Problem Analysis: Technical Information
28 June 2016 | Marina de Papeete
Bill, in the know
A piston moves up and down in a cylinder, alternately drawing in air and compressing it. During the end of the compression cycle, the air is highly compressed (23 atmospheres or so) and very hot. Into this environment, diesel fuel is injected at high pressure, up to 2600 PSI. The fuel combusts in the heated air and delivers power to the piston and engine drivetrain. It’s a very simple system, needs no electricity to run (no spark plug), and is very efficient. If no fuel is injected, of course, the cycle ends.
We are fortunate that there’s an English-speaking Nanni dealer here in Papeete and that we contacted him as early as possible. His main mechanic, Daniel, arrived at 0800 today (rather than on Thursday as planned) on the boat and we went through all of the easy stuff, first: clogged fuel filters, bleeding the system. We then removed the high pressure lines from the injectors and watched fuel dribble out. Fuel from a running diesel is injected into the cylinder at very high pressure, so this was an indication of a problem. I was misled because there is some fuel, but not enough to run the engine, so when I bled the system, I did see fuel.
Daniel departed and returned with his boss, Bruno LeBrun. In years past, due to other engine problems, I had exchanged emails with Bruno, so we had something of an acquaintanceship already. With Bruno, we checked a few items that we hadn’t with Daniel.
So, we have a fuel supply problem. We cranked the engine and metered the fuel arriving at the secondary fuel filter and the bleed valve on the injector pump. Both showed plenty of fuel entering the injector pump. We removed the metal tubes that transfer pressurized diesel fuel to the injectors and there was only a weak squirt from the uncovered ports on the pump top. Fuel enters, little comes out: a damning diagnosis for the injector pump.
Bruno will contact Nanni directly and determine all of our options, and I’m working on the other end, contacting my Nanni parts guy in England. In either case, we’ll be buying and shipping a new injector to Papeete and having it installed. Yippee!
We’re ahead of the game by two days and I’ve contacted my England Nanni guy as soon as knew for sure that the pump was the problem. With luck, we can have the new pump here in 4-5 days, and then get it installed in a few hours. Man, will we know Papeete!
We’ve gotten some post cards off to family, we had a fine meal at a local sidewalk cafe at which we’ve had good meals the past few years, and have enjoyed living, on the cheap, in downtown Papeete. As long as we can get an injector here with alacrity, we’ll be fine.
BTW, if you have an old but functional Nanni Diesel injector pump that’s just lying around, let us know.