HOBBS LOW FUEL PRESSURE SWITCH SET UP & installation.
04-19-2007, 09:34 AM
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HOBBS LOW FUEL PRESSURE SWITCH SET UP & installation.
Can Anyone Tell Me How To Install A Low Fuel Pressure Warning Switch Made By Hobbs ? Do I Need A Relay ?
04-19-2007, 10:59 AM
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The Hobbs switch will have 3 posts. A common, that goes to the pump, a normally open that goes to a keyed power source, and a normally close that goes to the starter S, soleniod terminal.
Here's how it works.
When you tern the key on, power goes to the normally open terminal. However, since there's no oil pressure, the treminal is open and no power gets to the common post powering the fuel pump.
Turn the key to the cranking, start position, and power is supplied to the starter and to the S post on the starter. This energizes the normally closed terminal and supplies power to the common terminal and the fuel pump.
When the engine starts and the oil pressure rises, the hobbs switch will switch from the normally closed to normally open terminal and the common terminal will be powered by the ignition circuit.
A high performane electric fuel pump can easily drain more current than the keyed ignition circuit can supply. So instead of the common terminal powering the pump directly, have it power a relay. That relay can be wired directly to the battery, starter terminal, etc. where ever to have a good current source.
Pumps wired to low current sorces, ie key switch, long wires, etc without a relay will not perform well and will burn out prematurely.
PS, remember to fuse everything.
Gary
Here's how it works.
When you tern the key on, power goes to the normally open terminal. However, since there's no oil pressure, the treminal is open and no power gets to the common post powering the fuel pump.
Turn the key to the cranking, start position, and power is supplied to the starter and to the S post on the starter. This energizes the normally closed terminal and supplies power to the common terminal and the fuel pump.
When the engine starts and the oil pressure rises, the hobbs switch will switch from the normally closed to normally open terminal and the common terminal will be powered by the ignition circuit.
A high performane electric fuel pump can easily drain more current than the keyed ignition circuit can supply. So instead of the common terminal powering the pump directly, have it power a relay. That relay can be wired directly to the battery, starter terminal, etc. where ever to have a good current source.
Pumps wired to low current sorces, ie key switch, long wires, etc without a relay will not perform well and will burn out prematurely.
PS, remember to fuse everything.
Gary
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04-19-2007, 02:55 PM
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OK after all that, I just realized you asked about a Hobbs switch for "fuel pressure".
I was referring to a Hobbs switch to operate an electric fuel pump, or shut one off, with oil pressure.
Soooooooo............
As Gilda Radner used to day.
"Nevermind"
I was referring to a Hobbs switch to operate an electric fuel pump, or shut one off, with oil pressure.
Soooooooo............
As Gilda Radner used to day.
"Nevermind"
04-19-2007, 03:28 PM
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Hobbs Low Pressure Switch
I Spoke With Norm At Teagues And He Said The One I Have All Ineed To Do Is Run A Hot Wire And A Ground Wire And Set The Desired Pressure.sounds Easy Enough.thanks For The Responses Guys.
04-19-2007, 09:12 PM
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04-20-2007, 08:31 AM
#10
9-$20.00
http://cgi.ebay.com/HOBBS-PRESSURE-S...QQcmdZViewItem
http://cgi.ebay.com/NEW-HOBBS-PRESSU...QQcmdZViewItem
http://cgi.ebay.com/HOBBS-PRESSURE-S...QQcmdZViewItem
http://cgi.ebay.com/NEW-HOBBS-PRESSU...QQcmdZViewItem
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