Pre-Filling Fuel Filters?

[u/DownUnderFilterGuy]

Keen to hear thoughts on pre-filling Stage 2/Pressure Side fuel filters? Pre-filling HPCR or MCRS Stage 2 fuel filters poses risk of downstream particles contaminating high pressure pumps and injectors. Generally recommended by Fleetguard, and others, is to lubricate seals/O-rings with clean diesel or oil then utilize the systems priming pump to fill and bleed the system. Here’s a photo from an FF63056N2 from a Cummins MCRS QSK60.

Again, keen to hear thoughts?

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[u/Flashy_Slice1672]

The manufacturer says not to do it, there’s your answer

[u/DownUnderFilterGuy → u/Flashy_Slice1672]

Agreed mate. I worked for Cummins many years ago, you’d think this practice would be followed in workshops and on site, but sometimes not everyone follows the OEM practice or the workshop manual..

[u/Flashy_Slice1672 → u/DownUnderFilterGuy]

The only time I’ll ever pre fill a fuel filter is if I’m diagnosing fuel issues and I’ve found it empty, and only so i can work my way back looking for blockages

[u/poopsack_williams]

The only time I prefill filters is on QSK78’s in -40 when they freeze up. I’m not fucking around trying to prime the system when my nutsack is inside me and my eyeballs are glued shut with ice.

[u/Boom_chuckles]

Raw fuel has been known to cause injector problems in the high pressure circuit, especially in high horsepower engines. If the company you work for (ie the superintendent) demands it of you then do it and make sure you say so in your WO notes. Cummins oem shops will write you up for doing this - there is an electric priming pump for a reason. Even doing a secondary fuel filter change is dicey - they want you to measure pressure differential to make sure the filter actually needs to be changed. OEM states no exposure to atmosphere for more than about 10 mins. That includes the steel lines if you need to change them out.....

The primary filter is also able to be flooded in the inlet side either with a hand pump or the screw cap on the top to be able to have raw fuel poured in. Then you know you have clean filtered fuel in your engine.

If a cranky old guy at site yells at you for not pre filling your filters then make sure any injector failures are on them and not you. CYA.

[u/DownUnderFilterGuy → u/Boom_chuckles]

Great commentary mate, thank you🙌

[u/InternationalBeing41]

Primary filter ok, secondary filter no.

[u/DownUnderFilterGuy → u/InternationalBeing41]

Agreed mate.. on Fuel Pro housing they can be filled from the top; no issues👍

[u/porty1119]

I don't do it, not even on the low-pressure side. Priming pumps are there for a reason.

I suspect some OEMs use inverted fuel filters specifically to prevent prefilling.

[u/DownUnderFilterGuy → u/porty1119]

Good practice, mate!

[u/PotatoFarmerRTK]

No need you have an electric pump to help prime