Perky's Perplexity Part 4

Greetings to all from Puerta Vallarta!   A number of our friends have asked us, “What’s up with Perkie?  Have you fixed the problem yet?  Do you have any brain cells still functioning?"

I wish I could report success, but I must admit in spite of our best efforts, and help from many of you, we haven’t solved the problem.  Now, we’re really scratching our heads!  Perky has proven himself to be quite an enigma, and we seem to be circling back and re-checking our prior attempts at making a diagnosis.

Allow me to update you on the latest events.  As usual, a stern warning to those not interested in diesel engines - read no further!   I promise I won’t take it personally.

Ok, here we go…

I’d like to remind you of the basic problem with Perky – a lack of power (i.e. failure to obtain desired RPM) when engaged in gear – equally poor in forward and reverse.  In neutral, we can rev the engine to 3000 RPM and it sounds great, but in gear, we cannot exceed 1400.  Engine always starts right away and idles smoothly without knocking.  No excessive smoke production at the exhaust and minimal oil consumption. 

Since our last communiqué, we had convinced ourselves that the problem stemmed from a dying fuel injection pump.  Since this is an expensive part, and replacing it requires a significant amount of upside-down engine wrenching and body contorting due to the low placement in the bilge/engine compartment, we did our best to exclude every other possible source of our engine troubles before honing in on this one. 

We also entertained many and varied opinions which seemed to point us in several directions.   More than a few of you have suggested that the prop is the source of the problem.  By our logic, since this same prop had been working just fine before the onset of our troubles, and nothing on it had been altered since the problem began, we simply refused to believe it could be the prop.   Certainly an over-pitched propeller could lead to engine overload and poor performance, but the folks at MaxProp have assured me that there is NO way the prop could have slipped its pitch setting without a catastrophic and obvious failure.  I dove (again) on the boat and spun the prop to observe the blades feather in forward and reverse – still silky smooth.  I’m sticking to my guns on this issue – it’s not the prop.  

On Monday, Andrew adeptly smuggled a new High-Pressure Fuel Injection Pump thru the Puerta Vallarta airport after spending the previous week in NYC.   With a couple of borrowed tools and some creative tool creation, I was able to install this new pump without too much difficulty.  Fortunately for me, many of you had given me some good advice on the procedure.   After nearly a day of working in the bilge, hunkered over Perkie, the new fuel pump was installed and fuel lines bled.  After cranking the engine for about 30 seconds, while the last bits of air purged from the high-pressure lines, the engine miraculously sprang to life!  It sounded so good to our ears that we were convinced we had finally solved the problem! 

Alas, there was no joy that day.  The engine stilled refused to achieve an RPM above 1200 while tied to the dock in forward gear.

Here’s what we’ve done so far (breaking it down by engine systems).

Fuel Supply

1. Changed both RACOR primary and engine mounted secondary filters
2. Removed all four injector nozzles and had them cleaned and inspected by a locally respected diesel laboratory in La Paz.
3. Installed new lift pump
4. Removed and inspected all rigid fuel lines (including injector lines)
5. Installed new High-Pressure Fuel Injection Pump
6. Ran the engine from a 5 gallon Jerry Jug connected to the RACOR to rule out a clogged tank pick-up or fuel supply line.
7. Removed return fuel line and measured rate of fuel return at various engine RPM’s and found the rate to be a consistent 100 mL/minute.  This step ensured an adequately functioning lift pump.
8. Measured fuel consumption at 0.7 gallons per hour while motoring at 1400 RPM and 5+ knots.  This differs from our prior consumption rate of 1.1 gallons per hour at 2000 RPM and 6-7 knots boat speed.

Engine Load

1      Disconnected propeller shaft from transmission and operated the engine dockside. In both neutral and forward gear.  Engine came up to speed without difficulty.  3000 RPM, no problem

2      Inspected transmission.  Clear pink fluid at appropriate level.  No evidence of metal particles or flakes.  Gear shifter operates thru appropriate range on the gearbox shift lever.

3      Ran engine test without the Large Frame Balmar Alternator loaded.  No change in engine power.

4      Inspected Max Prop in the water.  No obvious damage to prop blades and smooth feathering in forward and reverse.  Shaft turns easily by hand.

Exhaust System

1. Tapped exhaust manifold with a 1/8” NPT fitting to measure back-pressure during operation.   See video of this test.  Results are below:

Transmission Setting	RPM	Fluid Height (Inches H20)	Pressure (PSI)
Neutral	1000	31	1.2
Neutral	1500	47	1.7
Neutral	2000	69	2.5
Forward	1000	33	1.2
Forward	1200	39	1.3

By Nigel Calder's book on Marine Diesel Engines, this back pressure is too high.  Agreed.  However, it's basically the same back pressure in forward gear as it is in neutral (RPM matched).  So I don't see excessive back pressure as causing our problem.

At this point, we’re totally confused!  Not only are we a little disappointed that our new, $750 Injection Pump didn’t make a bit of difference (although I am a bit proud that I was able to install this baby!) we’re also at a loss regarding the next obvious step.

We’re presently considering:

1.     Removing the cover on the transmission to more closely examine the internal gearing.  We’d also take a sample of the tranny fluid to the local lab for examination and put a timing light on the prop shaft to ensure a 2:1 reduction ration coming thru the tranny.

2.     Hauling out at Marina La Cruz (near Puerta Vallarta) to fully inspect the prop and shaft.  We don’t know the exact pitch settings and we should confirm that the prop is pitched appropriately for this motor.

3.     Removing the injectors again and have them inspected a second time.  We will ask for specific measurable parameters such as pop-off pressure and spray pattern.

4.     Leaving the boat in Puerta Vallarta and traveling Mexico by bus!  We’ll go much farther, faster and considerable cheaper!

Keep your suggestions coming!  Maybe we can solve it before the New Year!