HP 5890 Series II Plus Reference Manual page 154

Detector Systems
Flame photometric detector (FPD)
3. Under some operating conditions, it is important to continue to hold
the ignitor switch in for several seconds after opening the hydrogen
valve fully counterclockwise.
4. Under some operating conditions, the flame may be more easily lit
with the rubber drip tube removed. After lighting the flame, reinstall
the drip tube and FPD cover assembly.
5. Under some conditions, the flame may be more easily lit with the
detector temperature raised to 200 C or higher (but do not exceed the
detector's maximum temperature of 300 C) and ignite the flame.
After the flame is lit, set the detector to the required temperature.
6. If none of the above are sufficient to light the flame, try increasing the
hydrogen supply pressure by 20-40%. After igniting the flame,
reduce the hydrogen supply pressure to the initial value.
7. If the flame still won't light after trying the preceding steps, there
may be a large leak in the system. This can result in measured flow
rates being significantly different from actual flow rates, resulting in
nonideal ignition conditions. Thoroughly leak•checkthe whole system.
154