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1993 coupe

 
wesley1
New User
Posts: 4
Joined: 02/13
Posted: 02/05/13 09:16 AM

I am needing help with my mustang.It has an air leak when you turn the switch on and not start the car you can hear it around the trottle body. I have check for leaks but am unable to find any.Do anyone know what it could be? I appreciate any help  

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waynep71222
User
Posts: 166
Joined: 04/12
Posted: 02/06/13 08:10 PM

when the engine is NOT running.. there is NO air movement through the intake..

what you might be hearing is the fuel moving thru the fuel rail and out into the return line from the regulator.. it will make a swishing noise..

i would like to know.. if somebody has modified your fuel pump wiring system..

usually the fuel pump turns on for 2 seconds when you first turn on the key then the ECM releases the relay..   the ECM will turn the relay back on to energize the fuel pump when you start cranking and the ECM sees RPM and on some models.. crank signal...

ECM sees the RPM thru one of the wires on the TFI module and the resistor to cut the voltage down but still have signal..


if your fuel pump is staying on with the ENGINE NOT running.. you have a fire issue...  

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wesley1
New User
Posts: 4
Joined: 02/13
Posted: 02/07/13 04:57 AM

Thanks for the help. I checked that and the fuel pump is running all the time when the switch is on. Is there an easy fix for that ? Thanks for all the help  

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waynep71222
User
Posts: 166
Joined: 04/12
Posted: 02/07/13 09:09 AM

well....

how good are you at reading wiring diagrams...

there are probably a dozen different ways to get the pump to run constantly when the key is on..


are you returning this to street duty...

do you have a wiring diagram for the 93????  they are several pages long... 4 pages as i recall..

i have one printed out somewhere around my desk area...  but i have not seen it in a few weeks..

AZ repair guides has it..

there are 2 relays involved... the ECM and the inertia switch...

order can vary depending on the year..

the key turning on... activates the EFI main relay....  this sends power to various fuel injection devices.... but also to the fuel pump relay power contact...   the fuel pump relay is controlled only by the ECM...

if the car is working currently... just leave it for now... be sure that you don't leave the key on to listen to the radio...  it won't hurt anything.. but it will drain the battery faster...

if you have any dribbling injectors it may fill the intake ports...  

in the event of a accident... the fuel pump may continue to run until the key is turned off if the inertia switch is bypassed also...  since it sounds like the fuel pump relay was also bypassed..

oh.. looks like the 93 is only a few individual pages... not 4 interconnected.. thats 94/95

http://www.autozone.com/autozone/repairinfo/repairguide/repairGuideContent.jsp?pageId=0900c15280069677


you should be able to print the diagrams you need from the link above...

ask questions.. if you have some...

one trick to know..

the EFI MAIN RELAY and the FUEL PUMP RELAY look similar.. but are slightly different...

easy way to tell them apart...

since the fuel pump relay coil is controlled by the ECM... it has a diode in the circuit diagram...

the EFI MAIN RELAY is controlled only by the ignition switch so no diode is needed to prevent high voltage kickback from the coil winding collapsing and burning out the computer circuits..  

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wesley1
New User
Posts: 4
Joined: 02/13
Posted: 02/07/13 10:07 AM

I appreciate all the help. Thanks for everything.  

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