Fuel line leak

[Adam Hicklin]

I have a small drip from the fuel line (in photo of tank fittings, the middle line with the compression fitting). There is about 12 inches of exposed line from the fitting to where it disappears in to the frame rail.  I’m assuming this is the supply line.  The leak is right where it was tied with a tie wrap.  Several questions here:  if possible, can that line be cut and repaired with a barbed coupling? (That’s how I repaired the return line leak in the same spot) Is it under pressure? If it can’t be spliced, I guess I would have to run a new line externally.  Any thoughts on that?  Does it go straight to the primary filter? Regardless of how it’s fixed, it will need to be purged of air, correct? (That will be another discussion!) Last question, What it the bigger hose with the pipe fitting? A vent maybe?

Thanks in advance.

[Lee Welbanks]

That fuel supply line is a flare fitting and it looks a lot like a Aeroquip reusable hose fitting. It can be removed from the hose and re-installed. Look up Aeroquip hose fittings and how they are assembled. This is the suction fuel line to your motor in the rear and it will not have any pressure in it but fuel will drain back out once disconnected. Once the hose is repaired the Cat mechanical lift pump will suck fuel all the way to your water separator. Your motor should fire right up as the fuel filters will still be full of fuel.

[Dave Atherton]

Adam and Lee, I do not think that looks like a fuel line to engine. We did have some problems with a fuel line about 5 feet long from primary fuel filter to the fuel transfer pump that was a Gates Hydraulic
Hose that had leaking issues. If perhaps this is the hose in question replacement hose should be
ID hose .500 with one end 1/2 JIC female on end and a 5/8 female on the other end of  5 foot hose.
Dave Atherton Retired Cat Mechanic

[Fred Brooks]

   Adam, Here is a pic of the hose Dave is referring to. I would NOT have looked for this hose, but Dave alerted us who have this configuration of the pending failure. As you can see, mine was leaking! It is the 5 foot hose from the output of the primary fuel filter to the fuel pump on the front lower corner of the C-12 engine. Not sure what hose is leaking on your coach. Perhaps you can remove and splice a repair? Fred

[Fred Brooks]

   Adam, I did something wrong with the photo, so I will try again. Fred

[Adam Hicklin]

Thanks guys.  Yes, I’ve read about the line from the primary filter to the transfer pump.  That’s on my list to change.  The line I’m referring to connects to the tank outlet at front of coach and runs down the frame rail to the back.  I’m assuming this is the supply line to the primary filter,  I know the smaller line in my picture is the return line to the tank.  I don’t know what the bigger line is with the pipe fitting.  I’m guessing that is the vent line. 

My leak is in that middle line (supply/suction?) about 8 inches from the fitting, before it disappears in to the frame rail.  My question is, can I cut out the pinhole leak and join the two ends with a barbed coupling connector and hose clamps?  If this is the supply line, would it be 1/2” ID?  Them if that is the fix, would I just be able to start the engine and it will bleed off the air in the line by itself, or will there be a procedure for that. 

As an aside, my primary filter does not have any black particles in the sight tube so I’m assuming the integrity of the hose is intact, at least for now.  I may change over to the CAT primary filter set up at the same time, but I need to make sure I solve one problem at a time, as not to confuse the issues. 

Thank you. 

[Dave Atherton]

Adam, you cannot splice the suction hose from fuel tank to primary fuel , the suction hose in
Question is hydraulic hose with steel braids, note a regular rubber hose would restrict fuel flow.
The hydraulic hose we are talking about is on the discharge side of primary fuel filter to suction
Side of fuel transfer pump which is a gear pump and hydraulic hose inside break down would go
I think the secondary fuel 1R-0749 and into fuel manifold on C-12 engine. Dave Atherton Retired
Cat Mechanic

[Lee Welbanks]

Adam, Almost any of these hoses can be spliced you just have to find out what kind of fittings to do it with. That hose end looks a lot like a Aeroquip reusable hose fitting. There are all kinds of stuff out there to make up or repair hoses. Once you figure out what the make up of the hose is you can get fittings to repair it. Aeroquip is a good place to start, back in the day trucks used a lot of aeroquip hoses and fittings and I've done tons of them. There are many others besides Aeroquip just do some searching.

http://aeroquipperformance.com/

[Dave Atherton]

Adam and Lee , the hose in question is the middle hose in the picture. If that is correct of which
It should be is a 2 ply hydraulic hose with a JIC female fitting that is machine crimp to hydraulic
hose. Have found many on Monaco and beaver motorhomes. The mfg name on hydraulic hose is
Gates. Yes there is a hydraulic fitting that will thread into splice is there is room to work. What
Problem that has happened is condition of the inside rubber liner, If connection will not leak.
The reason when ieaking has occurred to outside has indicated inner rubber liner is end of its
life and rubber liner is cracking and hydraulic hose is hard and stiff. Again several hydraulic fuel lines
between the primary fuel filter and fuel transfer pump has shown area of failure. Also if this
mfg brand Gates, follow up on information printed in white on hydraulic hose is not rated for BIO
Fuel . I have several pictures with camera of inside liner missing and person can see the Steel
Braids instead of rubber liner.  Dave Atherton Retired Cat Mechanic

[Adam Hicklin]

So Dave, you would suggest replacing the entire line from the fuel tank to the primary filter?  Are we all in agreement this is the suction line?  I don’t see any other hoses coming off the tank, but that doesn’t necessarily mean there aren’t any.  Could the suction line come from the top of the tank?  I can’t see any marking on the hose as to the brand, but I have no trace of the black particles in the primary filter sight glass, like the pictures Fred B has shown.  As I see it all those particles came from the line between the tank and the primary, not from the hose from primary to fuel transfer pump.  Would that be correct?  Lee, if I had the room to work, would one of those Aeroquip couplings work on this line?  Dave, what do you think?  Any idea what size the line is?  Would it be 1/2 inch ID?

[Dave Atherton]

Adam, yes that is a 1/2 inch line. The one in the middle will look same at primary fuel filter
inlet. Have one question where can I see the leak as per photo. The reason mfg used hydraulic hose versus regular rubber hose the hydraulic hose will kink. If there is no room to install non-crimp
JIC fittings because you will need two hands and two wrenches to install into the 2 ply steel braided
hydraulic hose. These non- crimp fittings work good except in steel braided hyd hose which can
be very interesting to install. Here is my suggestion, make sure that you have a fuel leak coming
from primary fuel filter. That can be hard starting because fuel drain back to tank from primary
fuel filter. Has the hose started leaking in bracket or just leaking with nothing around hose. What
that will tell you condition of hydraulic hose if it is wet and see fuel drops on outside of hose.
With that will tell you condition of hydraulic hose, replacement or repair. Again if hydraulic hose is wet with diesel fuel and nothing would indicate damage caused from outside to hose, than repair
Is just a running band-aid that will keep moving along hydraulic hose. Last if you feel and
Replacement is required, I would suggest going with 5/8 plastic air line hose along with Brass
air lines fittings. Very large savings of money versus hydraulic hose. The later motorhomes
use 5/8 plastic air line for there fuel system. Dave Atherton Retired Cat Mechanic

[Adam Hicklin]

Thanks Dave. I will try to get a picture of the leak.  It appears to be a pinhole right where there is a plastic tie wrap bundling together some other hoses.  I can see a wear mark where the wrap has indented the fuel line.  It doesn’t appear that the whole section of line is seeping fuel as line break down would indicate. It’s a drip coming from a specific spot.  About a drop every couple minutes. Either way, if it’s repaired or replaced, along with replacing the primary filter outlet line to the transfer pump, is there a procedure to purge the air in the line?  Last question:  should it be driven, for instance, if I just drove it to have it repaired, would it/could it, cause damage?

[Dave Atherton]

Adam, what you are telling there is a little damage to the outer hydraulic hose rubber . Than there is
a small pin drop fuel leak. As I explained your hydraulic hose make up starting from center of hose.
You have a hose within a hose with 2 braids of wire covering the inner hose on the outside. Than
you have a outer rubber hose that is the protection cover. Point to remember as hose over time gets
older the outer takes lot of external wear. The inside rubber hose wrapped in a woven steel  wire outer
cover. As I indicated and you answered what in my above post ( over time inside hose starts cracking )
and than will leak to outside. Reason old age of hose and BIO fuel causing break down of hose. The
answer remember hydraulic hose is under suction which indicate the center of the fuel line has failed
Where it’s dripping on its own without any pressure applied.  Suggestion it will not hurt to keep
running as you indicated just a few drops no stream of diesel fuel coming from hose. In addition
to this statement the fuel transfer pump will over come any diesel loss and not affect engine operations. Just wrap so you do not get big mess. Last at some point would suggest to change out
your fuel line with plastic 5/8 plastic air line and brass air line fittings. Dave Atherton Retired Cat Mechanic

[Dave Atherton]

Adam, sorry forget to answer your question , bleeding air after hose replacement. The bleeding
of air will not be nessary being you are not changing out the secondary 1R-0749 fuel filter. Engine
will start right up.

[Adam Hicklin]

Thanks. After looking at all the options, it looks like I will change the whole line. And while I’m at it, I’ll change over to the CAT primary filter and replace the fuel line between the primary filter and the fuel transfer pump.  Went to CAT today and they were helpful.  I think there is a lot of “Ask Dave” and “Ask the Forum” in my future.  First question: has anyone run a new fuel line from the tank back to the primary filter on a Magnum era coach?  Ideas?