I am looking for a how to on how to troubleshoot my bus's fuel system. The short story is my bus died, and the mobile mechanic tells me that I need a new fuel pump. Thing is, I just replaced it a few months and 300ish miles ago with one I found online. The mechanic told me that I should replace it with one purchased the pump from the dealer, but I wonder if there is more going on.
Now, for the long version-
A couple months ago, I was driving the bus when I experienced a loss of power. In the span of 30 seconds, the bus went from normal operation, to losing power, to not being able to idle, and not even starting. I had it towed home, and had a mobile mechanic come out. He determined that the fuel lift pump was bad. I put a new one on, and the bus started again. However, I had problems with sometimes not having full power. It seemed hit or miss. I did still have air in the fuel system, and repriming the fuel system (using the hand pump and releasing air through the valve on top of the fuel filter housing) seemed to help. I thought maybe I had a very small leak in the fuel system, letting it suck up some air. I was still able to get it up to speed though, so I thought I was still working air out of the system.
On a recent trip, however, it kept getting worse. Towards the end, the Warn Engine light would come on sometimes under heavy load, and turn back off when I got to the flats. Finally, it sputtered and died when we pulled into the campsite (at least it waited until the campsite, and not the highway!). At this point, it would not restart. I had a different mobile mechanic out to look at it, and he was able to get the bus to start by pumping the hand pump. Based on that, I believe that he is right that the replacement fuel pump went bad. I am having the bus towed home (again - at least I have Good Sam now to help with this tow) and plan to work on it at my leisure. With all that said, could there be other things at play? Could something else cause the pump to fail? Basically, how can I troubleshoot my fuel system?
Also, any advice on a diagnostic system to talk to the computer?