PUMP GP-FUEL INJECTION 4190680 - Caterpillar

(C) Removal Of Display Assembly
1. Remove the rear cover and circuit board as shown on page 11. 2. While holding display assembly (1) around the edges, use a small screwdriver to remove two screws (2). Remove the display assembly from the printed circuit board. Be careful not to touch the display except at the edges. 3. If flexible conductors [Zebra strips] (3) are to be removed, use tweezers to carefully remove them from the slots in the display bracket. Do not touch the flexible conductors; skin contact can leave oil on the conductors.(D) Cleaning The Display Assembly
1. The LCD can be cleaned by gently wiping it with a soft cloth. IMPORTANT: Rubbing the LCD too hard can remove the contacts deposited on the edges of the glass.2. The flexible conductors (Zebra strips) can be cleaned by dusting them with a camel's hair brush. If grease or fingerprints are on the conductors, the conductors may be washed with clean alcohol, and then air dried. Do not wipe the flexible conductors with any material that could leave lint or other deposits on the flexible conductors. 3. Contacts (1) on the circuit board can be cleaned with a pencil eraser.(E) Installation Of Display Assembly
1. Put display bracket (1) in position on the printed circuit board. Use tweezers to carefully position flexible conductors (2) in slots (A) of bracket (1). 2. Being careful to touch display (3) at the edges only, hold the display to the light and observe the numbers and decimals "1.8.8.8". Put display (3) in position on bracket (1) so the decimals are at locations (B). 3. Install display cover (4) and two screws (5). Make sure the screws are tightened evenly so the display and flexible conductors make good contact. Install the printed circuit board and rear cover. If the display does not operate correctly (segments missing) after assembly of the fuel rate indicator, press the display cover while the indicator is on. If this corrects the problem, either cover (4) is not fastened securely or the terminals are oxidized (still dirty). If the correct digits do not appear, make sure the display has not been installed upside down.Block Diagram
Parts Layout
Schematic Diagram
Component Function
INPUT - J5IC1 is used to invert the polarity output of IC7 so that the display reads a positive number when a positive voltage exists at TP1. IC1 is also used to invert the backplane squarewave in order to drive the decimal point. The decimal point is on whenever the unit is on.LOW PASS FILTER - IC2The signal is next taken through the low pass filter IC2, which has a cutoff frequency of 0.4 Hz. This stage has a gain of -.75 (inverts the signal and has a gain of 3/4).DISPLAY - IC7/LCD1/IC1A single chip voltage to digital (A/D) converter IC7 changes the filtered and calibrated signal at TP3 into a digital output on LCD1. This IC requires a very stable voltage reference at pin 36. A drift in this voltage will cause proportional errors in