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Fuel pump won't work

 
jeff69
New User
Posts: 16
Joined: 06/13
Posted: 06/18/13 02:46 PM

Hi all, I have a 1992 mustang gt, and the fuel pump won't run.  I bought a new relay but it still won't run.  Sometimes I tap or move the relay and the pump will run but won't shut off till I turn the key off. It has a A9L computer in it.

I bypass the relay and the pump will run, but car won't start.  I'm thinking that the puter is faulty but not sure.  Was gonna try to find the fuseible link and test that(not sure where to find it).  I tested the pin #22 wire from the computer for voltage and only got 5-volts. not sure why there isn't 12v.

Any help would be great.  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/18/13 11:03 PM

the EEC4 main relay is turned on by the ignition switch...  does this turn on ?????

the fuel pump relay has several sources of power...

the coil winding positive comes from the EEC4 main relay...     the negative winding is controlled by the ECM and pulled to ground to activate the relay...

since you can jump the power terminals on the fuel pump relay and get the fuel pump to run...

then we need to examine the 92 5.0 wiring diagram closely..

you can short pin 926 to ground on the diagnostic connector.. to force the fuel pump relay ON...

Dlc Eeciv Zpse2a607e9



now .. at the eec main and fuel pump relays...

key OFF...  

main relay.. should have power on the YELLOW wire..
fuel pump relay should have power on the Pink and black striped wire.

both of these fusible links are at the starter relay on the inner fender...

KEY ON..

power on the red wire out of the main relay..

and on the

RED and green wire to the relay coil  from the ignition switch..

you should also have power on the RED wire into the coil windings of the fuel pump relay...

if you ground pin 926 above.. light blue and ORANGE striped wire into the EEC4 diagnostic connector.. when the key is on.. you should hear the fuel pump relay click...  and then have power on the dark green and yellow striped wire to the inertia switch then the fuel pump..   the dark green wire also runs to the ECM pin 19.. so the ECM can monitor the fuel pump ON signal..  

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jeff69
New User
Posts: 16
Joined: 06/13
Posted: 06/22/13 08:48 AM

Thanks for the diagram, but I'm not good at electrical.  Can you tell me how to easily check the computer?  I have 5 volts coming from pin # 21, shouldn't there be 12v?  thanks for your help.  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/24/13 11:51 AM

jeff.. sorry i took so long.. got distracted... so this morning i did some art work...

warning... FORD wired the relays for the fuel pump and EECIV main power differently than whats done on the drawings...

follow the colored numbers... to match the drawings...


91 93 EECIV 50 Fuelpumprelaywiring Zpsfd8d7168  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/24/13 11:52 AM

here is the full diagram...

91 93 50 EEC4 Enginecontrolwiring Zps655c81e0  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/24/13 12:12 PM

jeff... lets go thru this.... and i think that some mustangs might use a big relay box called a CCRM... it will look like a computer..  but be  black and have probably a BC on it..

test part one...
key OFF... do you have power on
the PINK AND BLACK Stripe wire into the FUEL PUMP RELAY
and on the
Yellow wire into the  main relay... and if you have it disconnected to PIN 1..

that is KEY off.. or even PIN ON...

~~~~~~~~~~~~~~~~~~~~
test part two
now... reach in and turn the key on...  do you get power coming out the RED and green stripe Wire on the main relay connector...

and then red wire coming out of the main relay and going to the fuel pump relay?????  this red wire also powers a bunch of other stuff on the engine...

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
test part 3.
now... with the fuel pump relay ready for testing... do you get power on the GREEN and yellow striped wire coming out of the fuel pump relay for 2 seconds when you first turn the key on.. and while cranking??????? yes or no...

can you hear the fuel pump run..???  does it build fuel pressure when you test it at the fuel test port on the fuel rail using the special adaptor and a fuel injection pressure tester..???

does any of this make sense???

the key turning on sends power to the red and green wire to activate the main relay...

the main relay sends power out the RED wire to the coil windings of the fuel pump relay and also powers things like the fuel injectors .. canister purge solenoid and the map sensor.

the computer sees the main relay send power to pin 37 and shorts pin 22 to ground for 2 seconds to prime the fuel system by closing the relay...   when you start to crank the engine and get signal from the TFI circuit on pin 4  it will close the fuel pump relay again to allow the fuel pump to run...

i wonder if you have a LOOSE terminal in the relay socket that is not gripping the pins on the relay tightly.. or were your relays upside down in the engine bay and they got filled with water..
i know you replaced it.. but the MAIN RELAY SENDS power to the fuel pump relay coil winding... so the computer can control the fuel pump relay...

print the diagrams..

follow the info i have written...  

post what happens...

there is another forum member who had almost an identical issue... but i don't remember if he was able to fix it other than bypassing the relay..  

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jeff69
New User
Posts: 16
Joined: 06/13
Posted: 06/25/13 04:47 PM

Nice art work.  I was out the last few days(30c) and tried spraying gas into the TB.
When I turn the key nd rolled it over, it ran till gas was gone.  I grounded the pump and when it was running I tried starting it, no go. I'm trying to test the main relay in the next day or so to see if I have power where I should. when the pump was running continusly (grounded) I pushed the shreder valve and only got a dribble, no spray.  Could this mean that the pump is gone?  I don't no how to trouble shoot this stuff.

I also tested the ignition switch, was told that I should have power to the 2 yellow wires all time, And I do.  I run 12v to the inert switch an it runs continuously. why won't it prime and then shut off?  Hope you can make some sense of my jibber.
Any help you got I'll take.  I'll get back to you when testing is done.  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/25/13 05:41 PM

jeff... you could have several issues...


you could have something as simple as DIRTY connections at the starter relay on the inner fender ...


follow the positive battery cable down to the starter relay on the inner fender... one of the big studs will have a bunch of wires on it...

disconnect the battery...   sometimes its easier to remove the battery..

count the wires on the same stud with the battery positive cable.. take the nut off... take the ring terminals off.. wire brush both sides of each one...   wire brush the stud and the faces of the nuts.. reassemble.. count the number of wires to verify you have reconnected all of them...

this is the first place i would check..

next... i might drop the knee panel under the dash... and carefully remove the upper and lower column shrouds...  some models you do have to slightly drop the column... or change the tilt position ...    examine the bottom side of the ignition switch...  see that its NOT separating.. its only held in place with little fingers.. and they break and the spring pressure from the sliding contacts pushes the switch apart...  

hint... use a long thin screw driver to dent the sides of the tamper proof screw heads... then angle the screw driver to knock them loose...   use needle nose to unscrew them.. this saves a bunch of time extracting them..  hah.. use the same screw to go back in.. ignition switches are under 20 bucks at almost every parts store.. and will drive you mad with hidden failures...  i chased issues for a year on my former landlords car... it would stall at stop signs and red lights...  but i could never duplicate it...  drove me and her nuts.. another shop.. had changed all kinds of stuff... except the ignition switch..

turned out that the contacts inside the switch were slightly burned away.. and when her big ring of keys she had would swing forward at stop signs would be just enough to shut off the car..  she always handed us a bare spare key.. so we could never duplicate the issue.. i spotted it one day when she was backing out of the driveway and the car stalled.. i had a test light in my hand.. i shoved the probe into the coil positive connector.. grounded the clip end.. and slowly rolled the ignition key from off to on and then into the cranking position.. when i released from the cranking position.. the light went out instead of staying on.. the key was in the ON position. but the ignition power was gone...  20 buck fix... no more issues...

other issue on her car was the other shop had replaced the water pump.. but had broken off the battery ground terminal at the engine block.. no problem.. they installed a new one.. but they used a #2 battery ring terminal end.. on the #6 wire. and just hammered it flat..  the wire was LOOSE in the ring terminal... this is where i found the voltage drop test handy...

as when the car failed to start.. i could get about 9 volts from the negative battery post to the engine block...   9 volts of difference only when the engine was attempting to crank..  hmm...

just thinking about that shop.. i should stop by.. i have not seen them in almost 20 years... i should show them the voltage drop test...

did i post that above...

Voltagedroptesting




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

below is the test on the ignition switch... use a test light into the coil positive and ground the clip end..

what happens???





Fordignitionswitchpinouts  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/25/13 05:48 PM

jeff.. you could also have a bad fuel pump...


hint... with 2 people... one seated and cranking the engine.. the other pounding gently with a big rubber mallet on the bottom of the fuel tank..  if it has a high pressure intank pump.. will sometimes get the pump started one more time..

if you have a low pressure intank pump and an external high pressure pump....

please disconnect the line going into the high pressure pump.. have somebody cycle the key on.. see if the intank low pressure pump works....   if it does.. then hook up the high pressure pump.. does it run when you first pull on the key??

external pumps have a high failure rate when the filters get clogged..  

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jeff69
New User
Posts: 16
Joined: 06/13
Posted: 06/25/13 06:50 PM

thanks for all your help, will try later when I get a chance, very frustrating to not no where or what to look for.  One day it worked and not the next.hmmmm.  Will let you no what I find.  

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jeff69
New User
Posts: 16
Joined: 06/13
Posted: 06/27/13 07:01 AM

The answer to you test 1 and 2 ?'s is YES.  Can't do test 3 alone.LOL  Will try later with help.  Can I bypass the eec relay just for testing purpose to see if fp will run?  Sometime when I shake the FP relay the pump will run steady???  Why can't I just get the pump to prime like it should with key on?  When I cleaned the starter relay wires and put it back together I got the FP to prime like it should, did this 3 times.  Then I went to crank it and it didn't start and I tried again and I didn't have a pump running this time....Frown   Getting frustrated.  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/27/13 07:39 AM

yes.. you can bypass the eec power relay.. but its NOT computer controlled.. it comes on when the key is turned on with the power to the red and green wire..



when you ground the blue and orange wire   this should make the relay click...  you should also get power out of the dark green and yellow wire.. even without the engine being cranked... this is a stand alone test of the ability of the relays to operate the fuel pump/s...

if you operate the relay.. or jump the 3 to 5 terminal with a proper jumper.. or take the cover off an spare fuel pump relay.. so you can close the contacts with your fingers.. the fuel pump should run...

i am thinking that if you shake the relay.. and you can make the fuel pump run constantly.. you have an issue with the relay... replace it.. they are under 20 bucks.

warning.. please verify the wiring colors to the fuel pump relay... i keep running into data that shows these models use a CCRM box for eec main relay and fuel pump relay controls..  

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jeff69
New User
Posts: 16
Joined: 06/13
Posted: 06/27/13 11:13 AM

When I jump 3 to 5 terminal I don't hear the fuel pump run.  no sound at all.  The FP relay that I tap on to get pump to run is a new one I just bought. Hmmmm. I'm very confused.  

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jeff69
New User
Posts: 16
Joined: 06/13
Posted: 06/27/13 12:12 PM

I just tested pin #19 0n the computer( Green/with yellow strip) that goes to the FPR and it tested a short(Grounded to body) this isn't good is, it?  I'm almost certain tha the computer is the Problem.  What do you think?  

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waynep712222
User
Posts: 124
Joined: 03/13
Posted: 06/27/13 02:18 PM

PIN 19... If the fuel pumps are connected will show a short to ground... right thru the fuel pumps..

i don't know what the ECM would show...

the wire that goes to PIN 19 is the fuel pump voltage monitor...

the ECM looks at the fuel pump circuit voltage... if the voltage is low..  the computer will set a trouble code... alerting any techs to the issue..


check your messages to the left of where you log out at..    call me...  

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