I have a goodman furance modal gmt115-5b. The flame at heat bar come on only for a few seconds then goes right off.

https://www.askmehelpdesk.com/heatin...ons-58313.html

Clean flame senser,and make sure it has a good tight connection,, does it run and quit evertime it tries to start up? Flame senser on goodman usually has 1 white wire going to it, are you sure you have good gas pressure,