Carb keeps flooding over after shutdown

Discussion in 'Technical' started by john_d, Jan 31, 2015.

  1. john_d

    john_d Member

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    Autolite Motorcraft 2100. Rebuilt twice. 3rd needle and seat.

    After the car sits for 10 minutes you see the fuel draining from the clear gas filter. Pop the top of the air cleaner, you can see vapor from the throat. Fuel is draining down the gullet.

    OK, so we rebuilt this carb now twice. Shall I continue to lower the float? Try a 4th needle and seat? What gives?
     
  2. 74merc

    74merc computer nerd

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    Power valve?

    I've got a Holley that does that, pretty sure I've got either a bad PV or the accelerator pump tube pinched the o-ring.

    Not much to go wrong in a 2100.
     
  3. john_d

    john_d Member

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    It was suggested that it is boiling in the bowl. But I have the 1" plastic phelieum (spelling :slap: ) installed.
    I am thinking it might be too much pressure so I am going to hunt down one of those round control units that will shut down the pressure to the carb. :yahoo:

    Taking the lid off, after it has been driven for a while, you can see a small stream of what looks to be air bubbles on the drivers side of the bowl, I am guessing that is the fuel boiling off.

    There "aint" no crack in the bowl so it has to be fuel boiling. I do have 2 filters on this baby. I did not clean the tank after sitting for a few years. I am collecting rusty grit (very fine) in the primary filter.....which I am changing every 50 miles.

    I might have grit in the float and seat.....not sure yet what it is doing.
     
  4. Maverocket

    Maverocket Bob Williams

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    Sounds like you have enough rust particles in the system to crud up the needle and seat in short order. With the needle not seated perfectly the residual line pressure at shutoff could slowly overfill the bowl.
     
  5. groberts101

    groberts101 Member

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    Probably have something called fuel pressure creep going on here as the gas expands(yes it does) during periods of heat soak. Phenolic spacers help delay and reduce the effect somewhat.. but heat soak still gets the best of them when there's no cooling affect from fresh incoming mixture.

    If the intake manifold has an EGR passage?.. that just adds insult to injury and can be blocked off with stainless shims in the manifold flange gaskets. Many performance gaskets come with these shims because they have larger than the stock port openings and also assume your running an aftermarket manifold without manifold EGR. I would also highly recommend getting a decent regulator as they will reduce pressure creep associated with fuel pump heat soaking the downstream side of the carb as well. Every little bit helps as these issues are usually a cumulative affect of heat soak in the entire fuel system.

    Using rubber lines instead of steel.. and especially aluminum which only compounds these types of issues.. will reduce heat soak as well. A really easy and obvious way to test for heat soak related pressure creep is to run a pressure gauge. A fan.. or two.. set to full speed blowing into the engine compartment with the hood popped open immediately after shutdown should give noticeable relief from this issue if in fact that's what's going on here.

    Good luck with it.
     
  6. schroensr

    schroensr knight Runner

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    Make sure your vapor return is open to the charcoal canister .
     
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  7. Krazy Comet

    Krazy Comet Tom Supporting Member

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    Having two filters also may add to the problem as they will retain a larger volume of fuel that can expand...

    I'd try the fan on shutdown as suggested...
     
  8. john_d

    john_d Member

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    OK, here is what is going on so far. Yes I am running two filters. The primary filter is catching the crap from the tank from sitting for 26 years in the garage. I've gone thru 6 of them so far. This one is clean without the red rust grit that is collecting at the 1st filter. The mid filter is a FRAM unit you can buy off the shelf at Walmart--you can see thru it. G-2?

    The other filter is the factory OEM that sits just on the inlet of the carb. I raised the carb a bit. It is now at 1 1/2 inches. AND, put a pressure regulator inline.

    (I did find a massive--ok, somewhat massive---ok, a vacuum leak). The port behind the carb on the factory intake. The large plug was leaking. OR cracked. So I swapped out every vacuum line on this engine.

    Idles a bit better. I am watching to see if the fuel boils again. The engine is just as I remember it in 1996. It hates to idle. The temp hits 230 idling then once you bring the r's up a bit it settles back down to 185ish. That cam I installed way back in the late of last century..... Even with a 4 core radiator and a good sized aftermarket flex fan.

    Also, the SPEEDO is 8 mph too fast. I need to pull the cable again and see what gear is installed. Once I put larger tires on this car AND drop the rear back to 2.79 from the current 3.08 (?) it might settle back down to a decent correct speed reading.

    GPS says it is 8 over at 55....
     
  9. Craig Selvey

    Craig Selvey Indiana State Rep - MCCI

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    You really need to drop the tank and get it cleaned out....or you will forever be getting rust out of it.
     
  10. john_d

    john_d Member

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    I know....I did this on the cheap. The float in the tank has bottomed out. The tank should be coming later this month when the shop that I use gets an opening.
     
  11. Wrighttime

    Wrighttime Member

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    Getting old is for birds!!!!
     
  12. john_d

    john_d Member

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    I just had a muscle spasm under my left knee upwards to my hip. This is what I get for all the climbing, twisting, and bending. There is a reason the Good Lord gave us grandkids. The problem is the GK's would want to drive my baby. Their dad has not even ridden in his car. Let alone drive it. It has been stashed in the garage from the time he was born to the present. He currently is piloting a CRJ700 from LAX to San Antonio Tex, then back tomorrow for 5 days off.
    I know he wants to drive this baby. Maybe we can swap, Let me drive the CRJ and he can take the Comet for a spin.....Delta would love that. (now where is the start button on this baby.....):LOL:

    I'd remind them that I have had this Comet GT longer than their dad has been around...so don't push it kids.:bananaman:
     
    Last edited: Feb 1, 2015
  13. Wrighttime

    Wrighttime Member

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    Thats Wright
     
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