diesel in crankcase

I was going to go through all the posts but there are 670 or so pages! can someone direct me to posts about DF in the crankcase on a 5 ton with a nhc 250 in it? I can't see how fuel gets past the fuel pump and into the crankcase and am looking for what else to check before delving into it much ...... it's 120 mile round trip to work on it.

One of two ways. Front seals in the pump or injector o-rings. Since the top portion on the injector is return, there is no real pressure there to speak of, but, if the o-rings are all hard, fuel will push up past all of them into the cylinder head and down into the CC. Or a cracked head, from injector bore to the injector hold down bolt....that's 3 ways. Guess I can't count.

Only real way to positively tell is to run it off of a bucket of dyed fuel and hit it with a black light. Anything else is guessing.

I"d suppose, since the engine was running fine before it started burbling diesel all over and that the engine was overhauled maybe a dozen years ago AND that it has no injectors, that they'd of seen the stack smoking like crazy which evidently wasn't the case. I'm still inclined to think the +side of the pump is leaking into the air pump crankcase and thence into the crankcase, a easy diagnosis and a easy fix but it's mid-winter (12 degrees this morning) and 120 mile round trip so i'd like to make this a two stop fix .... one trip to effectively diagnose and remove defective pump if that's the issue and the next trip to purge the fuel lines and change the oil and install pump (if that's the issue!) and have it run enough to insure the engine is solid again. (fingers crossed)
what do you put into diesel to see with black light?

Dye made for oil/fuel,


Keep in mind, you should have the light from the mfgr of the tracer because all are not the same. Example, the UV tracer that Cummins uses will not illuminate with the lights that Snap-On, Mac, Matco, etc sells, it only works with the system supplied from Cummins.

And, a failed top o-ring will not make the engine run bad. Niether will a center one, until it is loaded, then there will be a loss of power. The PT system does not make pressure until higher RPM, it only has flow, so if a center or top o-ring is as hard as a hookers heart, it is possible to pass fuel past the o-rings and out on top of the head. And unlike a Bosch injected system, there is a mess of return fuel all of the time at the injectors.

The pump is the easiest but expensive thing to do, the injector o-rings are the least expensive, but are labor intensive and is a bit technical when it comes to re setting the overhead.

thanks for the input here. I am looking for a tm with a diagram of the fuel pump. The most 'popular' one has omitted the injector/fuel pump but another poster included it. I just have not been able to locate it again, i am in particular interested in the sealing means on the drive shaft to the fuel pump, it seems it may be on the diagram for the air compressor?
If anyone knows where that diagram went to I'd sure appreciate knowing! I seriously do not see much that would stop fuel from entering the air compressor crank case via the idler shaft or the drive shaft to the fuel pump, thx, Jim

I think this is it,


The reason I did not include the pump and injector info is that one cannot just order the parts called out, assemble a pump and injector. It takes calibration stands and some tool to do correctly.

The front cover needs to come off of the pump, drive gear comes off the shaft, drive coupling comes off, shaft and bearing pushes out then the seals can be replaced. It is supposed to be done with an oven so the adhesive on the seals bonds to the housing. When going back together, there is a tool needed to set the governor plunger depth. Can it be done w/o the tools, yes will it be correct, maybe.

Better to take it off and send to a shop. If it is the ULSD causing issues, the shop will handle it with a refresh, and they can bump the fuel too if you like.

page 29 of the manual looks exactly like the pump on this truck. I failed to view the RH side of that engine, nor take a pic of the data plate in the cab or on the engine. It is likely that I will have insufficient info to order parts and will have to make another visit t Refreshed 1987 Jeep Grand Wagoneer 4x4 | Hemmings.com o accomplish that.
thank you for the info you've provided. I now have it downloaded for reference. after I know what i am doing It could be a straight forward repair? stay tuned!!

Nope, page 29 is the gear pump. 26 would be the part of the pump that will let fuel into the CC. See the 2 seals marked #17? Those are the ones that will allow fuel into the oil. See the line that goes through all of those parts? All of that needs to come out to put those two seals in.

See the part marked #29 and all of the parts in front of that? That is the governor assembly. If you do not get that together correctly you can have no throttle or, when you fire it, it will go wide open.

Page 26 is just the gear pump portion of the pump. Pages 24 thru 30 are all the components of the pump. When you remove the pump, DO NOT start at the rear where the fuel goes into the pump and work your way forward....yes, I have seen that done.....The 4, 7/16 bolts that attach the pump to the compressor is where it is removed from the engine, those and the supply line, return line, pump outlet line and FSOV wire need to be removed.

And the manual shut off cable

I do not remember if when I put the original parts manuals up, the ones w/o the F/P and Inj data, I was part of the moderator staff, but, the reason for that being put up like that was so that IF someone just decided to just build a pump or delve into it by using the parts manual, as jimmr is about to do, and IF there were to be an issue that had a not so good outcome, be it property OR , God forbid, a body, there would be nobody pointing their finger at SteelSoldiers or @steelsoldiers himself for having the info posted here that lead to the issue. IMHO, the other manual that was posted by JP, should not be there in it's entirety, the F/P data should be removed/deleted, for just that reason. The injector data is really nothing, if built wrong the engine will just run crappy but a F/P that is set up wrong can go sideways and cause some damage.

In my opinion, leave the F/P to a person or company that does it for a living. I worked for one of those companies and can tell you that there were MANY people that attempted doing their own repairs on PT pumps only to have a catastrophic failure after their "fix". I am gonna say 50% of those "fixes" were under warranty and the reasoning from the customers point of view was that doing a simple repair themselves saved them down time. After they "fixed" the issue they were having and immediately had a failure, the truck would be towed to us, we would tear it down to see what the failure was, locate it then determine why it happened. I was part of those teams as well as "hard to diagnose" issues. After discovering that a F/P mis-repair was the root cause of failure, the customers were usually REALLY mad. Guess their less down time decision wasn't so less down time.

ok Will, I'm glad you're here! I grew up in a shop and though I've done many things I did finally finish with a chiefs oceans unlimited and I know when to stop, You've convinced me i'll just buy a reconditioned unit to bolt on if steel soldiers has them, I've yet to call them. I never took a pic of that truck and had a hard time visualizing it from the diagrams as a whole. and of course printing, it'd print 5 pages ahead and with the kat attacking the printer I am lucky I finally have it all. I am not sure i have all the info they require but i guess i'll just call and see what they need before I order this. If they don't have dx (direct exchange) rebuilt units maybe they have ideas.
thanks again all, Steel Soldiers is definatly a resource I shall be sticking with and as a USA retiree I'm glad to be here.

Fuel in oil trivia. Worked on ships for decades. Fuel in oil is/was a big deal. Simple precautions taken. On "generator sized" diesels, broken, cracked, and leaking fuel lines constant issue. Many of the diesels had separate oil system for "rocker box" vs main sump. Main oil filtered and purified. Smaller top-sump got lots of crud and diesel- basically a "just change it out" thing. Unburnt fuel can and will get past rings. Did simple viscosity test, sometimes daily. Ramp type "slide board" thing. 1 side gets virgin oil, other side from sump. Tilt it up and "flow race is on"- thru an orifice. If in use oil out flowed virgin by too much it was considered to thin- full of fuel, and correction pursued. Just trivia for your amusement. If your truck is "new too you" , consider last broe head could have cranked it to near death, washing out cylinders. Keep It Simple- good luck.

WillWagner said:

One of two ways. Front seals in the pump or injector o-rings.. Or a cracked head, from injector bore to the injector hold down bolt....that's 3 ways. .

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I didn't expect the spanish inquisition (let's see how many have seen the skit)

ok, i guess i'm on the way to diagnosing. I'm visiting that truck today to take photos and see why the owner is convinced it's the FO pump. If/when I get it running it looks like i'll be watching the haps under the valve covers closely! stby for pics in a couple days.

thanks for all the help and ideas so far folks. On my last visit the owner wasn't there but his son who was heading out to feed found me in the ''yard'' and wondered who i was, what i was doing etc. kinda amusing of course. i took some photos and am now using a new computer and will have to learn new dog tricks to show photos. eric p51, yes, sounds like you worked more than row boats!, i did matson, msc, chevron, ready reserve things but eventually finished up retired from NOAA early (heart issue) . .... best job i ever had and many success stories.

Small world . Sorry to hear of your ticker- take care! May have earned tattoos . AMO. USNR reserve, MSC, Maersk, US Steal, ARC, Crolley, OTHERS. Paid alimony. Actually old enough to sail a bit on my Cheif's Steam ticket. Retired 10 yrs. Best luck.

STEAM?!! the Chevron Mississippi was steam, I was a JR. Eng back then, sailed as pumpman, good food but nervewracking loading the first time in Valdez where I had too much list! I worked commo in army but one 2 week ''vacation'' summer camp i fixed a water maker on the big LCT and the warrants wanted me so i xferred to the ships (Tacoma). I understand they've gotten rid of the ships now and went all in with connex operations ............ I doubt that'll work well in bad climates. The ships had EVERYTHING, dynamotors, sheer shop, casting shop, they could build anything and the spare iron they hauled around would be the envy of any manufacturer.

msgjd said:

I didn't expect the spanish inquisition (let's see how many have seen the skit)

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Nobody expects the Spanish Inquisition...yup, dating myself again.

Wreckclues said:

Nobody expects the Spanish Inquisition...yup, dating myself again.

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jimmr said:

STEAM?!! the Chevron Mississippi was steam, I was a JR. Eng back then, sailed as pumpman, good food but nervewracking loading the first time in Valdez where I had too much list! I worked commo in army but one 2 week ''vacation'' summer camp i fixed a water maker on the big LCT and the warrants wanted me so i xferred to the ships (Tacoma). I understand they've gotten rid of the ships now and went all in with connex operations ............ I doubt that'll work well in bad climates. The ships had EVERYTHING, dynamotors, sheer shop, casting shop, they could build anything and the spare iron they hauled around would be the envy of any manufacturer.

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Yup- Steam. Graduated US Merchant Marine Academy in 1992. Cadet sailed Howell and Almeria Lykes- 900#, 24,000 shaft horse power off of 1 boiler, each. (were APL previously) Sailed on License USNS Comfort (600#) and on Great Lakes more than a bit where the "gentle " 450# plants don't Rust away- real time capsules. Ironically, one of my last deep Sea jobs was bringing back shot up "Steel Soldiers" from the Persian Gulf. MWraps, 5 tons, misc. and a tank or 2. Was Second Assistant Engineer so I had to climb over them for my weekly Fuel Soundings. M/V Honor-ARC company, Ro-Ro Type. Had long legs- wert pretty much round the world before I fueled her a Million Gal. at Gibraltar. #320 black oil- not much better than the "C" on the Steamers, Except Suzler Diesel 7 Cyl. . 120 mm bore, 30,000 Shaft Hp , more or less, if memory serves. I do miss the Machine Shops- and the Over Time with the big DC welders and racks of 6011 rod in up to 50# cans. What the Slugging Wrenches can't remove the torch would, right? Great respect for the Navy Machinists, Hull Teck welders, and Boiler Tecks. Hope I didn't offend- High Jack your Post-Thread too much. I don't reminisce much anymore. 8.3 Cummings did show up as emergency generators. Tunned at 200KW capacity- again if memory serves.

I think you've probably spent more time on big iron that I have. Always had respect for school education, I hawespiped it. I think the biggest generators I worked were about 850kw. except for some RR fleet gas turbine and chevron i was all electric.
here's a couple pics of my issue. Steel soldiers lists pumps for M813 and several similar followers but not the 812 but I'll have to call them monday if they're open.

jimmr said:

I think you've probably spent more time on big iron that I have. Always had respect for school education, I hawespiped it. I think the biggest generators I worked were about 850kw. except for some RR fleet gas turbine and chevron i was all electric.
here's a couple pics of my issue. Steel soldiers lists pumps for M813 and several similar followers but not the 812 but I'll have to call them monday if they're open.

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They are the same. NHC250. The pumps can look a bit different, depending on the pump body used, but the calibrations are the same, even up into the 900 series with the NHC. They are bolt on.