No injector pulse

I'm a automotive technician, customer had vehicle
towed in intermittent no start. Had replaced fuel
pump and filter. Started and ran but same as b4.
Would run for a week, two weeks ,then nothing.
(Note. Had same problem before fuel pump was
replaced) checked all grounds, checked fuses,
relays, fuel pressure, spark finally no injector pulse
didn't have voltage to injectors with koeo. Nothing
new to me most common problem was ignition
control module. Swapped no fix. Replaced injector
harness got voltage to injectors. Still no start.
Noticed at this time I had no rpms swapped crank
sensor. Still no pulse. New ignition (switch and
tumbler/key) did relean process" never had theft
light solid or flashing" still nothing.  Any ideas?  I've
heard the chip reader for the key. And putting in
resistors.(not tried yet) I've heard knock sensors,
I've heard cam sensor , I've heard oil sending unit.  
All of which I'm up to try . Just never seen a sensor
work then not then work again. Unless related to
tempature or some sort of physical force. I got a
few things left to try but I'm getting short on time ,
other vehicles to fix. Any ideas appreciated. Also
note no codes (checked with 2018 versa scanner)
will start on brake clean. (55psi fuel pressure)