It all started back in 2013 when we purchased 8 International conventional school buses with the Navistar V-8 diesel engine known as the MaxxForce 7. I personally have never experienced a reliable V-8 diesel engine. Maybe it’s the designing around a V-8 engine block that makes it weak in some areas. One failure that was covered under warranty was a cracked cylinder head. This type of failure is disturbing when you consider the light load a school bus goes through. The block and heads are the strongest part of the engine.
The back story is when the driver was pulling away from the fuel dock the engine just quit and would not restart. I have to mention that after the bus sat for a couple of days it started right up and ran perfectly. So the next step was to give it out to a driver to test it on their run. Sometimes I feel bad for them knowing that something could go wrong while on a run but I made sure it was a local route.
I was right about something could go wrong. The bus broke down 6 blocks from the shop so I got the tow truck to hook it back. When we scanned the engine code 3055 FMI 1 came up which luckily was very straight forward. The code was low fuel pressure at start up so that made perfect sense. Now we had something to go on. After looking at the code description the first probable cause was the wiring harness to the high pressure fuel pump. That makes sense being an intermittent problem. All of the other possible causes checked out so replacing the wiring harness was the most logical step to take.
As I pointed out in the video there is a lot of work to replace the harness. Heat shields and exhaust parts had to be removed along with the exhaust brake and Thermal Management Valve. I am not one hundred percent sure this is going to fix the issue but my confidence tells me it’s going to work. Intermittent problems have mostly been electrical in my experience. There was also the updated harness which tells me the old one was causing trouble. This is the first time we have seen this type of failure on our MaxxForce 7 models.
At this point the engine is almost back together so I will leave a comment under the video or update this post when it’s running like normal again.