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C7 Cat starts hard.

Logger72 ยท 2022-07-20 20:11

I have a Cat C7 in a FL 80 , after it sits a day or so it is hard to start, it fires but only on a couple of cylinders, when it finally starts it blows blue smoke, after that it runs fine. Any ideas what may be causing this? Thanks

Replies4
  1. #1Coaldust2022-07-20 21:12

    Yeah. The plastic fuel lines and quick disconnect fittings that Freightliner used are horrible. Cat issued a number of Bulletins on the subject. They will leak air, but not leak fuel. Installing a Cat hand-primer pump is a nice addition. The restriction fitting, fuel return check valve thingy on the cylinder head can be an issue, as well.

  2. #2Logger722022-07-21 12:49

    Thanks,I will check all that over.

  3. #3JPV2022-07-21 13:17

    If that stuff checks out ok it could be the temp sensor for the engine ecm is bad. You will have to plug something in to monitor it but if it is reading hot when the engine is cold it will start like that. I have seen that before on a C7 in an excavator. After it started the sensor would snap out of it and work properly. I am not familiar with whether or not Freightliner uses the computer sensor for the temp guage on the dash or a separate sensor, if they use the same sensor just watch the temp guage to make sure it is reading right when cold. Paccar uses a separate sending unit for the dash.

  4. #4Truck Shop2022-07-21 19:43

    Depends on years and models.