Engine/Transmission (1998.5 - 2002) Fuel filter change based on FP gauge readings?

[Schlickenmeyer]

So now that I have a FP gauge, should I just use this to determine the fuel filter

change intervals? If, as I understand it right, the filtration improves as it ages until it restricts too much to be of use. So if I am past the mileage interval, but still get 12+ psi at idle and can't drag it under 7 psi WOT, then no need to change the filter, right?

(stock LP and get 12-13 psi at idle with a new filter)



Thanx!

 

[Mundgyver]

If you want to use fuel pressure/flow to monitor our filter, you need to install two guages. One after the filter and one before. In an ideal world, the gages will match with a new filter installed.



As the filter starts to pack up with particulate, you should see a difference in pressure start. The input side will show higher pressure than the output side for a differential in readings. The trick is to understand when and at what differential readings between the two guages, to make the change in the filter. It can become a science.

 

[RustyJC]

I have a Westach dual combo fuel pressure gauge measuring pre-filter and post-filter pressures. With a new filter, I see about 1 PSID across the element with warm fuel. I have 16K on the current filter and it's up to about 2 to 2. 5 PSID, so I'll be changing filter elements before we head out for the Smokies this summer.



Rusty

 

[Todd T]

I have only one pickup tee'd in at the VP inlet. I see about a two PSI gain in 10-15k of driving. I change every 15K anyway!

 

[keimmmo]

I have only one guage just ahead of the VP. I change filters when I see about a 2 psi drop from normal...commonly running 30-35k miles between filter changes.



Yes, the more plugged a filter is without becoming restrictive, the better it will filter.



I have heard some say you should change the filter every year regardless of mileage because the filter deteriorates after that long. I can not confirm this, but it sounds reasonable.



Changes in elevation will effect your fuel pressure. I go up and down between 6000 ft and sea level several times every year. I see 2 psi less pressure across the range at 6000 ft compared to sea level.



If you have quite a few miles on the filter and you are looking at a long trip, it might be a good idea to go ahead and change it anyway. I have plugged filters on long trips a couple of times. It isn't fun to change it in a rest area in the middle of the night!



A tip to tell if the filter is plugging or if the LP is dieing is to shut off the motor when you see the pressure starting to drop. Bump the starter to make the LP run without starting the motor. If the pressure slowly comes up to a normal level, the filter is plugging. If it remains low, the LP is probably "going south".



Steve Keim

 

[DonS]

Changes in elevation will effect your fuel pressure. I go up and down between 6000 ft and sea level several times every year. I see 2 psi less pressure across the range at 6000 ft compared to sea level.

That's interesting. So the gauge (or sender) is calibrated to a "known" ambient pressure, and isn't just measuring the difference between fuel and ambient pressures?

 

[keimmmo]

I just have a cheap liquid filled Summit gauge hooked up without an isolator. It works well. But, the pressure DOES go up and down with elevation changes!!! Most people wouldn't change elevation enough to notice it. But, I drive anywhere from sea level to 8,000 ft commonly... once in a while even higher.



Steve Keim

 

[bmoeller]

Fuel temps will probably affect it as well. Have fuel filter restriction gauge on the KW. Reads higher til the fuel warms up. Normally 2" on a new filter, or warm. Up to almost 5" with cold fuel in the winter. Once the fuel warms up in the winter, the number comes down.