Intermittent fuel leak help

[mattlb7]

Hey guys I am new to the forum and new to owning a diesel. Ive been searching this site and some others for almost a week and cant seem to answer my own question so I figured I would go ahead and ask. I have an 01 LB7 that has an intermittent fuel leak. It only seems to leak after it has sat for an hour or so. It will leak quite a bit then stop. Almost like its building pressure then finally bleeds off somewhere. It starts fine and for the most part runs fine although I did notice yesterday it would miss a little when it shifted gears. The leak is coming from around the back of the motor but I have yet to actually see it drip. Any help would be greatly appreciated.

Matt

 

[Awenta]

Welcome!

Top of the filter head wet? Can you see fuel anywhere? That much fuel shouldn't be hard to find. Try filling the tank with about 10psi of air.

Fuel in the valley?

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[mattlb7]

The filter seems dry and I cant see pooling in the valley either. back of the motor and oil pan are wet though. The fact that I cant see any fuel leaking when its running has me confused big time. I let it run in the driveway for over 30mins yesterday and never saw a drop. shut it off and still nothing. drove to work last night checked it when I got here still nothing. at 5am had a guy come find me said there was a huge puddle under truck but when I crawled under it I couldn't find any active drips.

 

[S Phinney]

Is it a clear fluid or dark fluid? What's your oil pressure like?

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[mattlb7]

Oil pressure is a little low but has been since I bought the truck a few months (Looking to replace sending unit and see if that helps) It has a definite diesel smell and is dark but not black. Oil on dip stick doesn't smell like diesel and is pretty clear still. Truck has 193000 miles on it and injectors were replaced at 100000 miles

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[motoking_1990]

The oil is clear? Are you sure it's not making oil? Have you tried the napkin? You put a drop of oil on a paper towel or napkin and if it is black with a clear circle around the drop. If it does you have an injector leaking. But like mentioned before that much fuel shouldn't be hard to find. Do you have any idea which side of the engine it's coming from? Which side is the fuel pooling up on the ground?

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[fastpunker]

The fact that it does it when the truck is off and not on leads me to believe its fuel line from the tank to the filter leaking somewhere. I wonder if there is an O-ring or something of the sorts that swells with the heat when the truck is running causing it to expand and seal and when the truck finally cools off the O-ring shrinks allowing the fuel to pass and leak. Maybe the 1/2" feed or 3/8" return line fittings on the driver side back of the motor?

When was the last time the fuel filter was changed?
I'm also trying to think of areas of pressure increase and drop... are you running a lift pump at all?

 

[mattlb7]

No lift pump and filter was changed around 2000 miles ago. Appreciate all the help.

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[mattlb7]

The oil is clear? Are you sure it's not making oil? Have you tried the napkin? You put a drop of oil on a paper towel or napkin and if it is black with a clear circle around the drop. If it does you have an injector leaking. But like mentioned before that much fuel shouldn't be hard to find. Do you have any idea which side of the engine it's coming from? Which side is the fuel pooling up on the ground?

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It's not clear but it's not black. I have not tried the napkin test but I will as soon as I get home. The pooling seems to be more on the driver side. Thanks again

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[fastpunker]

It's not clear but it's not black. I have not tried the napkin test but I will as soon as I get home. The pooling seems to be more on the driver side. Thanks again

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If you could grab some pics of where you are seeing it on the back of the motor and oil pan that would be helpful... would give us better insight of what you are seeing

glad we can offer some help

 

[mattlb7]

If you could grab some pics of where you are seeing it on the back of the motor and oil pan that would be helpful... would give us better insight of what you are seeing

glad we can offer some help

I'll try and get some if I can get it to show up.

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[mattlb7]

Ok had a buddy that's mechanic come look at the truck. There is definitely fuel in the oil. Does this mean for sure I need new injectors? Still haven't figured where the external leak is tho

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[fastpunker]

Sorry to tell you, but yes most likely it does mean new injectors. The lb7s generally eat injectors every 100k. Have someone that has a Tech-II, Snap-on Solas, or EFILive check the balance rates. The rates should be around 0.0 and the tolerance from gm is +/-4. but a bad injector will not always be near or over 4 though.

I feel your pain. I bought my truck with 196k on it, checked the rates at the dealership and they were almost all 0's (perfect). 9 days, not even 300 miles, later one or more of them blew up and I was billowing white smoke out the tailpipe. I don't wish that kind of bad luck on anybody.

You might luck out and have one of the high pressure lines leaking and might just need to be snugged down.... depending on where it is leaking, it could be leaking into the oil and onto the ground. Keep my fingers crossed for ya.

 

[mattlb7]

Sorry to tell you, but yes most likely it does mean new injectors. The lb7s generally eat injectors every 100k. Have someone that has a Tech-II, Snap-on Solas, or EFILive check the balance rates. The rates should be around 0.0 and the tolerance from gm is +/-4. but a bad injector will not always be near or over 4 though.

I feel your pain. I bought my truck with 196k on it, checked the rates at the dealership and they were almost all 0's (perfect). 9 days, not even 300 miles, later one or more of them blew up and I was billowing white smoke out the tailpipe. I don't wish that kind of bad luck on anybody.

You might luck out and have one of the high pressure lines leaking and might just need to be snugged down.... depending on where it is leaking, it could be leaking into the oil and onto the ground. Keep my fingers crossed for ya.

Appreciate it. Rates are all showing good but when we drained the oil it was super thin and drained almost 7 gallons out of it. Also not showing any signs of white smoke.

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[fastpunker]

It does sound and look like injectors... 7 gallons?!? holy crap! The balance rates don't always show bad injectors. When mine blew up I checked them again and they were between O and 2.5, nothing higher.

Look around on here for the best place to get replacement injectors, make sure they are actual Bosch ones. Best of luck to ya. :thumb:

 

[Awenta]

Dead 0.0 isn't a good balance rate.

Could be a leaking return line but it's probably a cracked body. Pull vacuum on the return line at the head.

LDS for replacements.

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[TheBac]

LDS - Lincoln Diesel Specialties (if you didnt know that)

7 gallons. *whistling* Guess you found your "leak"? Im surprised oil/fuel wasnt oozing out of every possible crack and crevice.

 

[motoking_1990]

Ok had a buddy that's mechanic come look at the truck. There is definitely fuel in the oil. Does this mean for sure I need new injectors? Still haven't figured where the external leak is tho

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I had a feeling when you said it was clear something had to be up. I could change my oil and drive 10 miles and change it again and it would be pure black. But 7 gallons though. Woah! Like said above it is probably a cracked body more than likely.

There are many places to get injectors. Exergy being probably the most reputable all depending what you want to pay and the plans for the truck. You get that you pay for.

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[mattlb7]

Yea we figured that with that much in the system it was poring out the oil separator in the pcv line after it set. That's why I couldn't find an active leak. One good thing is my oil pressure is back to normal after we changed it lol. Appreciate all the help guys. Going to take it easy until I can get the money for injectors.

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[mattlb7]

One more question guys. Do I really need the injector removal kit in order to replace the injectors?

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