Defective Heater: Troubleshooting & Repair

Hello.

I have an old Eberspächer B1L air heater here.


'When I just plug it in and start it, it starts to glow and pump fuel, but it doesn't ignite. And I'm worried about letting it run for too long until the control unit shuts it off after 3 minutes, because before that, it might start sputtering flames out of the exhaust (because it's flooded with fuel). The glow plug is new (but I don't know if it's the right one), and there's this white/gray, burnt-looking stuff around the glow plug inside the combustion chamber. Could it be that there's still some kind of metal piece missing?'


'If I briefly unplug the connector from the dosing pump for about 30-40 seconds, the heater starts and continues to run normally. When you plug the connector back in, it works as if you were slightly restricting the exhaust. Are there specific minimum lengths that need to be observed? I haven't been able to find any instructions anywhere for the B1L/D1L models, and no one at Eberspächer is responding to my emails.'


Is there a way to distinguish between a B1l and a D1l?