General Boards > Technical Support
C9 missing
Richard And Babs Ames:
We have replaced two injectors on our MH in 100,000 plus miles. First set a code (check engine light) and the second did not but it showed up whe they hooked up the computer.
The CAT RV help line
http://catrvclub.org/cat_rv_contacts.htm
is a great resource to see if there are any service advisories in reference to your problem. Be sure to have your engine SN and Build when you call them.
Ken Sair:
Thanks all. I have not changed fuel filters yet, since it happened only twice in one year. The thing thats got my brain working overtime is the problem 'fixes' itself after its shut down for 30-45 minutes. And, each of the 3 times its happened its been immediately after long use of the exhaust brake, which to me doesn't relate to fuel delivery. And, the symptoms are identical to the ones that existed when a previous fuel pump failed. My brain is hung up on it occuring after exhaust brake usage. Except for these 3 instances it has been performing flawlessly.
Guess I'll run it into the shop. Called the CAT hotline and the nearest facility that handles C9's is the Freightliner dealer in Fortuna CA. Even thats 50 miles away.
Joel Ashley:
Like Daryl, I'm still suspicious of the exhaust brake, though you said you thought it was OK, and whether it's operating properly when things are hot and its valve is supposed to be fully open.
Edward Buker:
I think you indicated that the last time you had the problem it was an injector and not the fuel pump that failed. You mentioned the fuel pump failing in your last post which is a bit confusing.
If it was the exhaust brake not fully opening I do not think it would create a shudder. My guess is that the shudder comes from going through a compression stroke without any fuel to fire which puts things out of balance. If all cylinders were firing and the exhaust brake was partially shut then I think things would be in balance but you would lack power.
These injectors and pumps have very tight tolerances to meter the fuel precisely in order to meet emission standards. It is concievable that you build higher temperatures in the injector while using the exhaust brake, especially after the heavy load and heat of climbing and it siezes the injector when the tolerances are reduced due to expansion. When your engine returns to lower temperature the expansion reduces and it starts to work again. To some extent the injector is cooled by fuel usage which you stop while running the exhaust brake. If this mechanism was taking place in the pump i think it would affect all the cylinders and provide another symptom. This is one possible explanation, Cat will have the real answer.
I mentioned in my last post on this subject that having a Cat sign on a Freightliner dealership does not make them experts. I was towed into a Freightliner dealer with a Cat sign near Denver. Two days later I called up the largest Cat dealership I could find in Denver and had my coach towed there. They had it fixed in 6 hours and the knowledge base there was worlds apart from the Freightliner dealership. If this is not a common issue you may want to discuss your problem with a major Cat dealership and see what they think.
Ken Sair:
Thanks all. The exhaust brake is working properly. Turns on/off as usual and is slowing the coach the same as when brand new. I have not had a fuel pump issue to date to my knowledge. The 'missing' is occuring after long downhill runs using the exhaust brake and then normal acceleration on the flat land or up the next incline.
Like I said, the symptoms are exactly the same as when I lost a fuel injector in Oct 2008. They are, engine missing like running on 5 cylinders instead of six. More throttle pressure increases the coach 'shudder'.
What has me baffled is that twice last week when it happened, I shut off the motor for 30-45 minutes and then on re-start the engine ran perfect. My opinion as the operator is that sometime during the extended use of the exhaust brake on long downhill runs , the fuel injector will stick open/closed (whichever applies), thus causing it to operate on 5 cylinders which causes the coach 'shudder'. Then after a small 'timeout', it resets (for lack of a better term) and works properly.
Go figure. Hopefully I drove it long enough for an engine code to show up. Calling tomorrow for a Wednesday appointment.
So, I called CAT hotline again and spoke with Mark. he recommended a CAT dealer in Riverside CA which is only 27 miles away. He wouldn't venture a guess but I'm leaning towards the injector. Thats after a long phone conversation with Gerald this am.
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