[e3sean]

ok i am yet to get my car started cause a few issues here is one..car ran when i pulled it into the garage changed the motor converted it to mass air so i swapped the wire harness.. i can not get it to turn on. looks like someone pypassed the inerta swith the plug is gone and it has a connector between the two wire.

where does the fuel pump get its power from?\
what are my options to fix it?


not sure if its any relation but i also can not get my lights to turn on...

 

[SALIV8]

have you plled up a schematic and checked fuses/relays/switches/etc?

 

[e3sean]

i checked all the fuses i found the relay under the driver side seat there is a power going to it but it wont switch it over to turn the pump on...

 

[SALIV8]

did u chek neutral safety switch?is it an auto? or your clutch not completely pushed?

 

[Onemanzu]

you know that the relay is good? i had a problem with an old Volkswagen relay... went through 3 before one worked

 

[e3sean]

it all worked before i pulled the engine out.. it has to have something to do with the new wireharness/computer or my error somewhere..

what i need to know is where the fuel pump gets its power source from like the ignition or a fuze box.

also when the car is running is the fuel pump always on?? if it is i can just wire it to an accessory 12v power supply

 

[ryans88gt]

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

This should help you. I would start by checking to see if you are getting 12v at the fuel pump when you cycle the key (maybe your fuel pump died while sitting).

If no 12V, check at the relay hot side (orange/blue wire). If no, blown fusible link. If yes, check the red/black wire should become hot when you cycle the key on and off (prime the pump). If no, your problem is in that circuit. If yes, most likely it is the relay ground, which is provided by the computer (tan green wire on the relay). try grounding this wire and cycling the key if everything else checks out. Hope that helps.

 

[crowbar73]

Dang Ryan, you beat me to it. I just went to my garage to get a wiring diagram. (I couldn't remember the wire colors). Oh well, I tried. P.S. your car is a rocket man!

 

[87 5.0]

Dang Ryan, you beat me to it. I just went to my garage to get a wiring diagram. (I couldn't remember the wire colors). Oh well, I tried. P.S. your car is a rocket man!

Since when did mustangs become ROCKETS????

 

[e3sean]

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

This should help you. I would start by checking to see if you are getting 12v at the fuel pump when you cycle the key (maybe your fuel pump died while sitting).

If no 12V, check at the relay hot side (orange/blue wire). If no, blown fusible link. If yes, check the red/black wire should become hot when you cycle the key on and off (prime the pump). If no, your problem is in that circuit. If yes, most likely it is the relay ground, which is provided by the computer (tan green wire on the relay). try grounding this wire and cycling the key if everything else checks out. Hope that helps.

i am getting power to the relay and it is not going to the red wire when the car is cycled so the green wire when grounded should put power to the pump? if that works its the computer..

 

[crowbar73]

if you don't get power at the red/black wire at the fuel pump relay when you cycle the key, i would go check at the inertia switch (in the trunk) and see if you have power there when you cycle the key. maybe there is a loose connection there. if no power on either wire there, you need to find the eec power relay and check for power there on black/orange wire. if no power on black/orange check fuse link G? If you do have power on blk/org it is probably an ignition switch failure. hope that makes sense?

 

[Black Five 0h]

any luck on this?

 

[ryans88gt]

He wasn't getting power at the red/black wire because his ECU relay was blown. Sean, hope you don't mind if I answer for you

 

[e3sean]

nope i forgot about this post.. yeah like ryan said it was the ecu relay was bad i replaced it and it all started working again.

just cause something worked when u used it last doesnt mean its gonna work next time u go to use it...i learned that the hard way...

 

[Derrik]

Going though this same thing i think idk

ok, i have no power to my fuel pump/shut off switch,
but i have power at the fuel pump relay where i think i am suppose to have it, not really sure what i have got my self into.. new at fuel injection only 18 just graduated haha. i can jump power to the pump and run it, car came with 2 computers not a good sign but i switched them out to see if something changed nothing did, wasn't getting spark at 1st but changed out ignition module, and solenoid, and spark plugs now i have spark and get it to kind of run of starting fluid, i thought maybe the red wire running from the relay to the pump was bad, so i traced it, it was good. not sure where to go from here any help would be nice.

 

[nolife]

In general.. You have to start by checking for a fuel and/or spark problem and go step by step from there.

Fuel Injected Mustangs "Crank and No Start" Checklist - Ford Mustang Forums

It seems you have done some of that already. When you say you have power to the fuel pump relay, what power?

The computer does a prime and powers on the fuel pump for a few seconds every time you turn on the key. After that few seconds of priming, the fuel pump shuts off and stays off until the car is running. If you are troubleshooting power to the fuel pump 2 or more seconds after turning the key on, you won't find any.

Here's the easiest way to check the fuel pump relay if you don't have diagrams or understand how they work.
Take the key from off to on four times. Each time measuring voltage on a different wire on the fuel pump relay to a good solid ground.
What you should see as soon as you take the key to on.
One thin wire, +12V for a second then nothing
the other thin wire, nothing maybe a slight fluctuation
One thick wire, +12V the whole time
the other thick wire, +12V for a second then nothing.

Every time you turn the key on, you should hear the fuel pump clicking. If all of that checks out good, your fuel pump relay and computer is good (at least as far as the fuel pump part of the computer) and the problem is most likely a wiring problem from the relay to the inertia switch or the fuel pump itself.