C-9 Flames out at low speeds

[Bob Dunlap]

Our 06 Beaver Monterey Venture IV has a new C9 engine (courtesy of Cashman Cat in Las Vegas) as of December, 2017.  In the last year, at very low speed (stop & go traffic) upon acceleration, the rpms would drop and the engine would die.  I would have to turn the key off, then re-start and it would be fine until the next slow speed condition.  It has good power going up steep hills and no problems accelerating from a dead stop.  It doesn't matter if the outside temp is hot or cold or if the engine is hot or cold.  Our local shop had a CAT mechanic diagnose the problem as low fuel injection pressure. They said this could be caused by dirty oil or bad oil filters, but I had just had the oil and filter changed before that trip.   They drained the oil, flushed the system, replaced the filter and filled with fresh oil.  The same thing happened and the same code appeared.  They replaced the ICP sensor and said if it happened again that I would need to have a high pressure oil pump installed.  On a trip through Los Angeles Traffic, it happened again.  Real leg-wetter.  We were in the middle of a 5-lane freeway and were barely able to make it to the shoulder.  It wouldn't restart.  After 10 or so attempts, I decided to start the generator to keep the batteries charged.  When I tried to restart the engine, it started.  Maybe is was not an oil pressure issue at all?  Might be electrical? We've had the power solenoid replaced and both chassis batteries replaced.   It happened several times again after that.  When I took it to my trusted mechanic in my old home town, he couldn't find anything wrong but suggested I double the amount of Diesel Kleen in added to each fill up.  I did that and haven't had an issue since.  Any thoughts on what might be going on?

[Joel Ashley]

Dirt or algae in the fuel tank perhaps.  The mechanics replaced the oil filter but not the fuel ones?  I’m no diesel mechanic, but it sounds like not enough pressure from the pump upon sudden demand.  I use Power Service’s Clear Diesel and Bio Kleen and have had no issues fuel-wise.  There is an additional fuel pump add on procedure also, that some have had done, and that our club’s “in-house” CAT mechanic, Dave Atherton, has espoused.  There may be a discussion of that in the Club’s Coach Assist section (see “Technical” menu on the Club’s main home page).  I’ve not had that extra pump added since our short, lower weight chassis has not had power problems.

Joel 

[Eric Maclean]

Bob
Do you know what the code was that the shop diagnosed the ICP sensor from and does this code return each time the engine quits?
If it does the code is pointing to low ICP ( injection control pressure)
And could be one of several things the sensor merely reads the high pressure oil in the cylinder head rail which is used to fire the fuel injectors
This high pressure oil is supplied to the cylinder head rail from a high pressure oil pump known as the HUEI pump this high pressure is controlled by
ECM controlled solenoid valve which the ECM duty cycles to vary the rail pressure from approx 1000 psi to several thousand depending on engine load
In this way the ECM can control how much fuel is delivered each time it commands an electronically controlled fuel injector to fire.
There are several faults that can cause low ICP .

1)failing HUEI high pressure ( not building enough pressure)
2) poor or failing ICP solenoid valve ( not controlling rail pressure properly)
3) bad ICP sensor ( sending false reads to ECM)
4) leaking 0 ring on one or more injector ( resulting in lower than command ICP pressure)

A mechanic will a Cat scan tool and cat et soft ware should be able to read the ICP pressure through the ECM and get a better idea of whether or not the pressure is dropping out at idle .he can also command ICP pressures through the scan tool to verify if the ICP solenoid has control of the pressure.

If it is one or more injector o rings failing it will eventually get to the point where the system can't produce the minimum 800 psi at cranking speed to actually fire the injectors and start the engine.

With the valve cover removed and the engine idling you should be able to see oil squirt up beside a injector if the o ring has failed.

As Steve stated Dave Atherton has been a CAT mechanic for many years and could be a great help to you to get you pointed in the right direction
He can be reached through the BAC Web site

Hope this helps
Eric

[Steve Huber Co-Admin]

Input from Dave Atherton; First check the key ring weight as significant weight can cause the ignition switch to intermittently fail and cut power to the ECM. There is a CAT service bulletin out on this. It could also be the Injection Actuation Pressure Sensor or the Atmosphere Pressure Sensor starting to fail. Both sensors are 5 volt and share the same signal wire from the engine ECM.
Steve

[Bob Dunlap]

All your replies were helpful but did not resolve the issue.  I don't have code information on the ICP issues, so I can't speak to that.  We thought we had this problem licked on our last trip (June, 2024), but it's only gotten worse.  Some days it might start and run for 10 or 15 seconds and then quit. When I restart it, it'll run just fine.  Many times, when in heavy traffic, if I let off the throttle and then redepress it, it'll die.  Real leg wetter when in heavy bumper-to-bumper traffic.  I thought maybe it was some debris floating in the fuel filter which might periodically block flow of fuel, and the problem starting occurring right after the fuel filters were last changed (May, 2023).  So, today, I changed the fuel filters, making sure the filters had fuel in them before screwing them in.  Now, it won't start at all.  Nothing but black smoke emits from exhaust.  I'm being told from some Cat mechanics who are in my RV park (by the way, I'm in Indiana, no where near an RV shop), that it seems to them that there is air in the fuel line.  They recommended that I spray ether into the air intake to get the engine running and when it does, it should purge the air from the line.  Will I hurt something by doing this?

[Eric Maclean]

Bob
If you have removed the fuel filters you need to purge the air out of the system before it will start again .
Your coach should have an electric priming pump with controls in the service bay .
If you have the older Raycor system there should be a Schrader valve next to the water separator on the housing unscrew the Schrader valve cap depress the valve core with a suitable tool and run the pump till you get clear fuel ( no bubbles)
Next loosen the secondary fuel filter a turn or two and run the pump until clean fuel spills down the sides of the filter and while still running the pump retighten the filter .
Next with everything tightened back up run the pump ( it will sound slower ) for approximately 45 seconds this is to move clean fuel up and through the fuel rail in the engine and out to the fuel pressure regulator.
Once all of that is done the engine should start ( run it at 1000 to 1200 RPM for 20 to 30 seconds to be sure you have moved any left over or traped air out of the fuel rail.

Your problem sounds like the system is sucking air somewhere ,on these engines everything from the engine drive mechanical pump back to the fuel tank are  on the suction side of that pump so if there is any spot where the system can suck air it will .
If your coach has the Raycor fuel separator pay close attention to the plastic site glass it has two O rings on each end of it and they are a common area where air can be sucked in .( Many here have upgraded to a cat pump setup as described in coach assist ) No sure if yours has been done or not.
Another area where an air leak can occur is anywhere in the fuel line between the separator and the fuel tank.
Some of the earlier coaches had a plastic fitting where the fuel line connected to the tank that would crack and create a problem.
I also believe Dave Atherton spoke of the mechanical gear pumps in those engines getting weak and that running the Cat priming pump ( which is rated as a lift pump ) continuously would cure the problem.
These HUEI engines need a constant supply of clean no air fuel to the mechanical pump in order for the mechanical pump to keep 60 or 70 psi on the fuel rail
Any air will make this near impossible and the engine will not run well have low power out put stall and over time will destroy fuel injectors as they rely on the fuel to cool them .

Hope this helps
Eric

[Bob Dunlap]

Thanks Eric,
Your answer is very in-depth but to technical for me to follow exactly.  I don't know what a Raycor system is or what a Schrader valve might look like.  I'll consult a couple of Cat folks in our park to see if they can follow your instructions.

[Eric Maclean]

Bob
The Raycor fuel separator is the fuel filter water separator if you go to the coach assist section of the forum under common problems you can see pictures
Of the system.and how to identify whether or not you have air in the system.
And a Schrader valve looks like a regular tire valve.

Eric

[Bob Dunlap]

Thanks Eric.  That helps a lot.
Here's where we stand today.  When I got up this morning, I was poised to contact a Cat mobile repair facility to see if they could help.  I thought I'd give it one more shot at starting.  It started right up.  Just had one little "burble" when I started to move forward and then the engine quit.  I started it again and it's been just fine.  Having said that, the anomaly has been just like that for the last year and a half, so I'm not sure changing fuel filters did the trick.  I'll follow up with your suggestions in your previous post checking other sensors. 

[Richard Davis]

Bob!  I also have an '06 Monterey with the C9.  I suffered with the same kind of issues you are having (mine did not get anywhere that severe).  The fuel pump on the C9 is a relatively small mechanical gear fuel pump.  CAT specs stipulate that the C9 should not be installed more than 10 feet from the fuel tank without adding an auxiliary fuel pump.  Motorhome manufacturers ignored that warning.  To compound the issue, builders also used plastic fuel line connectors that tended to suck air as they aged.  The fittings did not ever leak out since they were sucking fuel into the engine fuel pump.  Diesel engines do not like air in their fuel as Eric pointed out.  After doing much research on the issue, I followed Dave Atherton's advise to replace the original water separator with the CAT primer pump (FYI, the '06 Monterey does not use the fancy water separator system Eric was referring to).  (There is a description of the process on the BAC forum along with a parts list for the project.)  I also replaced the plastic fuel line connectors with brass compression fittings so there would be no more air leeks.  If you have not already done so, replace the fuel pressure regulator that is attached to the return fuel line on the rear of the engine (front of our engines since they are in backwards).  There was an upgrade on the fuel pressure regulator for the C9.  Dave gave me the new part #.  A failing pressure regulator can cause the kinds of problems you are having.  I suspect most of your problems are coming from a loss of adequate fuel pressure at low RPMs.  The CAT primer pump solved these issues for me.
Good luck.  Richard         

[Bob Dunlap]

Thanks Richard,
I will give that a try.
I made it home to the Texas Hill Country on Thursday but with several scary episodes.  The anomaly became so frequent that it even occurred at freeway speeds without warning.  I was passing a slow-moving semi when the gremlin attacked.  Fortunately, there was no traffic behind me or behind the semi and I was able to pull over to the shoulder and shut it down.  After 20 or so attempts it started and ran fine for another 100 miles.  I took it to a Holt Truck Center in Longview, TX where I was told the codes suggested it was an oil pump sensor.  He would have changed it right then and there, but didn't have lift space to get it up high enough to pull the starter and access the sensor.  Good thing I "limped" home and didn't get that done as it might have been leading me in the wrong direction.  Are the modifications you suggest something I can do in my garage, or do I need to take it to a shop?  I'm pretty capable and have tools for most everything. 

[Richard Davis]

Bob!  The primer pump upgrade is a relatively straight forward upgrade.  After ordering all the parts from the parts list, I did the install in my driveway.  There is a nice write-up in the Technical tab section under Common Problems along with a parts list.  If you have not been there, you must log in to the main BAC web site (link in bold on the upper right of the BAC forum page).  Click on the Technical tab and then the Common Problems tab and then the CAT fuel priming item.  Reading the installation write-up will let you know if it is something you want to tackle yourself.  The only downside is that the CAT parts are very expensive.  I was tempted to install a generic electric fuel pump to save some money, but decided to bite the bullet and use the recommended CAT parts.  It has worked well for me.  It has been 5 years and I have had no issues with the system.  Good luck and I hope you can get your problem solved.  I have no idea if my problems were caused by low fuel pressure or if they were caused by air intrusion in the fuel.  Dave Atherton has some troubleshooting instructions somewhere that use a clear fuel line instream to allow you to see if you have air in the system.  I decided rather than doing that, I would replace as many of the original plastic fittings as I could get to with brass compression fittings.  It all worked for me, I hope it does for you as well.
Richard 

[Bob Dunlap]

Thanks Richard,
You've been very helpful.  I have a very large garage and can perform most anything there.  I'll see if I can locate the instructions you mentioned and go from there.
Bob

[Bob Dunlap]

Richard,
Please clarify for me which component is being replaced by the Cat fuel priming pump. Richard's article says it replaces the existing primary fuel filter, and you said it replaces the original water separator.  The photo in Richard's article shows orientation in the Contessa, and I don't see anything familiar in my Monterey. Help!

[Richard Davis]

Bob,
I think you are confusing yourself.  The water separator IS the primary fuel filter.  It is where the fuel is first filtered (primary).  On your Monterey it should be located in the battery storage bay right behind the battery tray.  I installed the CAT priming pump in its place and ran the wires thru an existing wiring hole into the electrical component cabinet above the batteries.  I installed the Smakn voltage converter there next to the Big Boy for convenient electrical hookup.  Hope that makes sense.
Richard