If you were using the valve cover as a ground for the spark check the valve cover is electrically isolated from the engine block by the plastic mount bolts around bushings

Have you jumped the # 1 fuel pump relay to confirm the pump can be directly powered to run ?

With the rotation of the key the pump will be commanded on for 3 seconds only

There is a small fuel pump control fuse that handles both pumps located at the rear

seat heelboard

 

I will double check spark with confirmed ground.
the fuel pump does not come on for 3 seconds.
the fuel pump pumps when jumpered.

 

With the fuel pump not being normally commanded on for 3 seconds points to the ignition switch and the ECU that the 3 second fuel pump command comes from

Swapped fuel pump relays as you have 2 ?

If it comes to the ignition switch you keep the key barrel installed as the switch is separate so no new key needed

Did you swap the 2 ECU power relays ?

 

I have swapped both the fuel pump relays and the ECU power Relays.
I checked again for spark with a definite ground connection, no spark.

I guess I will have to measure my way to find the culprit. Any tips to quickly check if it is the ECU or ignition switch?
I have read the diagrams but sometimes it's hard to translate the order of things to reality.

Again all the relays seem fine and I still do not have any fuel or spark.

 

The first power to the ECU is commanded by the ignition switch from pin X to pin 5 which pin 5 is a car frame ground that can get corroded on the switch connector or disturbing the car frame ground connection

If it gets to it replacing the ignition switch does not need a new key barrel or key

The second power or the ECU Control Relay is commanded closed by the ECU and brings power back into the ECU and some engine sensor including the control power directly " sitting " on the fuel injectors

The ECU will provide a command in the form of a ground to momentarily open the fuel injectors with 6 independent wires



This is a pic of the V - 12 which has the same first power / ignition switch
relationship




So by combining a starting and engine regulation print the link to the right engine bay fuse box relay to close is on pin X of the ignition switch

7 stop sign double hash is the point we're looking at which requires a 3rd schematic page

Still editing


X is pin 3 on the ignition switch , notice the inertia switch that can be easily bypassed if pressing does not reset the inertia switch

 

Today the car started!

The worrying thing is I'm not sure why. After measuring the pins and seeing that there seemed to be no problem with the ignition switch I decided to check on the large ECU relay again. The relay had not been in place since I tried jumpering it last time so I pushed the relay in place and to my surprise I heard the beautiful relay click and fuel pump from the back, I turned the key, and voila! The engine runs like a charm.

I wanted to make sure that the old intermittent immobilizer issue was not the culprit. First, I removed my forced ground cable to the bpm for the CEL, and it still lit up the dash. Even more surprising, I could completely unplug the SCLM immobilizer connector and still get CEL in the dash and able to start. So my guess is my reprogrammed ECU does not need any security clearance.
But the question remains. Why did it start now after putting in a relay that I have troubleshooted multiple times?

I'm beginning to think this car has a mind of its own

 

There is a connector you did not bother that is above the fuel tank on the trunk side that can be connected but intermitent

This is the BT4 connector carrying the wires between the SLCU and the engine ECU up front , also the fuel pump enable from the engine ECU and the # 1 fuel pump relay

It should have a tie wrap on the lock over bar to hold it clamped / engaged

The trick with this connectors is that it has layers of sheet metal cut out so it can clamp fully

The problem is engaging the lock over bar pins and not breaking them by forcing the connector closed in the process

So this is something you would have to if you remove it reinstall it with patients.

This connector is the same as the LS3 and RS3 up front that we may get to tinkering with later

 

But there is an easier connector under the hood to look at

This connector has to do with fuel pump enable

With no start with starter fluid , do you get a couple of combustions on one of a few cylinders ?

Did you change fuel injectors that can be the wrong injectors

Can you measure 43 PSI fuel pressure ?

 

Place your finger on the # 1 fuel pump relay and feel for it to click 2 times on -off for 3 seconds only with key rotation

You can swap this relay with the # 2 fuel pump fwd of your battery

The relay can click closed but still be bad and not properly power the fuel pump on the relay internal power contacts

 

The relay case is fairly easy to prise off then you can clean the contacts with emery paper.

Cheers,
Jeff.