I used my R155 kerosene heater for years in my garage without any problems. Then the 097061-01 solid state relay went out. I replaced it with new part number 107850-01. At the same time, I also figured I would replace the filters & gasket (HA3017) and the rotor (HA3004). When putting it back together, I used the HA1182 low pressure gauge I bought to set the psi to 5.0 psi like the manual said. Upon doing this, it would only blow out a cloud of atomized kerosene and not light. If I put my finger over the adjustment screw and let the pressure increase toward 10 psi, it would light but then go out as it returned to 5.0. I tried increasing the pressure. At ~6 psi would allow it to stay lit but your eyes burned from unburnt kerosene as it ran longer and longer. I decided to replace the other components related to the fuel air mixture (HA3010 nozzle and PP211 spark plug). No improvement. I increased the pressure to 8.0 psi which made the end cap glow slightly but it would stay lit and not put out a cloud as it tried to start.

Can you help give me some guidance as to what is wrong or what to check??

Have you inspected the air filter located at the rear of the heater? What about the fuel filter located inside the tank? Sounds like you are working toward the price of just replacing the whole unit. Be careful and not spend too much on the current heater.