Gas and Oil Home Heating Furnaces - Furnace Problem

I need some help troubleshooting my furnace. It is an OLD (70's) Bard Oil burner. Monday, received fuel. Mon night it stopped working.
Tue Repair man shows up. Replaces Tank Filter, Nozzle and transformer. Works Great of a day. now no work again. If I hit the reset it will burn, lots of fire in the chamber. I can watch the "thermostat" that controls the blower on the ducting rise. After a couple resets the temp is high enough the blower will run. I am good to go until the blower shuts off then the burner trips out again.
Any help will be greatly appreciated.

It is a Bard Furnace not sure of the burner of had, believe the motor started with FL. The Reset box is newer in the last 8 yrs, again unknown brand/model.
The flame starts and runs up to 90 sec or so then kicks out. After a couple times the blower tstat kicks on the blower.
Once the blower was running it ran for a couple hours until the house came up to temp. Although the register heat didn't feel as hot as normal.
After the blower kicked off, the red light on the reset was lit again.
The next time I was able to do the same things to get the continuous run but the furnace shut down before the house was up to temp.

I'd call the service company back since they just serviced it on Tue.

something is set up wrong.

Did they do a draft/smoke test?

Can you see if the fire is burning really crisp looking (sharp-edged fire with no smoke inside the burner box) and no soot is visible coming from the chimney outside? Can you tell if the draft is good?

I would like to thank everyone for the help on this. After future investigation it appears the even the slightest crud on the photocell will cause it to shut down. I clean the lens and reinstalled an the furnace is working as good as it was.

Again, thanks for the help.