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Thread: What's the scoop on Fuel Filters?

  1. #1
    Senior Member
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    What's the scoop on Fuel Filters?

    I've had a on and off fuel running condition problem with my Weber carbureted 2.0 SWB for the last few months. When I clean the circuits out, it then runs fine, but eventually the problem returns again. I'm starting to think the problem may coincide with the installation of a 100 liter fuel tank from a few months ago. The filter screens to the tank and the Weber inlets are all still in place. After the third incident, I pulled the fuel filter, a glass type that allows you to replace the filter element inside the glass housing. The element looked clean, although it is low micron type element and I'm beginning to think that tiny debris maybe getting through it. I also found some small metal chips on the corner of the glass housing. I have no idea where these would come from other than maybe the 100 liter tank. But again the outlet screen is still in place. I want to clean the system and replace the fuel filter with a higher micron rated filter. Any suggestions on a quality micron efficient fuel filter for Webers?

  2. #2
    Senior Member
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    If the tank is old and has had ethanol gas in it you may have a rusty tank?
    Mike

  3. #3
    There are three basic sources of debris in the float bowl:
    • Dirt in the fuel (upstream of the filter) getting past the fuel filter or internally decaying fuel lines downstream of the fuel filter.
    • Dirt bypassing the air seals on the air cleaner (or rust in the troughs where the air seals are installed) and entering through the holes and vent pipes in the top cover of the carburetor body. Also, the breather pipe in the forward end of the air cleaner that vents the oil tank is a good source of rust & debris. And the drain pipe from the air cleaner that connects to the vent pipe ahead of cylinder #6 needs to be looked after since this draws air in and is unfiltered.
    • Rusting of the inside diameter and internal bits of the vent pipes in the top cover of the Weber. This is typically missed as a source of debris.


    I used self-adhering, closed-cell, neoprene foam around the sealing surfaces of my air filters to provide a compliant seal which cured my issues with clogging the idle jets. Vent pipes on Webers rust and drop flakes of rust straight down into the float bowls.
    Paul Abbott
    Early S Member #18
    Weber service specialist
    www.PerformanceOriented.com
    info@PerformanceOriented.com
    530.520.5816

  4. #4
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    The Carb setup is an open stack style with screens in place of the vent tubes. No crankcase breather to the carbs as well. The 100 liter tank was cleaned and re-coated. All the fuel lines were changed. I didn't have any problems the first 1000 miles. Over the last 150 miles this problem has occurred 3 times, sometime after the 100 liter tank installation. Tonight I disconnected the fuel hose at the fuel filter from the fuel pump outlet and the fuel was clean after running a quart or so from the fuel tank. I'm going to get into the carbs and clean the bowls and ports next. I'm looking for a quality micron efficient fuel filter for this setup. Any recommendations?
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  5. #5
    Regis turd ab user
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    I've seen these recommended and used by a few people. Racor 110A

    http://www.4land4sea.com/shopexd.asp?id=463

  6. #6
    Check the filter screens in the banjos for holes, tears and accumulated debris to see if you can get a grip on type of junk is entering the carbs. Air filtering looks really sanitary...nothing obvious. I assume the vent pipes were removed and not cut down to fit under the Emulsion tube-well air screens.

    Typically, is it your idle jets that clog up? If so, then is there one that is routinely clogged or do all six have the same type of issue?

    Is it humid there? Is your gas from a good supplier? Perhaps there is water in your float bowls either from condensation within the bowls or from your supplier. Open the tops of your carbs, take out the floats and look into the fuel well with a flash light to see if there is a issue with water collection at the bottom of the bowls.

    The fuel filters and the screens in the banjos will prevent anything from getting through that would clog an idle jet. This is why I was chasing the rust issue from the air cleaner or vent pipes or grit bypassing the seals on the air cleaner filters; obviously not the problem.

    Another item to consider: I have seen fuel in the carbs turn to a creamy goo, kinda like napalm... Actually more like a thick hand cream. My understanding is that some of the coatings used in recently cleaned fuel tanks actually react with the fuel and turn the mixture into the goo. More mileage keeps the stuff from congealing, garage queens suffer the most. Again, take the tops off the carbs without draining, remove the floats and have a good look at the bottoms of the wells.
    Paul Abbott
    Early S Member #18
    Weber service specialist
    www.PerformanceOriented.com
    info@PerformanceOriented.com
    530.520.5816

  7. #7
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    I will pull the carb tops off and remove the floats and see what's down there in the wells. The vent tubes were removed, not cut off. Additionally, I will check the tank outlet screen as well as the carb inlet screens. Let's see what I find...Thanks for the tips Paul.

  8. #8
    Senior Member
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    I've got an article coming out next month about fuel filters. If you get down to 3 microns the filters plug very quickly. There's a a sweet spot between effective filtration and filters clogging very quickly.

    "Ten years ago Kinsler developed a two-layer fuel filter element. It has an inner layer of 3-micron precision grade fiberglass filter, with an outer layer of 10-micron paper. The paper takes out about 90% of the dirt, so it protects the 3-micron layer."

    K&N filters start at 25 microns so they seldom plug up. WIX have a 5.9 micron rating.

    Be careful with the cheap paper filters. The paper actually breaks up and gets into your fuel system.

    Richard Newton
    Race Car Images

  9. #9
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    Last night I removed the carb tops and the floats. I checked all four float bowl wells in both carbs and a I found a black soot looking powdery substance down in the wells. I removed a sample and examined it under a lighted magnified glass. Except for the occasional metallic spec here and there, it appears like a fuel hose maybe has disintegrated from the inside, somewhere between the fuel pump and the carbs. All 4 float bowls had this black powder substance in them. I cleaned the float bowls, idle jets (one was blocked) and the attaching ports within the carbs by removing the mixture screws. I will need to pickup some 7mm cloth webbed fuel hose and I will replace all of the hoses (again), looking for the culprit as I go.

  10. #10
    I'd replace every fuel hose and don't forget the one coming from the tank under the car. Be sure all clamps are the type that does not cut into the hose (rather than the typical hardware store type). Most importantly, use an ethanol mix rated barrier hose. The new fuel formulations will destroy any rubber hose made more than a few years ago. Gates makes a barrier hose, and I'm sure others do now too.

    There are at least two people who make up hose sets and fittings - they are mentioned in another thread somewhere.

    You don't want to be thinking about how you lost your beautiful car while lying in a burn ward.

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