TM 9-4940-342-14&P Table 5-1.  Troubleshooting - Continued Malfunction Probable Causes Corrective Action 2.  Low fire switch closed, burner does not ignite - Continued e.  Fuel valve or lines restricted or plugged. e.  Disconnect  fuel  tubing  to  burner  at burner.  Turn  low  fire  switch  on  and observe fuel flow from line. Visually inspect     fuel     lines     for     leaks     or crimping. Disconnect fuel supply line from   pump   to   fuel   valve   at   valve, observe fuel flow from line. Replace or repair fuel line as necessary. f.   Fuel valve solenoid coil loose or burned out (open). f.   Check tightness of coil retaining nut. Tighten nut. Disconnect control circuits 6 and 2 (high fire) or 7 and 2 (low fire) to solenoid coil from lower control terminal board. Check continuity   across   the   coil.   If   coil shows open, replace coil. g.  Flame failure lockout. g.  Red   flame   failure   light   on.   Deter- mine    cause    of    flame    failure,    see malfunction   8.   Flame   signal   below 2V  DC.  Remedy  cause  and  depress failure reset button before restart. h.  Flame safeguard contacts dirty. h.  See  service  of  flame  safeguard.  Use a burnishing tool or fine crocus cloth to clean contacts. Never use a file or sandpaper to clean contacts. i.   Defective ignition transformer. i.   Low or zero voltage between control circuits  4  and  2  at  control  terminal board.   Check   for   loose   or   broken conductor   in   circuits   4   and   2   to transformer.    Repair    or    replace    as necessary.   Remove   electrode   wires from  burner  and  hold  terminals  1/8- inch  apart.  Turn  on  low  fire  switch and    observe    if    an    electrical    arc develops     between     electrode     wire terminals. If electrode wires are good (see   step   m)   and   there   is   no   arc, check  continuity  across  transformer secondary. Replace as necessary. j.   Wire loose or broken. j.   Check  conductors  of  control  circuits 3  and  1  from  control  terminal  board to low fire switch and limit switches for  tightness  and  continuity.  Check conductors of control circuits 1, 2, 3, 4  and  7  from  control  terminal  board to flame safeguard terminal board for tightness    and    continuity.    Tighten, repair     or     replace     conductors     as necessary. k.  Low fire start switch defective. k.  See malfunction 1, step h. l.   Electrode wires loose, broken, disconnected or shorted. l.   Check    terminals    for    tightness    at ignition     transformer     and     burner. Observe     that     terminals     are     not grounding out to any adjacent metallic parts or burner. Check wires for    continuity.    Tighten,    repair    or replace conductors as necessary. m. Electrodes out of alignment. m. Remove  burner  and  check  that  gap of  electrodes  is  adjusted  to  1/16  to 3/32-inch. Adjust electrodes to proper dimensions. Connect to ignition   transformer   and   cycle   low fire   switch.   Observe   spark   is   suf- ficient to light burner. 27