ENGINE DIAGNOSTIC TEST PROCEDURES Section 6 • SUPPLY PUMP PRESSURE 400 Series On-Highway (with Robert Bosch MW Pumps) FROM FORM NO. CGED-365 SUPPLY PUMP PRESSURE (MEASURE AT HIGH IDLE) [NO LOAD] * 8 A. 1. HEADER w/VENT PLUG TEST @ FINAL FUEL FILTER VENT. 2. HEADER w/o VENT PLUG TEST @ FINAL FUEL FILTER OUTLET. INSTRUMENT GUIDELINE DATAp 1st CHECK 2nd CHECK PRESSURE GAUGE (160 PSI RANGE) IF PRESSURE REMAINS LOW AFTER REPLACING FUEL FILTERS, PERFORM STEP B B. TEST SUPPLY PUMP INLET RESTRICTION: 6 HG. (MAX.) VACUUM. MEASURE AT FULL LOAD AND RATED SPEED INSTRUMENT GUIDELINE DATAp 1st CHECK 2nd CHECK VACUUM GAUGE * Engine must be at normal operating temperature. p Refer to "Performance Data Guidelines", in this Section. A. SUPPLY PUMP PRESSURE 1. Remove final filter vent plug on top of fuel filter header    (if    equipped).        If    no    vent    plug    is available refer to Figure 18b. 2. Connect  1/8  in.  fitting  to  the  vent  plug  orifice, with  a  line  to  a  0-160  psi  pressure  gauge  [ (SE-2239)   Beyers   Model   100   Pressure   Test Kit]. Figure 18a.  Fuel Supply Pump Pressure Test (With Vent Plug) 3. Measure supply pump pressure at high idle RPM, no load (Figure 18a). 4. Record the pressure in the 1st check block. 5. If the pressure less than the guideline data shown in this  Section,  PERFORMANCE  DATA  GUIDELINES, replace the primary and final fuel filter. 6. If pressure is still low, perform inlet Restriction Test. Figure 18b.  Fuel Supply Pump Pressure Test (Without Vent Plug) CGES-240-4 Printed in United States of America Page 26