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If you suspect it could be the switch reading the resistor on the key, there is a dongle that can be substituted (or you can make your own) to eliminate that part of the equation. Ecklers and many others carry them. You need to have your key read or use an ohm meter and if you buy the setup, it's plug and play. Find the right wires coming out of the column, unhook the connector and plug in the dongle.
Another is the neutral start switch on the clutch pedal, if you have an manual. The switch is at the top of the clutch by the pivot point. Unhood the connector and jumper the 2 wires together and it's done.
I'd like to turn on the ignition, and enable the fuel injectors is it possible without keys, using jumpers
You either need to correct the PROM (remove the FEDS) OR use for an earlier GM a 30Hz generator along with a resistor to defeat the key resistance. With "jumpers"? I guess but it might be a struggle to just "carry along" UNLESS you created connectors to the harness (weather-pack or similar) so that you could easily connect the required devices.
If you know the resistance required for the key I might consider using a "mating connector" to the VATS connector so that if I had a failure to crank I could remove the hush panel and plug in the correct resistance. I have friends that have done this, I have the connector to accomplish it but haven't done it.
I've always thought that this might be a real "carry along" for anyone with an earlier VATS system. The ignition cylinder generally fails without notice. If you use the tilt often I'd think it increases the likely hood of failure.
It gets maybe more complicated if you actually want to by-pass the start enable relay etc for a completely trouble free crank & run. All years aren't the same. Start-enable bypass is generally only done maybe on '91 and earlier. '92?