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Sunday, June 19, 2011

Smoking Gun?

It's been quite awhile since we've posted to the blog. Allow me to catch everyone up:

We made it to the marina in Mazatlan. Stayed our first month in the Singlar (don't say Cingular!) marina for the month of May. We tore the boat down for the summer, all sails and running rigging are removed and the dinghy is put away. I built a 'Catio' for Ziggy so he can hang out outside at night. Linda flew to Bothell, WA to stay with MJ for the summer. I started working on two main boat projects; 1) rebuilding the top of the hatch turtle and 2) rebuilding the engine.

Whoa! Rebuilding the engine!? Is that really necessary? We came to Mazatlan to answer that very question. There being a Yanmar trained mechanic available through Total Yacht Works, we figured this would be a good place to handle the work.

'Lil Thumper', our Yanmar 3QM30, has got 5100 hours and is over 30 years old. It has two problems; 1) fuel is getting into the lubricating oil and 2) it can be very hard to start. It's not far fetched that it would need at least a set of piston rings. But after spending 15 minutes bent over the running engine, Javier pronounced its compression good ("there's no blow-by, you don't need rings"). Huh. So much for the big rebuild. But what about the hard starting, Javi, not to mention the fuel-in-the-oil (FITO) problem? "We'll change the simple things first; start with the lift pump to fix the FITO and then move on from there." I should say at this time that I consider myself to be a good amateur mechanic, and have already replaced the lift pump (about two years ago when the oil problem first started). But if Javi says to replace the lift pump again, that's what we'll do! I got the spare out and he put it in.

The thing to do now was to run the engine and see if the oil level changes and see if the starting problem comes back. I waited a week before starting the first time as the starting problem seemed to get worse the longer the engine sat. After a week it started hesitantly, but well. After 3 hours the oil level hadn't changed (when fuel leaks into the oil, the level on the dip-stick raises). So maybe the FITO problem is fixed.

On the second day, the start didn't go well at all. It took maybe 20 seconds to get going, the whole time doing the ka-chunk-ka-chunk-ka-chunk thing. I resolved to bleed the fuel system at various points before starting it the next time to see if I get bubbles anywhere (a sign of air in the fuel system which would cause the ka-chunk starting).

On the third day bleeding at the injection pump showed a few bubbles. Humm, maybe the problem is there. It started and ran well, oil level steady. Fourth day, the same. A few bubbles, good start, steady oil.

My theory at this point was that there was air being drawn back into the injection pump when the engine is off. The tank is low and there's no doubt a bit of negative pressure on the fuel system cause by the diesel trying to siphon back into the tank. The question was: where's the air leak?

Today, Sunday, is the fifth day and I resolved this morning to give myself the day off. Oh but maybe I can just bleed the injection pump to see if I get bubbles. Open the engine compartment, unscrew the bleed screw, pump the lift pump, a couple tiny bubbles, tighten the bleed screw, break the head of the bleed screw off! I'm sure even the least mechanically inclined will realize that last step shouldn't be there. It seems the bleed screw may have been in the process of shearing off for some time, making it very hard to get a good seal on the injection pump. All the screwing and unscrewing finally did it in. (Javier also had to crank that screw to bleed the system after replacing the lift pump.)

As I said, it's Sunday, so there's nothing to do about it today. But tomorrow I get to ride the buses looking for 1) an appropriately sized screw and 2) a machine shop to drill a hole in it (the bleed screw has a tiny hole to let air out when it's unscrewed).

{GMST}23|16.120|N|106|27.35|W|Marina Mazatlan|Maz{GEND}