Ad Radar
  • Subscribe to a Magazine
12 Last
Item Posts    Sort Order

fuel pump for 87 mustang

 
87stangld
New User
Posts: 9
Joined: 03/13
Posted: 03/27/13 03:53 PM

I am having trouble with my fuel pump relay I have power at the org and blue stripe wire at 12volts the tan and light green have 7 and the same with the red wire but no power at the pink and black   with the cover removed from the relay I can activate the switch and get power to the system and the pump runs and car does too  any ideas on what is caussing relay not to activate properly  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 03/28/13 05:27 PM

print this diagram first...

87 50 EECIV Fuel Wiring Diagram Zps7c96dd4a  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 03/28/13 05:43 PM

I have power at the org and blue stripe wire at 12 volts   this is normal..  as it is hot at all times.


the tan and light green have 7   this is a place to be careful when testing.. i am glad you used a digital volt meter.. this TAN and LIGHT GREEN wire is connected to the ECM and when the ECM wants the fuel pump to run.. it pulls this circuit to ground  to activate the coil winding to close the contacts..   the TAN and LIGHT GREEN wire also connects to the self test connector.. ground that with a test clip and the fuel pump should run...

since the volt meter shows 7 volts.. can you check the output voltage on the red and black.. is it full battery voltage as that is fed from the EEC main relay..

if the ECM looses its multiple ground connections..

if the ECM does not see IGNITION SIGNAL on the Dark green and Yellow wire to PIN 4 it will NOT pull circuit 22 to ground closing the fuel pump relay contacts...   when the Ignition switch is turned on.. the fuel pump relay should CLOSE for 2 seconds..  this proves the fuel pump turns on properly....


by the way...   even though the fuel pump relay.. and the EEC4 main relay look identical..

they are NOT....  the FUEL PUMP RELAY has a DIODE in the coil circuit to dampen the high voltage created when the pull to ground circuit is disconnected..  it can create a spike just over 100 volts...  the electronic components in the computer burn out at about 18 volts..  

the power transistor or triac... that control circuit 22 are also only rated for slightly less than 1 amp.. if you used a test light or shorted this circuit ..  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 03/28/13 06:02 PM

7 volts on  the red wire but no power at the pink and black   this could be a BAD inertia switch.. they do get corrosion and melt internally once in a great while..  usually when they are installed in the pink and black circuit to the fuel pump..



lastly...

lets follow the power to the coil winding of the fuel pump relay...

black and orange wire from the starter solenoid terminal. with a fusible link.

to the EEC main relay...

comes out the Orange and black wire that feeds around  to various things like the injectors and other controlled devices under the hood...

do you get full battery voltage on those circuits when you have the ignition switch in the ON position...

if you do.. good...  

if not..  one of the items above could be SHORTED.. or the EEC main relay contacts are dirty and need to be either cleaned or the relay replaced..

if the contacts are dirty.. it may not let enough current thru and the voltage will be too low..

7 volts is NOT enough to close the coil contacts..

please post what you find...  

Post Reply
87stangld
New User
Posts: 9
Joined: 03/13
Posted: 03/30/13 04:38 PM

There is 7.46 volts at the tan and light green as well as the red a d black  the car ran one day just fine the very next day this problem occurred  all the other circuits have the appropriate  voltage I'm gonna look for the test conector to see if grounding it out will make system work. Also I have replaced the eec relay and the fuel pump relay already this seems odd to not work next day. But I can pinch fuel pump relay together and runs so I feel its a bad ground?  

Post Reply
87stangld
New User
Posts: 9
Joined: 03/13
Posted: 03/30/13 04:39 PM

Also would the self test connector be under the dash or under hood?  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 03/30/13 07:40 PM

the test connector is UNDER the hood... please VERIFY  the wire by color... before probing...

or grounding...


8 volts IS NOT enough to close the relays...  it takes over 9 volts...


let me look at the wiring diagrams again...  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 03/30/13 07:50 PM

There is 7.46 volts at the tan and light green as well as the red and black

this is NOT going to work....  there should be FULL BATTERY VOLTAGE on the tan and light green.. as well as the red and black.. i am talking over 12 volts..

take the wiring off the starter solenoid ONE stud at a time... COUNT The wires before you remove them....  use a wooden handled stainless steel wire tooth brush to remove any oxidation... wire brush the threads.. the base of the stud.. the connector side of the solenoid nuts...

the wire terminals you are going to want to clean are shown below are # 4, 5, 6, 7...  all on the same stud..

reassemble...


you should have FULL BATTERY VOLTAGE on the Tan and Light Green as well as the Red and Black..

Ford Starter Solenoid Flat


follow the wiring on the diagrams.. the fusible links are RIGHT at the starter solenoid above..

10 goes down to the starter...  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 03/30/13 08:06 PM

if you can squeeze the fuel pump relay and get the engine to run....

please RUN THIS TEST  then post results.. by number.. this test can be done in under 2 minutes.
practice the 4 part test on another car first so you can see what your results are..


Voltagedroptesting



~~~~~~~~~~~~~~~~~~

can you see the 4 green squares where the ground wires connect in this mustang diagram
i have found so many of these that are LOOSE or corroded...  since electrons flow from Negative to positive.. if the ground connections to the body are loose.. you won't have enough current to build enough voltage to operate the circuit as designed..


1992Mustang50batterycablegrounds


this is a 92 ..

1992Mustang2300enginewiring  

Post Reply
87stangld
New User
Posts: 9
Joined: 03/13
Posted: 03/31/13 05:54 PM

Thanks for all the tips with today being Easter I didn't have a chance to look at car will have time Tuesday ill post all result as soon as I get them thanks again for the help so far  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 04/01/13 07:59 PM

by the way... if you get a chance....


pick up one of these.. stainless steel wire tooth brushes from the local hardware or paint store..

this is what i use to clean various ring terminal and studs...

Stainlesssteeltoothbrush2

these are under 5 bucks usually and will last for years..... conventional steel versions will rust out.. plastic handled versions usually have thiner wire that does not work as well..  

Post Reply
87stangld
New User
Posts: 9
Joined: 03/13
Posted: 04/02/13 02:26 PM

Okay I did the Voltage drop test and got the acceptable readings if u ground the test clip the relay still does not operate voltage for the tan and blue a d red and black are still 7.46  I cleaned up all grounds and cleaned starter solinod not sure what else it could be  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 04/02/13 05:02 PM

7 volts at either of those 2 wires is NOT enough to close the contacts in the fuel pump relay...




can you verify from the those wires to the positive battery post...   positive to positive with the key on should be very low.. perhaps 0.04 or 0.08 volts..
or USE a JUMPER... to supply power to that circuit... to bring the voltage up to battery voltage.. for testing...

what is the BATTERY voltage????   positive to negative..???  see the chart above...



those wires should have BATTERY voltage on them..

8 volts is not enough voltage to build a big enough magnetic field to pull the relay closed....

it usually takes just over 9 volts..

now... if you have an item that is powered by that circuit.. it may have enough load that the voltage drops...  

Post Reply
87stangld
New User
Posts: 9
Joined: 03/13
Posted: 04/02/13 05:58 PM

Battery voltage is 13.92 off and 14.77 when I jump relay to start car  ill check the power from positive to wire in am as well as trying to jump power to complete circuit  

Post Reply
waynep712222
New User
Posts: 41
Joined: 03/13
Posted: 04/03/13 07:46 AM

lets check the voltage at the relays again....


fuel pump relay..

orange and light blue should have full battery voltage at all times...

red and black wire has voltage thru the inertia switch and the EEC main relay.. should have battery voltage when the key is on...


be careful if you attempt to PROBE the TAN and light green wire.. if you overload that circuit.. it will damage the ECM..

because you say that you can ground the tan and light green wire at the EEC4 test terminal and the relay does NOT close.. and there was at some point only 7 volts there..  i am thinking that you may have a problem perhaps.. with the inertia switch..
when you squeeze the relay contacts closed.. you should have close to full battery voltage ont eh PINK and black wire to the fuel pump...

in looking at above.. i think that since you can squeeze the relay contacts and get the engine to run.. that you are actually having voltage issues tot he red and black wire from the inertia switch that is fed by the red wire and that gets power from the Orange and black wire from the EEC main relay..

where is your inertia switch.. is it behind the kick panel next to your left knee??? or is it in the trunk... i have had these burn internally and take out the voltage to the fuel pump relay coil windings kinda like you describe..


lets go over the EEC main relay....

black and orange wire should have full battery voltage... at all times...

RED and Green wire is from the IGNITION switch.. power in RUN and crank ...  this turns on the relay and closes the contacts..  this sends power to the RED wire and ECM pin 37. but also to the orange and black wire that supplies a bunch of stuff...

including the red wire to the inertia switch. the diverter valve, the idle air control motor.. the fuel injectors..  the canister purge solenoid.  the EGR vacuum regulator solenoid.  the TAB and TAD solenoids next to the EGR solenoid..

the Orange and black wire should have close to full battery voltage when you turn the key on as the relay contacts should be closed now...  .

this is the inertia switch inside... they are available at many parts stores..
Inertia Switch

please check the voltage on the red wire going in and the red and black wire coming out..

they should be the same...  if there is less on the red and black wire.. you have a bad inertia switch that is limiting the current and voltage to the fuel pump relay windings.. and that is why there is only 7 volts on the tan and light green...  7 volts is not enough to build enough magnetic field to close the contacts...

i have had other forum members with burned inertia switches...  that prevented the car from running..


if you squeeze the fuel pump contacts closed.. get the engine running.. you should have almost the same voltage on 3 of the 4 wires on the fuel pump relay...  

orange and light blue.. full battery voltage..
pink and black .. full battery voltage.
red and black.. full battery voltage... this is the circuit i think you are having problems with..
if so... test the wiring at the inertia switch as i described..  

Post Reply
12 Last