I have a 2003 3500 with a cummins 5.9. Recently it has been taking a long time turning over before it starts. I changed one of my intake heater relays which was hooped. This helped clear up some of the smoke on startup but didn't fix the starting problem. When it is cooler it will crank for what feels like 10 seconds before it fires. Previously it would crank over 3-4 turns and fire. Any suggestions on where I should be checking out. Thanks in advance.

 

Sounds like an injector issue. Mine kept gradually taking longer and longer to start, finally took it in under warranty yet and they did a flow test, #1 injector was bad. Started just fine since then.