Part 2 - Diagnosis Lifter

Being prepared for a less than well maintained vehicle, I ordered air, fuel and oil filters from World IMPEX before picking up the truck.  I was expecting a less than well maintained engine, so the first thing I did once I got the truck home was to perform some routine maintenance.  To my surprise, I found a relatively new and clean air filter (which I replaced anyway) and a fuel filter that appeared to be as old as the truck.

Though it looked guilty, the fuel filter was not the culprit

 Unfortunately, I ordered the wrong fuel filter, so the next day I went to the local parts store and picked up the correct filter.  A quick test drive revealed that the filters were not the problem.  With thoughts of partially or completely disassembling the motor, I decided to wait until after fixing the dead cylinder before changing the oil and filter, rather than potentially waste some perfectly good Mobil Delvac-1. The next step was to perform an "Idle Speed Drop Test", which involves starting the engine, then cracking open the fitting on top of each injector, one at a time.  Cracking open the fitting relieves some of the very high fuel pressure used to open the mechanical injectors used in Diesel engines, preventing it from opening.  If the idle drops when the fitting is cracked open, then the injector is working.  If not, then that injector is suspect.  All four injectors tested good, so the problem is an obviously malfunctioning fuel injector.

Stumped, I decided to record a .wav file of the engine noise, and posted a link on the VW Pickups and Wasserwerks e-mail lists.  One good suggestion was that the engine was "nailing" on one cylinder; meaning that one of the injectors was not holding sufficient pressure, and was firing prematurely.  Several people also recommended that I get the injectors rebuilt, if for no other reason because of their age and mileage. 

After researching rebuilt versus new injectors, I ordered new from Adirondak Parts Brokers, along with new injector seals.  A trip down to the local dealer netted me some new return line hose.  Excited to get the truck running right and needing to run errands this weekend, I tackled replacing the injectors after work.

The first thing I did was soak the injectors where they thread into the cylinder with Deep Creep the night before, to prevent any damage while taking them out.

Mmm...shiny

When it came time to start the actual job, step one involved cutting off the existing rubber return lines that run between each injector and the return port on the injection pump.  Next, I removed the hard lines from between the injection pump and the injectors.  From there, the job closely resembled replacing spark plugs on a gas engine.

Halfway home with the injectors

 Using a torque wrench, I broke each injector free, then unscrewed it from the head.  I then removed the sealing washer from the bottom of the open port, replaced it with a new washer, then screwed in the new injector, torquing them to 52 ft./lbs, as indicated in my recently purchased Bentley manual.  After buttoning everything back up, I got back in the truck, crossed my fingers, and fired it up, and took it for a test drive around the block. While replacing the injectors did solve the "nailing" issue, the truck was still running on three cylinders.  Dejected, I parked the truck, and went back to the two e-mail lists with my results.

The next good suggestion was the check valve lash.  Unlike the mechanical camshafts in the small block V8 engines I learned on, as the valve train breaks in and wears on one of these motors, the valve lash decreases.  Shims are used to maintain the proper valve lash.  Armed with this information, I went back and pulled the cam cover. 

It didn't take too long to finally have the cause of the dropped cylinder.  I found one of the shims missing from the exhaust valve lifter for cylinder #3.  The lifter was chewed up around its edges, and the lash was something close to infinity; I'd be amazed if the valve opened at all.  I found the shim lying in the bottom of the head, with obvious damage from floating around in there for a while.  Amazingly enough, all eight camshaft lobes look to be in excellent, almost new condition, as if the cam had been replaced at some point.

Arrow points to chewed up lifter, missing shim.

Mystery solved, the next step is to replace the bad lifter.  While I'm at it, I will replace the timing belt, and probably clean and paint the cam and timing belt covers  Look for an update on this in Part 3, as well as the installation of the stereo and clean up of some of the electrical issues.

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