PRESSURE CONTROL GROUP 3S6920 - Caterpillar

in design and engineering has become obvious in all equipment systems, especially hydraulic and electrical systems. That which is considered sophisticated in design or engineering is considered complex and confusing when it gets down to troubleshooting or diagnostics.
Today's vehicle support systems have become extremely complex. Electrical and hydraulic systems are mazes of wires and tubing, switches and valves, connectors and relays. When they fail, most mechanics become perplexed and frustrated by this mass of "designed confusion." Where do you start looking for the problem?
Not long ago the family car failed to start. Naturally, since this happened without warning after it had been running well the night before, the electronic ignition was blamed. About two weeks before this happened, the car had been tuned--new wires, cap, etc.--so it seemed logical that the problem had to be with the electronic ignition system.
After installing a new electronic control and ballast resistor, the car started, but it was running on six of the eight cylinders. Off came the distributor cap and there was the problem as plain as can be, a broken rotor. A new rotor was installed and the car fired immediately but still ran roughly, just like before. The only improvement was the fact that it started more quickly. After a long and thorough check, it came to light that one of the neighbors had tried unsuccessfully to get the car started earlier. Back to the distributor cap. A quick check of the ignition cables revealed that numbers five and seven had been crossed. When this problem had been corrected, the car started and ran beautifully.
In going back over the sequence of events to arrive at a final diagnosis of the problem, it became obvious that the problem was caused by the broken rotor. Right! There never was a problem with the electronic ignition system.
Had basic troubleshooting procedures been followed from the start, the problem would have been solved almost immediately and at considerably less cost. The whole point of all this is to say that no matter how sophisticated or complex a system may be, to find the cause of a problem you still have to go back to basics.
It doesn't matter how sophisticated or complex a system may appear to be, it is still the basic system with add-ons. The confusion is in our attitude towards it. Because it has electronics or servos or microcomputers, we immediately feel that it is this sophistication that is causing the problem.
It isn't. Usually the "add-ons" have improved some aspect of the original system, but rarely do they eliminate the basic problems that have always caused frustration. No degree of design or engineering can eliminate the results of "crossed ignition cables," nor can they eliminate the possibility of this happening.
Whenever you approach a problem, remember the basic purpose of the system and its basic design concept. Start troubleshooting at the beginning rather than at the end or middle. Even if you are sure of your pre-inspection diagnosis, take the time to go