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fuel mileage drop weber conversion.

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Offline scotrf

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fuel mileage drop weber conversion.
« on: November 13, 2011, 11:15:53 AM »
i have a stock 88.5 sammy w/74,000 original miles and put a weber conversion on it. my mileage dropped to 16mpg. have adjusted carb several times and it seems to be running right. looked at plugs they are getting a clean burn. timed by ear as no timing light at this time. before the stock carb started giving me trouble was about 24-28 mpg depending on my driving and conditions. read everything i could find on doing the conversion bfore starting. read somewhere on here about a fuel pressure regulator but cannot find it now. dont remember the exact carb spec but it is the one mentioned numerous times in the posts looked at. went with electric choke. any help will be greatly appreciated thanks

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Offline Capt

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Re: fuel mileage drop weber conversion.
« Reply #1 on: November 13, 2011, 03:17:52 PM »
Reilly Auto parts has a "Cheap" fuel regulator which is adjustable.
Summit Racing has a affordable fuel pressure Gauge for 0-10 psi range.

Don't go by the dial numbers on the pressure regulator, you will have to use a fuel pressure gauge.
I plumbed my gauge to a Brass 90 degree fitting installed in the plugged port on the other side of the
fuel line input fitting. this so it faces out to the front, EZ to read.
Mine runs good at 1 1/2 to 2 psi.
Note: I "Gasket Matched Ground" my intake manifold at the carb mounting surface,
          and the adapter that came with my kit for better air flow.
          Also I opened up the stock air cleaner adapter from the same kit.
I am getting about 20 mpg, but I was looking for more "Zip In My Do Da" than MPG. and I also have
a 4.9 transfer case running 31x10.5's which ain't a mileage maker.

CAPT

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Offline ebattleon

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Re: fuel mileage drop weber conversion.
« Reply #2 on: November 14, 2011, 11:06:19 AM »
From personal experience Weber's on Samurai's are for power increase over fuel economy.
If you are using 32/36 DGAV Weber you could try going down to 125/125 Fuel jets with no other changes. But looking for better than 20 MPG in a lesson in futility. >:(
Common Sense Absent

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Offline scotrf

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Re: fuel mileage drop weber conversion.
« Reply #3 on: November 15, 2011, 06:32:56 AM »
thanks for the info. found a timing light at a garage sale so i will use it instead of my ear. will be adding the regulator. not looking for super great mileage would like to get into the low 20s but anything over 16 i will take with a smile.

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Offline scotrf

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Re: fuel mileage drop weber conversion.
« Reply #4 on: November 28, 2011, 07:17:50 PM »
sammy started running rough would not idle. put on regulator and adjusted carb 3 times, it would run for a minute then no idle rough running. found that the adapter to manifold bols had backed out. so off came everything to do with the weber. while it was off cleaned up excess gasket material, the gasket that sicks out on the inside between all mounting pieces of the weber. used blue loktite. put it back together and all is good again. fuel regulator is cheap mr gasket one from orielly. dont have a pressure gauge so i started at lowest setting until it ran out of gas. repeated this until it ran down the road without running dry on fuel. its sitting on the 2. no idea what the actual pressure is. now will have to start over on fuel monitoring. cannot time it as i am unable to locate my repair manual. will look that up online n check timing and adjust as necessary. thanks for input and suggestions.

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Offline Drone637

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Re: fuel mileage drop weber conversion.
« Reply #5 on: November 30, 2011, 03:56:02 PM »
Glad it's working better!
96 Geo Tracker, x-SJ-410,  x-White Rabbit, x-Project Trouble
Crawlers NorthWest
x-Trouble Racing

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Offline ebattleon

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Re: fuel mileage drop weber conversion.
« Reply #6 on: December 16, 2011, 07:43:32 PM »
Trust me you do not need a fuel reg in a Sammie to run a happy Weber...
the pressure to carb from the stock fuel pump is about 5 psi. The most effective
adjustment I have found with Weber carbs and Sammies was Float adjustment...

Adjust the float so that the movement from full open to closed float valve is about
2 mm full swing and you wont need to do much adj internally after that.

Also you need to make sure you get insulated fibre spacer for  your Weber as you
will run rich when you warm up and if you can get one find a Hot idle compensation
unit and connect it to a spare vacuum point on the intake manifold. This will help
with your fuel economy.
Common Sense Absent