Fuel System Vacuum with Racor "Dual Pleat" Filter

[OC_DMAX]

I changed my OEM fuel filter and my supplemental frame-mounted Pre-OEM Racor R60S fuel filter over the weekend. In the OEM position, I installed one of the new and improved Racor "Dual Pleat" filters. I took a couple of measurements at the fuel system test port, using a Kent-Moore Vacuum-Pressure gauge, to see what the differences in fuel system vacuum were between the two filters in the OEM position (original OEM Racor and new/improved "Dual Pleat" Racor).

There was virtually no difference in fuel system vacuum between the two filters. With the old original style OEM Racor installed, the measured vacuum at the test port was 2.5 inHg. With the new "Dual Pleat" Racor installed, the measured vacuum was still 2.5 inHg. (Note: the old style Racor that was installed prior to the filter change was hardly used, maybe a 1/2 inch circular band at the bottom of the filter.)

The picture below is the fuel system vacuum (engine idling) with the "Dual Pleat" Racor installed in OEM position along with a Racor R60S supplemental fuel filter installed on the frame rail. Those running their trucks with a supplemental filter should be able to use the new "Dual Pleat" Racor OEM filter and not worry about fuel system vacuum levels. Just remember to change the filters in a routine interval.


http://img109.exs.cx/img109/5686/fuelfilterchange1r7oi.jpg

[More Power]

Thanks OC,

Let us know whether you see a faster increase in vacuum over time (as the filter becomes more used), compared to the original elements.

Shorter service life can be a result in using finer or more effective filters. This may be one factor in GM's recommended service interval change from 30K to 15K.

MP

[MIKE MOG]

OK, I READ IT AND DON'T UNDERSTAND IT. YOU MEAN TO TELL ME YOU CAN LOOK AT VACUUM AND TELL IF YOU HAVE A PLUGGED FUEL FILTER OR AM I MISSING SOMETHING HERE.
MIKE

[madmatt]

Yep! you shouldn't have more then a few inches @ idle if your filter is good and no more then 8-10" under hard acceleration.

[MIKE MOG]

HI MATT, WHERE SHOULD I GRAB A VACUMM TAP AT. DO YOU THINK IT WOULD BE WISE TO PUT A A VACUUM GAUGE IN THE CAB TO MONITOR VACUUM.
MIKE

[OC_DMAX]

Stand in front of your truck with the hood open. Look just to the immediate left of the alternator. You will see a small black cap. This cap covers the access to the fuel system test port. Unscrew the cap and you will see what looks like a large schraeder valve. This is where you hook up the gauge to monitor the fuel system vacuum.

I do not think this is something you would need to monitor in "real time". As you approach 10K miles, you may want to hook a gauge up to check to see how your filter(s) are doing.

[madmatt]

No, I wouldn't put a gauge on it full time as it may develope a leak. There is a test port on the right front of the engine to the right if the alt. It looks like an A/C service port when capped. the J tool number for the gauge is J44638. Trust me, you'll know when your vaccum gets excessive. We get'em towed in all the time for plugged fuel filters.

[madmatt]

yeah like OC said...he just beat me to it!

[Madd Max]

Hey fellas,

I think what is confusing Mike Mog is he is thinking manifold vacuum instead of fuel system vacuum. We have no vacuum, we have boost.

Dennis

[jbplock]

Heres a picture of the Kent-Moore Gauge connected to the Schrader Valve Test port.

http://image03.webshots.com/3/1/51/8/73315108BBKdiI_ph.jpg
More Vac Gauge Pics (http://community.webshots.com/album/73314886FLnSco)

John Kennedy also sells an nice Vacuum/Pressure gauge that connects directly to the custom Schrader Valve Test Port.

JK's Fuel Filter Restriction/Lift Pump Psi Gauge Kit for Duramax (http://www.kennedydiesel.com/detail.cfm?ID=289)

smile.gif

[Kennedy]

I'll have to go back and do some testing on this somne time with new filters on my LLY. Fuel level, angle of inclination etc all affect the readings.

The 2.5" reading in the pic on my site is on my 2002 with a Mega kit and non operational lift pump in the system. The movement on my liquid filed gauge is extremely smooth where the KM unit was notchy at best, and if you so much as touch it or change position the readings can change.

[OC_DMAX]

FYI - My testing was done with a fuel tank that was at approximately the 20 gallon level (of 26 gallons). What I was looking for in this test was the difference between the two filters (not necessarily the absolute vacuum number).

I know what you mean by tapping the KM gauge or moving it to a different location, the needle movement does seem to be "notchy".

I tried to minimize the errors by leaving the gauge sitting in the same place during both measurements.

If I remember "Mdrags" reporting from the "Mega Filter System" debugging days several years ago, the fuel system vacuum was typically higher than 2.5 inHg with the Baldwin filter installed (though I could be suffering a "memory fade").

Maybe Bill (JBPlock) remembers what he was measuring with the Baldwin filter installed prior to his lift pump install.

[ 04-06-2005, 10:43 AM: Message edited by: OC_DMAX ]

[Kennedy]

I've made a lot of changes to my system since then. I also believe Mdrag was using my KM gauge for his testing.

If you pump pressure up, you can see how truly jerky the gauge is as the pressure drops.

[mdrag]

Kennedy's correct - I used his KM gauge to take fuel filter vacuum measurements that were posted in this topic (http://forum.thedieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=3;t=005344;p=2).

==============================================
I measured the Dmax fuel filter restriction at normal factory idle/high idle (rev limiter) after the truck was up to operating temps. Results are inches Hg vacuum:

OEM Racor with 1.6K miles 3.0"/3.5"
OEM Racor NEW filter 2.5"/2.75"
OEM Racor/KD Megafilter(both NEW) 3.5"/3.75"

===============================================

I don't recall if I recorded the fuel level when these measurements were made - I don't think that I did...but I believe there was a full or near full tank. These measurements were done before we realized that the fuel level, gauge positioning etc. would affect the readings.

I remember noting a 1-1.5" increase in vacuum occuring over a few days. Kennedy suggested that it might correlate with the fuel level :eek: The measurements returned to near baseline after filling up - confirming JK's reasoning :D

[OC_DMAX]

==============================================
I measured the Dmax fuel filter restriction at normal factory idle/high idle (rev limiter) after the truck was up to operating temps. Results are inches Hg vacuum:

OEM Racor with 1.6K miles 3.0"/3.5"
OEM Racor NEW filter 2.5"/2.75"
OEM Racor/KD Megafilter(both NEW) 3.5"/3.75"

===============================================

Glad to see the memory is not fading too much!!


The extra vacuum required by a lower fuel tank is (in my opinion) just the work required to raise the fuel an additional 1 foot or so in height (and overcome gravity). Similarly, the extra insertion loss of the Mega Filter System is the work required to offset raising the fuel from its mounting position at the tire level back up to the fuel filter.

In any event, the purpose of the post was to present my findings as far as insertion loss difference between the old/new style Racor filters. And as best I can measure, the differences are insignificant.

[MIKE MOG]

thanks guy's i got it now. yea i was thinking manafold vacuum forgetting about the turbo. I think Ill just do it the easy way and change the filter at 10k.
Mike