I've got an '02 Freightliner Columbia with a C12 in it.  It has 510,000 miles on it.  I put a boatload of money into little nickel and dime things this Spring and ever since then I've had issues with it.  When I start it in the morning, or after it has set for an hour or two, doesn't run right.  It will idle just fine but when I try to accelerate it will sputter and blow white smoke.  After 10-20 seconds (occasionally longer) it will start firing on all cylinders and run fine until the next shut down.  Also, it doesn't do it every time.  Probably 75%.

It started after I had them repair the engine brake.  If I recall they replaced the injector harness (sounds suspicious?).  I took it back and they said the hand pump was leaking and I was loosing prime so they replaced it and it ran fine when I took it home.  Dad drove it this summer with the tender trailer and I did some too and I got preoccupied with spraying that I forgot about it.  Now it seems to be getting worse.  What will they find when I take it back in?

Your mechanics need to get some sight glasses on the fuel "supply" and fuel "return" lines and see "WHERE" air is getting into the fuel system and trouble-shoot from there.

Yes, there is a possibility that you might have a problem with "fuel return check valve" (# 5 in photo) but normally a fuel pressure test will determine if that tends to be the culprit (meaning with a mechanic's mechanical fuel pressure gauge installed, and run engine; then shut off engine, then fuel pressure "should be" trapped (=if you have a good fuel return check valve AND a good fuel hand priming pump) The trapped fuel pressure will probably read at least 50 psi; with engine just being shutdown. {If it drops immediately to 0 psi, then try a new fuel return check valve(#5) and retest.

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(c-12 fuel fitler base photo.jpg)

sight glass troubleshooting tools.png (11KB - 1444 downloads)

c-12 fuel fitler base photo.jpg (77KB - 1102 downloads)