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Old 24-09-2015, 17:23   #1
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Mechanical Help Needed.

I have a '96 phoenix 34' sfx. powered by a pair of 3116t a cats. it is a great boat with one exception. after running for a couple days (not a constant 24 hours but run a few hours and anchor for a while then move again.......) my starboard engine will die. it doesn't just stop but rather it seems like it is running out of fuel. we've had a mechanic look at it and, naturally, the engine ran fine.

I've had the tank cleaned and fuel polished, cleaned and rebuilt the racor, and made sure that fuel flowed through the hoses. the mechanic checked the fuel pressure and said that it was within spec.

I've been told that it could be the fuel pressure regulator, but I don't want to just through parts at it and hope that it works. is there a way to test the regulator? or should I just replace it? or could the problem be something else entirely?

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Old 24-09-2015, 17:26   #2
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Re: mechanical help needed.

Boat is your best bet for help

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Old 24-09-2015, 17:28   #3
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Re: mechanical help needed.

Thanks, I'll go check them out.
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Old 24-09-2015, 17:33   #4
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Re: Mechanical Help Needed.

My guess is a fuel issue... as it often is.
Possibly tiny air leak?
Or fuel restriction.
Clogged fuel tank vent will do that... creates a vacuum in the tank until the engine quits. Separate tank for each engine on your boat?
Does the engine speed up erratically as it's stopping?
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Old 24-09-2015, 17:35   #5
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Re: Mechanical Help Needed.

no, it's one big (300 gal) and the port engine and generator run jut fine.
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Old 25-09-2015, 04:45   #6
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Re: Mechanical Help Needed.

My guess is air leak, such that fuel seems OK when tested but eventually air seeps in.

Just first guess, though.

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Old 25-09-2015, 09:33   #7
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Re: Mechanical Help Needed.

Could be a faulty check valve on the fuel supply side. As Cat parts go they're cheap, I always carried spares.

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Old 25-09-2015, 11:51   #8
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Re: Mechanical Help Needed.

If you had fuel pressure and vacuum gauges you could easily troubleshoot this yourself.
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Old 28-09-2015, 22:15   #9
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Re: Mechanical Help Needed.

Here is some possibly helpful information:

I would check the fuel lines from the tank to the primary and secondary fuel filters. The 3116 has a history of the steel lines along the governor side of the block rubbing through and creating cavitation. If the hole is small you might not really notice a difference at first. This is where I would start. Once it dogs again check the fuel filter, if it's close to empty you obviously aren't getting the fuel you need. If you have a fuel priming pump start using that when the engine starts to die off, this will also tell you that the fuel system is lacking flow. One other tip is to put the fuel line before the secondary filter (closest to the governor) into a clean bucket of diesel and see if the engine runs better. But, I would definitely start at the steel fuel lines first......

From a school bus mechanic blog:

~~~~~School Bus Mechanic: Cat 3116 Troubleshooting No Power
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Old 10-10-2015, 17:18   #10
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Re: Mechanical Help Needed.

I had a similar problem when I brought this boat home. I had a small air leak from the fuel line rubbing a hole on the engine beds. My engine room has a day tank the mains and 2 generators draw fuel from. Only 1 main was affected. Sometimes the hole would be covered enough that fuel was supplied normally. I had to disconnect the fuel line and do a pressure test to find the hole.

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