Saturday, November 13, 2010

Problems with Perky

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:

  1. Lack of adequate power
    1. The engine fails to reach desired RPM when operating under load. 
    2. This problem appeared abruptly without obvious warning signs.
  2. Oil consumption
    1. Approximately ½ liter in 15-20 hours operation
    2. Not sure if this is new or long-standing
  3. Moderate amount of grey smoke when operating under load.
Despite the lack of power, the engine:

  1. Starts very easily
  2. Idles very well without miss-firing of knocking
  3. Smooth revving to 3500 RPM in neutral
  4. Minimal grayish smoke at idle  (definitely not blue or black)
  5. Oil pressure in operation runs consistently at 45 psi
  6. Engine temperature 180 degrees F at 1500 RPM
  7. Good, clean raw water exhaust flow without oil sheen.

What we don’t yet know:

  1. What is our compression?  Difficult to measure in a diesel without glow plugs.
  2. What is our current fuel consumption?
  3. 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.
  4. Could the engine be overloaded from excessive friction in one or more cylinders?
  5. 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!


    1. JJ Clyde has a Perkins too, but we've not had these problems. The grey engine spoke is definitely a normal Perkins characteristic. I've emailed your story to sailor friends who know more than me and might be able to help. Stand by.

      And April, thanks for the great photos of you, and the Dorado. You look....marvelous! Dad and Megan

    2. Hi; Got your problem from a friend. Our 4-108 had the same overheating problems, (identical), until we changed out the fresh water pump assembly. It totally solved the overheating problem. I believe your other problem is in the transmission. Put it in neutral and see if you can turn the shaft freely by hand. If not you have a transmission or stuffing box problem. Our Hurth transmission had a pressed gear slid just a little that caused ours to slip. If it slid the other direction it would have frozen. Does the tranny get hot when you are under power?

      Carl Berdie

    3. Here is a response I got from a cruising friend:

      Our first boat (Mariah) also had a Perkins 4-108 and developed similar problems near Little Currant, ON. I felt that the mechanical lift pump was the problem as the fuel requirement is much greater under load then running free, even though the RPM is thee same. I rigged a gravity fuel system at sea using a jerry can up high in the cockpit and a rubber hose to the inlet of the lift pump. The engine now ran up to the desired RPM. Once in Little Currant I purchased an add on electric pump and mounted it near the tank. Then reconnected the lift pump and let the electric pump just pump through the mechanical pump. This scheme also helps when bleeding the lines, just start the electric pump and open the bleeders, forget about pumping the little lever up and down.
      Their oil consumption sounds about right given the hours and likely doesn't relate to low power.
      Dave Steffens"
      Larry Carpenter

    4. Here is another response to your problem. An email contact is at the end of the response:

      "Hi Larry,
      Read the blog. Unfortunately I'm on a system to today that doesn't allow blogs so I will forward this through you. I have a few questions re the 4-108:
      What is the maximum RPM they have ever seen in no wind/waves in gear and how fast was the boat moving?
      Is the prop fixed? Size and pitch is?
      Which Hurth (Gear ratio)do they have?
      Have they replaced the lift pump?
      What is the pressure drop across the Racor again? Is this a suction pressure or drop across the filter?
      Is the engine exhaust black when throttled up near full throttle?

      My general impression is that the engine is starving for fuel. At 3000 plus hours the time is coming that an overhaul is on the horizon.

      I have overhauled many engines including the 4-108 and worked in Onan's nation service department for several years so helpfully I may be able to lend a hand.
      Tom Davison
      Home address is

    5. For Luke: You guys are right down the road from La Ventana, where Wyatt Miller has a hotel/windsurfing rental:

      You gotta go and do some sailing and meet Wyatt, who is not only an amazing windsurfer (he's a pro...won the Gorge games in 2007), but he's also a really great guy, and he knows Phil! BTW, I hit my first forward last week!

      Here's a blog post on your diesel that might help:

      The first thing I thought was that clearly there's not enough water flow through the exchanger. It sounds like this is a two pump system, unless it circulates raw seawater right through the block. Either way, when you put it in gear one of the pumps is not hooking up like it should. The fact that you can rev. to 3500 in neutral indicates there's no fuel or engine problem. The engine takes the same fuel/air per combustion stroke whether under load or not.
      Good luck with the engine, I'll stay tuned.

    6. From Puget Sound: "... the symptoms/diagnostics they've described seem pretty thorough to me; sounds like they already know what they're doing. The only other thing I could think of might be a partially clogged air intake or filter. They didn't mention if there's a turbo charger, but that could also be the problem. Usually a turbo kicks in at a specified RPM, and without a functioning turbo the engine will not perform well. But I'll certainly check around to see if I can find an expert who might offer some guidance. Good luck. b" April's Mom