Possible Cause Of A Low Idle Misfire And/Or Backfire{1278,1076,1250}
Usage:
3400 Series Engines Equipped With An Air/Fuel Ratio Control
If a 3400 Series Engine equipped with an AFRC (air/fuel ratio control) has a misfire and/or backfire, check the diaphragm in the AFRC for damage. When these engines are operated at low idle, there is a negative boost (vacuum) in the inlet manifold. If the diaphragm has a hole in it, oil from behind the diaphragm can be pulled into the inlet manifold and then the cylinders. At low idle, this oil can cause a misfire and/or backfire. At higher rpm the engine will operate smoothly but there will be excessive (too much) smoke during rpm increases.
Caterpillar Information System:
1980/05/12 New Part Available To Check The 3S1467 Plunger And Barrel Assemblies{1251,1252,0652}
1980/05/12 Boss Can Be Removed From Spacer Plate Cylinder Block To Get Clearance For Oil Filler Tube{1201,1316}
1980/05/12 "I checked everything but..."{0100}
1980/05/12 Improvements To Engine Oil Lines Group Makes Installation Easier; Prevents Reverse Connections{1307,1318,1155}
1980/05/12 Use The FT1525 Alignment Pin And FT1526 Fixture When Reconditioning Earlier 3208 Sleeve Metering Fuel Systems{0626,1264,1286}
1980/05/05 Hardened Washers Now Used On Bolts For Fan Shroud{1353,1360}
1980/05/05 Improvements Made To Water Separator Groups{1263}
1980/05/05 Changes To 9S240 Rack Position Tool Group; Revision To Special Instructions{0653,0374,1250}
1980/05/05 New 6V2120 Spline Sprocket Improves Depth Control Of 5P4175 Boring Tool Group{0663}
1980/04/28 Use 6V3044 Polishing Belt For Crankshaft Reconditioning{0622,1202}
1980/04/28 Boring Machine, Adapter Groups And Sleeves Available For Repair Of Damaged Cylinder Blocks{0622,1201,1216}
1980/04/28 New 1N3270 Auxiliary Drive Group Available As Attachment{1165}
1980/05/12 Bushing Bores In Boom Can Be Machined In The Field{6501,0664}
1980/05/12 Changes To Oil Level Gauge Group Improve Accuracy Of Oil Level Indications, Increase Oil Capacity Of 245 Excavators And Front Shovels{1300}
1980/05/19 Important: 7V2253 Anti-Creep Slides Must Be Correctly Installed, And Adjusted With The Seat Belt{7327}
1980/05/19 Turbine Wheel Shroud Design Changed; Snap Ring No Longer Used{1052}
1980/05/19 "Viscor Cup" Available To Check SAE J967 Calibration Fluid For Fuel Injection Test Bench{0651}
1980/05/19 New Plug With Straight-Threads Used In Engine Variable Timing Drive{1272}
1980/05/26 6V97 Engine Stand Is Available{0626}
1980/05/26 New Check Valve Used In Fuel Injection Pump Assembly{1251}
1980/05/26 Four Fabricated Tools Available To Adjust Carrier Bearing Preload And Backlash (Tooth Clearance) For Bevel Gear And Pinion{0611,3258,3256,3257}
1980/05/26 6V6 Electrical Connector Pliers Available{0613}
1980/06/02 Improved Procedure Can Be Used To Adjust Voltage Gain{4467}
1980/06/02 Reverse Flow Check Assembly Now Used In Fuel Injection Pump Assemblies{1251,1272,1254}