Duramax Question

[WMonroe]

A guy I know from work has an 04 gmc 3/4 ton duramax/allison and it has trouble starting. He said it will start all right in the morning so he believes the glow plugs are working, but when the engine is warm it cranks for a long time (about 5-10 seconds, it varies from time to time). It seems like it is getting fuel because it tries to run but it just won't fire enough to start. He said he replaced the fuel filter, and he always does oil analysis and he says everything comes back "normal". Anyone have any ideas?

Thanks in advance.

Will

 

[DF5152]

crank or cam sensor may be building resistance when hot and not giving the signal needed to start