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Gas mileage ea71 weber

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Running an 80 brat with weber. I’m getting horrible gas mileage(mid teens). Seems to run good, carb is adjusted and falls with in specs(idle and mixture). Cap and rotor don’t look bad, Im running a junk yard coil, and rebuilt 83+ disto. All smog equipment is bypassed, disto is only vac line used. 

I smell gas on hot days, how much could I be loosing to evaporation. Should I reconnect the charcoal canister system? 

Could low fuel pressure cause bad mileage? Plugs look good. coil? Plug wires? I have checked for vacume leaks, i think I'm good. 

I am not expecting anything great, i seldom hit the freeway, and my average drive is <2 miles. 

Any suggestions would be greatly appreciated. 

Thanks in advance 


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There's your issue.  First off, your fuel pump is probably overfilling the carb, IIRC Webers want only a few psi of fuel pressure and the stock pump pushes a few psi MORE than the Weber likes.  You may need a pressure regulator.

Also, your fuel tank wants to be vented, so make sure that you haven't capped off the return/vent lines, or on hot days you'll have a pressurized fuel tank pushing even MORE fuel into your over-fueled carb.

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How is the return line routed from the weber, i haven’t seen this before. The vent still leads to the charcoal canister. I was under the impression that the weber wanted the same fuel pressure that the stock pump puts out. 

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The stock pump is 1.35-2.06 psi.Certainly not more than the Weber likes.

You will be hard pressed to get higher mileage w/an average drive  <2 miles.

New cap and rotor is almost always good for at least a slight improvement.

If it does not stall,overfilling is quite unlikely.You can add a fuel return by swapping the Y fitting from the inlet of the old carb.


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Edited by naru2
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Thanks guys, i swapped plugs and wires, cap and rotor look good, they are pretty new. Checked timing, and it is sitting at 14*. I am out of room on adjustment. Running 83+ distributor and diy bracket, im going to try getting a bracket from pick and pull, see if that helps. 1 notch on disto was to far. Will update if it helps. 

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