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Topic Summary

Posted by: Rus Curtis
« on: January 31, 2021, 04:59:25 PM »

Quote from: Mytwojeeps2020
PS: On the “Original technical questions, answers, observations” page, I posted a thread called “Oil filler tube upchucking oil into my oil bath air filter.”

Question for possible discussion: Could the unvented gas cap have caused all those problems? I had replaced the old vented cap with the non-vented cap at the same time I bought the first “new” fuel pump. It could be just a coincidence, but who knows?


Quote from: SteveKfl on January 31, 2021, 12:52:16 PM
I can't wait to see what the "experts and experienced" respond to that.  Great question.

Well, I'm no expert but, my .02 is barely worth that, so.......

I believe the end result of m2j's upchuck problem was a bad pump (most probably a ruptured diaphragm) dumping fuel into the oil pan causing the oil/gas mixture to fill up and squirt out the filler tube.  At least when replaced, it stopped doing that.

I'm going to guess that with a non-vented cap, there would be a vacuum (difficult to draw fuel forward) until the cap was removed to equalize.  But if left to sit in warmer temps, that would allow the fumes to expand causing more pressure to "push" gas forward (possible flooding) until the the cap was removed to equalize.  I don't know how much extra pressure an old diaphragm could handle, but if weak, I suppose it could be possible to get the leak started. 

I don't know enough to say impossible. 

Posted by: SteveKfl
« on: January 31, 2021, 12:52:16 PM »

Quote... PS: On the “Original technical questions, answers, observations” page, I posted a thread called “Oil filler tube upchucking oil into my oil bath air filter.”

Question for possible discussion: Could the unvented gas cap have caused all those problems?
 
I can't wait to see what the "experts and experienced" respond to that.  Great question.
Posted by: Mytwojeeps2020
« on: January 31, 2021, 10:19:31 AM »

Problem solved!

Like you suggested, I took off the gas cap and let her run. A little rough for a few minutes, but then the idle returned to normal. I then put my new, vented cap on, and gave it a good run. The pressurization problem is no more. All is right with the world!

My egg timer is back in action!

Thanks, all!

PS: On the “Original technical questions, answers, observations” page, I posted a thread called “Oil filler tube upchucking oil into my oil bath air filter.”

Question for possible discussion: Could the unvented gas cap have caused all those problems? I had replaced the old vented cap with the non-vented cap at the same time I bought the first “new” fuel pump. It could be just a coincidence, but who knows?
Posted by: Mytwojeeps2020
« on: January 27, 2021, 04:52:38 PM »

Quote from: SteveKfl on January 27, 2021, 11:59:28 AM
Are you using ethanol by chance?

Nope. I’ve been using ethanol-free gas for a number of years.

I should have more info in a few days (Jeep is stored out of town)
Posted by: SteveKfl
« on: January 27, 2021, 11:59:28 AM »

Are you using ethanol by chance?  I've had that happening in gas cans inside my garage with plastic cans that aren't vented.  They can really get puffed up.  I switched to non-alcohol and it isn't so bad.     
Posted by: Mytwojeeps2020
« on: January 27, 2021, 10:42:52 AM »

Quote from: PercyUK on January 27, 2021, 06:45:26 AM
Hi, does it idle and run OK with the cap off altogether?

I don’t know. I can’t get back to it for another week to test this theory.
Posted by: Mytwojeeps2020
« on: January 27, 2021, 10:41:35 AM »

Quote from: Chuck W. on January 23, 2021, 11:34:04 AM
I am not sure I understand how a gas tank can build pressure with only one line running from it to the fuel pump.  Is the jeep sitting in the hot sun or something that is causing the gas to expand? I would've thought you'd have the opposite problem, a vacuum in the tank if it was un-vented with the engine running.

No, it doesn’t sit in the sun, and here in Central Florida it is cool most of the time now. It still continues to pressurize even with the engine off and cold.
Posted by: PercyUK
« on: January 27, 2021, 06:45:26 AM »

Hi, does it idle and run OK with the cap off altogether?
Posted by: Chuck W.
« on: January 23, 2021, 11:34:04 AM »

I am not sure I understand how a gas tank can build pressure with only one line running from it to the fuel pump.  Is the jeep sitting in the hot sun or something that is causing the gas to expand? I would've thought you'd have the opposite problem, a vacuum in the tank if it was un-vented with the engine running.
Posted by: Mytwojeeps2020
« on: January 23, 2021, 03:57:18 AM »

Quote from: Bruce_W on January 22, 2021, 07:26:01 PM
Don’t tell me, let me guess - Omix-ADA?

Good question, but I don’t know.
Posted by: Bruce_W
« on: January 22, 2021, 07:26:01 PM »

Don’t tell me, let me guess - Omix-ADA?
Posted by: Rus Curtis
« on: January 22, 2021, 04:30:53 PM »

Quote from: Mytwojeeps2020 on January 22, 2021, 03:44:54 PM
Bruce & Rus. Good advice, thanks!  I can’t get back to where it’s stored for two weeks, so I’ll post the results then.

Rus, you’re aware of my previous issue about the gas pump pumping gas into the crankcase, I believe I’m onto a conspiracy.

I bought the new fuel pump (that turned out to be bad) at the same time I bought my new gas cap. This may be a foreign entity trying to disrupt our country: make Jeep owners miserable and thus bring down the country...

Hmmm.  Interesting.
Posted by: Mytwojeeps2020
« on: January 22, 2021, 03:44:54 PM »

Bruce & Rus. Good advice, thanks!  I can’t get back to where it’s stored for two weeks, so I’ll post the results then.

Rus, you’re aware of my previous issue about the gas pump pumping gas into the crankcase, I believe I’m onto a conspiracy.

I bought the new fuel pump (that turned out to be bad) at the same time I bought my new gas cap. This may be a foreign entity trying to disrupt our country: make Jeep owners miserable and thus bring down the country...
Posted by: Rus Curtis
« on: January 22, 2021, 12:06:37 PM »

Quote from: Mytwojeeps2020 on January 22, 2021, 10:21:04 AM
With my new gas cap, I’m getting a lot of pressure built up in the gas tank like I’ve never seen before.

Apparently, my old cap was vented, and this new one is not.

Now, whenever I take the cap off, a solid rush of fumes blows out - even if the Jeep has not been running for for a week or so.

If I put the cap back on (with the engine not running) for 15 seconds or so, when I take it off again, I still get a small rush of fumes.

My engine has also been running rough, and will not hold an idle.

I’m guessing that with the tank pressurized like this, the fuel pump can’t draw gas fully into the carb.

Any thoughts?

Quote from: Bruce_W
If it’s building pressure in the gas tank, it would actually do the fuel pump’s job for it, and possibly overpower the carb’s inlet valve and flood the carb, resulting in a rich mixture and a poor idle. You need a vented cap
  Another problem with a non-vented cap is that the fuel pump will pull a vacuum in the tank and then you get the “failure to deliver fuel “ problem. Air must enter the tank to get fuel out.
BW

I was about to post the same thing as Bruce.  The only thing I'd add is try unscrewing the cap to break the seal while running to see if there's a difference.  My suspicions are that there's a separate issue with your carb and it's just coincidence that they are overlapping.
Posted by: Bruce_W
« on: January 22, 2021, 11:58:06 AM »

If it’s building pressure in the gas tank, it would actually do the fuel pump’s job for it, and possibly overpower the carb’s inlet valve and flood the carb, resulting in a rich mixture and a poor idle. You need a vented cap
  Another problem with a non-vented cap is that the fuel pump will pull a vacuum in the tank and then you get the “failure to deliver fuel “ problem. Air must enter the tank to get fuel out.
BW