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Case Magnum 305 won't start when hot

10K views 6 replies 5 participants last post by  cihmech 
#1 · (Edited)
Hi I'm Gary of AGSERVE MOBILE DIESEL SERVICES , located in Kapunda, South Australia. I service mostly Case headers and tractors to the Mid North region of South Australia.
I have come across a problem with a Case Magnum 305. It won't start when hot, it cranks over fine & puffs out black smoke, batteries are excellent, but will not start until temp drops to 82*C or below.
 
#4 ·
Black smoke is a good thing, it's not compression as it would not start when cold. You are headed toward a fuel problem, I would check lift pump pressures first, even fuel filters before you move to the injection pump. When cranking feel the injection lines for pulse, listen for injectors poping, listen when cold compared to hot
 
#5 ·
Lift pumps will cause starting problems but its usually when you start it the first time. After that it reprimed. There is a way to test the accumulator but you will need a cnh laptop or someone with cummins software. Disconnect injection control valve try to start eng and watch the Fuel pressure on laptop. If the actual pressure and setpoint pressure are not within a couple hundred psi. The accumulator is bad.
 
#6 ·
the fuel pump that boosts the pressure to the high pressure pump is likely the issue, it bolts on to the back of the high pressure pump with 4 or so bolts, it has a little drive coupler on it. if the pressure does not meet the spec[ around 150 psi] it will not start. the electric pump runs for up to 55 seconds to prime the system and then the midrange pump takes over for the duration of the runtime. changed quite a few over the past few years, random start issues and no hot start ability. if the ecm does not see required pressure it will not allow permissive for a start. also check your crankshaft pickup for integrity, if it has metal fuzz onit or has any oil in the connection it can cause an issue as well.
 
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