SERVICE INFORMATION BULLETIN

Transcription

1 Fuel System FS September 30, 2003 All IC Models Using Aisan LPG Regulators SERVICE INFORMATION BULLETIN Subject: Troubleshooting LPG Regulator Problems Page 1 of 5 MODEL APPLICATION: All IC Models Using the Aisan LPG Regulator Return To FS Index Return To Main Index GENERAL INFORMATION: During continual evaluation of failed regualtors received via warranty return, Toyota and its vendors have discovered that many of the regulators that have failed did so due to various maintenance reasons. Failures due to maintenance reasons should not be approached by just replacing a part, it requires addressing the maintenance issue to prevent subsequent failures. Prevention may include educating the customer, adjusting the PM service interval or by approved modifications that will allow the fuel system to endure the conditions of the particular application. The purpose of this bulletin is to provide troubleshooting information that will help the forklift technician identify potential maintance or application condition that can cause fuel system failure and how to remedy the situation. REPAIR INFORMATION: The most common symptoms with regualtor problems can be catagorized in one of two conditions, under-fueling or over-fueling, with the most common being under-fueling. When troubleshooting a fuel system problem it is important that the entire fuel system is taken into consideration. The fuel system begins with a tank filled with fuel, tank valve, high pressure fuel hose from the tank valve to the regulator, the Aisan LPG regualtor, engine coolant hoses from engine to the regulator and a low pressure hose to the carbuertor/mixer. Potential Under-Fueling Causes & Corrections. LPG Fuel Tank- If a steel tank is being used it is most likely an older tank since the aluminum version has become the tank of choice. Steel tanks are more suseptable to internal contamination due to rust and scale and built up contaminants from years of use. These contaminats can cause clogging of the ceramic filter or accelerate the accumulation of tar in the regulator. Tank Valve- The most common problem with the tank valve is that it is often not fully opened. This restricts the flow of fuel and simulates an underpowered truck or a truck that is running low of fuel. This condition can easily cause the TWC light to illuminate (if equipped the 3-Way Catalytic Muffler Option) due to the lean fuel condition.

2 FS Troubleshooting LPG Regulator Problems Page 2 of 5 Aisan Regualtor- The regulator may be affected by several of the issues listed below. 1- Clogged Filter- The filter should be checked and cleaned or replaced as necessary. Refer to Service Information Bulletin (SIB) FS for cleaning and replacement information. 2- External Filter- An external filter (p/n ) can be installed in the LPG high pressure hose as a pre-filter. This filter will remove the larger contaminants and allow the ceramic filter to more effectively filter the smaller contaminats. This filter should be mounted in a secure, out-of-the-way location where it can still be easily serviced. 3- Drain Regulator Chambers- The regulator chambers may be filled with tar deposits. The regulator should be drained of any deposits during regular PM service. The plug or the optional drain cock (see illustration below) should be opened and the tar allowed to drain out. If allowed to accumulate excessively the regualtor will need to be dissassembled and cleaned and reassembled with new diaphrams. NOTE: Before opening the drain plug/cock, the LPG tank valve must be closed and pressure released from the LPG system. It is best if the truck is at operating temperature, the tar will be at its most liquid state and drain easier. Refer to the Repair Manual titled LPG Device Pub. No. CE610-4 page 1B-11 for more information. To install the drain 1 each of the following parts should be ordered and installed U Cock, Drain, U Pipe, U Gasket,. Refer to the Repair Manual titled LPG Device Pub. No. CE610-4 page 1B Excessive Tar Accumulation- An available in-line thermostat (p/n ) can be installed in the return coolant hose on the regualtor if the regulator rapidly fills with tar deposits between PM intervals. This condition may occur if the truck is regularly run hard in hot locations or with contaminated tanks/fuel. High coolant temperatures in the regulator can cause the tar deposits to condensate in the regulator at a faster rate. The in-line coolant thermostat will maintain the regulator

3 FS Troubleshooting LPG Regulator Problems Page 3 of 5 at approximately 140 F which is ideal for LPG vaporization. The thermostat must be installed in the regulator coolant return line in order to work properly. The hose should be cut and the thermostat placed in the line with hose clamps. An arrow on the side of the thermostat shows the proper direction of flow. When properly installed the arrow should be pointing towards the engine. Connect this end to the engine side cooling hose In-Line Thermostat Connect this end to the regulator cooling hose 5- No Start When Hot- An external lockoff valve (p/n ) can be installed for those trucks that run long and hot and have the symptom of hard starting or won t restart after shutting down when engine. It has been reported that when under very hot conditions the fuel lockoff solenoid on the Aisan regulator will fail to open after the truck has been run hot. Installing the external lockoff valve will insulate the valve from the heated regulator. During installation it will be necessary to make the following changes; a. Install the external solenoid to the regulator using a ¼ male pipe nipple (brass). b. Move both of the wires from the Aisan lockoff solenoid to the new external solenoid. The solenoid should not be grounded throught he body of the lockoff valve or regulator. c. Remove the valve seat/plunger and spring from the Aisan fuel lockoff valve. The solenoid valve assembly should be removed, the seat/plunger and spring should be discarded and the solenoid valve assembly reinstalled on the regulator. See illustration below. Cut this wire off the body of the solenoid. Make Connections to the two wires from the original lock off solenoid Remove & Discard the plunger and spring. Re- the solenoid install

4 FS Troubleshooting LPG Regulator Problems Page 4 of 5 Poor Performance- There are many reasons for an engine not to perform properly. Timing, compression, transmission problems etc all have an effect. This section will address the adjustment of the regulator and carburetor for proper air-fuel mixture. Idle Speed Inspection & Adjustment a- Bring the engine up to normal operating temperatures. -Coolant temperature to 176 F (80 C) minimum. -Engine Oil Temperature to 158 F (70 C) minimum. -Hydraulic Oil Temperature to 122 F (50 C) minimum. b- Install engine tachometer c- Inspect and adjust engine idle speed. 1- The carburetor linkage stopper screw & nut is not a part of the idle speed adjustment, it should not be touched. 2- Adjust idle speed to the specified value (refer to repair manual) by turning the carburetor air/power adjust screw. 3- Slowly adjust the regulator air-fuel mixture adjust screw CCW or CW until the engine is at its highest rpm. 4- Re-adjust the air/power adjust screw so that the engine rpm is back to the specified idle speed value. 5- Repeat steps 3 & 4 until the engine rpm s highest point is the specified idle speed value. 6- Slowly turn the regulator air-fuel mixture screw CW until you find the spot where the engine speed just begins to fall. Then, turn the regulator air-fuel mixture screw CCW 45 from that spot. Note: The above adjustment procedure, if performed properly, should result in a CO value at or near 2%. LPG regulators for TWC (3 Way Catalyst) systems are preset and have a steel plug over the air-fuel mixture screw preventing adjustment. Toyota cannot recommend that this plug be removed and the regulator adjusted, removal of the steel plug will void the truck warranty. If it is determined that the air-fuel mixture is not correct the regulator should be rebuilt with the available service parts or replaced. Regulator Air-Fuel Mixture Adjustment Screw Steel Plug Non TWC Regulator TWC Regulator w/plugged Fuel Mix Screw Air/Power Adjust Screw

5 FS Troubleshooting LPG Regulator Problems Page 5 of 5 3-Way Catalyst Systems- Trucks equipped with the 3-Way Catalyst systems are especially sensitive to under fueling. Any of the above causes of a under fueling (Lean) condition may result in the TWC warning lamp to illuminate. The root cause of the lean condition must be addressed in order to prevent TWC warnings. Potential Over-Fueling Causes & Corrections. LPG Regulator- LPG regulator failures are the primary reason for an over-fueling (rich) condition. A list of possible reasons for an over-fueling condition is listed below. 1- Defective primary or secondary diaphrams. Pin holes or tears in the diaphrams may cause full tank pressure to be applied to the carbuertor. Rebuilding of the regulator is required. 2- Primary chamber valve seat sticking in housing due to build up of contaminants or tar. A change was made to the valve seat plunger that change it from being round to three sided. This change in shape reduces the possibility of contaminants from wedging between the plunger and housing bore. This new shaped part is included in the service overhaul kit. 3- Mis-alignment of the secondary valve face to the housing seat can cause a constant flow of fuel to the carbuertor. Although not a full tank pressure it will still cause an over-fueling condition. Refer to the Repair Manual titled LPG Device Pub. No. CE610-4 for procedures on pressure checking this valve seat. 4- Mis-adjustment of the secondary valve seat lever. Refer to the Repair Manual titled LPG Device Pub. No. CE Mis-Adjusted air-fuel mixture. Refer to the adjustment listed previous in this bulletin or Refer to the Repair Manual titled LPG Device Pub. No. CE610-4 Note: In order to properly rebuild and adjust the regulator it is necessary to have available the below listed SST s. These tools are available through Toyota Service Parts and their use is described in the Repair Manual titled LPG Device Pub. No. CE & 4 2 SST List Hose Bending Tool Bending Tool Union Gauge Pressure Tester