Kjet stranding, starts and immediately dies

1981 240 kjet ci
Starts, dies in 2 seconds
Ran great, now I'm stranded.
Feels like start injector gets her going, then dies when.key released,and main system doesn't put fuelout
Jumpered pumps, no change.

Was symptom when I acquired car, found big hose toairvalve off under manifold, ran ok after fixing that, then I redid all sorts of stuff and she ran great until now.all pressures were good, overall shape is great, new vac line s, cleaneddistro and CPR, new harness, all was clean and orderly.
No vac leaks right now, what is going on?

Sounds like you're losing spark. Have you tried bypassing the ballast resistor?

was fuel pump relay, part that activates ignition, I jumpered 12V+ to the brown wire at coil, she stayed running and got home.

Weird thing is, exact symptoms when I bought car, thought I fixed it by vacuum leak fix, btu it spontaneously fixed itself and failed months later again.
weird

I got dam tired of replacing the K Jet fuel pump relay so I did this: https://www.240turbo.com/fuelpumprelay.html
I had a 30 A Bosch 5 pin relay sitting around so you shrink wrap the center pin and follow the diagram, the factory relay runs a lot cooler now. The downside is the noise from the extra relay is noticable, but I will swap to a modern relay to stop that minor issue.

Part of the problem was the relay plug was melted from the excessive heat, causing a bad connection/arcing on the #30 pin, burned up 3 relays in a few months till I figured out the relay pug needed to be fixed. Got that stuff from Dave Barton also, it's pretty cheap.