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Old 08-14-2010, 08:35 PM
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MYGOAT MYGOAT is offline
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Default Fuel Drain Back

OK, so I have the common issue of the fuel draining out of the carb bowl/fuel line meaning after the car sits for a few days I need to crank for ages before the car will fire.
I was thinking of fitting one of those cheap inline electric fuel pumps only to prime the fuel line before cranking. I wasn't intending to run this electric pump after the car starts as the mechanical one does the job quite well.
Question is, if the electric fuel pump is not running will it still let the fuel through it so that the mechanical pump still does its job.
Any feedback or advice on this idea or any other potential fix for this problem would be greatly appreciated.

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Old 08-14-2010, 09:10 PM
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pfilean pfilean is offline
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Even if the electric pump would allow flow (which I doubt especially if it is a geared pump) I would expect so much resistance to the flow that the mechanical pump would not get enough flow. Kind of like having the sock filter in the tank plugged. And the biggest part of your problem is really that the fuel evaporates out of the float bowl and it takes time to pump it full again.

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Old 08-14-2010, 09:14 PM
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snakepod snakepod is offline
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I had a Holley red pump below the tank. It would run fine with the red pump on, through the mechanical pump. If the electric pump was off, the car would die at the top of second gear. The electric pump was causing too much resistance when off.

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Old 08-14-2010, 09:47 PM
Joel Koontz Joel Koontz is offline
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Your fuel may not be draining back, it may just be evaporating, at least I think that's what mine does. Several posts about this if you do a search. I am running an in-tank FI Pump so not a big issue for me, as I can refill the carb before cranking the engine, but the pump definately runs some to fill the carb back up when I first turn it on after setting for a day or more.

I think some electric pumps are designed to let fuel be drawn through them w/o much restriction, but I'm not sure which pumps. I think I have heard that some of the Carter Electric Pumps are designed to allow draw through, but not sure it's true.

Tom V. has posted about a system that he has used. It involves 2 Ts (or Ys, Ys preferred for better flow), a check valve and electric pump. Split the line that comes out of the tank with a T/Y, and put a check valve in the one line and the electric pump in the other line, then rejoin the lines with the other T/Y. The check valve keeps fuel from the electic pump from just running in a loop and lets the mechanical pump pull through the check valve W/O the restriction that many electric pumps would impose.

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Old 08-14-2010, 10:28 PM
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MYGOAT MYGOAT is offline
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Thanks guys, all good info.
OK, agreed, it's more fuel evap than drain back.
Found a FACET inline fuel pump on the net for about $45 Aussie dollars, rated at 4~7 psi at 35 gal/hr. I think this will do the job if I leave it run full time in series with teh mechanical pump. If this doesn't work I can plumb it in as per Tom V method.
I will do a post search as well.

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Old 08-15-2010, 02:36 PM
john5670 john5670 is offline
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If it is hard starting after it has been warmed up you are probably having vapor lock issues. Another thought may be the fuel presure left in the in the fuel line is causing fuel to draining into the intake causing flooding.

my 2 cents

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Old 08-15-2010, 03:00 PM
Craig Hendrickson Craig Hendrickson is offline
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Any rotary vane fuel pump (HP Carter, Holley) will restrict the fuel flow if it is turned off. However, a pulse type presents virtually no restriction when turned off.

Because of the fuel evaporation problem, I installed a Carter pulse type fuel pump with 3/8" nipples on both ends on the side of the fuel tank above the rear spring on my 1979 TA W72. Of course there are other places to put it, but that was convenient.

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