MEP-004A Injection Pump Repair, Then Major Short Circuit

[1800 Diesel]

Greetings to everyone. Been away for a few years, mostly working away from home, but now back for awhile and trying to give some attention to a few languishing MEPs.

For this one, it's 1977 vintage unit showing signs of neglect based on the mixture of sludge/water in the fuel tank. Day tank also had the same junk--resembling a blend of brown gravy and pancake syrup. Also found in the day tank were white "globules" about the size of rice grains--assuming this was a rare species of algae. To get to the question, I spent several hours cleaning the fuel system--all hoses flushed and both tanks cleaned. Predictably, both priming pumps were clogged with the same fuel tank mush. Also had to replace the float switch assembly in the day tank since one switch showed continuity whether up of down. Also, the tube had a 2" long crack from prior maintenance over-tightening the set screws on the collars.

Once all the fuel issues were resolved and the system was primed, I attempted a light-off but the IP produced no high pressure fuel delivery. To troubleshoot, the following steps were taken:

1. Removed the return fuel tee fitting and cleaned. (At this time, left the ball check in place.)
2. Removed the governor cover to inspect/test the stop solenoid. With 24v applied to the terminals, the solenoid would not pull the shutdown arm in. After spending a little time cleaning up the solenoid assembly, it began to function properly.
3. With the cover off I noticed what I believe is the metering valve linkage stuck. With mystery oil I was able to free up this and the connected governor linkage.
4. I reinstalled the solenoid, taking care to verify the shutdown arm assembly was in the correct location. (Not much choice here, as the governor cover plate is positioned by three small bolts.)
5. Removed IP timing cover and gasket and flushed clean fuel through the pump body using 24v pumps. A few specs of "coffee grounds" were seen flowing out.
6. Reinstalled everything, loosened fuel banjo fittings and cylinder #1 & #4 injector line nuts and then attempted cranking.

After seeing fuel flowing from the HP fittings I tightened all loose fittings, cranked again and with much relief, the engine started right up. Speed hunted for about a minute or so but then stabilized and I set the speed for 60hz. The problem showed up when I did a shutdown with the S/R/S switch (32). The engine slowed down, but did not do a "clean" or quick shutdown. I actually had to manually shut the engine down using the shutoff lever on the side of the injection pump. When I did this I could feel an interference or detent on the lever that I had to overcome in order to do the shutdown. Has anyone run into this one? I plan to remove the governor cover again and attempt a new re-install. If this doesn't work, I'll try installing a different solenoid assembly.

 

[Ray70]

Sounds like you have something wrong under the IP cover. When you open it up, check the springs and the linkage to make sure nothing is gummed up or out of place. There is also a little "hydraulic dampener" in there ( like a cylinder and plunger with a small relief hole in the side ) if that is gummed up it could bind things up.
Since everything else was gummy and you said the engine speed hunted around for a minute or so, I'm guessing you need more cleanup under the IP governor cover.

 

[Guyfang]

I think Ray probably right here.

Also, the L1 fuel cut off solenoid is often reinstalled improperly. Take the time to check it out. See if you got it back in right. And take the time to reinstall it right after checking it. I once saw a 60 KW with the L1 reinstalled improperly, go to over speed. We could not get it to shut off. And we foolishly disconnected the IP linkage to try and shut it down. Then it really went to over speed! It vibrated so bad, bolts broke off all over the set. So pay attention to what you are doing with the IP and L1. If you felt resistance, that could be the reason why.

Also, resistance could also be because the S2 start switch my not have cut the 24 VDC off to the L1. It happens. Not often, but I have seen it numerous times on the 15-60 KW gen sets over the years. All you need it a K1 relay to be bad, and that happens.

 

[1800 Diesel]

Sounds like you have something wrong under the IP cover. When you open it up, check the springs and the linkage to make sure nothing is gummed up or out of place. There is also a little "hydraulic dampener" in there ( like a cylinder and plunger with a small relief hole in the side ) if that is gummed up it could bind things up.
Since everything else was gummy and you said the engine speed hunted around for a minute or so, I'm guessing you need more cleanup under the IP governor cover.

Thanks--I remember seeing a fuel squirt coming out the small relief hole but it wasn't much. I'll do some more cleaning in that area.

I haven't gotten to the solenoid swap out, but will do that tonight. Unit still does not want to shut down with the solenoid, but only manually.

 

[Guyfang]

After turning off the S2 switch, measure for 24 VDC at the L1. Should be ZERO volts there if S2 is in the stop position.

 

[1800 Diesel]

I think Ray probably right here.

Also, the L1 fuel cut off solenoid is often reinstalled improperly. Take the time to check it out. See if you got it back in right. And take the time to reinstall it right after checking it. I once saw a 60 KW with the L1 reinstalled improperly, go to over speed. We could not get it to shut off. And we foolishly disconnected the IP linkage to try and shut it down. Then it really went to over speed! It vibrated so bad, bolts broke off all over the set. So pay attention to what you are doing with the IP and L1. If you felt resistance, that could be the reason why.

Also, resistance could also be because the S2 start switch my not have cut the 24 VDC off to the L1. It happens. Not often, but I have seen it numerous times on the 15-60 KW gen sets over the years. All you need it a K1 relay to be bad, and that happens.

Well, good to hear from you stranger! Happy to see you're still helping folks out. I will be very careful about re-installing to top cover having read about the possibility of an overspeed when the arm is placed on the wrong side of the linkage. What I've been doing is landing the cover a little forward of its position (towards battery end) and then easing it aft (towards the control cubicle). This seems to put a slight pre-load on the arm and I believe if closes the air gap a little to allow the solenoid to pull in when energized. I believe this solenoid may be a little weak (if that's possible) as it won't pull in when connected straight to 24 volts at the battery terminals. But if I move the arm a little closer it will snap over. (This test was done off the IP.) When installed, the solenoid will snap one time but will not function again unless I move it a little side-to-side or up and down... Later today I'll pull another solenoid from another unit and check its function...Prior to start up, I'll also remove the air filter in case I need to do a "Detroit Diesel" shutdown.

On the detent/resistance I felt with the manual shutdown lever, I have to admit that it was caused by my placement of the positive lead on the top cover. After tightening, the crimp connector was in the path of the linkage rotation--technician error!

I have tested for 24 volts at the L1 fuel cut off solenoid positive terminal with S2 start switch in run position and S7 battle short switch on. Have not done this test while running, but have to assume L1 is getting voltage since the engine will run at the proper speed.

I did not consider a bad K1 relay though and will check that out later today.

Thanks!

 

[1800 Diesel]

After turning off the S2 switch, measure for 24 VDC at the L1. Should be ZERO volts there if S2 is in the stop position.

Zero volts at L1 with S2 switch off.

 

[1800 Diesel]

Bad, bad news....

After swapping out the K1 relay and restarting the unit I immediately got a short circuit fault and instant shutdown. (At least the stop solenoid functioned properly but now I might have a parts unit.) This is painful after spending so much time in solving one problem after another and with the unit starting to function normally....

After shutdown, I smelled burned wires at the special relay box. Removed all cannon connectors and found a small piece of the J50 connector housing partially burned/melted. See photos.

J2 connector and associated cable connector damage.

J2 Connector thread "blowout"....


Inside special relay box....


Cable burns to J15 connector inside special relay box.

Cables found overheated but no apparent dead shorts under reconnection board.

So the only electrical change I did was to swap out the existing K1 relay with a known good one. No tools left inside the unit, no liquids or anything else that would have posed a short-circuit risk....is this a pure coincidence or some kind of fluke? If anyone has any clues as to cause, please weigh in. At this point I don't know where to go from here. Should I replace the damaged special relay box and the one damaged cable harness? I would also do a thorough inspection of all the cables under the reconnection board and repair any insulation damage, etc. But even if I replace/repair anything that appears damaged/burned, without knowing the root cause, there's a possibility of a repeat of the incident and more component damage. Hopefully someone else has seen this scenario and can provide some guidance.

Thanks in advance for the support!

 

[1800 Diesel]

New photo to add---noticed today one of the current transformers is leaking a strange fluid. Didn't see this last night...

 

[Guyfang]

Dude,
Glad to hear from you. Sad to see the pictures. This is a mess.

So the only electrical change I did was to swap out the existing K1 relay with a known good one. No tools left inside the unit, no liquids or anything else that would have posed a short-circuit risk....is this a pure coincidence or some kind of fluke? (The changing of K1 did not do this. The K1 funtions do not include AC voltage, and you sure have some here in this damage.) If anyone has any clues as to cause, please weigh in. At this point I don't know where to go from here. Should I replace the damaged special relay box and the one damaged cable harness? I would also do a thorough inspection of all the cables under the reconnection board and repair any insulation damage, etc. But even if I replace/repair anything that appears damaged/burned, without knowing the root cause, there's a possibility of a repeat of the incident and more component damage. (I agree, you need to find out what happened. This is bad enough, to do it twice would cause me to jump from the roof) Hopefully someone else has seen this scenario and can provide some guidance.

Well, kinda seen something like this. Been a while since I saw one this bad.

The small wires on the CT are the circuits to S8.
The A5 card is toasted. And we have AC volts there. The K7 circuit.
The A4 card is toast. I don't remember AC being there.
What wire at J15 burnt up`Or more then one wire?
The wires that burnt to the J1/P1 plug in the SP relay box. Are they burnt completely away?

I am going to try and send the pictures to someone who I know. He might have an idea. It kinda looks like AC got crossed to the DC circuits. That's not something that the A4 or CT could have done. It looks like it started in the SP relay box, BUT because the J1/P1 is so heavely damaged, and the A4, it could have started in the control cube, and went to the relay box. I need to look some more at the pictures.

 

[1800 Diesel]

Guyfang,

Been off the grid for several days but back to home base now. Will be doing an "autopsy" of the damage with a goal to identify the burned cables (or at least their pin connection points on the cannon plugs since all the insulation is burned off). Also will be taking a closer look under the reconnection board. I'll report this info as soon as I'm able--hopefully within 24hrs.

Moderator--would it be possible to relocate parts of this thread, starting with my post #8? At this point I believe the subject matter has changed from a fuel issue to a major short circuit . The new thread could be titled "MEP-004A short circuit damage and after action troubleshooting".

Finally, I mistakenly had caps-lock on when I typed in the title to the original post. Apologize for this, didn't mean it to be in caps. If I can alter this, please advise, or if you can correct this I would appreciate it!

Thanks for the assist!

 

[Guyfang]

Can you send me the disaster pictures to my email? When I try and copy them from SS, they are so small my old buddy and I need to use a spotter scope to see them. Thanks!

 

[1800 Diesel]

Can you pm your email or is it in your profile somewhere?