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Factory fuel water separator ?

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This may be a dumb question but I’ve never owned a diesel truck but all of my tractors have a fuel/water separator.  Does the L5P come with a fuel water separator that I can drain? I have not had any problems but a buddy of mine who has a Chevy Cruz diesel had to do extensive work because of some bad fuel/water. I think our trucks come with a sensor that would tell you if you had water in the fuel but I would like to have some kind of protection before it hits the engine. And on that same topic how often should I change the fuel filter because normally I don’t trust the electronic filter life in the dash. 



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Filter used on the LML was known to be an EXCELLENT water separator.


If a L5P gives a 'water in fuel' warning, instructions are to drain the fuel filter, so I'm betting it is as well. 

They do have a water sensor and will give a message.

There is a drain valve on bottom of filter. 


I'm really fussy about fuel source, but I've never had a water-in-fuel problem on any of my diesel trucks or diesel equipment.

( I have helped drain water from fuel in others equipment.)


page 49:

Water in Fuel
Improper fuel tank inspection or cleaning, or contaminated fuel from
suppliers, can cause water to be pumped into the fuel tank along with
the diesel fuel. If a WATER IN FUEL SERVICE REQUIRED message
displays, the water must be drained immediately. 


page 51:

Removing Water from the Fuel Filter
To drain water:
1. Turn the engine off and apply the parking brake.

2. Place a container under the filter drain valve.

The filter drain valve is on the bottom of the fuel filter.

The filter drain valve is under the vehicle on the driver side, inside the frame rail.
3. For 8-cylinder pickup and 4-cylinder van models, open the drain valve by turning it counterclockwise. Allow the filter to drain until all of the water has been removed.
Close the valve.
For 4-cylinder pickups, open the fuel filter drain valve by turning it two to three turns.
Allow the filter to drain until all of the water has been removed. Close the valve hand tight.
4. Properly dispose of the water contaminated fuel.
5. Start the engine and let it run for a few minutes. During the draining process, air may have entered the fuel system. If the engine stalls, the fuel system may need to be primed.

See “Fuel Priming” following.



For fuel filter changes, the DIC should be reasonably accurate.  It measures the restriction of the filter.


Seems like the L5P filter is going to require changing much earlier than the on on the LML. 


Based on monitor percentages I'm seeing and other dmax forum reports, I'm expecting/planning that a convenient interval to change the fuel filter will be at every other engine oil change.

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Excellent information. 


just a cap but no valve to drain it... so if you are on the road then you have no way to drain it if you have no tools....is there an aftermarket one with a drain valve? 





Thank you 

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Isn't the drain valve opened by the smaller hex inside the large hex on the bottom of the folter housing? 


(I haven't crawled under and tried it, but that was may understanding) 


pics in this thread: http://www.duramaxforum.com/forum/2017-l5p-duramax-powertrain/972034-l5p-fuel-filter-replacement-noise-question.html

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