petcock
#1
05-15-2011, 06:56 PM
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petcock
guys trying to remember, on fuel petcocks with vacumn if you turn fuel on or reserve should fuel start to flow, or does engine have to be turning over to create vacumn to make fuel flow?
#3
05-15-2011, 07:04 PM
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#5
05-15-2011, 07:33 PM
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Well one says running one says gravity...crap now I gotta go out and remove fuel line and turn it on..to see
#6
05-15-2011, 07:39 PM
Road Captain
your kidding right?
If you have a petcock then you have a carburetor with a float, the fuel flows out of the tank by gravity and the float shuts the fuel flow off when it reaches its set point.
The engine has to be turning over to pull fuel through the venturi in the carb and into the engine.
If you had fuel injection there would be no petcock and there is an electric fuel pump inside the tank.
If you have a petcock then you have a carburetor with a float, the fuel flows out of the tank by gravity and the float shuts the fuel flow off when it reaches its set point.
The engine has to be turning over to pull fuel through the venturi in the carb and into the engine.
If you had fuel injection there would be no petcock and there is an electric fuel pump inside the tank.
#7
05-15-2011, 07:41 PM
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Well this one starts flowing as soon as fuel is on or reserve..no cranking req. this dont seem right..I thought that was the purpose of the vacumn line
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#8
05-15-2011, 07:48 PM
Turn the petcock to off, remove the fuel line from the petcock and loosen the petcock just enough to be able to turn it so you can access the four phillips screws on the back side where the vacuum diaphragm is. Hold the diaphragm housing to the petcock while removing the screws, there is a spring that will try to push off the housing you are removing. As you remove the housing from the petcock, notice where the spring is in relation to the diaphragm? Put the spring on the other side of the diaphragm and reassemble.
Here's a link with photos..you can do this while it is still installed in the tank : http://crapmods.com/phpBB3/viewtopic.php?f=16&t=8954
Last edited by Freebee; 05-15-2011 at 07:54 PM.
#9
05-15-2011, 08:44 PM
Road Captain
You have a "Failed Ptecock" there's a reversal procedure to bypass the vacuum diaphram take like 15min. however it will be manual off / on from that point on.
Turn the petcock to off, remove the fuel line from the petcock and loosen the petcock just enough to be able to turn it so you can access the four phillips screws on the back side where the vacuum diaphragm is. Hold the diaphragm housing to the petcock while removing the screws, there is a spring that will try to push off the housing you are removing. As you remove the housing from the petcock, notice where the spring is in relation to the diaphragm? Put the spring on the other side of the diaphragm and reassemble.
Here's a link with photos..you can do this while it is still installed in the tank : http://crapmods.com/phpBB3/viewtopic.php?f=16&t=8954
Turn the petcock to off, remove the fuel line from the petcock and loosen the petcock just enough to be able to turn it so you can access the four phillips screws on the back side where the vacuum diaphragm is. Hold the diaphragm housing to the petcock while removing the screws, there is a spring that will try to push off the housing you are removing. As you remove the housing from the petcock, notice where the spring is in relation to the diaphragm? Put the spring on the other side of the diaphragm and reassemble.
Here's a link with photos..you can do this while it is still installed in the tank : http://crapmods.com/phpBB3/viewtopic.php?f=16&t=8954
#10
05-15-2011, 09:05 PM
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nP Fireman, if I was so smart I would'nt have asked the question..thanx guys for the input now I will get a new petcock