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Old 07-25-2017, 02:39 PM   #1
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Racor new filter - vacuum still high

I have a Northern lights 8kw on my Grand Banks. 42 Racor 500 30 micron. The vacuum gauge reads very high, even after replacing with new filter. The engine even stopped from starvation. The other 2 Racor 900's for the cats work just fine. What could be causing the vacuum? All valves are open. I see no collapsed fuel lines..... All fuel goes to a central manifold with 3 valves for the 3 filters.

Thanks Mark
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Old 07-25-2017, 02:50 PM   #2
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Greetings,
Welcome aboard. 2 things I can suggest...Does your vacuum gauge read "0" when you replace the filter element or when the engine is stopped? If not AND the gauge is a liquid filled one, there is a rubber plug on the top of the gauge. Carefully lift the edge of the rubber plug to "burp" the gauge and it should return to "0" (engine stopped when you do this please).

The other is a possibly a fuel line that is collapsing internally. Fuel lines are made up of layers of rubber/cord/fabric/rubber that originally is vulcanized into one layer but over time, the inside layers may separate and close/collapse under vacuum. Externally the hose may look fine but it is, in fact, not.
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Old 07-25-2017, 02:51 PM   #3
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High vacuum means there is a restriction somewhere......Filters, intake pipe etc. When I had that issue I had a clogged intake pipe off one of the tanks. Blowing some pressurized air through the line cured it, then chemicals helped dispurse the reason for the clog..
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Old 07-25-2017, 04:16 PM   #4
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Fuel lines can delaminate on the inside. I'd use a primer bulb or small transfer pump rather than the genset to debug this.
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Old 07-25-2017, 08:05 PM   #5
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Quote:
Originally Posted by RT Firefly View Post
Greetings,
Welcome aboard. 2 things I can suggest...Does your vacuum gauge read "0" when you replace the filter element or when the engine is stopped? If not AND the gauge is a liquid filled one, there is a rubber plug on the top of the gauge. Carefully lift the edge of the rubber plug to "burp" the gauge and it should return to "0" (engine stopped when you do this please).

The other is a possibly a fuel line that is collapsing internally. Fuel lines are made up of layers of rubber/cord/fabric/rubber that originally is vulcanized into one layer but over time, the inside layers may separate and close/collapse under vacuum. Externally the hose may look fine but it is, in fact, not.
Thanks, My Racor vacuum gauge is the thin cylinder type. that replaces the handle on top of the unit. When I stop the engine and then press the release button on the top - it takes a good minute to slowly go to zero vacuum. So there is an obstruction somewhere. The boat is a 2002, and I would not think the inside layers would separate that fast.....but I will have it checked during winter lay-up.
I can't think of anything else........ Thanks again
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Old 07-25-2017, 08:39 PM   #6
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Post Fuel line is cheap.

I have see this before - just like the guys above said - fuel line can be cause. I have seen it many times. Even chunks of asphalteen can be stuck in there.

Also inside the tank at the just inside of the out flow pipe it can be plugged with scaling or debris.

The junction block can also be plugged.

I would replace the fuel line -- as in boat units ($) -- it is relatively cheap & not worth risking have the power stoppage of gen set due to this issue.

Blow back through the lines backward of the flow with a little compressed air to free any plugging that is loose.

Next ----------

Next Make sure the water level shut off check ball in the RACOR filter is on the correct side of the upper rubber seal - I have seen these get in the upper side & cause exactly what your experiencing.

To test - remove the check ball completely & refill & prime RACOR & then run it & see what happens with vacuum & fuel starvation.

That is a good one every one misses.

Good luck.

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Old 07-26-2017, 05:51 AM   #7
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"Blow back through the lines backward of the flow with a little compressed air to free any plugging that is loose."

Perfect first step!
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