03 duramax with 125k
 

Am purchasing this truck from gm dealer and had starting problem before I agreed to purchase had aftermarket fuel pump mounted on it they removed because said caused hard start problem been driving it for about 3 weeks took back cause wouldnt start after warm and had code for low rail pressure they said was fuel filter, they changed and wad ok for few days and now will not start after driven and shutoff takes about an hour have tried bleeding and primer don't make diff any ideas???

Injectors

injectors
 

Dealer said
Not injectors and no fuel in oil either

?how do they know. what tests did they preform? fuel in oil is not always the indicator that the injectors are bad.

injectors can crack/leak fuel under the valve cover and put fuel in the oil. they can also have the ball/seat erosion problem and return excessive amount of fuel to the tank.

this would cause a low fuel pressure symptom which would make it hard to start.

it could also be a worn out CP3 or bad regulator, but i doubt it. LB7s where notorious for injector failures. the dealer may be just trying to get out of replacing the injectors as it is time consuming to do on the LB7s

-have them do the balance rate test on the injectors
-check the actual vs desired fuel pressure during cranking and idling -have them command max fuel psi during idle while monitoring actual vs desired fuel pressure
-they can also check for excessive return on the injectors and CP3
-last but not least are the batteries, week batteries can sometime do this

post back any results and we can take it from there

what type ofof aftermarket fuel pump was on it