low fuel pressure light diagnosis (help)

1132 Views 1 Reply 2 Participants Last post by 144, Sep 20, 2007

ALEXANDERHULSE

Discussion Starter · Sep 20, 2007

First Post Long Time Reader
1980 Spider Stored For 20 Years Close To Perfect
Stereo Stolen Hence The Wiring Problem
Idiot Light Wires Cut Or Disconnected. Figured Out Most Of Them
Car Has Not Been Drive But Runs And Starts Easily Have Cleaned All Wire Grounds And Connections .

What Is Wrong Low Fuel Pressure Light Does Not Work. Fuel System Gone Thru Like New . As I Understand The Circuit If The Sensor Light Is Grounded The Light Should Come On. (it Does'nt). The Light Works If Power Is Put To The Sensor Wire (dont Understand This Because No Ground).there Is Power To The Light Via A Pink Wire And Green/white To The Sensor On Fuel Filter For The Ground.

My Question Is Why Does The Lamp Light When Power Is Applied To The Sensor Wire When There Is Already Power To The Pink Wire .how Is This Circuit Completed Any Help Will Be Appreciated
Alex

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144

· #2 · Sep 20, 2007

Sounds to me like there's some wires crossed. This is as simple a circuit as is possible. The dashboard light has 12v power to one wire and the other wire runs to the fuel low pressure sending unit. When the fuel pressure is below 7 psi, the sending unit's internal switch closes and grounds. This completes the circuit for the dash light illuminates.

You can check the operation of the sending unit by connecting a test light to it. Run one wire to the + terminal on the battery and the other to to the spade terminal on top of the sending unit. Turn the key switch on. The test light should come on momentarily, then go off after the pressure builds to above 7 psi.

Sounds like you need to check the continuity of the present circuit wires.

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