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Cummins Bronco issues

754 views 5 replies 6 participants last post by  total newb 
#1 ·
Wasn't sure where to post this so whatever.

I recently swapped a 12v ve pump cummins into my bronco. All new fuel lines. The damn truck looses a prime after sitting overnight. It starts after cranking for a while, and runs like shit. If I bleed like 3 injectors it runs runs like normal.

Any ideas?! Things gonna drive me to drink!
 
#2 ·
I'm not a diesel expert by far but there is a leak somewhere in the system. Just thinking aloud here ... is it possible that one or more injectors are bleeding down overnight and then it runs like shit in the morning until it clears the extra fuel in the cylinders?

EDIT: Google "cummins 12-valve losing prime." Apparently a very common issue.
 
#5 ·
Any small leak in the fuel system will cause this. The leak let's air in so fuel can return to tank overnight. Check water separate valve on fuel filter, orings in fuel heater above fuel filter, there are also several spots on the rotary pump witch can leak. These are all on an early 12 valve with rotary pump. The p pumps have different fuel system.
 
#6 ·
What type of fuel filter did you use? The cast alum housing that mounts on the dside rear of the motor uses 3 orings. I missed the smallest inner oring and it would lose prime after a few min of sitting sometimes.

Stupid but it happens
 
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