Replacing a Fuel Line

[Rod Ogle]

The fuel line on our 2004 Patriot Thunder, 505 C12, running from the primary filter to the engine (transfer pump?) is showing some cracking and checking.   There are no signs of leakage yet but I want to avoid being stranded along the road with diesel fuel leaking all over the place.   Can one of you tell me if removing the line will start a siphoning action?  If so, how can I avoid significant fuel loss?

[Bill Borden]

Hi Rod,

I had the same fuel line concern, I took my fuel line section off and down to fuel line, Hydraulic and fitting company.  They made me a new fuel line to higher specs than original, I asked for higher heat resistance and burst pressure.  It installed without a problem.

No problem on the fuel draining or anything like that.

The name of the company was Pirtex, Fluid Transfer Solutions.  I believe this is a national chain and this one is a local distributor in the Sacramento area.

Good Luck,

Bill

[Dave Atherton]

Rod , there will be no problem there.make sure to cover both openings. also making up new fuel hose
before putting on i would make sure inside of hose is clean. ran into a problem like this where tech
was in a hurry and installed hose full of contaminates ( just a suggestion that will save you some
problems after new hose is installed.) Dave Atherton Retired Cat Mechanic

[Rod Ogle]

Thanks Bill and Dave for your input.  It is good to know that I will not have all 150 gallons of diesel on my shop floor!!  When fixing a leaky fuel supply line to my generator I was surprised to see the fuel just keep on coming. I spilled a lot of fuel before getting a pair of vise grips on the line

Also a good suggestion to make sure the new hose is clean and clear of any junk.  I would have not thought of that.

[Edward Buker]

Rod,

When you get the old one off I would be curious to know the construction of that hose. I thought what was on the surface that is cracking was a rubber hose cover layer, possibly followed by a braided metal or a synthetic braided layer, and then an inner rubber core hose that carried the fuel. That may be wishful thinking on my part.

You could clue us in by cutting your old one once it is off and let us know if the cracking material is actually the single hose material that is carrying the fuel or if there is more layers to this or not.

Later Ed

[Dave Atherton]

Ed , ask question I thought the fuel lines have been in most cases plastic for electrontic engines. I
used to see the fabric covered rubber line but before the newer engine came into play. The same when
Cat used a nylon braid plastic lines for hydraulic pilot controllers ( reason inside of line would not
break down ). been around severl 04,05 motorhomes fuel problems and line from fuel tank to engine
has been plastic with Cat engines. Dave Atherton Retired Cat Mechanic

[Edward Buker]

Dave,

If you open the rear engine hatch (C12 engine) and look down towards the right there is a rather large diameter hose for a fuel line that goes into what looks like a fuel pump. The outer portion apparently is prone to cracking, mine looks that way and others are having the same issue. Because of the diameter I was thinking this was an outer cover shield type arrangement that was cracking and that there were layers involved in the fuel line construction but I do not know. Trying to sort out if this is a blemish in an outer layer or a defect we need to change out that can go through to the fuel side of things, if this is a single layer of hose material. Really not sure. There has been no talk about changing a leaking one, nor do we want to wait for that.

Later Ed

[Dave Atherton]

Ed, looking back on fuel lines with KC post thinking the setup from fuel tank up front to his primary filter than is replaceing fuel line to fuel suction side of  transfer pump are all suction lines and there in no pressure involved . At Branson I'm going show what has been found in fuel related problems, now age and miles have
started showing up. Keeping a problem part is worth a thousand words for what is ahead for many motorhome owners. I have found MFG. has not put alot of thought into system other than cutting cost.
my Monaco motorhome bought new 2001 ISC cummins had the fabric covered rubber fuel lines with reuseable fuel connections with JIC fitting ends. After 12 1/2 years same as KC outside started cracking.
This is a very good subject to many problems we are having with motorhomes today. ( what is the condition of
your fuel lines )  Dave Atherton Retired Cat Mechanic

[Rod Ogle]

Ed.

   I got the new fuel line installed today.  The company that made up the new line checked out the old hose and told me the construction was two (2) outer layers of rubber over one (1) layer of braided metal which protects the one (1) inner layer of rubber which carries the fuel.  The old hose was rated for max pressure of 2325 PSI.

   The chances of the fuel line actually braking are small.  However, I bent the old hose near the cracked area and I could see the braided metal.  I did not cut the old hose open to inspect the inner portion of the line.   The new fuel line is of similar construction but rated for max pressure of 4250 PSI which is overkill IMHO.

  I had to replace a fuel filler hose in our coach that connects the fuel tank to the filler neck.  Age and constant contact with diesel took its toll on that line, rotting the rubber.   I assume the line I replaced today would eventually become a problem for the same reason in spite of the multiple layer construction.

 BTW removing the old line was simple, finding enough clearance for the proper wrench was the biggest challenge.  I only lost about one pint of fuel, of course it missed the bucket I placed beneath.   Cost of the replacement line was $52.00 and took less than 5 minutes to make.

[Edward Buker]

Rod,

Thank you a lot for following up on this request. It is good to know that the cracking that we see is an outer sheath of rubber and that there is more redundant layers involved in that section of fuel line. That being said it is hard to trust the construction when the outer layer gets ugly. I will keep my eye on all of these fuel lines.

Thanks Ed

[David T. Richelderfer]

So the risk in a cracked fuel line is 1) a small diesel leak when the coach's engine is not running, and 2) getting air drawn into the line when the coach's engine is running (due to suction as Mr. Atherton pointed out).  In either case, the owner has a problem.

[Dave Atherton]

David, answering low power request and working hands on with some motorhome owners Ed has
started a very good talk Fuel lines and problems starting to pop up with age and miles. I did answer
thoughts about plastic lines seems to be the trend on some motorhome. What you talked about with fuel
hose is a 2 ply hydraulic hose working pressure around 2300 psi. this is real over kill when this fuel
hose is on the suction side of fuel transfer pump. there are going to be , I can see two problems happening.
first hose getting hard and brittle and cracking inside( Air )  Second as the rubber breaks down with heat and
age now we are going to get flaking of rubber inside hose into the fuel system, ( which means going
through fuel system complete. ) I have mentioned many times most all problems with diesel engines
come back to fuel system. One of the main causes of low power.Dave Atherton Retired Cat Mechanic