Postby VStar650CL » Wed Dec 28, 2022 5:02 pm
This all assumes you've already popped a coil and a plug to make sure you have spark and that the plugs aren't soaking wet. Nothing Nissan will start when flooded, and of course you need good spark. On Nissans the ignition timing is determined by the crank sensor (CKP), so if the coils have power but there's no spark, immediately suspect a bad CKP.
Checking for a fuel starvation issue is easy, pop the airbox and spray something combustible like Brakleen or Gumout down the barrel. If it starts and stalls then it's fuel starved, if it starts and stays running then it probably has low fuel pressure (most likely a balky pump). If it doesn't start then you've excluded fuel starvation as the cause. The fuel systems on Nissan VQ's with port injection are dirt-simple, the check valve and filter are both built into the pump, so there's really nothing besides a bad pump which can cause low pressure.
The MAF is hard to check without a scanner that can stream data, but I'm pretty sure your Blue Driver will do that. The rule of thumb is that you should see a bit more than the engine's displacement in grams per second at idle, so a VQ40 should read something around 5 GpS at idle and about 1.5 GpS when cranking. Some scanners give pounds per minute instead of GpS, to convert it multiply by 7.5. The reading should be reasonably steady and go up predictably when you tap the gas. When MAF's go bad, the most typical symptom is inconsistency.
Nissan VQ engines have a useful trait that you can use to check the CKP and cam (CMP) sensors. First, understand that a no-codes no-start occurs when one of the sensors is lying but not dead. Dead sensors will give you codes. On VQ's, if the CKP is good but both CMP's are dead, it will start on the CKP alone after a long crank. If both CMP's are good but the CKP is dead, it's the same thing. So you can exclude the CKP by disconnecting both CMP's and see if it starts. If it does, the CKP is vindicated and one of the CMP's is implicated. If it doesn't start, reconnect the CMP's and disconnect the CKP. If that starts it then the CKP is bad, if it still won't start then the problem is elsewhere.