C9 engine surges at idle and fast idle

[Roy Deeble]

Dave Atherton,

I also have 2005 Monterey Bayview IV like Neil.  My C9 engine is #9DG01381 and my questions are:

1.  Are dryer part numbers provided to Neil the same for my engine?
2.  Can you provide me with the test data for my engine?
3.  My engine when cold surges at idle and is most prominent on fast idle where RPM fluctuates between 1150 and 1250 continuously, but normalizes at operating temperature.  I assume this is a fuel related issue and not too serious, but really would appreciate your thoughts or that of anyone that has experience with this problem.  I have no problems starting the coach, at least, in balmy So. Cal. temperatures.

Thank you!

[Dave Atherton]

Roy information requested,  Cat C-9,  S/N 9DG0381,  A/R number 249-8278,  Build Date
2004 - 04-05,  Test Date  2004 - 06-05,  Load Power 400 HP,  Full Load Speed 2100 RPM,
High Idle 2370 RPM,  Low Speed Idle 700 RPM, Boost Pressure 32.5, Fuel Pressure 81 PSI,
Fuel Rate 15.3 GAL/HR, Intake Manifold Temp 120 DEG, High Oil Pressure 47.9 PSI, Low
Oil Pressure 22.5 PSI, Air Intake Temp 122 DEG,  Temp Water Pump Inlet 192 DEG F

Air Governor 4N-9680.   Question when cold surging of engine, Your are still in the cold mode
on the engine ECM and intake heater will cycle on and off for 13 minutes and things will start
to smooth out. That sounds like what is going on.  Dave Atherton Retired Cat Mechanic

[Roy Deeble]

Dave,

I assume you are saying the engine surging is somewhat normal when cold and nothing to worry about.  If so, I will move on to the next coach issue on my never ending list.

Thank you,
Roy

[Jim Edwards]

Hi, You are not alone. Mine does a similar thing when in cold mode. 

[Ken Sair]

Ditto here. C9 in a 2007 Contessa. I call it my five cylinder idle. I let it run 60 seconds then use fast idle. Seems to level out around 6-7-8 minutes. I also always use the engine preheat. Ken

[Dave Atherton]

Roy, Jim , Ken, starting in the cold a person must remember how the C-9 HEUI system
operate. First we start at the engine oil pan and work toward the HEUI pump ( of which
is a hydraulic pump ) than on to operation of the injectors and return back to where you
started at the oil pan. Going back to bedroom than turning key to start and waiting for
the wait to start light to go off, listen close to engine you will hear a buzzing sound going
on under the valve cover. This buzzing sound is what is called warming up the injectors
so the cold oil will flow more easy along with the engine intake manifold heater. When engine
starts again it take up to 13 minutes to warm up engine and for engine to smooth out and
for white smoke to clear up. Depending how cold it is outside, the engine ECM monitors the
air/fuel in engine and will keep engine in the cold mode untill water temperature 104 F DEG.
When it is cold outside take the extra time and warm engine along with your power steering
etc. Last thing at startup do not hold foot pedal pressed down, this has no bearing on starting
operations because the way the heui pump operations work. Many people may think engine
starts easier holding down on accelerator or pumping accelerator this is incorrect.
Dave Atherton Retired Cat Mechanic

[Roy Deeble]

Surging fast idle solved!  Living in So Cal means lots of freeway traffic so I always drive with my exhaust brake engaged, but lately my wife's illness has kept us home bound.  Consequently, with the coach in storage, no electrical hookup and a cover over the solar panel I need to run the generator and engine to charge the batteries weekly.  Yesterday while doing so, on fast idle, my engine surging was again prominent, that is until I noticed the exhaust brake light on the dash shining brightly.  Lo and behold with a flip of a switch my C9 began purring like docile kitten. 

[Dave Atherton]

Hi Roy, is this a new problem or the problem that you posted last January. Before we were
talking about startup and run in the cold mode, or are you talking about something new with
engine surge. If this is something different we can approuch subject from a different direction.
Dave Atherton Retired Cat Mechanic

[Roy Deeble]

Hi Dave,

Yes this was the same issue where my RPM ranged between 1150 and 1250 every second or so on fast idle before the engine warmed up.  This was an interminent problem which seemed strange at the time, but disappeared at normal operating temperature.  As it turned out leaving the exhaust brake on caused the problem and as soon as I turned it off the engine immediately leveled off at 1200 RPM.  Normal idle was a little rough too and it stabilized at 750 RPM.  I guess I would say to anyone having a rough unstable idle / fast idle at startup make sure the exhaust brake switch is turned off.  Not sure about a Jake brake though.  Thanks for your help with our Beaver issues, it's appreciated.

[Dave Atherton]

Roy, sounds like when you start up in the cold mode than speed up engine, you have a little air
within your fuel rail  leaving sitting over night. In A.M. Starting
engine fuel transfer pump has to catchup up to recharge fuel rail, by speeding to higher idle the faster
this is happeningfaster. What would be causing this is the return fuel check valve regulator on the
back side of engine head ( note: diesel fuel has little air bubbles that settle out when engine
is not running that is normal ) some engines take a little longer to warm up in cold mode
depending how cold it is.  Dave atherton Retired Cat Mechanic

[Joel Ashley]

Roy, the "pac-brake" exhaust brake switch light should have been on in your dash cluster, and should've been noticeable as out of place when your ignition switch sequence was being waited upon before moving to Start mode.  I'm not sure the valve would've been actually closed at that point either, but if it was you'd have noticed the Exhaust Brake Engaged lamp also, in addition to the Exhaust Brake Switch On lamp. 

Others here more mechanically astute than I probably know for certain, but I'm thinking the valve shouldn't be closed at startup or idle, regardless of the position of the switch.  If that indeed was happening and causing the erratic stumbling, then there may be something awry with the pacbrake-engine-tranny electronic interconnections.

Just my uneducated 2 cents.
-Joel

[Dave Atherton]

Hi gentleman, back with little more information on engine surge. The engine ECM with
engine running has several sensors that adjust engine to run and idle correct. The injection
timing is determined by the ECM inputs from components. Coolant temp. Sensor, Air temp.
manifold sensor, Atmosphere pressure sensor, Boost temp. Sensor. Fuel injection pressure
control from ECM by injection actuation pressure control valve regulates hyd pump outlet
pressure by control of flow. Any air in engine fuel rail ( talking about small air bubbles that
settle out with engine being stopped ) will make engine surge untill engine clears cold mode.
Engine exhaust brake will have little affect on Preformance on the above engine operation cold mode.
The Cat HEUI injection has no moving part for actuation other than oil pressure and fuel pressure.
Joel thanks for your come back because there may be a additional problem with the exhaust
Brake sticking in closed position. Dave Atherton Retired Cat Mechanic

[Roy Deeble]

Joel, your most recent post caused me to take a closer look at my exhaust brake dash lights on a cold startup which are normally obscured with by the closed front drapes.  Yesterday I opened them when charging the batteries and observed the following:

1. Exhaust brake switch turned off coach idles perfectly when cold.

2. Exhaust brake switch is on, the exhaust brake dash light is on and the adjacent brake engage light flashes continuously; idles (Low & Fast) surge as described previously.

3. Engine temperature reaches approximately 120 degrees the flashing exhaust brake engage light no longer illuminates and the exhaust brake light is on; engine again idles perfectly.

I'm of the opinion my coach is functioning as designed, however the previous owner stored and used this rig primarily in Colorado at 8,000 feet and perhaps a modification was made to accommodate the elevation and cold. 

Lesson learned, open the drapes so the dash board is visible when starting the coach.  I relied on the Aladdin for RPM, temperature, and battery charge and viewed it by lifting drape just enough to see it, never realizing my exhaust brake switch on was the culprit all along.  Enough said!

[LEAH DRAPER]

WE ALL LIVE AND LEARN DON'T WE, AS PAINFUL AS IT SOMETIMES.  GLAD YOU HAD RESOLUTION.

[David T. Richelderfer]

When I close the front curtain, which I rarely do anymore, I push it forward up on the dashboard and forward of the Aladdin screen.  Normally during the day I always have the Aladdin screen turned on showing the House Electrical Status so I can monitor from my usual seat the shore/generator incoming voltage and amperage demand, the solar panel output, and the House battery charge status.  This way the front curtain is not blocking the view of the Aladdin, dash lights, etc., and is covering about half the dash protecting it from direct sunlight.  This past winter while in Quartzsite I chatted with a Beaver owner who had a dashboard cover custom-made to fit tightly over the dashboard contours.  It fit almost perfectly and offered 100% direct sunlight protection - from street-side window to curb-side window and from windshield to dashboard's aft edge.  Until I find a similar dashboard cover I will continue to place large towels and the front curtain over my dashboard.