Cummins ISB, Series 60 Dyno Engine, Freightliner Coronado

This week we brought a Cummins ISB down from the upper floor, and it was my team's task to see if it would start, and if not, why not. According to our instructor, this engine has not been started once in the last 4 years.

It is good practice to check fluids before starting any engine or transmission that has been worked on, ESPECIALLY by another person. I was told by a classmate that the fluids were good, however I think back to my instructor's words of wisdom "verify, then trust." I have seen this in action in the real world, I think a good habit to get into.

Cummins ISB, 5.9L diesel. On the battery charger, fluids checked, ready to start - hopefully.

With the fluids good, diesel in the fuel tank, a battery charger on the battery, I turned the key. Nothing. We hooked up a second battery in parallel, which doubles amperage but gives us the same cranking voltage. Turn the key, it cranks but barely. We left it to charge for 10 minutes. Cranking improved but only marginally. We attempted to connect diagnostic scan tools to it (notably Cummins Insite) but had technical difficulties with our software. We did manage to hook up a different scan tool and pulled all active engines codes of which there were 3. Stay tuned next week as we progress on this project.

So we moved on to our Series 60 Dyno Engine, which has recently been made to run. We started her up for a minute or two. However, we are unsure about the lubrication and requirements of this old dyno that hasn't seen action in years, so for now I was instructed to remove the driveshaft so we could run the engine without the actual dynamometer hooked up. So what did I find?

Never worked on this kind of yoke before. Time to learn something new?

I have experience with half-round and full-round driveshaft yokes, but not this kind. The u-joint is held in with snap-rings, and I am still not entirely sure I had to unbolt the yoke "strap" part at all. Due to the awkward position of the snap-rings I needed to remove, and the inability to turn the driveshaft like I would working on a truck, I had access issues to one of the snap-rings.

These pliers were a huge help with solving my accessibility issue. I have made note, and will likely be seeking to add a pair to my own toolbox in the future.

 I was successful in removing the snap-rings, but it was time to clean up and head home before I could make any further progress.

Finally, and a bit out of order as this was pulled in before anything I have just written about, we got a chance to take a closer look at a brand new Freightliner Coronado on loan to us from Matheny Truck Center. It was the task of another team to do an inspection on this vehicle.

If only I could work on trucks this clean.

My reflection:

In addition to all that I have just written about, we also had our midterm to take first-thing in class. A busy day, for sure! Multitasking is yet another skill a good mechanic needs to be able to do. Whether we have multiple projects going on at the same time, or quickly switch from one to the next. This is a lesson I have learned working at a real shop as well. This is simply another reason why organization of parts and tools is so important, as we try to seamlessly move between projects. Paperwork and documentation also plays an important role here.

Series 60 Coolant Level Fault

This week on the Series 60 we had a Coolant Level Low fault to fix. This code was set last week when we tried to get it running after refilling it with the coolant we drained. The system uses a coolant level sensor in the fill tank on top of the radiator.

Active fault code for Coolant Level set by the ECM, as shown on the scan tool.

Our first task after retrieving the code off the ECM was to refer to Detroit Diesel's Power Service Literature to find out what exactly this code means and what procedures are recommended for troubleshooting.

Looking up service literature for this fault code.

Detroit Diesel recommends ensuring that coolant level is actually correct first.

Coolant fill tank on top of radiator, with coolant level sensor right above the radiator fan.

What we found after taking the pressure cap off was the coolant was indeed low. It took almost 2 gallons to fill it up to the correct level where we could see it in the tank with a flashlight.

No more coolant fault code.

The service literature says that following this procedure, the fault code should no longer be set. Of course, we cleared the rest of the codes manually, but there was no active fault for coolant level after we put the scan tool back on the truck.

My reflection:

It's not always a bad sensor or faulty wiring that can set a fault or cause a problem. Sometimes it's the simplest solution that is the correct one. So here our first question for a "coolant level low" fault on a truck should be, "does it actually have enough coolant in it?" And our first action should be to check that it does.

Sometimes it's best not to overthink things and keep it simple.

Sensors & Scan Tools

This week we finished testing the list of 5 sensor we were given to remove and test. Among the list:

1. Thermistor.
2. Pulse generator.
3. Variable-capacitance pressure sensor.
4. Piezo-resistive pressure sensor.
5. Potentiometer. 

The first 4 we tested off a Series 60, and the last one, for ease of access, we tested off a running stand-engine, a Cummins ISX 600.

Test procedures vary for these sensors as they operate on different principles, but the similarities all these sensors share is that they are designed to send a voltage signal back to the ECM to let it determine engine operating conditions. This information can then be used to adjust output parameters such as fuel injection timing, or used as fault detection for driver warning systems.

We also broke out the scan tool and used it to help test these sensors. A multimeter works just as well, but a scan tool can be faster and easier. For instance, we hooked up a gauge and pressure booster to the manifold boost pressure sensor, and with it connected to the ECM and the scan tool hooked up to the truck, we were able to match boost pressure in PSI on the pressure gauge and on the scan tool. This tells us the sensor is good and working as intended.

This could also be done with a multimeter, but would specifications telling us how to interpret voltage readings to a corresponding pressure value.

Applying pressure to the manifold boost pressure sensor with our pressure gauge.

Scan tool data from the ECM match our pressure gauge readings, indicating that the sensor is working as intended.

My reflection:

Not all these tests went flawlessly. We had some technical difficulties involving a crankshaft position sensor, which would not produce voltage when a magnet or piece of metal was passed across it, and a throttle position sensor which gave us readings in reverse of what we expected from specifications. We will likely be revisiting these next class.

The question I might raise then is how would a technician in the field deal with these technical difficulties? How would their methods differ from ours? Did we perhaps make a mistake in our tests, or is there an actual technical problem with the sensors, electrical systems, or tools we were using to test them?

Crankshaft Position Sensor

This week we moved on to "pulse generator" sensors. These include wheel speed sensors for ABS, crankshaft position sensors, and camshaft position sensors.

For ease of removal on the Series 60, we chose the crankshaft position sensor. It is simply bolted to the bottom of the block and works by creating a magnetic field as the crankshaft gear turns, sending voltage signals back to the ECM. A missing tooth is used to tell the ECM engine position.

Crankshaft position sensor prior to removal.

Crankshaft position sensor after removal.

My reflection:

We did not get to test this sensor yet, however it can be tested by putting a multimeter across the electrical terminals and reading voltage as a magnet is passed over it. Failure of this sensor could result in a cranking, no-start condition.

Worth noting on this sensor was how difficult it was to remove due to the fact that the O-ring had swelled up. It took a fair bit of prying and pulling to get this thing out of the engine. Just another testament to the fact that when working with vehicles... it's hardly ever as simple and straight-forward as the textbook says!