Welcome to Mustang Evolution.
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01-02-2006, 01:16 AM
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#1
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fuel pumps don't come on
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dana
Join Date: Jan 2006
City: Renton
State: Washington
Posts: 13
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I had an 86 mustang 5 speed and put the gt40 motor with aluminum heads, gt40 manifolds, s trim vortech supercharger which came with the msd boost retard and fmu, msd ignition, the mass air conversion kit (came with 24 lb injectors 70mm mass air sensor and i think a cobra computer, and a bunch of other stuff. That car was hit in the rear and totalled so I got a 91 mustang and transferred everything over to it. It was an automatic when I got it now it's a 5 speed. anyway when i turn the key on the fuel pumps don't come on. anyone know what would cause this? I unplugged the fuel pump relay and jumped across 2 of the wires and they came on so i put a switch between those 2 wires so I can drive it till I figure out why they don't come on with the key. anyone have any suggestions? |
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01-02-2006, 03:03 AM
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#2
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Re: fuel pumps don't come on
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Evolution's Finest
Join Date: Dec 2005
Posts: 29
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ok, this may be a stupid question but sometimes the obvious is what bites you the hardest.
Did you try swapping relays to see if the relay was just bad?
__________________
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01-19-2006, 07:11 AM
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#3
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Re: fuel pumps don't come on
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Registered User
Join Date: Feb 2004
Posts: 6
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Sounds like you need to replace the fuel relay.. |
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01-19-2006, 08:24 AM
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#4
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Re: fuel pumps don't come on
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sʞɔns ʇuǝɹq
Join Date: May 2003
City: Macon
State: Georgia
Posts: 10,741
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check under the carpet in the trunk, right behind the left taillight. There is a fuel pump cut off switch. try pushing the red button down, it should fix your problem if it has been triggered.
__________________
-Jimmy I drive a station wagon.
GO BRAVES
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01-21-2006, 03:59 AM
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#5
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Re: fuel pumps don't come on
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dana
Join Date: Jan 2006
City: Renton
State: Washington
Posts: 13
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already did all that and they still don't come on. |
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02-15-2006, 10:52 AM
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#6
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Re: fuel pumps don't come on
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Registered User
Join Date: Feb 2006
City: Port Huron
State: Michigan
Posts: 11
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neutral kill switch for the automatic trans |
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02-18-2006, 03:36 AM
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#7
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Re: fuel pumps don't come on
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dana
Join Date: Jan 2006
City: Renton
State: Washington
Posts: 13
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i have a manual transmission. Could it be that that part of the ecm isn't working. If so that very well could be what it is. |
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02-18-2006, 07:16 PM
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#8
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Re: fuel pumps don't come on
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Registered User
Join Date: Sep 2005
City: Puerto Rico
State: Other
Posts: 28
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....or an open relay wire going to pin 22 in the ECM, or an open wire between the EEC relay and the FP relay (they share Ign On voltage). My 2.
__________________
1986 Mustang GT w/ T-Tops 
NOW: 5.0L Stock shortblock, X303 Cam, SP Offy. Port-O-Sonic, 700 cfm DP Holley, 289 '66 Small Port Heads, 1.7 RR, Richmond Gear 4+1 Trans., Centerforce DF kit, 2.73 Gears
WIP: 3.90 Gears, LS Overhaul, Adj. LCA's (New Design Granatelli Aluminum), Adj. UCA's (Granatelli), New Valve Springs (FRPP, done), Subframe Connectors (MM), Caster/Camber Plates (MM), T-Top weatherstriping and rear braces bodywork 
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02-19-2006, 01:45 PM
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#9
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Re: fuel pumps don't come on
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Blown' through!!!
Join Date: Feb 2006
City: Ingleside
State: Texas
Posts: 8
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I dont think that will fix his problem.....no to argue though. If the fuel pumps come on while jumpin wires that means the problem is from the relay to the ignition switch...not to the pump. |
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02-19-2006, 05:12 PM
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#10
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Re: fuel pumps don't come on
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sʞɔns ʇuǝɹq
Join Date: May 2003
City: Macon
State: Georgia
Posts: 10,741
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that is true. sounds like a relay problem then.
__________________
-Jimmy I drive a station wagon.
GO BRAVES
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02-22-2006, 03:08 AM
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#11
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Re: fuel pumps don't come on
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dana
Join Date: Jan 2006
City: Renton
State: Washington
Posts: 13
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i've unplugged the fp relay and took 2 of the wires and jumped across them and they came on so for now i put a switch between those 2 wires and manually turn the pumps on before i start it then off when i stop. To me it seems like i should have way more power than i do overall for everything that the car has in it. |
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02-22-2006, 10:21 AM
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#12
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Re: fuel pumps don't come on
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sʞɔns ʇuǝɹq
Join Date: May 2003
City: Macon
State: Georgia
Posts: 10,741
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have you tried putting another relay in so you don't have to use the switch?
__________________
-Jimmy I drive a station wagon.
GO BRAVES
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02-23-2006, 02:03 AM
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#13
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Re: fuel pumps don't come on
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dana
Join Date: Jan 2006
City: Renton
State: Washington
Posts: 13
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yes. I've also replaced the eec relay |
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02-24-2006, 07:06 PM
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#14
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Re: fuel pumps don't come on
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Registered User
Join Date: Sep 2005
City: Puerto Rico
State: Other
Posts: 28
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Dana;
Check the wiring diagram attached (Courtesy of Veryuseful.com) for the '91, it will help you in tracing the wires. 
You should have voltage all the time at the Pnk/Blk wire. Voltage at the Red wire with Ign On only. Otherwise, need to trace either back for an open to the fuse link or the EEC relay.
Dk Grn/Yel wire goes to the FP, no problem there.
Now, the Lt Blu/Org is the wire that gets the ground from the ECM to activate the relay, thus the FP. Check it out bet it's a wiring SNAFU. LUK
__________________
1986 Mustang GT w/ T-Tops
NOW: 5.0L Stock shortblock, X303 Cam, SP Offy. Port-O-Sonic, 700 cfm DP Holley, 289 '66 Small Port Heads, 1.7 RR, Richmond Gear 4+1 Trans., Centerforce DF kit, 2.73 Gears
WIP: 3.90 Gears, LS Overhaul, Adj. LCA's (New Design Granatelli Aluminum), Adj. UCA's (Granatelli), New Valve Springs (FRPP, done), Subframe Connectors (MM), Caster/Camber Plates (MM), T-Top weatherstriping and rear braces bodywork
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