil is drained? I know when I was out there yesterday, whatever that device was is totally caked in oil from its previous owners.

 

[Chainbreaker]

Yes, that is location for oil pressure switch. Just jumper the two wires going into it any way you can. You can even attach one wire to the other one to complete the circuit.



Yes, the S1 Master switch does have a no connect position. Here's a pic of the 7 wires going into it on one of mine:



Stick with the trouble shooting. You have a repeatable problem and it should be easy to trace down to one point of failure given the suggestions everyone has provided.

Good luck with the weather!

 

[Chainbreaker]

Also for reference - you should have a circuit schematic riveted to the top of your control box (hopefully yours is legible, if not refer to the TM's schematic). If you are facing the front of the control box and looking at the schematic at the top right quadrant, there is the circuit where both S5 (oil pressure sensing switch) and S4 (temperature sensing switch) are depicted just beneath the "K2" the Preheat Relay symbol. You can see that both S4 & S5 are on same circuit and the circuit they are on connect to S1 Master Switch, shown as S1 to the left with the long rectangular box outlined in dashes. That box also identifies all the wires going into S1 and their proper terminal locations. So if either of those switches fail while unit is running it will cause it to stop running just as you are describing.