Author Topic: Laboured starting but only when warm  (Read 2281 times)

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Offline ptas

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Laboured starting but only when warm
« on: December 15, 2018, 09:47:22 AM »
Cat C9 (9DG02935) - 2004 vintage - Country Coach Hood River RV - now resident in the UK when not touring mainland Europe and north Africa

The engine has run beautifully for the last 8 years - starting both hot and cold with just a tickle of the ignition key - (I do use the block heater to help and link the leisure and chassis batteries to provide ample 'amps' for starting)

stopped at a fuel station enroute recently and the engine required considerable 'turning over' before she fired - thereafter the engine ran sweetly, as normal
Started when cold subsequently, with only a tickle of the key
Yesterday, again, stopped for fuel - several seconds spent turning over before she fired - there is no noticeable smoke from the exhaust when 'she' does eventually start - again ran / idled sweetly thereafter

I am looking for pointers at this stage please - that might allow me to either 'live with' / repair in order to return to the UK after the winter to a 'shop with which I can converse in detail and who know the RV - I am unfortunately not overly blessed with workshop facilities at the minute as much wild camping (boondocking) is involved

First thoughts would be 'new' fuel filters, but that she runs sweetly once started suggests this is not the problem ??

Any assistance / ideas greatly appreciated

Ian S.
based Exeter UK - but usually elsewhere !!

« Last Edit: December 15, 2018, 10:14:17 AM by ptas »

Offline Brett Wolfe

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Re: Laboured starting but only when warm
« Reply #1 on: December 15, 2018, 09:59:59 AM »

And so we are all dealing with the exact symptoms, when this issue occurs, engine turns over at normal speed, but starter has to run longer before the engine actually starts AND when it does start. Any puff of white smoke? And, once started, it runs fine.

No change in coolant level, oil level or sign of problem with fuel contamination?  If you have a manual fuel pump on your fuel filter, unscrewing and pumping shows that it is HARD to pump (if easy, that indicates air in the fuel system and would suggest checking for a leak on the suction side of the fuel system).  The leak would be IN (air in) not a fuel leak out.
« Last Edit: December 15, 2018, 10:16:57 AM by Brett Wolfe »

Offline ptas

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Re: Laboured starting but only when warm
« Reply #2 on: December 15, 2018, 10:05:56 AM »

Turns over normally just for longer - no white smoke - once started runs fine

Will investigate resistance of manual fuel pump / primer tomorrow - dark here now

« Last Edit: December 15, 2018, 10:15:14 AM by Brett Wolfe »

Offline David.e.atherton

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Re: Laboured starting but only when warm
« Reply #3 on: December 16, 2018, 07:09:26 AM »
PTAs, welcome to the Diesel Club, first of all your Caterpillar C-9 Engine is a very good
long life low maintance unit. First of all in determining why the extra time to start can come from several things, but let’s start with the simple things. ( note: most all problems with your
engine are minor and most are connected to what Caterpillar calls event codes that will
come and go but you do not need to worry to much about. ) Exhaust smoke is very important,
you indicated very little if none. If your push down fast on pedal you should see a big puff
of smoke than no smoke or under load going up big hill see smoke. Little or no smoke
Fuel filter change there should be amber light come on dash and low power. This is very
Important use only Caterpillar 1R-0751 2 micron fuel filters. You engine computer has a
engine fail safe derate mode and requires this fuel filter only or your engine fail safe will
not preform. Engine startup engine computer has another safety mode called ( Cold Mode )
Your engine will not have very much power until engine warms up and water temp comes
up . This cold mode prevents engine injection system damage forcing cold oil to operate the
injectors.  Change engine oil around 7,500 miles Do not entend oil and filter change periods.
Will stop here but my advice remember most engine problems revolves around the injection
System and only thing that operates your injectors is clean warm engine oil, clean 1R-0751
2 micron fuel filter and last let your engine warm up forcing cold oil to operate injectors can
cause damage. Ask Dave, Dave Atherton Retired Cat Mechanic

Offline ptas

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Re: Laboured starting but only when warm
« Reply #4 on: December 16, 2018, 08:54:18 AM »


Will change out both 'water separator' and 0751 filters (have brought spares with me) - initially and monitor when we start moving back towards the UK .

Will report back - some weeks away, as largely 'settled' in sunnier climes for the winter.

Thank you for the pointers

Best wishes all for the festive season, wherever.

Offline ptas

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Re: Laboured starting but only when warm
« Reply #5 on: December 16, 2018, 08:59:20 AM »


Perhaps only half a stroke without any resistance

Will further explore air ingress if Dave's suggested filter change out doesn't solve the warm starting

More later - but not for several weeks as largely settled for the winter / not moving regularly / frequently

Best wishes from east of the pond, somewhere

Offline ptas

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Re: Laboured starting but only when warm
« Reply #6 on: June 07, 2019, 10:41:07 PM »
To close out this topic

Fuel filters NOT changed
Made it back to the UK - warm starting issues persisted
Disconnection of the IAP sensor did not resolve issue - suggesting sensor and HEUI side of things not responsible
Replaced both the coolant and air intake sensors - the least expensive items !!
All seems good, after several trials / shorter journeys
(Still yet to test 'old' sensors to check if one / other failing when hot and sending erroneous signals to the ECM)

Recent diagnostic interrogation with CAT ECT
No faults logged (save our disconnection of the IAP) - no help there !!
Atmospheric sensor readings good  - the atmospheric sensor is the third temperature sensor that talks to the ECM when warm starting
HEUI pump / operation pressures checked and responding as should - no pump issues confirmed

Time will tell but 'normal service' appears resumed  :) :)

Thanks to all who contributed