I've connected the jumper but the check engine light is not flashing?

 

Does the check-engine light come on when you KOEO? It should.
If not, check that the bulb is there and is good.

The same thing happened with my 4.9l, '87 vintage...with a good CEL at KOEO.
You may have luck using the analog voltmeter method, outlined here: https://www.f150forum.com/f10/how-re...es-obdi-10907/

-phil

 

had 4 bad resistors on the pc board of the EEC. Replaced them and now it works fine... Thanks for your reply