This is an older Bryant furnace, model 394GAW.

It has electronic ignition. Pilot lights fine and stays burning when thermostat
Requesting heat. Burners ignite, but then only for about 4-5 secs, then go out. This
Will repeat about every 30 secs or so. The blower never starts.

I found numerous posts on internet about replacing the 3 wire pilot/flame sensor, which I did, and it didn't make any difference.

I checked the circuit to the gas valve, and on the leads by the valve to the burners,
It will read 0v and then 24v and the burners will ignite (assuming that this opens
The gas valve to the burners) returns to 0v in about 1 sec and burners then go out.

Any suggestions?