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8V71 - Diesel in the oil...

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2 months 2 days ago #251270 by prodrive
Righto brainy people, we need your ever lovin help...
Old Red Ken, thats the 1966 Cabover Kenworth with the 8V71 in it.
It's done about 2000 k's since it was rebuilt, not to mention a gazillion hours spent TRYING to fix oil leaks. (Still leaking out of the rear main, the bloody thing) 
Anyway.. Runs beautifully, starts perfectly, doesn't smoke, sounds sweet.
I check the oil often, and it looks clean as a whistle, with me thinking "gee what a good rebuild, not even really black yet" .
But I pulled out the big tub underneath that catches the leak from the rear main, and man, it was runnier than... than...I dunno, but runny.
Upon inspection, its bloody damn near diesel, not oil. So.. that's why the dipstick looked so clean...
So we've drained the oil, sure enough, it was just like black diesel, oily, but no where near the viscosity or the "feel" that it should be. So it's obviously getting fuel in the oil. It even had a bit of "clear" run out at the very end of the diesel, alongside the black watery stuff that was supposed to be oil, but looked and felt more like black diesel.. 

Here's where it gets tricky-
1) The dipstick was not overfull, so therefore the amount of diesel getting in the oil must be damn near equivalent  to the amount of oil being burned. Strange, but not unthinkable. with a pretty new motor that still may be bedding in?? (doubtful, it's done s few miles here and there).
2) The obvious fault, according to a few smart people, and the interweb, is the injector pipes in the head. So we have pressurised the system to approx 50 lb., in the return and the pickup. No sign of any leak, at any end of any injector line. 
3) Then we've ran the engine with the rocker covers off, just in case we are missing the air leak. Nothing. All ends of the lines look dry and perfect, except where the jakes are dribbling oil on to the top of one of them so it's hard to see- but still looks good.
4) Pulled the injector pipes off. They all look good, no cracks, tiny bit of a "burr" on some of the flares, but nothing more than you would expect. 
5) No sign of any "washing" from diesel anywhere, although the heads are very clean as they are so new. So that is hard to see anything, but certainly nothing sticks out as obvious. (one head was new, one was reco)  
6) The service manual tells us that if the injectors are not seated properly on the inside on their "check" valves, diesel can force its way up and back along the pushrod that turns the rack, that adjusts the throttle setting for the injector. But they look very normal, once again, no sign of washing or clean bits where diesel is coming out backwards etc.  
7) The diesel injection fellow in Geelong tells us that he thinks it's unlikely that they are leaking there, he has no way of checking them, he'd just have to do them all up, which is bloody expensive and he's damn busy so... ....Not ideal, as we will not know if we have fixed anything, or just spent money needlessly.
8) Cutting edges have them C/O, total cost $3300, plus core charge.. Same issue as above.   

Has anyone ever heard of the fuel pump leaking back along it's shaft? It seems highly unlikely, from what we can find out. Also the dribble hole is dry, so it makes us think it's very doubtful. 

So I'm a bit stumped, and if anyone has any experience with this, please let me know! We are just not sure which was to go next, short of throwing injector pipes, injectors, and a fuel pump at it- and not even able to know whether we are wasting our time and money or not..
Hope someone may know or be able to suggest something,
Cheers
Rich


 


         
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2 months 2 days ago - 2 months 2 days ago #251271 by Lang
Replied by Lang on topic 8V71 - Diesel in the oil...
Rich from other people with the same problem


Dye looks the go! See video.

1.  Your problem is going to be an injector(s) or injector O-rings. Fuel can leak out of the solenoid of the injector into the oil, or the injector o-rings can leak into the oil also.19 Oct 2012

2. 
If I had that problem I thank I would start by putting dye in the fuel, probably in a 5 gallon bucket to fuel filter supply. That way I would not have to buy excessive dye. Have the valve cover just sitting on the head and idle the engine about five minutes and shut it off. Pull the cover and look for dye, use a black light if none is seen. A bad injector I would thank. I do not know about plugs in the fuel galley, under the valve cover, on 60's but I had one leak out the back of an 8V92 about 2 years after an inframe. 12? hours labor to tighten a plug.

3.The injector tube and o-ring seal coolant, not fuel. Fuel leaks are usually traced to the 2 fuel tower washers, or the 2 fuel lines connecting the fuel towers to the injectors. 2 each per injector. Check also fuel transfer pump.

4.I think I have pinpointed the leaks using a modified stethscope.I capped off the fuel return line and applied air pressure to the fuel line after disconnecting it from the filter. You can hear the air leaks.

5.Old timer taught me cotton buds whilst running for chasing fuel weeps, on a Detroit has yet to fail me.

6.I had a leak in the side of an injector. I found it by blocking the return and pressurizing the supply inlet. The fuel runs at about 60 psi, so I used 90 to make sure. The leak will be evident as a fuel "Fog" will show up. It will be either from the injector or the supply/return lines. Very rarely will it be the head (cracked) and certainly not the injector tube.

7.
Last edit: 2 months 2 days ago by Lang.
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  • Swishy
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  • If U don't like my Driving .... well then get off the footpath ...... LOL
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2 months 2 days ago - 2 months 2 days ago #251273 by Swishy
Replied by Swishy on topic 8V71 - Diesel in the oil...
RichMan
gudday m8
we had a KW 'S' model with a 6v-71 (238 HP)
it developed a simular problem
under the rocker covers everthing was spotlessly clean ,,,,, normally black oily mess
we ran the motor with out the covers on ..   and we noticed one of the injector tubes was loose
we nipt it up =  all ovr red rover
LOL

keep in mind 
each injector is its own fuel pump with huge pressure being squirted in to burn
there is a fuel scavange pump th@ supplies low pressure of fuel to the injectors
inector tubes can develop a split that might not be noticeable 
injectors and tubes need to be tightrnd to a torque wrench number ( not sure of the numbers)
Cya

OF ALL THE THINGS EYE MISS ................. EYE MISS MY MIND THE MOST

There's more WORTH in KENWORTH
Last edit: 2 months 2 days ago by Swishy.
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2 months 2 days ago - 2 months 2 days ago #251274 by jon_d
Replied by jon_d on topic 8V71 - Diesel in the oil...
Not sure if this is relavant or not.....

On Isuzu's the lift pump is driven off a lobe on the cam.   They can leak diesel into the block if the sealing O ring fails.

Further to this,  this link shows the Detroit lift pump. You could have a worn seal or shaft.
h-t-t-p-s-://dieselpro.com/detroit-diesel-fuel-pumps/8v71-fuel-pumps/detroit-diesel-5195078-fuel-pump-repair-kit.html
Last edit: 2 months 2 days ago by jon_d.
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2 months 2 days ago #251275 by mammoth
Replied by mammoth on topic 8V71 - Diesel in the oil...
Don't know anything about Detroits however had a problem with an International tractor with a rotary injector pump which was lubricated from the engine oil system. The fuel lift pump was driven by an extension of the injector pump shaft with just a 20 cent oil seal separating the two systems. So with a worn seal running on a warn shaft fuel was being pushed into the sump of the injector pump and thence to the engine. No leaks evident anywhere unless you had a hunch to disassemble and an eye for lazy design.
Engine sump was so full that I was leaving a trail when going up hill.
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2 months 2 days ago - 2 months 2 days ago #251276 by 180wannabe
Rather than just looking for signs of a leak under pressure, maybe try pressurising the fuel system, and see if it will actually hold pressure?, perhaps proving if there is actually a leak or not, and narrowing it down from there.  Maybe even take the pump off, and pressurise it in a tin of diesel, and look for bubbles past the seals.

And although the dribble hole in the pump is dry, is the hole actually clear/open to atmosphere?, and not giving a false indication.
Last edit: 2 months 2 days ago by 180wannabe. Reason: alter wording
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2 months 2 days ago #251278 by JOHN.K.
Replied by JOHN.K. on topic 8V71 - Diesel in the oil...
Split jumper lines have been eliminated ..........the fuel pump is on the blower,and they are pretty reliable .......and very easy to change over......all the easy to find causes are eliminated ,say the OP.........i have a set of new injectors Im saving for a rainy day...N65 or N70 dont remember .
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2 months 2 days ago #251280 by roKWiz
Replied by roKWiz on topic 8V71 - Diesel in the oil...
From the 8 71 shop manual regarding the fuel pump and seals.

 

Heritage Stonemason
In order that the labour of centuries past may not be in vain during the centuries to come... D. Did
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2 months 2 days ago #251281 by prodrive
Thanks Lang,
That dye looks like a damn good idea, I'm going to get some i reckon...Cant see any 'fogging: or anything else that would help in any way.

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2 months 2 days ago #251282 by prodrive
Swisho,
"we ran the motor with out the covers on .. and we noticed one of the injector tubes was loose
we nipt it up = all ovr red rover"

do you mean the injector TUBE of the injector? Or the injector pipes, one of the crossover pipes that feed from the head to the injector and return?
Everything like that LOOKS good, just like you'd expect it to- that's what so hard about the bloody thing...

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