Results 1 to 8 of 8

Thread: Fuel pump dumped gas into crankcase - how?

  1. #1
    Speedster Member voxnut's Avatar
    Join Date
    Feb 2013
    Sacramento, CA

    Fuel pump dumped gas into crankcase - how?


    I suffered the same fate that I have heard some folks have gone through - a steady smoking problem led to me discovering a crank case that had fuel in it as well as oil. Fortunately, the engine wasn't run long in that state. So over the weekend the carter fuel pump was removed, and a replacement installed, along with fresh oil and filter. I took the time to change the oil filter lines while I was at it.

    So the $64 question is, what exactly allows the fuel pump to dump into the crankcase? If the pump had gone bad, I'd guess that it woulnd't be able to draw fuel -add to it, that up until my car made the neighborhood think there might be a new pope, the car ran fine.

    I'm not understanding the design of the Carter pump well enough to see how it could pump fuel to the carb and into the crankcase as well.


    Dean Seavers
    Sacramento, CA

  2. #2
    Golden Hawk Member DEEPNHOCK's Avatar
    Join Date
    Oct 2004
    Brooklet, GA, USA. Planet Earth

  3. #3
    President Member TWChamp's Avatar
    Join Date
    Dec 2014
    The fuel pump diaphram would have to leak gas, then the diaphram shaft seal would also have to leak to allow gas into the oil, and allow oil out the vent holes in the fuel pump.
    That's exactly what happened to my 50 Champion after 10% ethanol took out the diaphram.
    That's also why the first thing I did for my 50 Commander is to change the diaphram to the new ethanol resistant diaphram.

  4. #4
    President Member bensherb's Avatar
    Join Date
    Jun 2015
    Tracy / Goleta Ca.
    It's actually very simple. The pump diaphragm (reinforced rubber disk) has a rod attached to it's center to which the actuating lever is attached. That rod runs through a small seal. That seal tends to wear fairly quickly but it doesn't really matter much as long as the diaphragm remains completely intact. There is no barrier between the diaphragm and the engine case beyond that seal. There are some fuel pump gasket designs that limit the size of the opening but, nonetheless, the opening remains. Once there is ANY breach of the diaphragm, fuel can find it's way into the crankcase. If the breach is small the fuel pump can continue to pump fuel while simultaneously pumping fuel through the diaphragm into the crankcase.

  5. #5
    Golden Hawk Member StudeRich's Avatar
    Join Date
    Dec 2005
    Ferndale, WA, USA.
    An Ethanol resistant Rebuild Kit from a Studebaker Vendor will fix that, do NOT dispose of a better than Good, Real OEM Carter V8 Fuel Pump.

    Carter Fuel Pump V-8.jpg Some have the Later version, Tin Filter Bowl with Paper Element, but all have that distinctive "U" Shaped Actuator Lever.
    Second Generation Stude Driver,
    Proud '54 Starliner Owner

  6. #6
    President Member
    Join Date
    Apr 2016
    Westbrook, MN
    As Above. As an Air Force NCO, my boss, a major and an ENT specialist went out with his cup of coffee and jumped into his 64 Impala. He hit the switch and was greetrd to a deafening explosion. The blow by on a cold, worn 283 ingited the gas fumes in the crankcase. There was just a tiny hole in the fuel pump diaphragm, but it allowed a tiny bit of gas to enter the crankcase without interfering with the function of the pump. The valve covers were destroyed and every seal and gasket required replacement.

  7. #7
    Silver Hawk Member
    Join Date
    Dec 2006
    Sacramento, CA, USA.
    That's why I never use mechanical fuel pumps. I always use electric. Mounted near the gas tank. Has worked well for me for many decades. And I gain a whopping 1/4 horsepower as a result. Now that's some serious power gain.

  8. #8
    President Member
    Join Date
    Apr 2005

    Proof. This is EXACTLY...why it's "NOT" a good idea to run an electric fuel pump thru a mechanical pump. Pick one OR the other, not both, or possibly suffer blowing the hood off..!


Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts