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+--- Thread: cm2350 fuel in oil (/showthread.php?tid=10409)
cm2350 fuel in oil - hct5 - 11-25-2025
we installed a new short block, head, fuel pump tappets and housing on this unit around 10k miles ago and it has been running great, last week we noticed that fuel is getting into the oil somewhere. we ran the truck on a bucket full of dyed fuel and did not see any injectors leaking. the fuel return line and check valve have been replaced. what could i check next to find the issue? could the fuel pump head be leaking into the pump housing?
RE: cm2350 fuel in oil - Rawze - 11-25-2025
== Fuel in oil is typically a cracked head.... though it could be the fuel pump, but that is much more rare.
== What is the power/torque?.
== What does oil sampling analysis show?. Only fuel in oil?. or coolant too?.
== are oil levels rising?.
== Is it deleted?.. and if so, who made the program?.
== OEM cylinder head?.
RE: cm2350 fuel in oil - hct5 - 11-25-2025
450hp and 1550 torque
i am sending an oil sample out today.
the oil level is rising but just a little every day. we have not had to add coolant and the pressure test shows no pressure drop.
it is deleted , by a trusted source.
yep new OEM head.
RE: cm2350 fuel in oil - marek4792 - 11-25-2025
Could be the fuel pump gear pump behind the high pressure pump. They are prone to oil/fuel cross contamination..
RE: cm2350 fuel in oil - hct5 - 11-25-2025
is there any way to test the pump to see if it is causing the issue?
RE: cm2350 fuel in oil - marek4792 - 11-26-2025
Without taking it apart, check if it's dirty/ leaking around the weep hole area and/or where it bolts up to the main fuel pump. Something to consider too is if it's got 500k+ miles and it feels like the power is falling off. The gear pump probably is getting tired before the seals outright failed.. Just from my experience replacing mine recently.