M923A1 multiple issues all at once

[sandcobra164]

Driving home today in my M923, had a breakdown. I pulled over because I had a burst of smoke in the cab, truck seemed to be running fine. Stopped quickly, shut down and noticed quite a bit of oil on the drivers side front and passenger side rear of the engine block along with quite a bit on the passenger side undercarriage. Check fluids, engine oil high and with a slight diesel smell, coolant fine, trans fine, power steering fluid is fine. Restart engine and it has a slight surge but idles down, it did that at the last restart but hey, they act funny sometimes is what I told myself. Big issue though is no oil pressure. Attach towbar to the front and wait for friend with a M923A2 to arrive. Applaud you A2 8.3 powered friends for the tow. Got home and attempted to start to reconfirm no oil pressure. Truck started but ran rough as if sucking air and shut off on it's own. I attempted to restart and it kept "almost" starting but gave up due to oil pressure concerns. Primer has no pressure but for now I think it's unrelated. Never had that happen before and I have not cracked anything on the fuel system in a year of so. Talked to a friend about the oil being everywhere and he pointed to some good directions to check. It appears that the leak is from the hard line from the oil pump to the front of the oil pan. Apparently the fan can sling it everywhere. I confirmed the oil pressure gauge is working correctly by grounding the wire from the sending unit and switching the truck on. Instant 120 there so I doubt the gauge is faulty. I removed the sending unit, cranked the engine over and it's spraying oil there. I don't think the sending unit is bad as I don't think it is likely that I'm slinging oil everywhere and the sending unit went out at the same time. I've dealt with the making oil issue on a deuce, does anyone have experience of this on an NHC 250? I'm worried based on the oil level that I need to pull the injectors and re-oring them. I've done this to CAT C7's many times. Is the procedure somewhat the same? Can they be removed from the rocker boxes or do the heads have to come off?

Lastly, does anyone else have an idea that I am overlooking. I certainly am open to ideas and have planned on taking the day off of work tomorrow to dig around. I'm going to replace the adapter that I broke going to the sending unit, add a T fitting to attach a mechanical gauge to mount on the fitting next to the engine for peace of mind when stuck on the side of the road, replace the fuel filter, change the oil, prime the fuel system, fix the leak I have identified, and see where I am at.

 

[wrenchturner6238]

It sounds like you have some o-rings on the injectors. the low oil psi is possibly do to very thin oil and the crank mixing up the oil. Take 2 oil drain pans with you there will be a lot! The oil leak is possibly from the over full oil too and being thin. I have not done injectors on a c7 but the injectors are just similar i am sure they are a dumb unit injector. I would remove the valve covers I would plug the return line and psi up the psi line if you have access to dye and a black light use it in a gallon of diesel and psi up the system to find out where its leaking they will all leak a little while not running and warmed up but you should notice a bigger leak.

 

[sandcobra164]

Drained the oil today. Plenty of diesel fuel in the oil, drained about 14 gallons out all together. I removed the filter, cut it apart and looked for any type of debris. Nothing noted. The drain plug magnet had some remnant of a very small coil spring, about the thickness of #2 pencil lead. I have no clue as to where that could have possibly come from so I'm all ears. It may have just gotten there or it could have been there for the past year. It wasn't there last time I serviced the truck. I will pull the rocker covers this afternoon and see what I can find in there. I have a friend who mentioned that the PT pump has seals that can fail and dilute the oil as well. I last checked the oil about 150 miles ago and it was at it's normal level. Gives me hope that the leak is rather severe and therefore should be easy enough to find. Any other thoughts are greatly appreciated. This will be my first time tearing into an NHC 250 but my wife pointed out an important fact. It's not "really" your truck until you've had to really tear into it! Made me smile for the moment so I'm thankful for that.

If a moderator could re-title this to NHC 250 leaking diesel into oil, it may be helpful for future people searching. I haven't found many threads similar.

 

[74M35A2]

sorry to hear about your news. I'd let it sit and then take an oil sample from the drain plug. At this point I would drain oil, replace with a minimal amount (NAPA has Rotella on sale this month for $12.95 a gallon) , and then check oil pressure with a known good mechanical gauge. Leak check the fuel side as mentioned if possible.

simp, 8.3 towed a 250 home. You got yo' ears on?

 

[sandcobra164]

Pulled the injection pump at the advice of a friend and quickly found my problem. The seal for the driving flange had ruptured. That is why I had fuel in the oil and also why it lost prime while being towed home. I spoke with the technician at R & S Diesel Injection about possible "why's". He said that the pump generated too much pressure internally to blow out that particular seal. I asked if it had to do with me turning it up 1/4 or 1/2 a turn on the main fuel screw in the throttle shaft and he said "probably not". He flipped the pump over and immediately zeroed in on the "emergency shutoff". If the fully forward position, it blocks about 20% of the fuel output. It needs to be rotated back about 1/8 of a turn from forward to be fully open. He's suggesting that I get rid of it to avoid future failure. He questioned why the military wanted this on there as the fuel solenoid will shut the truck off and only has one failure mode. If it fails, no fuel unless we screw in the solenoid bypass. The truck will be down for a few days but he quoted me $325 to rebuild the pump to which I happily agreed. He claims he'll up my fuel rate about 10% over stock and said that's about the max he would recommend. Since I don't have a fuel pressure gauge, I suppose I'll stay there for now on as I'll be under warranty for a year. I'm glad to have found the issue and even happier that I'll get to drive my truck to Durhamtown even with this unforeseen visit from Pvt. Murphy.

NHC 250 Owners, I've not seen it posted elsewhere but check your "emergency shutoff". Rotate it clockwise an 1/8 of a turn and drive your truck. You may find yourself with a slight power boost and you just might save your pump if you run your truck as hard as I run mine.

 

[74M35A2]

Nice work, that was quick.

 

[sandcobra164]

I've got a Rally to go to. My friend with the A2 offered to let me use his truck but I feel I set the 250 crowd back enough already being towed by an A2. My pride unfortunately is not worth the cost of a commercial wrecker tow when you have friends close by.

 

[74M35A2]

I hear you. I have a tow bar, and keep it on board at times, soon permanently. If I ever have to get my 8.3 towed home by WildChild467's 135hp LDT powered M35a2 (lives close), that will be a difficult phone call to make.

Congrats again on your quick find and resolve.

 

[clinto]

he quoted me $325 to rebuild the pump

Oh wow, that's cheap. Last multifuel pump I had built was $800.

 

[Swamp Donkey]

He questioned why the military wanted this on there as the fuel solenoid will shut the truck off and only has one failure mode. If it fails, no fuel unless we screw in the solenoid bypass.

I disagree with this part of his statement. While it is designed to fail closed, it can also fail "not as designed" or get hung open. There is a return spring inside that returns the plunger to the closed position after the solenoid disengages or fails. If the spring fails then the plunger won't close. Trash or gunk can also hang the plunger open.

The spring inside mine failed at the beginning of last year. When I switched the truck off it just kept running. I did this multiple times and it never missed a beat. I pulled the wire off the solenoid with no change. I finally pulled the E-stop cable to shut it down. I found my spring was broken and the plunger just moved freely. I replaced the solenoid and all was good again. Without the E-stop cable it would've been far from convenient to stop the engine. This is actually the only time I've used it.

The part about the valve going past center to partially closed is interesting though. I'll have to check that out since I've got a return spring on mine to return it to open after it's been pulled. The spring was added after I used it that time. Don't know if it even works because I haven't used it again. I'll definately check that out though.

 

[sandcobra164]

I'm thinking of adding a butterfly valve to the air intake horn and making that my emergency stop. I have an engineer friend with a shop but that will be a winter project.

 

[Swamp Donkey]

I'm thinking of adding a butterfly valve to the air intake horn and making that my emergency stop. I have an engineer friend with a shop but that will be a winter project.

That sounds like it'll work well. Glad the repair is taking place quickly and that cost was very reasonable. I have a core pump that only cost me pennies, but have held off rebuilding it for now because of the cost. I might have it done sooner than later now so that I'll have a spare.

 

[sandcobra164]

I would, I considered just letting the shop fix what was broken but when looking around after talking to the injection pump guru. The actual technicians are getting quite old. They hire on family to write on the sales ticket and they hire young help to pull the pumps. A commercial shop turned me down. $325 to have it gone through seems like a good investment either way to know I have a rebuilt pump. They quoted me $10 an injector to bench and flow test them. Guess why my truck will be down after the Ga Rally! People like these are fading quickly so we might as well give them one more job. R&S came highly recommended from a close friend who just had his multifuel pump gone through. Looking at it, a C or a D pump but either way, he has pushed all of his work that way for years. If you want to pass off the pump in question, I will get it down there for free. I think I found a good shop and the only thing these pumps have to do is pressurize diesel fuel and keep it out of the crankcase. We'll discuss in detail at the Rally but it'll mostly be me talking like a dumb monkey on the shop floor, cue beer!

 

[wrenchturner6238]

Glad you are getting it fixed up. I am sure the shop will clean up the pump and clean the weep hole in the drive end but it may be a good thing to check. When that seal goes out it should leak the fuel out there instead of getting fuel into the crankcase.

 

[sandcobra164]

The weep hole was unfortunately packed with 30 years worth of crud from an inexperienced owner not even knowing it was there. Some fuel did come out of it though, right onto the oil filter canister. Roughly 7 gallons of diesel found it's way past it though and judging by it's location, a slow leak would go right past the air compressor and right into the front cover anyways. At R & S, the technician showed me a housing from a commercial variant and it's weep hole is more towards the bottom and it has what appears to be a miniature sump built into it. Mine has the weep hole almost centerline with the drive flange.

 

[sandcobra164]

Ok, once again I have overthought the process. Swamp Donkey, we would likely be miles ahead and alot less work involved it we simply inserted a drill bit into the "emergency shutoff" and adjusted the position of the set screw device on the cable. Full fuel would be available and an engine shut off device would still be operational. It would also eliminate the possibility of blowing a pump seal unless it was turned way past stock. It will require removing the fuel line to the cylinder head and searching for the max size rod that can be dropped into the emergency shutoff to find "open". I will post more specifics when my pump is ready for pick up. Hopefully will be back together on Saturday.

 

[Swamp Donkey]

Ok, once again I have overthought the process. Swamp Donkey, we would likely be miles ahead and alot less work involved it we simply inserted a drill bit into the "emergency shutoff" and adjusted the position of the set screw device on the cable. Full fuel would be available and an engine shut off device would still be operational. It would also eliminate the possibility of blowing a pump seal unless it was turned way past stock. It will require removing the fuel line to the cylinder head and searching for the max size rod that can be dropped into the emergency shutoff to find "open". I will post more specifics when my pump is ready for pick up. Hopefully will be back together on Saturday.

I think I might fiddle with it after the rally. It's at the point now where it'll be tough getting parts in time to replace if something doesn't go right. You definately got my curiosity up though.

 

[sandcobra164]

I got a phone call from the injection pump shop. He felt like both seals on the drive flange failed simultaneously. I asked if it was because I had upped the fuel screw and he laughed. He claimed that it still was not to factory specs with my 1/2 a turn. I asked if it had anything due to running a 50/50 mixture of filtered waste transmission fluid and diesel and he remarked that the inside of the pump was as spotless as he's ever seen. No major issues and he claims that I'm going to notice quite a difference once back on the truck power wise. He also raised the governor back to spec of 2100. I'm excited to see how it runs tomorrow.

 

[sandcobra164]

The 5 ton lives! Installed the injection pump, bled the lines and boom, it is back to life! I had a few loose ends to tie up but got called out once again by the National Guard. A few observations though. The truck will hit 2,200 rpm very quickly and sounds stronger than I have ever heard the old 250 rev up. It idles soundly and jumps at any provocation of the throttle. I can't wait to get it all back together as I intended to do today but life happens. The good stuff is that I had the chance to use my new to me M984A4 Wrecker to haul an M1078 LMTV with a M149 water tank hooked behind it. The combo maintained just fine on the hills and I may have actually loaded the Cat C15 enough to seat the rings. A little delay to actual progress but it was fun!!!

 

[74M35A2]

Amazing the difference it makes when fuel is routed to the injectors instead of the oil pan.

Seems you grabbed a really good deal. Is it allowed for you to post the place which did it in case others are interested in having theirs gone through also?