Fuel line leak

[Adam Hicklin]

Here come the questions:  has anyone replaced the fuel line from the tank to the primary fuel filter?  There’s no way to remove the old line and run the new line through the frame rail.  It will need to be re-routed and it looks like I can route it fairly protected (behind slide, etc.) for most of the distance.  There is about 6 feet that will need to drop down and be run along the bottom of the coach, exposed to the road.  I can’t see any way around it.  Any suggestions?  Question 2:  went to CAT and they suggested using a CAT rubber, heat resistant fuel line.  Does that sound correct?  The line in use now is a hydraulic line.  Dave A. Suggested an air line.  Thoughts?  Question 3:  is it worth the trouble changing over to the CAT primary filter set up?  It’s much larger and will take significant modification in my fuel bay, if it can even be done.  My current Racor set up works fine.  Not sucking air.  Sight glass and screen seem to be in good condition.  Thoughts? Thanks in advance for the input.  I’m flying blind here but excited to get this behind me. 

[Gerald Farris]

Adam,
When it comes to routing a fuel line, you should be able to route the hose through the basement along the outside of the frame, and above your holding tanks. This would get you into the engine compartment where you could terminate at the primary fuel filter. However, if your fuel hose is in good condition other than the end connection, I would investigate the possibility of splicing a short section onto the end instead of replacing the entire line. There are hydraulic hose connectors available to repair a line that if installed properly, will not leak fuel out at the connection or air into the fuel stream.

One of the issues in the use of hydraulic hose for a fuel line is that a few of the applications, after many years of use have experienced a failure of the rubber lining in the hose (probably a reaction to the diesel fuel) resulting in rubber pieces in the fuel stream. If this happens in your case, the rubber pieces will be very obvious in the primary fuel filter prescreen sight glass. The biggest problem with getting these rubber pieces in the fuel stream is if it happens after the primary filter and clogs the engine fuel transfer pump that is located before the secondary filter.

When it comes to the Racor primary fuel filter, that has been discussed in depth on the forum. So do a search on it and read the numerous opinions that were previously expressed. 

Gerald

[Adam Hicklin]

Thanks Gerald.  I’ve been waiting for your opinion!  I do not have any indication in the pre-screen sight glass that my hose is deteriorating.  I heard different opinions in this thread about the possibility of repair.  It’s my understanding that this is just a suction line.  It holds no pressure, correct?  I may just try a repair first. It’s very tight, but maybe worth a try.  What’s the easiest way to cut a hydraulic line?

[Gerald Farris]

Adam,
Yes, the fuel line from the tank to the engine, including the primary filter, is a suction hose that normally runs under a slight negative pressure, and that is why you have to be very careful to prevent any air leaks. The negative pressure in the fuel line will vary with the fuel level in the tank from almost 0 with a full tank to moderate with the tank close to empty.

The negative pressure at the Racor filter is the root of the problem with it if it is not properly maintained. The O rings on the slight glass column will loose their sealing ability over a very long period of time and cause an air leak into the fuel stream. This can cause a no start condition if excess air gets into the fuel or a runability problem and injector wear over time. Leaking O rings will also usually manifest themselves with a slight fuel seepage at the O ring when the tank is full and the engine is off for several hours. This O ring issue is the reason that Dave Atherton suggest replacing the Racor system with a Cat primary filter.

Cutting hydraulic hose is difficult. In tight quarters, I use a hack saw or a small cutoff tool. The issue is that you will fill up the hose with debris. There are several commercial hydraulic companies that have the smooth knife saws and crimping tools to do the job right at a reasonable price to insure that the repair will have no leaks. If you do not have any experience with hydraulic hoses or the tools to repair one, I would suggest you look into having the repair done by a professional hydraulic hose company.

Gerald

[Adam Hicklin]

Thanks again Gerald. I’ll try calling a mobile repair and see what they say.  When I disconnect the line from the tank, will fuel siphon out of the tank?  The tank is full.  The fitting is at the top of the tank.  Obviously I’ll have to catch whatever flows back down the line.  What can I expect?  Also, when the repair is made, I’ll need direction on priming and purging the air out of the line.  Dave A. Said to just start it.  Where does all the air go?

[Gerald Farris]

Adam,
The electric priming pump on your Racor primary filter assembly will purge the air from your fuel system (the reason I will not remove it from my coach). If you need assistance, just call me. 713-254-4156 The phone service is spotty here in Alaska, so if I do not answer, just leave a message and I will call you back when I get a phone signal.

Gerald

[Dave Atherton]

Adam, think your are getting ahead of yourself with this problem. Subject adding electric fuel
Pump into your C-12 system in not nessary because the fuel system setup is complete different
than on the HEUI injection systems on Cat C-9 and down. Understand that the fuel transfer pump
gear pump ( has a larger volume and pressure ) on Cat C-10 and up including your C-12 engine.
Diesel fuel is delivered through the secondary fuel filter 1R-0749 and within that secondary fuel
filter base there is two check valves that holds fuel pressure in a fuel manifold on your C-12
engine and maintains 90 psi at all times. Your injectors on the C-12 are a two stage injector
Electrical and mechanical of which a mechanical push rod operates injector and electrical from
engine ECM meters the fuel. ( see Ask Dave picture of C-12 secondary filter base with check
Valves ). As Gerald indicated removing air via: aftermarket add on if condition is not allowing
entry of air.  Caterpillar OEM secondary filter has a Hex bleed plug that is little harder to get at
But will pick up diesel fuel almost instant because the fuel manifold is retaining diesel fuel.
Again not to confuse you but we are talking two complete different fuel systems than what your
reading about. Dave Atherton Retired Cat Mechanic

[Adam Hicklin]

Thanks Dave.  I think Gerald was just referring to the Air Purge pump that is currently part of my Racor primary filter. Believe me, I want to do this fix the simplest way possible and get back on the road!  I appreciate all the help and input. 

[Adam Hicklin]

Update:  Turns out the leaking line could not be repaired.  Tech said besides there not being enough room, the line just seemed to be weeping fuel.  Couldn't identify a pinhole leak.  From the forum discussions, this is indicative of a compromised line.  So, I will figure out a way to run a new line from the tank to the primary fuel filter.  I'll also replace the line from the primary to the fuel transfer pump.  I'm wondering if this weepy line can be the reason for the constant diesel smell in my storage bays?  I could never detect any evidence, but the smell was constant. 

[Fred Brooks]

Hi Adam,
   Reasonable sure the fuel line is the culprit, My wife can detect diesel fuel 2 blocks away! Soldier on...…
   Fred

[harry kew]

Adam keep up posted I’m interested on how you rough the line
 

[Mike Shumack]

I posted some info on the types of "fuel line" available in this thread "Semi urgent. Engine serial number". Mentioning now just in case your interested.

If you're replacing cloth/braided fuel "hose" with nylon fuel "tubing", the tubing has a smaller OD (for same size ID as the braided hose) so that will make it easier to run.

Ideally you would run the new tubing through the same route as the existing fuel hose but access to the support clamps along the frame may be difficult. In that case abandoning the old the fuel hose in place is probably the best.  I recently ran some four-conductor wire (about the same OD size as 1/2" tubing) from front of coach to rear and it was not too hard (other than getting into some uncomfortable positions). I ran it along the wiring harness routing inside the frame rail - so I'm sure you can get your replacement fuel hose from front to back.

Good luck.

[Adam Hicklin]

After countless trips to various hose and tubing specialists, and getting a different opinion from each one, I finally decided to go with the CAT recommendation (picture attached). Both CAT Parts and Maintenance agreed that this was the correct line to use.  I really considered the plastic tubing route, but I couldn’t really find anyone to help, including the ParkerStore, that makes the stuff.  They looked at me like I was from mars and had never seen the stuff I had printed out for them.  And, I couldn’t blindly order parts on line, not knowing exactly what I would need.  So, CAT was beyond helpful and it’s their engine, so they ought to know, right?   It’s another hydraulic line that is supposed to be diesel stable, and it was cost effective, about 30 cents an inch (much better than the $15/ft Teflon stuff one company recommended.  Adds up when you need 45 feet!) I also had them make the line from the primary to the transfer pump from the same stuff.  Incidentally, they said this was the same line used from the transfer pump to secondary filter, when the engine was manufactured.  I can run the new suction line in a way that it can be removed without too much difficulty, if it ever needs to be replaced.  Hopefully that happens long after I’m gone!  Thanks for all the help on this. 

[Mike Shumack]

Did you have the fittings crimped on? Or what fittings will you use?
Also what is the inside diameter of that hose (1/2", 5/8", etc.)?
Good luck

[Adam Hicklin]

Inside diameter is 1/2 inch, like original.  JIC fittings will be crimped on, Like original.  Bought extra so I could loosely run the line, mark it to the exact length, then I’ll ill take it back to CAT and have them crimp the fittings.  Then back home for final installation.