350 mag mpi 5.7

[Bigsam1343]

My 350 mag mpi 5.7l (closed cooling) crank but wont starts.
Tried several times but no start, just cranking, after a week it starts with no issue at all.
Now the problem persists again!!
( ive put new batteries, changed the 90 amp fuse, new alternator, and new water pump beside ive Changed all the filters and oils)
My engine sits on a beautifull amberjack 270 model 2005
Any ideas guys?

 

[MiLoII]

When it's just cranking and not starting you need to figure out what ingredient is missing, spark or fuel. When you first supply power to the engine, i.e. on the battery panel and engage the starter switch to the middle position do you hear the fuel system priming? I would guess since the issue is intermittent leads to a short somewhere, fuel relay etc. You need to trace and isolate

 

[Bigsam1343]

When it's just cranking and not starting you need to figure out what ingredient is missing, spark or fuel. When you first supply power to the engine, i.e. on the battery panel and engage the starter switch to the middle position do you hear the fuel system priming? I would guess since the issue is intermittent leads to a short somewhere, fuel relay etc. You need to trace and isolate

Is it bcz intermittent, would isolate high and low pressure fuel pumps?
If yes where do u recommend to check?