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Re: [GMCnet] In tank fuel pumps, or external pumps. [message #316397 is a reply to message #316363]

Fri, 21 April 2017 13:57

A Hamilto

Messages: 4508
Registered: April 2011

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Senior Member

BobDunahugh wrote on Fri, 21 April 2017 00:24

...I just don't see how moving the pumps just outside the tanks can help reduce vapor lock to any measureable degree. That 115 degree gas might hit the external pumps at 118 degrees. That's along way from vapor lock temps. I don't see in tank pump as a bad idea. I just would like to find a reason to justify the extra work for me. Bob Dunahugh

Its simple Bob. Outside the tank requires enough suction to raise it some PLUS overcome the resistance to flow over the distance from the in-tank pickup to the pump.

For a pump at the bottom inside of the tank, that rise and length is zero. That difference in "negative" pressure can easily mean the difference between vaporizing a component of the fuel at the pump inlet and NOT vaporizing it.

I don't know if anyone has numbers. But like I keep saying, if an in-tank pump cavitates, the universe has aligned to stop your progress. Get as comfortable as you can, and wait for the temperature of the fuel at the inlet to the pump to drop low enough to not vaporize/cavitate.

You might never see it with external pumps. You pays your money and you takes your chances. But remember, if the engine won't run, the Onan probably won't either. No dash AC and no roof AC while you wait for sundown.

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[Message index]

		[GMCnet] In tank fuel pumps, or external pumps. By: BobDunahugh on Wed, 19 April 2017 22:36
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: USAussie on Wed, 19 April 2017 22:41
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: A Hamilto on Wed, 19 April 2017 23:19
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Ken Burton on Thu, 20 April 2017 00:14
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: A Hamilto on Thu, 20 April 2017 16:49
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Glenn on Thu, 20 April 2017 17:17
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: kerry pinkerton on Thu, 20 April 2017 18:38
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Ken Burton on Thu, 20 April 2017 22:20
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Chris Tyler on Fri, 21 April 2017 13:10
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Emery Stora on Fri, 21 April 2017 13:31
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: USAussie on Fri, 21 April 2017 15:15
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: BobDunahugh on Fri, 21 April 2017 00:24
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: USAussie on Fri, 21 April 2017 05:32
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: kstockwell on Fri, 21 April 2017 06:27
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: lqqkatjon on Fri, 21 April 2017 08:02
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: BobDunahugh on Fri, 21 April 2017 09:42
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: emerystora on Fri, 21 April 2017 10:21
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: emerystora on Fri, 21 April 2017 10:30
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Matt Colie on Fri, 21 April 2017 10:32
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: James Hupy on Fri, 21 April 2017 10:29
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: A Hamilto on Fri, 21 April 2017 13:57
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Larry on Fri, 21 April 2017 08:28
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: James Hupy on Fri, 21 April 2017 09:22
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: jimk on Fri, 21 April 2017 09:35
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: k2gkk on Fri, 21 April 2017 11:00
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: James Hupy on Fri, 21 April 2017 11:04
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: Larry on Fri, 21 April 2017 13:24
		Re: [GMCnet] In tank fuel pumps, or external pumps. By: kerry pinkerton on Fri, 21 April 2017 13:58

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