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Old 10-09-2019, 07:10 AM   #24
Dave R
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Originally Posted by Denny Crane View Post
I think I'm at my limit mechanically so if anything else comes up it might be the end!
Not even close. The next thing that comes up just means you get to learn something else and maybe get to (justifiably) buy more tools. It gets easier and easier the more you do it.

One of my favorite recent troubleshooting events happened like this:

My wife and I were visiting our slip neighbors on their boat after dinner one evening this past Summer. The boat captain is very handy and the conversation eventually turned to boat troubles. He confessed that he was confounded by a problem with his generator. 3 minutes later, we're in the engine room troubleshooting, of course. Mind you, it was probably 9 PM by then, but we are both kind of OCD about this kind of stuff...

Anyway, the genset would not crank and the battery and starter worked fine. He had found and replaced a faulty "ground" cable (problem 1) on the engine earlier that day with no improvement. I took a quick look and noticed that there was an arc suppression diode on the starter solenoid. I got my DMM and tested it, and found it was shorted (problem 2). Removing the diode did not help (it can work without the diode, it's just there for solenoid longevity) so I suggested the main controller board had been damaged by the shorted diode and a few minutes later, proved it (problem 3). The main board had acted like a fuse and one of the copper conductors (lands) on the board had been vaporized. I went back to my boat and got my butane soldering iron, a spool of solder, and a piece of bare copper. A few minutes later, the board was fixed and the engine was finally cranking over like it should. Unfortunately, it would not start. On to problem 4...

We determined that the engine was not getting fuel, so the first check was the fuel filter which was clogged (problem 4), we cleaned it out only to discover the engine was still not getting fuel. Next step was to look at the fuel pump. We opened it up and found that water in the gas had caused it to rust a bit and lock up (problem 5). We freed it up and got it working again pretty easily, put it back in place and still got no fuel flow. We traced the fuel line back to the tank and found a check valve at the top of the tank. We took it off and found it had rusted closed (problem 6). Like the fuel pump, it took little effort to get it working again and we got it re-installed. Now the engien was getting fuel, but it still would not start...

The next obvious check was the carburetor. We took it off, took it apart and found lots of crud. There was one particular chunk of crud blocking the pilot jet completely (problem 7) and when we removed it, put the carb back on the engine, and cranked it, it fired right up and the genset has worked great ever since.

We put a new diode on the solenoid the next day and added a fuse so that it cannot cause the same problem again. We also got rid of the water in the fuel tank.

That's my idea of an interesting evening. FWIW, I had only recently learned about arc suppression diodes this year, on the internet, and if not for that, I think we would have never got past problem 2, that night. I also just happened to have a bag of 100 spare diodes on hand (that I got on ebay for a couple of bucks) because my 27 year old boat has them installed on every one of the dozens of switches and relays.
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