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New fuel filter

Tags: filter fuel

Probably the original
While the car was in the garage getting exhaust work done, I figured why not change the fuel filter as well?  While I was at it, I ripped apart the old one to check it's dirtiness -- turns out it was plenty dirty, but I'm not sure if a clean filter will make a difference in the overall operation of the car.

As the filter does its job, what it catches will reduce the flow rate through the filter, meaning the pump will need to work harder to provide same amount of fuel as a clean filter, or the car will have figure out how to run with less gas that expected; in practice, both are probably happening.

Location and Removal

The filter's is in front of the passenger side's rear wheel, it's easy to spot. I had the car lifted while working on something else; accessing the Filter could be done with all four wheels on the ground if you don't fee like lifting anything.  The extra few inches made things easier. If you have the front tires up ramps for an oil change, you'll have great access to the filter.

Here's what you'll need to to the job: 
  • 9mm socket or flathead screwdriver
  • Quick release tool
  • Basin to catch any fuel in the system
  • Motorcraft FG986B filter (got mine from Amazon)
Fuel relay location
I didn't bother to run the system out of fuel (thus de-pressuring the fuel lines) by removing the fuel pump relay and cranking the engine.  If you want to go that route, here's the battery junction box with the relay circled.  Remove the relay and turn over the engine.  When it stops running (or after a few cranks with no start), the fuel pressure will be very low in the system and not much gasoline will splash on you when removing quick release.  For my car, the front-end was raised for about two weeks, so I figured that would be enough to result in low fuel pressure.
Fresh from HF

Quick Release

Next, before loosening the clamp, I used a quick release tool (a few bucks from
Harbor Freight) to free the lines from the filter.  The basin caught a few tablespoons of fuel, about what I expected given the cars non-running status the past few weeks. The quick release tool fits around the hard part of the line and is then pushed against the connector, wedging underneath to unclip the connector.  While not fancy, the tools for this purpose worked flawlessly.

Push towards fitting
The clamp was then wound back and the old part slipped out by pushing it toward the driver's side of the vehicle.  Despite being on the underside of the car, nothing was rusted to the point of no longer working -- I expected fasteners to be rusted and PB Blaster to be sprayed -- that wasn't the case, removal was uneventful and took just a few minutes. My guess about the pressure in the fuel system was correct as well, a few drops dripped from the connectors during removal. All in all, an easy job so far.  Beware, the filter itself will contain about a quarter cup of fuel that will pour out the now disconnected fittings, so have a place to catch that fuel so it doesn't pour over yourself, the floor, etc.  Don't attempt to look into the filter before dumping it's contents, because fuel might pour out on your face, that's exactly what didn't happen to me.

Note: flow direction arrow
points towards driver's side
Pushed the new part in the clamp, making sure the flow arrow pointed away from the tank.  With a click, I fastened the connectors and tightened the clamp with a few twists.  A few cranks of the engine and it started.  No leaks! We'll call this done.

How dirty was it?

Looking at the outside of the canister doesn't tell one much about the state of the filter, the interesting part's on the inside. Let's dissect the old filter like a middle-school frog and see what it trapped over the years.  I was tempted to use my handy Dremel, but figured sparks and gasoline fumes would result in some unwanted outcomes.  So I made an initial cut with a hack saw and used metal shears for the test, working my way slowly around the can.

I have a picture of the filter, showing the feed side next to the filtrate side, where the feed side is on the bottom and the browner, dirtier filter side is on the top.  For those asleep during chemistry: there's three things in a filter system:
  1. Feed, what goes through the filter. In this case the gas from the tank
  2. Filtrate, what remains after passing through the filter.  In our example, cleaner fuel
  3. Residue, what the filter catches and what we can see in our illustration.  Looks like the filter paper itself has a red tint and the feed side looks covered in a greyish haze compared to the more vivid filtrate side. 

Juat a few taps...
I let the filter paper dry overnight. With a little tapping, a nice pile of residue willingly fell out of the filter.  Some of this detritus might have been the paper disturbed when disassembling the filter, but the finer material is certainly residue. Without a basis for comparison, it's hard to tell how clogged the filter is compared to a new one and how the residue interferes with the flow through the medium and thus how much harder the fuel pump needs to work to compensate.  A more constrained fuel flow should result in a less-efficient engine as well, translating into lower fuel efficiency.  We'll see how the gas mileage changes over the next few tanks.

This post first appeared on 500 Dollar Car, please read the originial post: here

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New fuel filter


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