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Under Pressure

Posted by on August 12, 2011

Editor’s note:  I started this blog post on July 30th, and had to heavily edit it based on the problems that I encountered. Read on to see why your average boat project takes 2.5 times as long as you think it should!

What follows is the first of (hopefully not too) many blog posts on diesel engine repair. Some of you might wonder why I’m writing about this mundane topic? For starters, I’m documenting it so I can remember what I’ve done in the future! The next reason would be to hopefully provide some information to other sailors that might have similar situations. Finally, I want this blog to illustrate our full journey.  Many cruisers joke that “Cruising is fixing your boat in exotic locations….”  Be aware folks, this blog won’t be all palm trees, lobster, and sunsets.

So here it is, ‘The journey of a thousand miles begins with a single socket set…’ or something like that. Stay tuned for the excitement of beautiful engine compartments and faraway grease covered tools!

The Westerbeke manual said that the easiest way to determine engine health was to perform a compression test. I quickly googled Westerbeke’s recommended compression attachment, and found it listed at around $110, plus I would need to borrow a compression gauge.  Next I popped over to Harbor Freight online for a diesel compression kit.  $29.99 and few days of shipping later, I now have a fancy new kit.  (Note, for the reasons that follow I don’t advocate Harbor Freight for anything you want to last, but I only needed this kit to last for four tests, so I thought I would be okay.  I have about a 50/50 success rating with Harbor Freight, either I’m happy and the tool gets the job done, or I’m angry at the packaged piece of junk they sold me.) 

My buddy, and dock neighbor, Bill, says he’ll give me a hand with the compression test over the weekend. Having never done one before, it’s nice to learn tricks and tips from a guy with a lot of experience on various engines. So I do my part to get the engine ready for testing and follow the steps outlined in the Westerbeke manual:

  1. Warm up engine
  2. Turn off fuel supply
  3. Shut raw-water seacocks
  4. Remove (now very hot) glow plugs
  5. Open brand new diesel compression tester
  6. Attach proper fitting into Cylinder 1
  7. Attach compression tester to fitting

And here’s where things get interesting.  At this point Bill hits the ignition on the engine, and the quick-connect on the tester separates itself from the fitting.  Forcibly. We also have another problem, the pressure release valve isn’t working on the tester.  So there’s about 500 psi in the tester that we have to release. That took some swearing.

We analyze the system and determine that the fitting we need was poorly machined and won’t seat properly on the quick connect.  But never fear, because Harbor Freight has a 100% guarantee on their tools!  It’s a decent drive, so the compression test is abandoned for a week until I can get back to the store.

Fast forward a week, the visit to Harbor Freight has been made, there are no questions asked, just a simple exchange of my non-descript red case for another non-descript red case.  I check the fitting in the parking lot, it is machined properly and fits tightly. I’m back in business!

This weekend my friend Steve is in town and he’s going to help me with the test.  So I reassemble the engine, repeat steps 1 through 7 above and  test the first cylinder: 520 psi.

Test second cylinder: 0 psi.  The air release button won’t close and therefore won’t allow the tester to pressurize. At this point two engineers proceed with multiple attempts to make this tester work. More swearing. Final result is the abandonment of the test for another week.

Fast forward another week, the visit to Harbor Freight has been made, there are no questions asked, just a simple exchange of my non-descript red case for another non-descript red case, they must do this a lot…. I assume ‘the 3rd time’s a charm.’

This morning I skip reassembly and steps 1 through 4 and dive straight into the compression test.The tester actually allows me to get through all 4 tests without too many problems (the tester still flies off the fitting once it is pressurized. Still forcibly.)  Results as follows:

  • Cylinder 1: 520 psi
  • Cylinder 2: 520 psi
  • Cylinder 3: 525 psi
  • Cylinder 4: 540 psi

The engine is great, excellent pressure and less than a 10% difference over the cylinders!  FINALLY.

Total time for me to do the test by myself this morning? Less than an hour.  (And that was with me re-installing the companionway steps every time I had to run up to the cockpit to hit the ignition.) Total wasted time because of poor quality tools?  8-10 hours.

I take two positives away from this process, I know the compression on the engine is great, and I know how to replace a glow plug in my sleep!

Engine with Compression Tester

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