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fuel pump wiring ? by Lou6t4gto
Started on: 08-09-2016 01:59 AM
Replies: 8 (274 views)
Last post by: Lou6t4gto on 12-01-2018 04:02 PM
Lou6t4gto
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Report this Post08-09-2016 01:59 AM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post

1986 GT with 3800SC- if the Fuel Pump is getting" Full Time Power' from both the Relay and the oil pressure switch,(" hot at all times" to the relay and to the oil sender, then to the pump) Why is the pump not running "all the time" ? maybe a dumb question, just seems strange. thanks

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phonedawgz
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Report this Post08-09-2016 03:56 AM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post

Wired per how GM wired the Fiero harness, and how I do it, both the relay and the oil pressure switch can act as a switch to turn on the fuel pump. You need to determine which device is turning on your fuel pump. Unplug each and note when the fuel pump turns off. That is the device that is either bad, or incorrectly wired.

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darbysan
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Report this Post08-09-2016 11:02 AM Click Here to See the Profile for darbysanClick Here to Email darbysanSend a Private Message to darbysanEdit/Delete MessageReply w/QuoteDirect Link to This Post

 
quote
Originally posted by Lou6t4gto:

1986 GT with 3800SC- if the Fuel Pump is getting" Full Time Power' from both the Relay and the oil pressure switch,(" hot at all times" to the relay and to the oil sender, then to the pump) Why is the pump not running "all the time" ? maybe a dumb question, just seems strange. thanks


The ECM will prime the pump for 2 seconds via the relay, then shuts off. The Oil Pressure switch provides power , but only when there is oil pressure present ( engine running). Once the engine is running, the ECM gets info that turns the relay back on.

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Fastfiero1
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Report this Post08-11-2016 10:42 AM Click Here to See the Profile for Fastfiero1Click Here to Email Fastfiero1Send a Private Message to Fastfiero1Edit/Delete MessageReply w/QuoteDirect Link to This Post

With a swap setup I am not sure how your harness is wired, so I am posting a pic of the original schematic for the 86GT and one from an 02 GTP with a 3800sc series II setup. Hoping this will help you.

Original 86 schematic:

2002 GTP 3800sc schematic:


------------------
Fiero's Owned:

1987 Coupe 2.5 5spd May 99 - June 03
1987 GT V6 5spd July 30 2012 - Current

[This message has been edited by Fastfiero1 (edited 08-11-2016).]

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Lou6t4gto
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Report this Post08-21-2016 12:11 AM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post

is the fuel pump "supposed to shut off' after it reaches "Pressure", or does it stay on all the time the engine is running ??? mine, the key is turned on, the pump primes, and keeps on running . 3800Sc in 86 GT. If it's getting power from the oil Sender full time, it's Got to keep running, correct ???? If it's supposed to shut off, WHAT is it, that's cutting the power to it ???? this is driving me nuts

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Lou6t4gto
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Report this Post11-30-2018 03:41 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post

been 2 years, still have not "solved it"

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Rexgirl
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Report this Post11-30-2018 04:28 PM Click Here to See the Profile for RexgirlSend a Private Message to RexgirlEdit/Delete MessageReply w/QuoteDirect Link to This Post

The F. P. runs any time it has electricity. See darbysan's post for the two sources of it's 12 volts. When the ignition is turned off, the fuel pump relay disconnects it's F.P. feed, and the engine's oil pressure also drops which opens the oil pressure switch, removing the second power connection.

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Lou6t4gto
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Report this Post12-01-2018 03:13 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post

Makes No Sense ! Brand New Relay, orange black Has Power full time, green /black Has power for 3 seconds when key is on, but pump will not turn on with relay
. IF i jump either orange/ black to tan, it will run, Or jump green /black to tan pump will run for 3 seconds if key is turned on. the relay is "supposed" to get 3 seconds of power from green/ black (ecm)which it Does, to connect orange /black to tan to run the pump, but it just Wont do it ! Any ideas?? What am I MISSING ??

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Lou6t4gto
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Report this Post12-01-2018 04:02 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post

AHA ! it wasn't a lack of power or bad part, it was the ground Wire going To the Relay ! I am so glad all this is finally over, I Just knew it wasn't the harness. Thanks everyone for your input

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