Measuring Fuel Pressure

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Lou Melancon
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Measuring Fuel Pressure

Post by Lou Melancon »

I'd like to measure the pressure of my bladder fuel systems. The measurements I want to make are:
<ul><li> Pressure of a bladder filled with 3.5 ounces fuel </li><li> Pressure after passing through needle valve</li><li> Difference in pressures of different diameter bladder tubing </li></ul>

Can someone advise what type of device is needed to measure these pressures and where one might be found?
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boiler
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Post by boiler »

Lou, use a piece of fuel tubing. I'm just guessing about 12 feet long, filled with water and have the open ends pointed up so it forms a "U" shape. When you insert the bladder tube in one end of the water "U" it will push almost half (I think) of the water out of the tube. The difference in the water levels in the two halves of the tube is the pressure in inches of water. If you don't like those standard units, you can go to a conversion table for pressure to get any other standard unit that you might like. Now if you can only find little pieces of tubing it's ok to join them with brass connectors. If my guess that 12 feet was too small, you can add more tubing. I tried to think of the simpliest method using what you can get easily. We geezers can't think too much or we would have to use a computer like the young whipper snappers.[:)]
Hat Trick
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Post by Hat Trick »

If you want less tubing use mercury! I'm sure there is some device that can read pressures in the range your looking for. Might not be cheap though!
Yawnego
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Post by Yawnego »

Lou,
You can get those cheap air pressure guages at Walmart, the ones that are used to replace a broken one on a portable air tank. Shouldn't be to hard to plumb up. Automotive guages would be pricey. One on each side of the needle valve hooked inline with a couple of T fittings should do the trick. Then again, Bobs idea sounds pretty good, if your into all of that calculating..;-) KIS Keep it Simple.
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boiler
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Post by boiler »

Watch it Hat. Those EPA people are nasty.... A kid brought a little mercury to school and let it get away. School was closed for 3 days and we got a bill for over $100,000 for the clean up. In the old days I had a pint bottle full of mercury that I would pass around to instill what density meant. I also made demo mercury barometers with my hands in a soup bowl of the stuff and a regular mercury barometer next to my head for over 20 years. The school doesnt have a single mercury thermometer now for obvious reasons. All the sump pumps that worked until the motors went out are replaced with ones that go out now when the motor is fine but the switch isn't the lifetime mercury switch any more so it fails first.
sgilkey
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Post by sgilkey »

geez it's like the asbestos thing, people flip out over relatively tiny amounts of potentially (emphasis "potentially") harmful substances. it ain't harmful if it's not ingested. I too played with mercury as a kid and look how normal I am. hmmm, i think i just blew my point....


Lou, how 'bout a manometer like is used for syncing the carbs on a motorcycle? i don't think a pressure gage is going to have the resolution you need, Bob's idea of a manometer is a good one but you used to be able to get pre-made ones for syncing carbs for what, $25? try denniskirk.com. of course that is made for measuring vacuum but you might be able to adapt it for pressure.
Lou Melancon
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Post by Lou Melancon »

Hi Scott,
I had forgotten about syncing those old SU carbs on my MGA. I used one of those gadgets to do it.

Incidentally here's a photo of me and that car in '69:

<center>Image</center>

McMaster Carr has quite a few gauges for 1-15lbs pressure on their web site. Most are pneumatic, and for fuel I need hydraulic but I think I am going to take the plunge and shell out the $10 to get one to try.
drewjet
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Post by drewjet »

Lou, are you sure you want to post a picture like that? HA! I guess this was before you joined up with the Geezers
Lou Melancon
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Post by Lou Melancon »

Drew,
That was 36 years ago, I was 18 then. I'd rather look at that picture of myself than the ones I take now.
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boiler
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Post by boiler »

Lou the set up I suggested is recyclable for flying so it costs nothing. It is actually a true manometer. You likely only need about 6 feet of tubing but I was trying to make it large enough that you wouldn't have to add afterwards.
Don Pruitt
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Post by Don Pruitt »

<font face="Arial">I removed the pressure gauge from a sphygmomanometer and ran a quick test with the 3/16â€
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