Saturday, June 20, 2015

Cummins ISC Diesel Engine CAPS Failure



Cummins CAPS Assembly Repair from John Whelan on Vimeo.

This Cummins ISC diesel engine is in a 1999 Thomas pusher school bus. The engine died suddenly and eventually we found the drive failed in the CAPS pump assembly. Luckily the fuel injection shop we deal with had a core in the back room. We got lucky because the replacement of the pump assembly is around 4,000 dollars.

Most of the ISC diesel engines in our fleet have required a new pump. What happens is multiple engine codes that don't go away. There's a lot going on in the CAPS assy. It develops and controls the high pressure fuel that is distributed at the right time to each injector.

Running at 250 horsepower they are a great engine well suited for a school bus fleet. Other failures were injectors but not very often. The crank and cam sensors act up along with fuel leaks at the electric fuel pump. Our fleet only has 3 of these buses left and they are standing up very well for being thirteen years old.

The fuel pressure sensor in the CAPS accumulator was a regular failure through the years. Cummins did come up with a update on the sensor along with a replacement harness. It only takes 10 minutes to replace the sensor. I personally think Cummins has always been the leader in medium duty diesel engines.

I was an International DT466 fan for years until the emission and electronic version came around. Mechanical fuel injection can not keep up to emission guidelines and the old DT had to be scrapped. They were the best fleet diesel back in it's day but sometimes good things have to come to an end.

At present Cummins has the ISB which runs on DEF (diesel exhaust fluid) and besides the extra maintenance they are the most reliable engines in our fleet. They run seamlessly with the Allison automatic transmissions and the operators really like them for power and we like them for reliability.
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Thursday, June 18, 2015

Cat 3116 Rear Seal Installer For Sale

If you're doing repairs on Cat 3116 diesel engines here's a rear seal installer tool that we're looking to sell. In a previous post I mentioned that we no longer have 3116 engines in our fleet. This tool does it all if you have to replace the seal.

I got a new price from CAT and they said $500.00 Canadian funds

This tool is used so we will sell it for $125.00  U.S. + Freight

Leave a comment below with your contact information.

I have a post on this blog that demonstrates how this tool works.  Check it out HERE 


Wednesday, June 17, 2015

Cat 3116 Fuel Solenoid For Sale

Since we sold all of our Cat 3116 engines a couple of years ago we have no need for Cat parts.

This fuel solenoid is new...never used out of the box. The last price that we had on it was $355.00 Canadian.

We will sell if for $100.00 U.S. plus freight. Contact me in the comments section below and let me know if you're interested along with your email address. I'll give the first response priority.

These solenoids are activated with the key on and the winding pulls in the piston to turn fuel linkage on in the governor housing. They screw in and are sealed by an o-ring.

 Here is more information regarding the Cat 3116 solenoid on a previous post. There you will find torque specs and operational details.

Check out this link which leads to all of the Cat 3116 related posts on this blog.

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Tuesday, June 16, 2015

Allison 3000 Automatic Transmission Turbine Sensor Replacement




Allison 3000 Automatic Transmission Turbine Sensor Replacement requires removing the bottom module of the transmission using a transmission jack. The module weighs around 50 pounds so it's much easier to lower it down easily while feeding the harness through the access hole in the transmission housing.

The turbine sensor is internal and is easily replaced once the module is exposed. This code is not very common but it was plain as day when hooked up to Allison DOC software. You can view a graph while road testing and the turbine sensor communication dropped out while on the road. There are 3 sensors on the Allison 3000 models. The engine speed sensor, output speed sensor and turbine sensor.

All these sensors have to be working properly for the transmission to shift properly. They can be tested using an ohm meter. Depending on the ambient temperature the reading should be around 300 ohms. The video gives you an idea on what the module looks like when removed from the main body and where the turbine speed sensor is located.

The 3000 series are very durable and most of the problems were in the wiring. The plastic convoluted loom that the harness is wrapped in is deadly on the wiring insulation. Through time vibration causes the loom to rub on the wiring and eventually expose the copper wire to the atmosphere. Years ago we would run new wiring to a sensor because of the resistance caused by exposure to the elements.

The special wire was twisted and shielded that fixed a lot of communication problems, Using the Pro Link was the first tool available for troubleshooting. Now Allison Doc software is the only way to go. Also I have to give a plug to synthetic transmission oil which in the past I refused to accept because of the price.

Believe me it's well worth the extra cost. Our mechanical failures are non-existent since using synthetic oil. It lasts longer and does not break down in the heat. Our services are 3 years between oil changes. You can't beat that when in our case we're running 77 school buses.

Getting back to our turbine sensor code repair. When removing the module I want to point out that you need to remove the 32 fasteners by hand. The aluminum threads in the housing wear out..... especially the filter housing retaining bolts. It isn't a fun experience heli coiling the threads on these units. We have a Kent Moore tool jig to re-thread the holes which is the only way to do it. I use a speed wrench to remove and replace the bolts.

I hope you enjoy the video and please make a comment and share this post. Cheers!  


Monday, June 08, 2015

Mechanics and Corrosion

The most difficult job when finding an electrical fault is when corrosion is involved. It's hiding somewhere in a connector or poking through the wiring insulation.

So what is the best way to troubleshoot corrosion in the electrical system? One way is to search and destroy the problem by opening the loom and exposing the green stuff but that is frustrating and  takes a lot of time. However it's necessary to make a proper repair.


Another method (when you know which circuit is faulty) would be to check for voltage drop in the circuit that is not functioning. If you can hook up a volt meter at each end of the circuit and see if there is a loss of voltage when the circuit is energized then you can be assured it's a bad wire. Checking the resistance is another check that works.

In our shop we've been using a load on the wiring circuit in question. A regular light bulb (non LED) hooked up to the one end of the wire will tell you if there is a lack of current when the light is dim after energizing with battery power. The wiring is either corroded or frayed restricting current flow.

If you have money to spend on tools you could use "diamond logic builder" software for International trucks to see the circuits working in a graphic form on a laptop. You can click on a circuit and actually see if the load is getting battery power. The pin outs on all the connectors are at your fingertips. I've used this software and it's a great tool to have compared to digging through wiring harnesses with a hope and a prayer.  

Sunday, February 01, 2015

Mercedes MBE 900 Diesel Engine Emission Code dpf out of range high



This code we're working on is a "DPF out of range high" on a Mercedes MBE 900 Diesel Engine. What triggers this code is a pressure differential between the inlet and outlet of the diesel particulate filter cartridge. In the video you can see the clamps on the outside of the muffler that can be removed allowing the cartridge to be removed for cleaning.

There are several shops in town that will do a cleaning of these cartridges. It's a two step process depending on how badly the blockage is. When using detroit diesel diagnostic software you can go in and see what range the filter is running at. It's 0 to 4 range with four being severe. Once the engine control module detects blockage it will run a regen while the engine is in service.

 In a perfect world that's all the emission system would need to do running regenerations to keep operating without any trouble. The DPF amber dash light illuminates when the regen process is taking place. There is no worries if it flashes on and off indicating a normal function instigated by the engine on board computer.

Mercedes calls the engine computer an MCM (motor control module). When hooked up with the laptop and software the tech can find the code and click on the "troubleshoot code" button at the bottom of the screen. This directs you to a step by step process to check one thing at a time then moving on to the next step. In this case the outlet braided pressure hose that reads outlet exhaust pressure of the filter cartridge has to be removed and tested for blockage.

It could be blocked with soot and ash build up and the best thing to do is replace it. This fault was cured replacing the hose. If it did not help the filter cartridge may be plugged up so a forced regen is a good idea. Eventually over time the filter cartridge needs to be serviced or replaced. Mercedes recommends servicing at 125,000 km or 75,000 miles.

We have 18 of these diesel engines in our fleet and have a good deal of experience which is your basic "hands on" experience that is of course the best teacher.

Saturday, January 24, 2015

Espar Diesel Heater New Impact Switch and Harness Replaces Original Push Button Version

All of our Navistar conventional school buses come with the Espar Hydronic 5 (E-Guardian) diesel coolant heater. The impact switches that came with the heaters are very sensitive and would pop when ever the bus went over rough roads.

We did a partial fix by using a hole saw and reaching in to the heater housing and resetting the switch. This was a hassle but necessary to keep them operating. Low and behold the engineers at Espar came out with a new impact switch and harness that does not cut out over rough road.

The part numbers for this unit are below. There are 3 harness options and just one impact switch. Impact switch number: 252800705050OZ . The harness that fits the Hydronic 5 we have is 25280070100200OZ. The International dealer can get you the parts or anyone who has dealer status for Espar.

A great advantage to getting Espar heaters is the software is free to download. Go to the Espar website to get the software. The heater comes on in cycles starting with the blower and fuel pump then the electrode to start the burner.

The fuel used is minimal about 1/2 a cup of diesel per hour. With anti idling laws around schools these heaters preheat the buses long enough to get the interior temperature up fast. They operate for 2 hours at a time during each cycle. The faster a diesel engine can warm up saves fuel due to less warm up time in the morning.

If you are interested in these heaters it's possible to install them after factory with a complete install kit. You just have to get a fuel feed from the tank and hook up the coolant plumbing and electrical. Our shop installed a Webasto heating system on an International conventional bus because it was parked out of town and we wanted more assurance that it was going to start in cold weather.

Thanks for viewing this page. Please comment and feel free to share this post.

Below is a video I did on setting the 7 day timer on an Espar

Friday, January 16, 2015

Allison 3000 Series Automatic Transmission Turbine Sensor Code Repair


The Allison 3000 series automatic transmission or the older label "MD3060" in my opinion is an excellent design. The modules come off one at a time and they are really quite easy to work on. You need the right tools and manuals of course but gone are the days of balls, springs and extra assembly parts that were common with older auto transmissions. 

The photo below reveals the turbine sensor which is internal. The bottom of these transmissions have an aluminum cast unit called the control module. It has all of the solenoids and valve body that controls shifting. The code we had was a turbine sensor which stopped working only at certain times during a bus run. The turbine sensor being a winding which delivers the turbine speed signal to the transmission control unit was failing when the oil temperature got to a certain level. 

Click on Each Photo to Enlarge


Using the Allison DOC software we were able to go on a road test and observe the turbine speed sensor and exactly what it was doing. The graph you see below in the photo show the activity of the output speed, engine speed and turbine sensors. These three signals are what the TCU reads to send the right information to the control module during operation for a proper shift at the right time and in the correct range.

Looking at the laptop image (click on the image to see more detail) you can see how great it is to be able to watch what the components are doing which makes it really easy to troubleshoot. What happened eventually when the transmission temperature got to around 140 degrees the turbine sensor flat lined on the graph reading causing the shifting to fail. At that time it was confirmed that the turbine speed sensor needed to be replaced and the labour to re and re the control module would not be wasted.



The control module is around 50 pounds so you need a tranny jack for sure. There are 2 dowels that line up the module to the main case and it's a bit of a fight prying the module down on to the jack. With some care it can be done including the removal of the wiring harness which slips through the access hole in the transmission case.

Once the sensor was replaced along with the necessary gaskets and seals the module was reassembled with new filters and sump suction filter (internal). The synthetic oil was added then running checks were performed. The road test was a success and the bus went back into service. Synthetic ATF oil is worth every penny in my book with anti foaming and heat resistant properties far superior than standard oils.

   
Valve body and shifting solenoids from the control module 


Here is a link to the Mechanic's Tips Handbook in pdf form. It has very good general information with torque specs for servicing and other useful tips.