90 civic dx flashing code 20. Cranks but won't start. It quit like you turned off the key. Nice car, it quit three blocks from home. Best guesses anyone?

20--Electrical load detector

It may require replacing the under hood fuse/relay box, which is not cheap, or the ECM. A Code 20 is not a good one to have, if it's a legitimate code. These are extremely rare. Does the CEL stay on, when the ignition switch is turned to ON (Position II)?

The CEL goes out in just a few seconds. I discovered Yesterday I'm getting no fuel pressure. I pulled the main relay, I will get time later to check that. I thought I heard the fuel pump Yesterday running weakly just once, but I never heard it again. I pulled the bleeder bolt, poked a piece of aquarium tubing in the hole to run the fuel overboard. Turned the key on and got nothing

The CEL will go off after a bulb check with key-on.
Check for power and ground at the fuel pump.
Power on the Yel/Blk wire and Ground on the Black one. You should have power there for two seconds after key-on.
Ground is constant.

OK here we go, Yes I have power at the connector under the rear seat. And the ground reads 0 ohms.
I get 13 volts briefly two seconds, then a steady 11 v.

I got the car to idle for two or three minutes earlier, after I reinstalled the main relay.( relay checked good)
After it quit again that's when I checked for power at the fuel pump. Do I need an adapter or something to hook up my fuel pressure gauge? Looks like a shrader (tire) valve on the gauge but I don't see one on the fuel system.