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  #1  
Old 01-03-2002, 10:23 AM
Dave Larson
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617 Diesel hard fuel line leak

The steel fuel lines on my 79 300SD (617 diesel 3.0L 5cyl.) have decided to begin leaking at the fitting. This began after the onset of our first really cold weather. I have tightened the worst offender (front cylinder) as much as I dare. This lessened the leak somewhat, but fuel still weeps from the area around the tubing where it passes through the fitting nut. All small rubber return hoses have been replaced, you can wipe the injector area clean and see the fuel leak from atop the fitting.

There is another steel line leaking to a lesser extent as well. I understand there is no seal to go bad, these are flare fittings. What can I do? Do these steel lines crack at the flare or something?

Thanks in advance for your help... Dave Larson

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  #2  
Old 01-03-2002, 11:26 AM
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Join Date: Jul 2001
Location: San Antone
Posts: 408
Dave:

It's unusual for the fuel injector lines to leak, esp. (as you point out) they have a special type of fitted surface that is self-sealing and does not require sealing washers. Since the problem first happened when the temp. was low it sounds like they need to be loosened and re-torqued to the correct torque since cold weather causes metal to shrink a bit more than when it is hotter. Unless some ham-fisted jerk over torqued them and damaged the contact surfaces - if this happened (as shown by deformed contact surfaces, ridges in the metal, perhaps even cracks) then the damaged ones will probably need to be replaced (a local junk yard may have them, or M-B & lots of $).

Do you have the special wrench made by Hazet that fits the injector line nut? This tool is a must have to properly loosen/tighten these nuts (its like a flare-nut wrench for brake lines, hydraulic lines, etc. only made to work for this application). I do not believe Fast Lane has tools, but try them first. If Fast Lane can't help then Performance Products sells this tool for $43.50, part no. 58-014.

The nuts are torqued to 18 ft. lbs. or 25 Nm.

If you still have problems the Diesel Forum members have a wealth of knowledge and someone may have experienced this same/similar problem.

Good Luck!
Tom
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America: Land of the Free!

1977 300D: 300,000+ miles

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  #3  
Old 01-03-2002, 11:37 AM
Dave Larson
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If the fitting wasn't over-tightened before I got there, it is now! I tightened it way beyond the spec in lessening the leak. Probably need a new line now, have the part #.

Thanks for the help! Dave Larson
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  #4  
Old 01-03-2002, 12:12 PM
LarryBible
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When loosening and retorquing, go ahead and remove the line and carefully clean all sealing surfaces.

Good luck,
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  #5  
Old 01-03-2002, 02:49 PM
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Join Date: Jan 2001
Location: Santa Clara, CA
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When I first got my second 240, it had a terrible case of bacteria in the fuel, to the point where it was eating through the steel fuel lines and causing leakage. Is your fuel clean and bacteria free? If you are getting black particles in your fuel pre-filter, you may also be infested. Pray that you aren't!
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  #6  
Old 01-03-2002, 07:20 PM
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Dave:

Did I say some "ham fisted jerk" over torqued the fuel injector line!! Of course, I was not referring to you since obviously you were trying to correct someone else's mistake!!

Ron offers some very good info. The dreaded algae/bacteria gremlin can cause all kinds of problems with the fuel system. Usually, the fuel filters catch most/all of the algae before it gets to the more delicate parts of the injection system. But, I have read about some cases where algae ruined other parts beyond the fuel filters. Ron has had an unfortunate personal experience with these gremlins that all of us would like to avoid like the plague!! See the recent post in the Diesel Forum about algae in diesel fuel and the various replies in that post have links to more very good info.

Larry Bible also provided very good advice and finishes off what I should have said - inspect the lines by taking them off (of course that is the only way to see if the ends are deformed, smashed, nicked, cracked, etc.).

Good Luck!
Tom

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America: Land of the Free!

1977 300D: 300,000+ miles

American Honda: Factory Trained Technician & Honor Grad.
Formerly:
Shop Foreman;
Technical Advisor to Am. Honda;
Supervisor of Maintenance largest tree care co. in US for offices in Tex.
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