Fuel System (low Fuel Pressure Will Cause Problems)

[Dave Atherton]

Good Morning, Keep adding to subject Fuel Line hydraulic hose failure. Point of interest to
further explain concern. Low fuel pressure can cause low power. Low fuel pressure can also
cause cavitation of the fuel which can damage fuel injectors. The following conditions can
cause low fuel pressure. Plugged fuel filters, Debris in check valves for the priming pump.
Sticking fuel pressure relief valve in fuel transfer pump. Debris in return pressure regulating valve in the fuel filter base or adapter assembly. Pinched fuel lines or partial open fuel lines.Old fuel lines
that have a reduced interior diameter that was caused by swelling. Fuel lines with deteriorating
interior surfaces. Looking at many , many post about owner coach in repair shop and it seems
replacement of number 5 or 6 injectors is very often. Why number 5 and 6 injectors because
There are at the end of diesel fuel that is ready to exit the cylinder head and above low
fuel pressure seizes up workings of injector (lack of lubrication from diesel fuel and heat) It
seems nobody addresses the fuel system which in most cases is the root cause for low power.
Addressing What cost will be for injectors for C-12, C-9 is not cheap plus additional parts. There
is a time when we need to look at our motorhome see if we need to update our system to
avoid down time and additional money outlay. Dave Atherton Retired Cat Mechanic

[Lawrence Tarnoff]

After reading this, it is a wonder that a coach makes it out of the driveway, let alone cross country 

Larry

[Dick Simonis]

OK, I'm feeling appropriately paranoid now.

Overall this has been an excellent topic and it made me go out and look at the primary filter to see if there was air present.  I never would have thought to look at it with the engine running....almost wish I hadn't done that since I found a LOT of air.

Time to schedule a trip to the CAT dealer.  I was going to have the oil changed and fluids analyzed now the trip has added some new items.

Replace the secondary filter fuel line.
Find and fix air leak.
Change fuel filters.

[Jeff Watt]

This is very interesting thread.

Dave is this fuel line issue unique to the C9-12 or are other units affected? I have a C13 in mine and I am wondering if I should be looking for these same problems/issues? On mine there is no (that I can see) see-through fuel bowl. Just the filter out back and the engine mounted cat filter.

Thanks,

Jeff

[Dave Atherton]

Hi Jeff, from what I can tell I think problem affects engine models 3126 A, B, E, C-7, C-9
Engines with heui injection systems. Engines with high pressure electronic injection system
C-10, C-12, C-13, C-15. I would suggest looking at your primary fuel filter discharge hose
that goes to the fuel transfer pump ( if this is a hydraulic hose with crimped fittings, it is
a hydraulic hose and I would suggest replacement of that hose ). One thing I would like to
add with my concern, engines with the gear type of fuel transfer pump, C-10, C-12, C-13, C-15.
Reason with a gear type pump and fuel starvation, the steel gears will be like a milling machine
sending metal from pump body through out fuel system. Metal in fuel system along is a mechanic worse nightmare. I do not know how I can sugar coat this problem and understand thoughts
a person may be thinking ( the problem is for real and I did not create the problem but I can
help everyone to correct problem.) Dave Atherton Retired Cat Mechanic

[LaMonte Monnell]

Dave, where is the fuel transfer pump located? I have tried to follow the line from the primary filter but there are so many lines there I can't follow it very well?

[Gerald Farris]

I think that the later model coaches (2004 or 2005 and newer) were equipped with plastic fuel lines instead of hydraulic hose for fuel lines. So if your coach has plastic fuel lines, the fuel line inner lining disintegration issue does not affect your coach. However, if your coach has hydraulic hoes for fuel lines, a check for rubber particles in your sight glass is warranted. 

If you see some air in the top of the Racor plastic pre-strainer with the engine running, this is normal as long as the pre-strainer stays approximately 1/2 full of fuel or higher. However, if it runs lower than that you probably need to replace the pre-strainer if it is cracked or the "O"rings at each end of it. 

Gerald

[Lee Welbanks]

I think Gerald is correct with the years for the fuel line change to plastic, I went and checked my 06 PT and it has all yellow plastic fuel line with Voss O Ring quick connect fittings from the tank to the water separator and also from there to the fuel pump on the motor. I did a little digging trying to find out what the O Ring material was and I haven't been able to nail down what they are made of.

[Dave Atherton]

LaMonte, your fuel transfer pump is located at rear of your HEUI pump ( I believe you have
A C-9 ) the hose in question looking up from bottom of engine on passenger side is located
Middle of engine block and is the bottom hose. Dave Atherton Retired Cat Mechanic

[Dave Atherton]

Lee, glad to hear you have plastic fuel line, might want to check with Jim Nichols with same o-ring
fittings allowing air to enter fuel system and what we have done to correct this problem. I do not know
what year that plastic fuel line started but Gerald is more up on this, but we did talk about the o-ring connection problem. Dave Atherton Retired Cat Mechanic

[LaMonte Monnell]

LaMonte, your fuel transfer pump is located at rear of your HEUI pump ( I believe you have
A C-9 ) the hose in question looking up from bottom of engine on passenger side is located
Middle of engine block and is the bottom hose. Dave Atherton Retired Cat Mechanic

I have a 2000 3126B 8YL62199 SERIAL NUMBER......

[Dave Atherton]

LaMonte, thanks for engine s/n number, your fuel transfer pump and fuel line is located in
location as the Cat C-9 engine. If you follow fuel line from primary fuel filter, the connection
to engine will be on passenger side of motorhome in middle of engine block about 6
inches  above oil pan, the hose to remove is the bottom hose ( looking close looking up from
bottom look at crimped end on bottom fuel hose and than compare crimped end to the crimped
at primary fuel filter. You will need a short 7/8 open end wrench to remove hose. This is the only
fuel hose that needs to be changed and take hose with you when you make up a new hose.
Have found on some engines 3126 and C-7 connection to engine has a hose end that is at 45
degree angle. Dave Atherton Retired Cat Mechanic

[Dave Atherton]

Gentleman, caution when checking for air/fuel in Racor primary plastic site glass. The
pictures that Fred Brooks taken for me at Quartzsite Rally. Picture number two will point
out fuel/air movement with C-12 engine at idle in site glass which is fast moving. Take
same picture on another motorhome at idle will reproduce same results as picture number
2. Take same motorhomes at high idle 1200 rpm ( C-12 ) the site glass looks like all foam
and fuel level just about on the bottom. As I have pointed out the ECM is always changing
the air/fuel and will adjust power to match ECM info. The C-12 has plenty of power so affect
At first fuel system allowing air to enter will not be picked up at first.
Dave Atherton Retired Cat Mechanic

[Edward Buker]

The plastic sight glass on the Racor strainer is a unique design and as Gerald has stated will always have a fuel void in it when running by design. Dave is pointing out that we need to keep air and debris out of these fuel systems and that the fuel line issue needs to be resolved with any indication of particles like Fred has shown or just changed out preventatively. It is an important subject and we have Dave to thank for bringing it to our attention.

Seeing a fuel void in the plastic column in the prefilter is part of the design and no reason for alarm. This plastic column should be inspected and changed along with the Orings if it shows plastic ageing (turning from clear towards yellowish), or if there is any sign of cracking, or if there is any fuel seepage around the top or bottom connection points, or from the plastic column. This area should be completely dry of fuel. If there is a leak sometimes a repeatable column of bubbles at idle from a given point where air is being pulled in will be evident. If there is no fuel seepage anywhere, no cracks in the plastic, and no evidence of an Oring leaking then this strainer is not introducing air into the fuel system. This little plastic strainer can bring a lot of concern in appearance and you need to sort out when it has a problem and when it is working as the design intended it to. I had some seepage and changed the plastic column and the Orings when the coach was about 10 years old as a guide. The particles in Fred's photos of the fuel line debris were visible because this strainer is the first filtration that the fuel sees and was designed in just to protect the priming pump. One good thing about this design is that gave us a visual of the problem, most filter systems do not. Hope this helps.

Later Ed 

[Dick Simonis]

What I found interesting about the original picture of the strainer with air is that the air bubbles were very small and caused the air/fuel combo to look like an emulsion or foam.  In my case the air bubbles are very large and, even at 2000 rpm, there is no foam just a lot of air bubbles sort of like a pot of water boiling hard.  Now i'm sure this means some thing but I'm not sure what.  Perhaps the difference between a small lead and a gross leak?

I have to believe that that much air would cause a power loss even with the ECU regulator fuel flow.