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fuel pump for 87 mustang

 
87stangld
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Posts: 9
Joined: 03/13
Posted: 04/04/13 04:07 PM

I checked voltage in and out of inertia switch it was 7.80 at both same at tan and lite green and red and black at relay  when I squeeze relay to start car I get battery voltage at org/blue and Pink/black but 7.55 at both tan/green and red/black my inertia switch is in the trunk I've tried to bypass it with jumper and still same voltage  is there any chance the comp just died?. I'm confused it was less then 24 hours between the car running and then not at one point tonight when I squeezed contacts together I got 13.87 volts to red/black wire but only for a split second then dropped to 7.55 again  I've also gone back and cleaned up all grounds with my grinder for flush contact to be sure   not sure what else to do  is there any way to connect fuel pump to a diff switch to get it to run  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/04/13 06:42 PM

where are you measuring ground at???????  if the grounds at the front of the car are bad.. you won't have voltage..

the other thing.. the fuel pump could be GOING BAD and pulling a LOT of current..??

does your digital volt meter have at least a 10 amp DC setting??   so you could measure the fuel pump amp draw...   7 amps is expected..

and yes... you can run a LONG wire to the back of the car.. or use some JUMPER Cables hooked together laying beside the car..   positive to one clamp...    clamp to clamp...  clamp to a short jumper wire to go to the wire to the fuel pump with the inertia switch disconnected...

you will have to look but i think its the red and black wire...


but i really wonder about the diagram.. if the inertia switch is in the trunk... is it in the fuel pump circuit.. or does it cut power to the relay like is shown...

i found a different book of diagrams.. let me scan and post a page..  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/04/13 07:16 PM

this is better....

it will take me a while to add some color..print this... or drop me a PM by clicking on my user name and sending me a PM..

if you shift it over or print this.. you will see that the inertia switch is shown on this diagram below right side...

87 Mustang50efi EECIV Zpse31c6dd7  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/04/13 08:10 PM

how about some color...

if you are getting only 7 volts at the red wire or the RED and black wire at the inertia switch..

go back and check both the ORANGE AND BLACK wire at the EEC main relay..

check the BLACK and ORANGE at the EEC main relay...

if you have 7 volts there... then you have an issue between the EEC main relay black and orange wire and the BLUE fusible link to the starter relay....

if you have good voltage at the ORANGE AND BLACK and BLACK and ORANGE  wire at the MAIN RELAY... but not enough at the inertia switch either wire.. then somewhere you have a broken wire...

because of the amount of devices that are operated off the EFI main relay wire.. Orange and black and the RED.. shown as dashed red on this diagram.. you could have one of the devices shorted and dragging the current down...

lastly...  you should be able to test the voltage at the RED and BLACK stripe wire at the FUEL PUMP RElAY.. there is NO LOAD between them directly..  but there are branches off to feed everything else..


this should be print able also..


87Mustangeecfuelpump Mainrelays Zps84909a1b  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/04/13 08:20 PM

oh... i compared the first colorized diagram and the second colorized diagram..

the inertia switch is in the same configuration..  between the switched power from the main relay and the fuel pump relay coil winding..

unplug the inertia switch... use a jumper lead right at the relays..

from the ORANGE and black wire on the MAIN relay .. to the RED and black on the Fuel pump relay..
that bypasses ONLY the inertia switch..   it does not need but ONE amp of power to operate the coil windings in the fuel pump relay..  at that point it should have a full battery voltage there..

now.. with the car running..  measure the voltage on the jumper.

you could also jump directly from the battery positive to the RED and black stripe wire at the fuel pump relay.. with the INERTIA Switch UNPLUGGED..   this will give the Fuel pump relay windings enough current for the ECM to pull them to ground..

look around the lower right corner where the wires all feed out in red color.,.
check the voltage at the TAB or TAD solenoid red wire..  or the red wire into one of the fuel injectors..  

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87stangld
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Posts: 9
Joined: 03/13
Posted: 04/06/13 01:22 PM

Okay I ran a jumper from the main relay to the red black wire at fuel pump relay it didn't activate the relay  it I did check the other points from the red wire and they all had 13.88 volts but fuel pump relay would still not run at this point I'm lost with this car .  I'm either gonna have to pay to have a shop look or I'm going to run the fuel pump off a fused toggle switch   if I do do that will the computer still function as it should  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/06/13 01:57 PM

the diode in the fuel pump relay COULD be blown out...

swap in another relay...  

with proper voltage at the RED and black wire...   when you ground the tan and light green wire... the relay should close... if no.. and the terminals inside the relay sockets are tightly gripping the relay pins.. then the relay diode is blown out..

you should be able to hear this.... click...

warning.. if you ever even for a split second put positive power on the tan and light green wire... the diode will blow...  in a Fraction of a second...


whats your phone number..?????

click my user name.. i will call you...  

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87stangld
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Posts: 9
Joined: 03/13
Posted: 04/06/13 02:15 PM

I just tried somthing differnt I put battery power from battery to red and black wire with inertia switch plugged in I then put tan and light green to ground and the relay powered like it should it ran fuel pump and car would run   what does that mean  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/06/13 02:33 PM

you have a wiring problem someplace between the main relay output.. and the red wire to the inertia switch... since you have measured reduced voltage there...


you can run your car without the inertia switch circuit...  as it only shuts off the fuel pump if there is an accident..  or hard impact...  taking a short cut.... will not hurt it..


now that its running... measure the out put voltage on the main relay...

black and orange wire bringing voltage into the MAIN relay contacts...

and the orange and black wire coming out of the main relay..

both of those should have battery voltage with the engine running...  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/06/13 02:37 PM

the relay connector kit is part number 600 at most autozone stores...

about 20 bucks...



could be a broken wire where its crimped in..

could be a loose terminal that does not grip the relay pin tight enough ...

a broken wire or junction point back in the harness...

rodent damage.. depending on where the voltage is being limited at???  

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waynep712222
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Posts: 41
Joined: 03/13
Posted: 04/06/13 03:07 PM

want to use your volt meter to find the issue..

set it to 20 volts DC... engine running...

one probe on the positive battery..

A. the other probe on the black and orange wire into the main relay.. 0.04 volts is good.. more than that is bad..

B the other probe to the Orange and black wire on the main relay.. 0.04 volts is good..

C.   the other probe to the red and black wire to the fuel pump relay.. 0.04 volts is good.. more is bad..

D.   orange and light blue into the fuel pump relay   0.04 volts..

E.   red or red and black coming out of the fuel pump relay.. 0.04 volts..

what are measuring is the difference in voltage between the positive battery post on the top of the battery and the  various circuit that should have battery voltage on them when the engine is running..  if you get more than 0.04 volts.. or so.. you will have found the circuit with the issue...

you can do a similar test with the test probe on the negative terminal...

but the positive to positive test is better... and has to be done with the engine running...

so there is current is flowing thru the circuits..


post the results next to the letters...


A....

***

***

***

e....  

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