Author Topic: Fuel in Oil  (Read 2649 times)

Offline Fred Mc

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Fuel in Oil
« on: November 10, 2017, 01:07:30 PM »
I have a GMPD4106 with the 8/71 engine and thought I might have fuel in the oil because of the oil appearance so I had an analysis done and my suspicions were confirmed today. The tech said it was 30% contaminated and to change the oil before running it which, of course, I will do.
Where would I start to look for the origin of this problem?

Thanks

Fred

Offline luvrbus

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Re: Fuel in Oil
« Reply #1 on: November 10, 2017, 01:16:33 PM »
Under the valve covers at the fuel jumper line tap each with a wrench if they ring they are good if you get a thud it is broken or loose if you have the non 0-ring flare type fuel lines,if the lines check out it could be a loose fuel stand or a injector   
« Last Edit: November 10, 2017, 02:47:23 PM by luvrbus »
Life is short drink the good wine first

Offline Fred Mc

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Re: Fuel in Oil
« Reply #2 on: November 10, 2017, 01:32:55 PM »
Thanks Clifford.

Fred

Offline chessie4905

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Re: Fuel in Oil
« Reply #3 on: November 10, 2017, 02:25:26 PM »
They say that the oil doesn't puddle up where the line comes out of the nut. Look for difference. Also look for washing of head surface around leak.
GMC h8h 649#028 (4905)
Pennsylvania-central

Offline Fred Mc

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Re: Fuel in Oil
« Reply #4 on: November 28, 2017, 06:18:28 PM »
"if the lines check out it could be a loose fuel stand or a injector   "

What is the fuel stand?

Thx

Offline eagle19952

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Re: Fuel in Oil
« Reply #5 on: November 28, 2017, 08:33:59 PM »
"if the lines check out it could be a loose fuel stand or a injector   "

What is the fuel stand?

Thx

what these are attached to...
Donald PH
1978 Model 05 Eagle w/Torsilastic Suspension,8V71 N, DD, Allison on 24.5's 12kw Kubota.

Offline Fred Mc

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Re: Fuel in Oil
« Reply #6 on: November 28, 2017, 09:49:22 PM »
Thanks

Fred

Offline bevans6

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Re: Fuel in Oil
« Reply #7 on: November 29, 2017, 09:21:11 AM »
Fuel stand is at the back of the head, hex about 2" long, hardened very thin steel washer underneath, should be torqued to 45 ft lbs.  As said, the non-injector end of the fuel pipes connect to them.  My fuel leak was loose fuel stands, when I changed by system over to O-ring fuel pipes (part of installing my jake brakes)  I did them up "tight" with a 3/8 drive socket wrench.  "tight" with such a wrench is not 45 ft lbs by a long shot.  Took a long time to find, and the torque spec is buried in the manual.

Brian
1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Allison MT-647
Tatamagouche, Nova Scotia

Offline buswarrior

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Re: Fuel in Oil
« Reply #8 on: November 30, 2017, 06:51:06 PM »
At Big Transit, the ruthless way was to remove the covers, and then run the engine, watching for fuel washing.

Shut down and watch for more fuel washing.

Of course, having the oil black and dirty really helps...

The diesel will show itself as the thinner/lighter river in the heavier/darker engine oil.

If it is an injector, you're already in there, might as well send 'em all in,
cuz you know what'll happen if you just do one and button it up...

happy coaching!
buswarrior
Frozen North, Greater Toronto Area

Offline Fred Mc

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Re: Fuel in Oil
« Reply #9 on: December 01, 2017, 08:20:16 PM »
I haven't looked into this much other than removing a valve cover to familiarize myself with what I'm looking at in there.
But something occurred to me that might tie in with fuel leaking into the crankcase.

If the bus sits for an extended period of time_(say 3-4 months) the fuel system looses its prime and in order to start it I need to remove the secondary filter(last one the fuel goes through before going into injectors) and fill it full of diesel. It then starts right up.

At any rate could this give me a clue as to what might be leaking. i.e. crossover pipe, or fuel stands or injectors).

Thanks

Fred

Offline lostagain

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Re: Fuel in Oil
« Reply #10 on: December 02, 2017, 06:44:01 AM »
If you loose prime, I think (assume) the fuel just returns to the tank via a leaky check valve. Nothing to do with anything downstream of the secondary filter.

JC
JC
Blackie AB
1977 MC5C, 6V92/HT740

Offline Fred Mc

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Re: Fuel in Oil
« Reply #11 on: December 02, 2017, 09:50:09 AM »
I realize the fule would return to the tank. However I think the reason that would happen is due to an air leak  in the system and was hoping this might help to pinpoint to area of the  leak.

Offline Utahclaimjumper

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Re: Fuel in Oil
« Reply #12 on: December 03, 2017, 07:32:50 PM »
Most busses have metal fuel lines from the tank to the filters,,these lines have a habit of corroding from the inside out to form a leak. All diesel fuel contains some moisture and when sitting for long periods will rust out the lines.>>>Dan
Utclmjmpr 
 EX 4106 (presently SOB)
Cedar City, Ut.
 72 VW Baja towed

Offline Fred Mc

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Re: Fuel in Oil
« Reply #13 on: December 06, 2017, 02:44:26 PM »
I am just getting set up to look for the leak in the fuel system.I plan to use ciompressed air putting it into the fuel system after the fuel filter(disconnect the line from filter and put on an air fitting) and plug the return line to the tank. Escaping air should pinpoint the leak(I hope).I read somewhere NOT to apply more than 10lbs air pressure. What is the danger in applying too much pressure?

Thanks

Fred.

Offline luvrbus

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Re: Fuel in Oil
« Reply #14 on: December 06, 2017, 03:05:23 PM »
On the up stream side from the fuel pump over 10 lbs won't hurt it, the fuel pump is the weak link you can blow a seal with too much pressure,the fuel pump will pump it up to 65 to 70 lbs fwiw 
Life is short drink the good wine first