Friday, May 30, 2014
'Basics boy, basics'
'In diagnosis, always check the basics first'. I learned that little nugget of wisdom back when I was about 7 years old. And another 'when something changes in terms of noises or performance, go looking for it, don't wait and see if it will fix itself'- I learned when I was about 10. I guess occasionally I need to relearn my own lessons again and eat a fat helping of my own advise... mmmmm, humble pie... tasty.
It has been cloudy here (Mar '14) recently and in my off-grid PV powered situation I need a really reliable generator for the cloudy days when the PV doesn't make enough power for me to write my blogs and do my research late at night, as I tend to do.
For over 15 years, I have been making my own power and I have built numerous backup generators for myself and clients that make more power, more reliably, more efficiently than any I can buy in a store or online. The last generator I built was based on a used 12hp garden tractor engine turning a big alternator via belt drive with a frame built of glued and screwed wood and plywood. This machine performed great for nearly 8 years when the 12+year old engine died a horrible, sudden, catastrophic death. So I set out to build what I hope is the last one I ever need to build for this land.
What I ended up building was a machine based around a 1.2L, 18 HP naturally aspirated, single cylinder ChangFa 1115 series Diesel engine. This beast is built mainly of cast iron and uses dual counterbalance shafts to get decent smoothness, has ball or roller bearings all the way around inside and uses high pressure pumped oiling system to keep everything lubricated and a full water jacket for cooling. This diesel runs sweet, starts right up even when the temperatures are waaaay below zero, and makes a boat-load of power while just sipping the fuel. The engine turns two big Delco alternators via v-belt and direct charges the battery bank in my utility shed via copper cable the diameter of my thumb. Watt- for- watt, this diesel setup uses less than half the fuel of what the old gasoline engine powered machine ever did.
Unfortunately, all cannot be perfect forever... I noticed recently that the beast wouldn't rev up and seemed to be losing power and running really smokey. And... it was getting worse and worse rapidly. Now, normally, if it were someone elses equipment I was being paid to work on, I would run through the basics and check everything thoroughly. Because it is mine tho, I figured I could cut corners, I thought I knew (YAY arrogance!!) what the problem was.
I strongly suspected that the injector was clogged with gunk on the pintle and was dripping fuel instead of spraying fuel into the cylinder in a clean conical spray pattern. Fuel dripping or dribbling caused by a clogged injector, or worn injection pump, can result in smokey operation and low power output.
So I pulled out the fuel injector- its a big single cylinder diesel engine, so it only has one injector- and found it a bit crusty, but cleaner than some I have seen. I cleaned and reinstalled the injector, then fired the engine back up. No change in performance- a bit cleaner burn perhaps, but performance wise- same, same.
So I shut it back down and went inside to study the mechanical breakdown drawings and parts list to learn exactly what I am looking at. I was about ready to tear into the injection pump- which I had only suspected because I was still stuck on the 'dripping fuel' theory and also because the repair kit for the engine came with an IP repair kit too.
This was the point when I heard my grandfathers voice in my head say “basics boy, basics”. Grandpa was a diesel mechanic back in the old days- the 1930's, 40's and 50's. He knew he couldn't take anything for granted back then when he was diagnosing a problem, same as I shouldn't now. Hearing his voice in my mind reminded me that a tune-up on a diesel is simple and takes no real time and in fact, a diesel tune-up happens constantly and most engines should not be run more than a few dozen hours without being inspected and checked over.
Nothing may need done, as is often the case, but checkups are still needed to confirm that nothing needs doing. So I reset my train of thought and went back to basics, tune-up style to make sure I caught any and all issues.
**Oil/ Coolant- all good- check.
**Air filter- Clean, dry, lightly dusty- check.
**Fuel and filter- Drained old fuel and added clean fresh diesel fuel with injector cleaner/cetane booster, checked the fuel filter housing for dirt/moisture- none found- all seems proper- check.
**Compression- No reason to suspect compression: The engine still bounces off of compression just by spinning the flywheel by hand- like it always has. Most importantly as an indication of compression, the engine still starts immediately dead cold- like it always has. So yeah, compression is still fine- check.
**Valve clearances- a normal part of routine check-ups- here is where things get interesting...
So I take off the valve cover- it has an oil line to it, banjo fitting style and a nut on a stud in the center of the cast-iron valve cover. Everything seems normal to the eye, so I grab the rocker arms and wiggle them by hand- YIKES!!! The exhaust side is fairly snug still, but the intake valve has nearly 3/8” (10mm) of slop! That will do it. The engine couldn't get a full cylinder of air- not even close. Deprive a diesel of its air and that’s what you get- smokey, no power, no revs... damn! Dead give-away there...
I complete the disassembly of the rocker arm system and find that the intake rocker arm has literally EATEN its center bushing. Great, I need to find new bushings now. Fortunately, closer inspection revealed that the rest of the valve stem and rocker arm assembly seemed fine, no damage done. So at least the bushing would be all thats needed to get the system operable again.
But curiosity- yes, the same what killed the kitteh- drove me to ask, as it often does, 'WHY??'. That is usually the first thought that drives me on to further investigation of causal determination. Actually, the thought in my head was "WTF happened and how can I make sure it never happens again!?!" Next post, this coming Tuesday, June 3rd, will cover the underlying problem I found and my hack solution to it... see ya next month...