Help us solve Perky's Perplexity and win an ‘El Tiburon’ T-shirt!
For those of you who have grown accustomed to the quality writing April has been providing this blog, please excuse my intrusion. It’s just that we’re growing increasingly obsessed with solving our diesel troubles, and knowing that our audience is so smart, we’re sure that one or more of you are more than capable of teasing out a solution.
One final warning before proceeding - if you're not mechanically inclined, or have no interest in discussing the finer points of internal combustion and the like (K2 Nolan – that means you) please skip this entry and keep on reading April’s reports, they’re terrific!
In July of this year, Andrew, Luke and I bought El Tiburon (Passport 42) with an original Perkins 4.108M diesel (4 cylinder, 108 cubic inches) with approximately 3000 hours run time. Sailing the boat on day trips in the Bay were without difficulty, although we never ran the engine for more than an hour at a time.
From previous maintenance records, we believe that the engine received regular routine oil and fuel filter changes. A new Hurth transmission was installed in ’99 and the valves were adjusted in ’00. Our fuel system has a primary Racor Filter and a secondary filter located at the lift pump on the engine.
In early October, we left San Francisco for San Diego and beyond. This would be our first trip with the El Tiburon outside the Bay. In preparation for the trip, we had our tanks polished and changed the Racor fuel filter.
During the trip down from San Francisco, the winds were light, requiring us to operate the motor for hours at a time. The engine ran well, except for a small problem with overheating at RPM’s greater than 1800. Typically, our diesel operates at temperatures of 170-180 deg F and uses a raw water cooled heat exchanger.
We noticed that running at speeds greater than 2000 RPM caused the engine temperature to exceed 200 deg F. Since those engine speeds didn’t appreciably affect our speed through the water, in the interest of fuel consumption and keeping the engine cool, we decided to keep the RPM’s at 1800 or less. This game plan worked fine all the way to Cabo San Lucas.
In Cabo, we refueled with diesel from a modern looking fuel dock. With plenty of expensive yachts in the marina, we felt safe to fill our tanks and chose not to use a pre-filter. Shortly after taking on 70 gallons of diesel, we noticed that the engine would no longer exceed 1500 RPM when the transmission was engaged in forward. In contrast, if we shifted to neutral, the motor revved to 3500 RPM with no difficulty. It was only under propeller load that the engine failed to meet the desired RPM. Of course, we dove over the side with masks to ensure that nothing was wrapped around the propeller, and that both prop and shaft spun freely. All seemed fine.
Since the problem began shortly after taking on fuel, we decided to approach the fuel system first. We changed the Racor fuel filter, the secondary filter, bled the fuel lines of air, cleaned the air filter, changed the crankcase oil and filter and restarted the engine. No change. The vacuum gauge immediately after the Racor displays it’s typical low reading (i.e. 0-5 inches of mercury), suggesting that fuel passes easily from the tank thru the primary filter. We checked the transmission fluid and verified that it was at the proper level. I peered inside the transmission case with a flashlight and found the fluid to be clear, devoid of dirt or metal particles.
In examining the exhaust, we observed that in neutral, there seemed to be a brisk exit of raw water but in forward gear, the raw water output decreased. Suspecting a clog in the raw water system, we cleaned the strainer, replaced the raw water impeller, de scaled the raw water cooled exhaust outlet pipe in muriatic acid and examined all hoses. We then measured the volume of raw water flow using a 2-gallon bucket and a stopwatch. At 1200 RPM, whether in neutral or forward gear, the output of raw water exhaust was exactly the same – approximately 2 gallons in 30 seconds. We also ran the engine bypassing the muffler to eliminate excessive exhaust back-pressure as a potential problem. Same results. We pulled the valve cover and checked the valve tip clearances – all were fine.
By this point, we had learned a ton about Perkins diesel engines and were fast becoming obsessed with solving the ‘lack of power’ problem. We pulled all 4 fuel atomizers and delivered them to the local diesel laboratory. The owner of the lab cleaned the injectors (told us they were quite dirty) and returned them to us in clean condition. We installed the atomizers the same day and started the engine. Again, same problem!
To summarize the symptoms:
- Lack of adequate power
- The engine fails to reach desired RPM when operating under load.
- This problem appeared abruptly without obvious warning signs.
- Oil consumption
- Approximately ½ liter in 15-20 hours operation
- Not sure if this is new or long-standing
- Moderate amount of grey smoke when operating under load.
Despite the lack of power, the engine:
- Starts very easily
- Idles very well without miss-firing of knocking
- Smooth revving to 3500 RPM in neutral
- Minimal grayish smoke at idle (definitely not blue or black)
- Oil pressure in operation runs consistently at 45 psi
- Engine temperature 180 degrees F at 1500 RPM
- Good, clean raw water exhaust flow without oil sheen.
What we don’t yet know:
- What is our compression? Difficult to measure in a diesel without glow plugs.
- What is our current fuel consumption?
- Is the engine getting adequate fuel when under load? The Racor vacuum gauge suggests so, but this doesn’t eliminate a faulty lift pump or injection pump as a source.
- Could the engine be overloaded from excessive friction in one or more cylinders?
- Have I completely ruled-out excessive friction in the transmission? I guess not. I’m just not sure how to go about testing it. Pull the prop and run the engine test again?
At this point, we’re considering a lack of adequate compression to be the most likely problem – either blow-by from a poorly seated piston ring, or incompletely seating valves. Of course, we haven’t ruled out a poorly functioning fuel injection pump, but since these rarely seem to have difficulties, we’re considering this to have a low probability.
In deciding what to do next, we’re thinking that the next obvious step would be to pull the cylinder head and service the valves. This would then allow us to examine the cylinder walls for excessive wear and eliminate the valves as a source. And if that doesn’t do it, we’ll consider a complete rebuild.
If anyone has any ideas about what to do next, we’d love to hear it!