The returnless fuel system first used by Chrysler in 1993 on their 5.9 liter V-8s, and now used on most models, uses the following components: combination fuel pressure regulator/filter and fuel pump inlet filter.
The metallic components are made of stainless steel for flexible fuel compatibility.

The regulator/filter is located at the top of the fuel pump module. The regulator consists of a diaphragm and spring mechanism that unload a secondary spring-loaded check valve to control the system pressure. The pressure regulator/filter is a single pass design; only the fuel needed by the engine is filtered, which results in longer filter life and allows a smaller, less expensive filter to do the job. The fuel pressure is maintained constant under all engine loads.

The system can be checked to determine if your low fuel pressure is the pump or regulator only on models that have a small return line at the tank. But not all models have the return hose at the tank. On the ones that do, you can restrict the return hose and see if the fuel pressure increases. However, on the models that do not have the small hose, it could be a fuel pump or regulator problem The parts are sold separately or as an assembly. It is your choice to do the whole assembly and be done with it, or do each part individually and do it twice. It shouldn't come as a surprise that most technicians are replacing the whole assembly, due to the time factor.

Caravan/Voyager
Understanding Interior Dimming
Starting in the 1991 model year, interior dimming is controlled by the Pulse Width Dimming Module. This module is located behind the dash and to the left of the steering column. There are six wires going to it:

• Terminal No. 1 is a tan wire and is the power feed for the module -- comes from fuse No. 9.
  
• Terminal No. 2 is an orange/white trace wire and it goes to the radio display.
  
• Terminal No. 3 is an orange wire that comes from the headlamp switch rheostat. This is the input for the module.
  
• Terminal No. 4 is an orange wire. It goes to all the interior lights -- dash illumination, cigar lighter, ash tray receiver, A/C and heater controls, overhead console, lift gate and rear defroster switches. This is also the output from the module.
  
• Terminal No. 5 is a black wire and is the ground circuit for the module.
  
• Terminal No. 6 is a yellow wire that comes from the headlamp switch -- this is the courtesy dome lamp manual "on."

• At terminal No. 1 you should have battery voltage with the headlamps "on." If not, you will have to check fuse No. 9. If OK, check for an open circuit.
  
• Terminal No. 2 will have a varying voltage going to the radio display. As the rheostat is increased or decreased, voltage on this circuit will be inverse compared to the interior lights.
  
• Terminal No. 3 will have a varying voltage from 0 volts to 5 volts depending on rheostat position. The dimming module does have a 5-volt bias on it and is taken to ground through the headlamp switch.
  
• Terminal No. 4 will have varying voltage from 12 volts to 0 volts. This is the output and will control the intensity of the interior lights.
  
• Terminal No. 5 should have less than 50 mv on this circuit, as this is the ground for the module.
  
• Terminal No. 6 should have battery voltage on it when the courtesy switch is turned on, and low voltage when turned off. This circuit does have a bias voltage of 9 volts from the module. When the switch is not activated, this voltage gets pulled to 0 volts through the headlamp switch.

Greg Montero is an Identifix DaimlerChrysler, Hyundai and Mitsubishi specialist. He is an ASE master with L1 certifications and has recently received his Accredited Automotive Manager certificate from the Automotive Management Institute.

This information is provided by IDENTIFIX®. IDENTIFIX® resources cut diagnostic time and provide repair solutions that increase the shop's bottom line. From Repair-Trac pattern failure quick fixes, to Diagram-Online wiring diagrams by fax, to the Repair Hotline staffed by 32 master techs who specialize in diagnosing complex problems by phone or fax, IDENTIFIX® helps techicians fix more cars in less time. For more information on IDENTIFIX, call (800) 288-6210, 8 a.m. - 6 p.m. Central Time. www.identifix.com. © 2008 IDENTIFIX. All Rights Reserved. © 1997 IDENTIFIX. All Rights Reserved.

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