Low Power Cat C-7 & C-9. ( Injector Replacement ) Dave Atherton

[Dave Atherton]

Searcy, AR. Rally motorhome owners attending ( not beaver members ) but have Caterpillar
C-7 & C-9 engines. Problem low power and injector replacement at different repair shops.
I have mention on several post about low power and what causes low power. I just finished
troubleshooting 2 cat engines low power problem with present, both motorhomes have had
Injector replacement within the past year and one within last 2 weeks ago. The service shops
replaced the failed injectors but did not address what caused injector failure or the Root cause.
What I had found on both engines low fuel pressure. Both engines cannot maintain or produce
with fuel transfer pump the mid or top idle pressure as per Cat spec by using a pressure gauge
at the secondary fuel filter. Use of a clear line on engine return fuel confirmed lack of fuel starting
at mid to high idle. Can look at problem in different directions but my personal thought is add
electric fuel to maintain fuel flow from fuel tank in front 35 feet away. This is the direction the 2
motorhome  owners are going to take. Have more information I can provide on this low power
With engines that HEUI injections systems.

[William Ervin]

Dave

Would your theory apply to 3126B HEUI injections systems as well.   I've been struggling with low power in my 330 Cat, Thinking maybe a Turbo issue with only about 23 in +/- of Manifold pressure at full throttle.  Makes sense though... less fuel, less power, less exhaust pressure, less Manifold pressure.  Vicious circle!

Ideas on the type of fuel pump I would need and the best places to mount.   

Thanks
Bill

[Dave Atherton]

William, the answer to that question is yes. Install of a electric fuel pump will make a
big difference for you in power. The Cat 3126 A or B model, what has worked using a
electric fuel pump for ford 7.3 engine. ( the ford 7.3 engine is a cat heui injection system
that has Cat 3126 A model heui injectors.) the electric fuel pump cost around $ 60.00
At parts store. Would suggest when mounting electric fuel pump to install after the fuel/
water filter. Last thought Do you have a Racor water/ fuel setup on your MH, Of which has
entry point for air if not maintained. I would read Joel post about trading out Racor setup
and install a Cat water/ fuel filter. Dave Atherton Retired Cat Mechanic

[Dale Walker]

Hi Dave, this thread has piqued my interest, that maybe another pump would help alleviate the strain on the HEUI system. I read this thread the other day and began to wonder about my coach, because it has an electric pump that the primary filter. Has my coach the only one with this setup?? Well, I'm sorry, but the pictures I have of it are to big to post. But it has a button to make it run, I think it was just to prime the filters, but, come to think of it, I have never checked to see if it runs when the engine is running. How much flow and pressure would be sufficient to handle what the engine uses?

[Dave Atherton]

Dale, it sounds like you have a Racor water/fuel filter setup. Do not take my post the
wrong way but I'm not out here to down grade motorhome or builder equipment that
has been installed at build. I keep hearing about the same problem low power and the
aftermath of failure ( injector replacement ) and the new injectors made motorhome run.
The real issues that has caused failure is lack of constant fuel supply to engine that is
not being addressed. Going back to your problem would suggest first in sending Jim Nichols
A thread about Cat C-9 low power and install of a Cat electric fuel pump and results today.
Second I can provide you with all information part numbers etc. to order parts from any
Cat Dealer. Also pictures of parts before and after install. third problem I want to address
with your year motorhome you should have plastic fuel lines from fuel tank to engine. Problem
also the type of fuel line connectors ( push in o-ring connector with plastic retaining clip.)
Finding air entering fuel system at connectors of which again reduces fuel supply under load
and low power. Caterpillar did not have this problem when engine built and tested, things
we're changed in a different direction at motorhome build. Dave Atherton Retired Cat Mechanic

[Dick Simonis]

Question regarding fuel pressure.  Can that be monitored by the Silverleaf???  And, if so is it a reliable indicator of the issue?? 

[William Ervin]

Dave I have the Winn now Parker-Racor system. (see attachment)  I'm aware of the air leak problems (usually in o-rings on the prefilter or cracks in the plastic case).  I've not had those issues yet and take great care to avoid causing them.

If I mount the ford pump after the winn system it would only be about three feet or less from the stock pump, the new pump would still be pulling nearly 40 feet.  Wouldn't that kind of defeat the purpose of installing it in the first place?   .

Bill

[Dale Walker]

Dave,

With those kind of connectors, where do they start, at the tank? I suppose they have at least one union in that line to the primary filter? I'm afraid I'm to far from home to investigate that, as I'm still in AZ. She's going to have to go home this way, for now. I was thinking about putting a Carter or Holley electric inline from the tank? Maybe alieve some of the stress on the pump?

[William Ervin]

Would the pump we're talking about be similar to this?

[Dave Atherton]

William Ervin, thanks for up date on picture on Racor water/fuel filter. This Racor setup,  if not
maintain will allow entry of air into your fuel system and low power. That little electric pump
in the Racor water/fuel is a filter priming pump and does not run all the time only when fill the
filter. I would suggest removing the Racor setup and install a cat water/fuel filter, than connect
fuel pump to discharge fuel exit port on new fuel/water filter. I'm by passing the Racor setup
because I know what you are going to find ( entry of air ). Have helped with several Cat 3126
A& B models by adding electric pumps and made difference in power. I can help with info to
Install electric pump. Dave Atherton Retired Cat Mechanic

[Dave Atherton]

Dale, with your C-9 engine I would only suggest using a Cat electric fuel pump. Reason
With the Cat C-9 opened to 400 hp. requires correct amount of fuel and correct pump
to provide that fuel flow. The smaller Cat engines 3126 A,B,E does not require the fuel flow
or fuel pressure used in the smaller heui injection systems. The pump that I'm telling
anyone with a Cat C-9 is matched with correct electric pump for that engine. A smaller
electric fuel pump would work good to mid idle and run out of correct fuel flow at high idle
and under load. Dave Atherton Retired Cat Mechanic

[Dave Atherton]

Dick, to answer that question I really do not know what information the silver leaf or
alladin reads out on screen. I have no reason because my Cat ET reads out information
that I use. you can install a pressure gauge at the secondary fuel and with engine running
at high idle, you will need a pressure reading of 81 psi. Dave Atherton Retired Cat Mechanic

[Jim Nichols]

I started out with  that size fuel pump and as I started looking for fittings I was going down in size to fit the pump in and back up to come out of pump. My C9 had 1/2" lines from the tank to filter. With Daves guidance I put a CAT fuel pump that exceeded the fuel demands especially at full throttle. At the same time I was having air in the fuel and was in the process of finding and curing it with brass compression fittings? It's like a new engine to us. I want to thank Dave many times over for his knowledge and patience helping me. 3126 eng may have different fuel demands than the C9.

[William Ervin]

I'm all in on it Dave... I've known I'd have to replace the Racor system eventually, its been troublesome for a lot of RV owners.  The prefilter on mine has always stayed full after filter changes and air purge so I figured it was still working correctly, I hadn't put the power loss and air in the system together though.

Do you happen to have the setup and a part number for the cat filtration system?   
Is the Ford filter the same one in my prior post?

Thanks
Bill

[Dave Atherton]

William Ervin, Joel Weiss just had a Cat fuel filter and filter base posted about two weeks
ago along with having a new fuel hose. Joel has the same set up and engine that you have.
Having other members jump in on subject I think is great because it gives everyone a better
look at problem. Looking at your picture of the Racor water/fuel setup I also noticed hydraulic
on the discharge port on filter that goes to your fuel transfer pump. ( location in middle of
engine hose on bottom just above oil pan.) this hydraulic hose will have Gates Global in white
printing on outside rubber jacket this brand hose is causing all the problems. Looking at the
hose and it says Parker print on hose Parker hose is rated for all diesel fuel and is ok. I just
wanted to point this out but getting kinda off subject but the fuel hose is also involved in the
Low power problem also. Dave Atherton Retired Cat Mechanic