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-   -   what is normal Primary Filter Pressure gauge reading? (http://www.sailnet.com/forums/diesel/89057-what-normal-primary-filter-pressure-gauge-reading.html)

brokesailor 06-26-2012 09:30 AM

what is normal Primary Filter Pressure gauge reading?
 
My Primary Fuel Filter Gauge on a 2003 Volvo Penta reads 5 " HG at cruising rpms. That is still in the white range but is it normal?

Maine Sail 06-26-2012 11:07 AM

Re: what is normal Primary Filter Pressure gauge reading?
 
Quote:

Originally Posted by brokesailor (Post 889213)
My Primary Fuel Filter Gauge on a 2003 Volvo Penta reads 5 " HG at cruising rpms. That is still in the white range but is it normal?

Ideally it should be much closer to zero. It sounds like you may be using a 2 micron element? Switch to a 10 or 30 micron and the vacuum gauge should read zero, until it begins to plug. We have a 44HP diesel and at WOT it still reads 0 but I use a 10 micron element. That element is changed anytime the drag needle moves beyond 1-2... I was working on a 370 HP diesel the other day and at cruise RPM vacuum gauge was reading 0.5 but the filter was a year old.

You may have a clogged filter, 2 mic element or a dirty pick up in the tank. Where is your fuel pump located in relation to the vacuum gauge? What is the fuel filter brand, model etc...

First things first I'd suggest changing the element and see if it improves. Use a 10 or 30 micron if you are currently using a 2 micron....

RichH 06-26-2012 12:37 PM

Re: what is normal Primary Filter Pressure gauge reading?
 
Precisely correct answer from MaineSail.

High Vacuum in a so-called primary filter means 1. clogging filter or 2. development of an obstruction somewhere between the primary filter and the end of the fuel dip-tube in the tank - most commonly a fouled 'screen' on the dip-tup entrance (Remove it!). A clean unobstructed with a newly installed (referenced to the engine running at near WOT) should be very close to 'zero' on the gage. Any vacuum gage thats reading close to more than ~4 in hg. vac. when the engine is running near WOT .... has a 'problem': crudded up filters or developed obstruction in the fuel delivery lines.

If you have a vac gage on both the primary and the secondary filters (and also the small engine mounted guard filter) ... suggests an obstruction between the primary and the tank, including a clogging primary filter, AND will also show as high vacuum in the 'downstream', or closer to the engine filter gages --- anywhere BETWEEN the engine lift pump and the 'restriction'.

Historically dirty systems:
30然 ---> 10然 ---> ~15然 (engine mounted 'guard' filter)

Historically 'clean' systems' 10然 --> ~15然 (engine mounted 'guard' filter)

brokesailor 06-26-2012 10:01 PM

what is normal Primary Filter Pressure gauge reading?
 
I am not sure of the filter size-I had the yard change it out last fall. I have two fuel tanks so I will see if there is a difference beteween the two. I'll probably change it out too just to be safe.

brokesailor 06-27-2012 01:59 PM

what is normal Primary Filter Pressure gauge reading?
 
I changed out the filter. Indeed it was a 2 micron filter. I changed it out with a 10 micron. Started the engine up and do is down near zero. Thanks Mainsail.
I could not get the lines bled using the lift pump lever. I pumped and pumped but never got any fuel out of the secondary filter vent. So I just started the engine and it ran fine after a few tries.
Mainsail my Racor filter is one of those that has an internal cartridge not the newer ones that the cartridge screws onto the bowl.

RichH 06-27-2012 02:11 PM

Re: what is normal Primary Filter Pressure gauge reading?
 
The typical 10然 filter on a boats fuel system will require 5 times less 'work' or 5 times less 'vacuum' to deliver the same amount of fuel as a 2然.

The most damaging particle on a small 'diesel' is in the range of ~20然. Most engine manufacturers supply the engine mounted guard filter at 15-17然. A 2然 filter anywhere in such a fuel system will prematurely clog, cause the lift pump to do unneeded work (& may shorten the life of the pump diaphragm).

If your 'really' think for some reason that you need a 2然 filter in the system, then the SURFACE AREA of the 2然 'must' be FIVE TIMES the surface area of the 10然 that it replaces; 15 times the surface area if you are replacing a 30然 filter with a 2然.
There is NO need for a 2然 filter in a small diesel engine fuel system ... unless actually (very rarely) specified by the engine manufacturer.

Historically 'clean' systems': tank --> 10然 (so-called 'primary') --> ~15然 (engine mounted 'guard' filter) --> engine


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