2nd week of electrical

Test

1st week of fall 2014!

Well this first week of electrical has been a good refresher since we had it last year, and there was a lot of stuff that we digested this week. There are of course the staples that we've know. A short to ground is gonna blow a fuse, and should be replaced with a "fuse that glows" to locate it. A short that bypasses a switch is a short to power. If there's no current flow then there can't be a voltage drop. Also going to the most negative point in the system (-battery post) with you lead leaving you with just a positive lead and your meter. One thing I'm getting more respect for is the number of connections that can be in a circuit and therefore can become a high resistance connection.

Kirchoff's current law makes a little more sense now. They way it seemed to be really useful is to use it to find the source or the load. It can also be used to figure out which circuit your on, and what direction you're going in (to or from the source). Also current flow testing allows you to see work being done. The sum of current flow in a circuit should be the same throughout the circuit.

I found it interesting in one test board that the primary and secondary circuit both shared the same bad ground. This caused the relay to turn on and off repeatedly as the Fuel Pump would actuate and cause enough of a VD for the Relay to not be able to energize. This is why a relay buzzes and will continue on in a loop until the ground is fixed.

Going to add the pictures of the starting/charging  tests I did on a couple systems. Phone died.

When heads are re-manufactured they use baking soda to blast all the corrosion, carbon, and dirt off.

The areas that are critical are mainly the valve seats, intake ports, exhaust ports, and this main area here where all the moving valves, springs, and cam takes place. It literally must be spotless.

Scan tools and Fault Codes

Our goal as a class for this assignment was to become familiar with not just one but many different operating systems for engine diagnostics. Every manufacturer has their own software that they use and they're all different. Even if you're a master of one you could struggle with a different software.

 

6/3/13

We went over the Detroit Diesel engine as a class. Jeff explained where the sensors were and where he likes to start approaching an engine that's new to him. Personally he likes to start with the fuel system and work his way around from there. You begin by identifying what you know and then branch out to the rest of the engine.
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Air pump

EGR system

Pressure sensor for the common rail.

Venturi valve.

Fuel filter and the delivery to the right of it.

Timing gears on the engine Jeff disassembled.

Going over the different types of valve seats and what an interference fit is.

3516 Assembly

For assembling the 3516 the first thing I did was clean everything spotless. After that I went ahead and tapped all the head bolt holes as well as die all the fasteners. Any engine work should be followed by using a tap and die set. The fasteners should be able to go in by hand and shouldn't require any torque. For assembly Caterpillar wants their components to be installed with assembly lube.

Cleaned head bolt threads

Used a die on the headbolt threads.

Rocker arm assembly.

Ready for the rocker arm assembly.

Adjustment screws and their locknut.

Valve lash adjustment.

Fuel linkage installed.

Using rapid tap along with a tap on all the holes.

Caterpillar 3516 Measurments

The biggest thing I took away from doing measurements on the 3516 is the attention to detail required. For every single component in the engine Caterpillar has a specification range and it has to be checked. There are many spec that you may never even use, but they're still there. For many of these components the range is so small that we're talking tens of thousandths (ie piston pin). There is literally no room for error.

You can see the crosshatch inside the liner.

For the connecting rod bore measurement you take the bearings down and torque the rod bolts to spec. 

To get the rod out you have to take out the snap rings so you can slide out the piston pin.

Temp Sensor

Here is the schematic for an Engine Coolant Temperature Sensor.

Schematic for an Engine Coolant Temperature Sensor

Here is a great video on how a Temp sensor works and it's short. It's a thermistor which acts differently when heat is applied to it. Instead of the normal resistance going up while heat goes up, the resistance goes DOWN as the heat increases.