Ihave a luxaire 90 gas furnace the inducer starts pressure swithch closes, hot surface ignitor glows burners ignite once the hot surface ignitor shuts down the gas valve closes, the thermacouple is working just installed a new one and I jumped out the rollout safety. Any ideas?

Hot surface ignition furnaces don't have thermocouples. Did you replace the flame sensor?

Describe in more detail what happens when the HSI heats up and the gas turns on.

You should have a flashing light on the control board giving you the fault code. You need a good equipment ground on the gas valve and control board for the flame sensor to work and sense the flame. If it's a pressure switch fault you need to make sure you have a clear exhaust and intake pipe. A restricted condensate drain will open the pressure switch also. Good luck I hope this was of some help.

Yes I am sorry I replaced the flame sensor and also jumoed out the roll out switch. The HSI lights up opens the gas valve and lights the burner but it seems that when the HSI shuts off the gas valve then closes putting the burners out tries that 3 time then goes on lock out I have 7 flashes on the led board

It should say on the door of the furnace what fault code 7 is. If you can locate it. It will help expedite trouble shooting.

How long do the burners stay lit before shutting off?

Finding the diagnostic code for the seven flash will probably confirm that the furnace is shutting off because the burner flame ignition isn't being detected.

Check to be sure that the wire from the flame sensor is properly connected to the circuit board and that the circuit board has a GOOD ground connection.

Also, measure the AC voltage between the flame sensor wire and chassis ground while the inducer motor is running and report that voltage here.

You may have a bad circuit board that is failing to detect the burner flames.