Carburetor difficulty:

Discussion in 'General Automotive Questions' started by agolfer7, Oct 7, 2017.

  1. agolfer7

    agolfer7 In Second Gear

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    Culprit: 1966 Ranchero, 200IL 6, Autolite 1100 Carburetor

    Problem: When driving under hard acceleration, the vehicle runs out of fuel. I can take the fuel cap off and there is a major inrush of air. I can then run for a little while before the problem repeats.

    Repairs done: Fuel tank removed and cleaned, fuel lines cleaned, filter changed, new vented fuel cap.

    Any suggestions on what to do next?
     
  2. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    That is a vent problem.
    Some modern 'vented' caps don't work the same way as the originals did.
    Take a tiny drill (1/64th is big enough) and drill a hole in the middle of the plastic part you see when you look through a hole in the center of the inside of the cap. Just drill through the plastic.
    That should solve your problem.
     
  3. beerbelly

    beerbelly In Overdrive SILVER MEMBER

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    Yes, it sounds like a vacuum is being created in your tank. I had the opposite problem with a "vented" cap from O'reilly Auto; my tank built pressure, releasing air out when I took off the cap. Here's a trick I posted previously to allow the cap to vent BOTH ways:

    I decided to try a "vented" gas cap from O'Reilly's (O'Reilly #6024), to see if that would help. Well, it appeared to "vent" one way INTO the tank to prevent a vacuum, but doesn't vent to atmosphere, so it retained pressure in the tank on hot days, eventually splitting my rubber filler hose. I was on the fence about making up a vent line or moving the fuel filler, so I decided to experiment with the cap to see if there was a way to make it vented both ways. I completely removed the plastic vent mechanism and had a good look at what was behind it. I noticed two small rectangular holes to the outside of the sealing edge, and wondered if these could be vents. I set the cap upside down on my bench and poured a little water in the center of the cap. Water flowed out of the two vent holes, indicating vents to the outside.
    It now works just as I'd hoped, vented in both directions, without holding pressure & no leaks. It's been months of daily driving through twisties & hills, down to Sacramento & back on Hwy. 1, with no gas down the side or fumes in the cab as before.

    And I suppose I need to include a disclaimer this day & age- I did this modification at my own risk, and you do it at yours as well.

    IMG_6231.JPG vent holes.JPG
     
  4. agolfer7

    agolfer7 In Second Gear

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    Thanks for the quick response and the information. I have been fighting this for a couple of months and the patience is very frayed. I drilled the hole and that seems to allow more air into the tank. I did a test run and still had the same problem. I opened the gas cap to relieve vacuum, tried to start it, no luck. An inspection of the system revealed there was no fuel in the filter, maybe the fuel pump is starting to fail. I will replace it and see what happens.
     
  5. beerbelly

    beerbelly In Overdrive SILVER MEMBER

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    Sorry to hear that that didn't work. Another issue I've heard about is that the 'sock' filter over the tank sender inlet is plugged, melted or degraded from today's fuels, blocking fuel from flowing. Might be worth a check, which requires removing the sender from the tank. You may need a new O-ring gasket if you do.

    10324.jpg
     
  6. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    If it still held a vacuum with the hole drilled, the cap is faulty.
    Also, look for collapsed fuel lines.
     
  7. agolfer7

    agolfer7 In Second Gear

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    Done that, o-ring difficult to find, made my own. thanks
     
  8. agolfer7

    agolfer7 In Second Gear

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    No vacuum, at least that is out of the picture. I speculate the earlier vacuum problem might have caused the fuel pump failure, if that is the problem.
     
  9. plumcolr

    plumcolr In Maximum Overdrive

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    Check for gas in the oil (sniff test) Very often a failed pump allows gas to leak inside crankcase.
     
  10. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    I'd like to find the engineer who thought that was a good idea, and shove a pump where the Sun doesn't shine...sideways.
     
  11. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    With electric pumps, that issue is moot.
    Aside from a belt driven pump, that was about the only choice they had, and belt driven pumps come with their own set of issues as well as cost.
     
  12. handy_andy_cv64

    handy_andy_cv64 In Maximum Overdrive SILVER MEMBER

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    True, maybe once again I missed something; I was thinking he had a stock recip pump.
     
  13. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    Pretty sure he does.
    I was just pointing out the limitations the engineers had to deal with beck then.
     
  14. Sophie948

    Sophie948 In Overdrive

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    Ribald, can you explain the limitations engineers had with electric pumps? And belt-driven pumps? Do they exist?
     
  15. ribald1

    ribald1 In Maximum Overdrive PLATINUM MEMBER

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    Yes, both pumps exist, external direct driven pumps are currently used with TDC injection where fuel pressures exceed 1000PSI.
    The limitations that engineers had with electric pumps in the past do not exist today. They mostly revolved around reliability and safety. The early 'buzzer' pumps were notoriously unreliable. Advances in small induction motors made reliable and safe electric pumps a reality, and car makers adopted them very quickly.
    Belt driven pumps create extra complexity and cost, so much so that even racers don't use them unless they have to. that situation still exists today. As a result, little research has been done into low volume long life externally driven pumps except for TDC injection.
     
  16. Jeff B

    Jeff B In Overdrive BRONZE MEMBER

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    I was having a similar fueling issue. I pulled the hose off of the line from tank, before the pump and blew compressed air thru it after removing the gas cap. Presumably I blew the "sock" off or apart doing so. Installed
    a large fuel filter before the pump and have had no further problems. A little "shadetree" but it got me going again until I have time to pull the sender and clean the tank.
     
  17. 1965 Ranchero 66G

    1965 Ranchero 66G In Maximum Overdrive PLATINUM MEMBER

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    Not shade tree at all, I was going to suggest that but was being cautious because of the backlash, once on a truck I had with duel fuel tanks (one of the tanks kept starving the motor of fuel) the other on one of my older tractors that although didn't have a sock on it kept starving because of a shop rag that had gotten into the tank,
     
  18. Sophie948

    Sophie948 In Overdrive

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    So how are things going now, agolfer? Any luck?
     

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