intermediate crank signal

[awesometool]

I'm having trouble with intermediate crank signal so when I turn engine over the rpms are at 0 but when I let off the key it jumps up then right back to 0. It will not start with no crank signal. I have tried changing starter, disconnected alternator, pull one fuse at a time, reground battery to block and frame, 00 starter wire, disconnected the dfu's, disconnected the fans, tec unit is direct batttery power and grounded well.
I do not have and electric water pump and the crank wire is well insulated. If the spark plugs are removed it has a perfect crank signal. I done working on it for today and I try again tommorrow. Any help would be appreciated.

[EFI69Cam]

Are the connections from the sensors to the ECU shielded with both ends of the shielding grounded? What kind of wire are you using?
What type of signal does the crank sensor put out? 12v saw tooth (hall effect) or sine wave?

[MonzaRacer]

What are you working on exactly?

[megaladon6]

here's a couple of SWAG's
IIRC the crank sensor is grounded through the block, but it sounds like yours is grounding through the ignition.
or the crank gnd goes to the ECM and yours is through the ignition