LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Ford >> 1984 >> Ranger 2.2 P >> Repair and Diagnosis >> Engine Performance >> System >> Fuel Injection System - Diesel >> Testing >> Glow Plug System
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Glow Plug System

  1. Place transmission in neutral. If engine coolant temperature is above 86°F (30°C), jumper connections at coolant thermoswitch. Turn ignition switch to "RUN" position. Using a voltmeter, check voltage at each glow plug lead. Voltage should be at least 11 volts at each lead for 6 seconds, then drop to 4.2-5.3 volts.
  2. If voltage is ok, remove jumper from thermoswitch and proceed to step 16. If voltage is present at 1 or more glow plugs, but not all glow plugs, replace glow plug harness and retest. If voltage drops to 0 volts after 6 seconds, proceed to step 7. If voltage is not present at any glow plug lead, proceed to next step.
  3. Disconnect glow plug harness from engine harness and glow plugs. Connect a self-powered test lamp between glow plug harness connector and each glow plug terminal. If test lamp does not light, repair or replace glow plug harness and retest. If test lamp lights, reconnect both ends of glow plug harness and proceed to next step.
  4. Connect a 12 volt test lamp between glow plug control module terminal 9 and ground. Turn ignition switch to "RUN" position. If test lamp does not light, repair and/or replace ignition switch and/or wiring and retest. If test lamp lights, proceed to next step.
    Fig 1: Glow Plug Control Module Terminals Module is located behind kick-panel on passenger side.
    G8707
  5. Connect a test lamp between glow plug control module terminal 6 and ground. Turn ignition switch to "RUN" position. If test lamp does not light, replace control unit and recheck voltage at terminal 6. If test lamp lights for 6 seconds, proceed to next step.
  6. Connect a test lamp between the No. 1 glow plug relay signal terminal and ground. Turn ignition switch to "RUN" position. If test lamp does not light, repair or replace wiring from relay to control module terminal 6 and then recheck for voltage at relay. If test lamp lights for 6 seconds, proceed to next step.
  7. Connect a voltmeter between No. 1 glow plug relay output terminal and ground. Turn ignition switch to "RUN" position. If voltage is 11 volts or more for 6 seconds, proceed to step 15. If voltage is less than 11 volts, replace the No. 1 relay and recheck voltage at output terminal.
  8. Connect a test lamp between glow plug control module terminal 10 and ground. Turn ignition switch to "RUN" position. If test lamp lights, proceed to step 11. If test lamp does not light, proceed to next step.
  9. Using a self-powered test lamp, check the functioning of both the clutch and neutral switches in both open and closed positions. With transmission in gear and clutch pedal released, both switches should be closed.
  10. With transmission in neutral and clutch pedal depressed, both switches should be open. If either or both of the switches does not operate as specified, replace switch and retest. If both switches operate properly, proceed to next step.
  11. Connect a test lamp between No. 2 glow plug relay signal terminal and ground. Shift transmission into Neutral or "N". Turn ignition switch to "RUN" position. If test lamp does not light, repair or replace wiring from control module terminal 10 to No. 2 relay and recheck for voltage at relay. If test lamp lights, proceed to next step.
  12. Connect a test lamp between the No. 2 glow plug relay output terminal and ground. Turn ignition switch to "RUN" position. If test lamp does not light, replace No. 2 relay and recheck for voltage at output terminal. If test lamp lights, proceed to next step.
  13. Disconnect dropping resistor from wiring harness. Connect a test lamp between the dropping resistor input terminal on wiring harness and ground. Turn ignition switch to "RUN" position. If test lamp does not light, repair or replace wiring from No. 2 relay to dropping resistor and recheck for voltage at input terminal. If test lamp lights, proceed to next step.
  14. Connect an ohmmeter to the terminals of the dropping resistor. Ohmmeter should read less than 1 ohm. If resistance is not to specifications, replace dropping resistor and recheck resistance. If resistance is correct, reconnect resistor and proceed to next step.
  15. Connect a test lamp between any glow plug terminal and ground. Turn ignition switch to "RUN" position. If test lamp does not light. Repair or replace wiring from No. 1 glow plug relay to glow plug harness and recheck for voltage at glow plug terminal. If test lamp lights, return to step 1.
  16. Disconnect leads from each glow plug. Connect 1 lead of ohmmeter to glow plug terminal and 1 lead to a good ground. Test each glow plug. If meter indicates less than 1 ohm, problem is not in glow plug system. If meter indicates 1 ohm or more, replace glow plug and retest.
scientia non olet · About LEMON Manuals