I must have missed a meeting

Somehow I became the Ford 6.0L Diesel guy in the shop. I think it was our second year in business when Chris and I were as eager as can be and as relentless as ever to NEVER EVER get stumped with a problem we couldn’t figure out. That was when one of our longest standing customers, and expatriate from the local Ford dealer decided to give us a shot. They had brought their 2004 Ford Excursion with an International 6.0L turbo diesel engine in after having it marooned at the dealership only to have gotten it back with a significant bill and unresolved problem. Chris went rounds with the vehicle and really went at it. Exploratory disassembly, endless oscilloscope waveform analysis, researching what “goog” looks like, and a few wild goose chases were just some of what he endured. I remember it well because, as technicians often do, he bounced his experiences off of me for collaboration on a diagnostic strategy. Keep in mind it was just a few years prior that we had been involved with the acquisition, custom buildout, and deployment of 134 F350 Superduty Pickups on a government contract. Just in the maintenance of the vehicles in their first couple hundred miles of life we first saw the nuances and premature failures that “got our feet wet” with these unique beasts.

This Ford Excursion turned out to be one of the early wiring harness eaters. It had an intermittent, hot-only problem in which signal wires or grounds were having connections periodically and momentarily broken sending the control systems out of whack. Perhaps it was the cerebral scars that this experience left on Chris that nominated ME the 6.0L expert from then forward. In the years since I have come to appreciate the engine. While it does have some unique nuance failures and common problems, it is also a shining example of where engineers at first “got it wrong” and the aftermarket stepped in to invent solutions for the factory weaknesses that resulted in an engine that “can be” significantly better than the day on the showroom floor.

For big diesel engines this is big because it is not uncommon for these vehicles to be used for more than a half-million miles before retirement.

Last week, just as I was thinking I had seen it all, a Ford F250 was checked in that had a problem of Heavy White Smoke constantly emanating from the tailpipe at idle and worse as you increased RPM. During my initial testing, it was so bad that on a couple particular restarts the engine knocked slightly and almost felt as though it wanted to hydro-lock on the dumping of liquid fuel into the cylinder. Even though it was a 2005 (a vintage of reasonably advanced monitoring technology) there were no faults stored in any on-board computers. Not in the Powertrain Control Module, Fuel Injection Control Module, etc. None. So, without a breadcrumb trail to follow, I went to monitor the live data. A few parameters looked out of whack but they were led a stray by the root problem and caused me to chase geese at first as a distraction.

I felt certain that a faulty injector bleed copious amounts of unwanted fuel into the cylinders would have to throw off the balance of the running engine and it should feel like a misfire. This was wrong!

Even a cylinder balance test produced results showing that every one of the 8 holes (v8) was doing its share of the work. Not a single bad actor in the group missing the mark on its turn to fire. I then recalled a tidbit I had learned years before. The fuel strategy on these is such that the fueling on other cylinders will be increased to compensate and achieve a smooth and balanced running engine. I remembered a trick I had used years before. You disconnect the two low pressure fuel supply lines that go to each bank of the engine. Disable the supply pump in the tank, and then tie small water balloons around each disconnected line. You do this when you suspect that combustion gasses are getting past the little copper crush washers that seal the tips of the injectors into the combustion chamber. Once these hot flame-gases pass these washers its just a few rubber o-rings that get cooked quickly and then allow passage into the fuel supply.

After tying on the balloons it was time to crank the engine. Sure enough, with every revolution of the engine the one on the left side would blow up a slight amount more while the one on the right remained flat. I knoew I had a problem with the left bank of injectors. Time for disassembly. I got approval from the customer to go deeper and away I went.

Once I removed the injectors I was giddy in anticipation of finally seeing my smoking gun culprit. I pulled them out, and took them under good light at the tear-down bench. There I began closely inspecting 360 degrees of every injector tip. I was looking for bunt suit above the crush washer. I was looking for sintered rubber o-rings. I was looking for brown and nast fuel inlet screens. I found none of that. “Well shit” I though to myself. Faced with the possibility of having wasted more time and remaining stumped, I though of one more test I could rig up. I connected each injector nozzle to shop air (about 150 psi) with a hose and clamp and then dunked each connected injector into a deep pan full of transmission fluid. When I found the one gurgling air through its internals and out the fuel supply screen I finally felt the rush of victory. A couple new injectors on the left bank and some maintenance parts along the way and this one went into the books.

 

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