'91 5.0 no go. Help!

Discussion in 'Fox 5.0 Mustang Tech' started by txstang347, Aug 9, 2007.

  1. txstang347

    txstang347 Member

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    I've done almost everything I can think of. I'll try to keep it short. 1991 5.0 Convertible. Symptoms: Car cranks and cranks but won't start. I have spark. The car starts when I shoot starter fluid in the throttle body, burns up, then dies. It sounds great when running so I don't suspect timing is an issue. The most odd sign is that I can hear the fuel pump priming, but it doesn't shut off after 2 or 3 seconds as it usually does. As long as I have the key in the on, engine off position the pump keeps priming (making that whine/hum sound). I thought it was a failed fuel pump relay so I replaced it but the one I got from Advanced Auto parts was crap and even when I took the key out the fuel pump stayed on. So I put the original back on and it stopped with the key out. This is what I've done so far:

    1. Siphoned out old gas. Put in new/clean 93 octane.
    2. Test fuel pressure at the shroeder valve. I got 40-42psi with key on position and 38-40 while engine cranking. So that is within the 35-45psi specs. (No fuel leaks)
    3. Replaced fuel filter.
    4. Replaced fuel pressure regulator (that was one hard piece to get to, I had to remove the throttle body, maf ducting, loosen the fuel rails, disconnect the heater core hoses just to make room for the hex tools and my hands to loosen the FPR!)
    5. Replace battery (wasn't holding charge).
    6. Cleaned carbon deposits from entire throttle body area.
    7. Tested injector wiring harness for voltage (good).

    The spark plugs are completely dry and the engine just keeps turning over. It does start and run with starter fluid until it burns up, then dies. So apparnetly I have fuel up to the pressure tester valve but it's not coming out of the fuel injectors. Is there a fuel injector relay or fuse? I've checked all the fuses and they are all fine. Could this be a bad sensor confusing the computer? I was told there was a fuel injector relay above the EEC IV, but I didn't see one and no parts stores carry a replacement. Has anyone ever heard of the fuel pump failing and still working (priming)? Could this be a vaccum issue? If so how do I test/check for vaccum pressure?

    I've ordered a Code reader so I'm waiting on that. Next step will be replacing the fuel pump (I'm going to be ****ed if I spend $100 on a pump and drop the tank and the car still won't start). After that I'll be at a loss.

    HELP!!!!
    Joe
     
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  2. HISSIN50

    HISSIN50 "How long does it take to get help in here?
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    Joe, the injectors receive VPWR (key-on constant 12 volts). There are individual drivers in the computer which provide the injectors with ground, thus energizing them. Use a noid light to check for injector pulsing. If none, confirm VPWR. Then check the TPS reading to ensure it is not above 3.7 volts. Go from there.

    Good luck.
     
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  3. enyawix

    enyawix Member

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    Remove the wire from a plug, try to start the engine, than smell the plug.
     
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  4. jrichker

    jrichker StangNet's favorite TOOL
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    Cranks OK, but No Start Checklist for Fuel Injected Mustangs

    Revised 29-Jun-2007 to update TPS testing procedure for 94-95 Mustangs

    All text applies to all models unless stated otherwise.

    Note: 94-95 specific changes are in red

    1.) Remove push on connector from starter solenoid and turn ignition switch on. Place car in neutral or Park and set the parking brake. Remove the coil wire from distributor & and hold it 3/8” away from the engine block. Jumper the screw to the big bolt on the starter solenoid that has the battery wire connected to it. You should get a nice fat blue spark.
    Most of the items are electrical in nature, so a test light, or even better, a voltmeter, is helpful to be sure they have power to them.
    No spark, possible failed items in order of their probability:
    A.) MSD or Crane ignition box if so equipped
    B.) Coil
    C.) TFI module
    D.) PIP sensor in distributor. The PIP sensor supplies the timing pulse to trigger the TFI and injectors. See paragraph 5A - a noid light will tell if the pip is working by flashing when the engine is cranking.
    E.) No ECC or computer power - ECC or computer relay failure
    86-93 models only: ECC relay next to computer - look for 12 volts at the fuel injector red wires
    94-95 models only: EEC or PCM power relay in the constant control relay module. Look for 12 volts at the fuel injector red wires.
    F.) No ECC or computer power - fuse or fuse link failure
    86-93 models only: Fuse links in wiring harness - look for 12 volts at the fuel injector red wires. All the fuse links live in a bundle up near the starter solenoid.
    94-95 models only: 20 amp EEC fuse in the engine compartment fuse box. Look for 12 volts at the fuel injector red wires.
    G.) Ignition switch - look for 12 volts at the ignition coil red/lt green wire. No 12 volts, blown fuse link or faulty ignition switch. Remove the plastic from around the ignition switch and look for 12 volts on the red/green wire with the switch in the Run position. No 12 volts and the ignition switch is faulty. If 12 volts is present in the Run position, then the fuse link is blown.
    94-95 models only: Check inside fuse panel for fuse #18 blown – 20 amp fuse
    H.) Computer
    J.) Engine fires briefly, but dies immediately when the key is released to the Run position. Crank the engine & when it fires off, pull the small push on connector (red wire) off the starter relay (Looks like it is stuck on a screw). Hold the switch in the crank position: if it continues to run there is a problem with either the ignition switch or TFI module. Check for 12 volts at the red/green wire on the coil with the switch in the Run position. Good 12 volts, then replace the TFI. No 12 volts, replace the ignition switch.

    See the following links for wiring diagrams...

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model cars
    Computer/fuel pump/ignition wiring diagram, 86 model http://www.autozone.com/images/cds/gif/large/0900823d80167158.gif
    Computer/fuel pump/ignition wiring diagram, 87 model http://www.autozone.com/images/cds/gif/large/0900823d8016715e.gif
    Computer/fuel pump/ignition wiring diagram, 88 model http://www.autozone.com/images/cds/gif/large/0900823d80167162.gif

    http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model cars
    Computer/fuel pump/ignition wiring diagram, 89-90 cars http://www.autozone.com/images/cds/gif/large/0900823d8019595f.gif
    Computer/fuel pump/ignition wiring diagram, 91-93 cars
    http://www.autozone.com/images/cds/gif/large/0900823d80195960.gif

    http://www.autozone.com/servlet/UiBroker?ForwardPage=/az/cds/en_us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model cars

    2.) Spark at coil wire, pull #1 plug wire off at the spark plug and check to see spark. No spark, possible failed items in order of their probability:
    A.) Moisture inside distributor – remove cap, dry off & spray with WD40
    B.) Distributor cap
    C.) Rotor
    D.) Spark Plug wires
    E.) Coil weak or intermittent - you should see 3/8" fat blue spark with a good coil

    3.) Spark at spark plug, but no start.
    Next, get a can of starting fluid (ether) from your local auto parts store: costs a $1.30 or so. Then pull the air duct off at the throttle body elbow, open the throttle, and spray the ether in it. Reconnect the air duct and try to start the car. Do not try to start the car without reconnecting the air duct.

    Two reasons:
    1.) If it backfires, the chance for a serious fire is increased.
    2.) On Mass Air cars, the computer needs to measure the MAF flow once the engine starts.
    If it starts then, you have a fuel management issue. Continue the checklist with emphasis of fuel related items that follow. If it doesn’t, then it is a computer or timing issue: see Step 4.

    Clue – listen for the fuel pump to prime when you first turn the ignition switch on. It should run for 5-20 seconds and shut off. To trick the fuel pump into running, find the EEC test connector and jump the connector in the Upper RH corner to ground. The EEC connector is near the wiper motor and LH hood hinge.
    [​IMG]

    If the relay & inertia switch are OK, you will have power to the pump. Check fuel pressure – remove the cap from the schrader valve behind the alternator and depress the core. Fuel should squirt out, catch it in a rag. Beware of fire hazard when you do this. In a pinch, you can use a tire pressure gauge to measure the fuel pressure. It may not be completely accurate, but you will have some clue as to how much pressure you have. If you have any doubts about having sufficient fuel flow/pressure, rent a fuel pressure test gauge from the auto parts store. That will tell you for sure if you have adequate fuel pressure.


    4.) No fuel pressure, possible failed items in order of their probability:
    A.) Tripped inertia switch – Coupe & hatch cars hide it under the plastic trim covering the driver's side taillight. Use the voltmeter or test light to make sure you have power to both sides of the switch
    B.) Fuel pump power relay – located under the driver’s seat in most stangs built before 92. On 92 and later model cars it is located below the Mass Air Flow meter. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
    C.) Clogged fuel filter
    D.) Failed fuel pump
    E.) 86-90 models only: Blown fuse link in wiring harness. Look for 12 volts at the Orange/Lt Blue wire on the fuel pump relay.
    91-93 models only Blown fuse link in wiring harness. Look for 12 volts at the Pink/Black wire on the fuel pump relay.
    The fuse links for all model years 86-93 live in the wiring harness near the starter solenoid.
    94-95 models only: 20 amp fuel pump fuse in the engine compartment fuse box. Look for 12 volts at the Dark green/yellow wire on the constant control relay module.
    F.) Engine seem to load up on fuel and may have black smoke at the tailpipe. Fuel pressure regulator failed. Remove the vacuum line from the regulator and inspect for fuel escaping while the pump is running. If fuel is coming out the vacuum port, the regulator has failed. Check the regulator vacuum line for fuel too. Disconnect it from the engine and blow air though it. If you find gas, the regulator has failed.

    5.) Fuel pressure OK, the injectors are not firing.
    A.) A noid light available from any auto parts store, is one way to test the injector wiring.
    The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in and it will flash if the injector is firing.
    B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it makes bubbles. Cheap if you have the stuff laying around, and works good too.
    D.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
    E.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).
    F.) No power and the 10 pin connections are good: look for broken wiring between the orange/black wire on the ECC relay and the red wire for the 10 pin connectors.
    G.) TPS voltage exceeds 3.7 volts with the throttle closed. This will shut off the injectors, since the computer uses this strategy to clear a flooded engine. Use a DVM, a pair of safety pins, and probe the black/white and green wires to measure the TPS voltage.
    On a 94-95 Mustang, probe the black/white and grey/white wires to measure the TPS voltage.
    It should be .5-.99 volts with the key on, engine not running. Note that if the black/white wire (signal ground) has a bad connection, you will get some strange readings. Make a second measurement using the battery post as the ground to eliminate any ground problems. If the readings are different by more than 5%, you may have a high resistance condition in the black/white signal ground circuit.

    6.) Spark & fuel pressure OK.
    A.) Failed IAB (no airflow to start engine). Press the throttle ¼ way down and try to start the car.
    B.) Failed computer (not very likely)
    C.) Engine ignition or cam timing off: only likely if the engine has been worked on recently).
    D.) Firing order off: HO & 351 use a different firing order from the non HO engines.
    HO & 351W 1-3-7-2-6-5-4-8
    Non HO 1-5-4-2-6-3-7-8
    E.) No start when hot - Press the throttle to the floor & try starting it if you get this far. If it starts, replace the ECT.
     
    #4
  5. txstang347

    txstang347 Member

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    :bang:
    Alright, I've gone through the entire list and this is what I've come up with and still NO START.

    I decided to buy a code scanner since I have three OBD Fords. Hooked up the code scanner to the Stang and got nothing. Tested the code scanner on '93 F-150 got code 111 (system pass) and same on a 90' Bronco II (code 11 system pass).

    I decided to pull the EEC IV from the Bronco II and hook it up to the Stang. I noticed that with the EEC IV from the Bronco the fuel pump primed for a few seconds and ACTUALLY shut off now. (The fuel pump would not shut off as long as it was in key on or crank position with original EEC IV) Bronco computer on the Mustang gave code reading of:

    (Key on Engine off testing)
    95 – Fuel pump secondary circuit fault (PCM to ground)
    AND
    89 – AXOD lockup solenoid (LUS) circuit failure or clutch converter override CCO circuit failure

    I'm assuming that code 95 is my starting problem, but what exactly is the secondary circuit? Is that the fuel pump relay? I've replaced the fuel pump relay once with a cheap Advanced Auto parts relay that made it worse. The fuel pump would not turn off even with the key out and the relay was hot as hell. I returned that stupid thing.

    Do I have an EEC IV problem? Did the computer crap out on me? Is there a way to verify/test that it's dead? Why would the original EEC IV not throw any codes, but the Bronco's did? Also, with the computer off the Bronco the engine sputters a bit now like it really wants to start but can't. With the original computer it would just crank and crank without sputtering.

    As for the 89 code I recently had an AOD rebuild and it sounds like that's the lock up solenoid in the torque converter. The tranny has or had been acting a bit funny.

    :bang:
    Thanks,
    Joe
     
    #5
  6. 86bluecobra

    86bluecobra Advanced Member

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    I'm not all together sure here but wouldn't the computer out of the bronco be set up for speed density not mass air? or is it just the harness you have to re pin?
     
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  7. txstang347

    txstang347 Member

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    Good Point!! That hadn't even crossed my mind. So do you think that that is the reason the car sounds like it really wants to start but won't and with the original computer it would just crank and crank? Is that a bad EEC IV?
     
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  8. txstang347

    txstang347 Member

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    I've narrowed it down to the fuel injectors not firing, but what would make all the injectors not fire? Any and all possibilities would be appreciated considering it's always the least likely scenario that happens to me.

    Joe
     
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  9. jrichker

    jrichker StangNet's favorite TOOL
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    You need to re-read the checklist - You missed something.

    See item 5.
    5.) Fuel pressure OK, the injectors are not firing.
    A.) A noid light available from any auto parts store, is one way to test the injector wiring.
    The noid light plugs into the fuel injector harness in place of any easily accessible injector. Plug it in
    and it will flash if the injector is firing.
    B.) I like to use an old injector with compressed air applied to the injector where the fuel rail would
    normally connect. I hook the whole thing up, apply compressed air to the injector and stick it in a
    paper cup of soapy water. When the engine cranks with the ignition switch on, if the injector fires, it
    makes bubbles. Cheap if you have the stuff laying around, and works good too.
    D.) Pull an injector wire connector off and look for 12 volts on the red wire when the ignition switch is on.
    E.) No power, then look for problems with the 10 pin connecter (salt & pepper shakers at the rear of the upper manifold).
    F.) No power and the 10 pin connections are good: look for broken wiring between the
    orange/black wire on the ECC relay and the red wire for the 10 pin connectors.
    G.) TPS voltage exceeds 3.7 volts with the throttle closed. This will shut off the injectors, since the
    computer uses this strategy to clear a flooded engine. Use a DVM, a pair of safety pins, and probe
    the black/white and green wires to measure the TPS voltage.
    On a 94-95 Mustang, probe the black/white and grey/white wires to measure the TPS voltage.
    It should be .5-.99 volts with the key on, engine not running. Note that if the black/white wire
    (signal ground) has a bad connection, you will get some strange readings. Make a second
    measurement using the battery post as the ground to eliminate any ground problems.
    If the readings are different by more than 5%, you may have a high resistance condition in the
    black/white signal ground circuit.


    Diagram courtesy of Tmoss & Stang&2birds
    [​IMG]

    See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.

    Ignition switch wiring
    http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

    Fuel, alternator, A/C and ignition wiring
    http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

    Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
    http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

    Vacuum diagram 89-93 Mustangs
    http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

    HVAC vacuum diagram
    http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

    TFI module differences & pinout
    http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

    Fuse box layout
    http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif
     
    #9
  10. Markstre302

    Markstre302 New Member

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    I had a similar issue once. Check the TPS voltage. Like it says in the checklist anything over 3.7 will shut off the injectors.
     
    #10
  11. ninety15.0

    ninety15.0 New Member

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    You also need to remember that the bronco is not going to use the HO firing order. You cant just toss the bronco ECU into the stang and hope that it works. The engine firing order is programed into the computer. So if your motor wanted to start you most likely have a computer issue....you are just telling the wrong injectors to fire at the wrong time. I think you should go through Jrichkers list and check the actual fuel injector and fuel pump circuits on the computer. Check his diagrams for the right pin and go to town with a test light or DMM. Good luck man..you'll get there.
     
    #11
  12. txstang347

    txstang347 Member

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    Thanks for the input ninety15.0. I agree, the bronco computer wasn't an attempt at fixing the problem. My original computer wasn't giving me any codes and the check engine light was blinking so I assumed there were codes to be had. Plugging up the Bronco computer was an attempt to pull the codes. I was hoping that the same codes would register and knowing that the Bronco computer had no codes they should've been valid.

    I had these two codes pop up:
    (Key on Engine off testing)
    95 – Fuel pump secondary circuit fault (PCM to ground)
    AND
    89 – AXOD lockup solenoid (LUS) circuit failure or clutch converter override CCO circuit failure [I recently had the AOD worked on and didn't have enought time with it to recognize a problem before the car broke down]

    The biggest problem is that the Mustang broke down in my hometown 6 hours away from where I live now. So I've been going down when I get a chance to work on it because I don't trust anyone to work on my car. I'm hoping to get her running on my next trip down in two weeks.

    Thanks to everyone who has chipped in their advise and Step # 5 is next on the list.
     
    #12
  13. Mike85000

    Mike85000 New Member

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    Good advice, but i think the EEC-IV in the mustangs are batch fire. Meaning the injectors fire in 2 banks, left and right, not sequentially. I could be wrong though.
     
    #13
  14. ninety15.0

    ninety15.0 New Member

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    I dont think that is the case. I use a tweecer to tune my car and one of the functions in the comp is firing order. It shows sequential injector firing....not bank specific. I might be misinterpreting that function but i think thats how it works. Someone else could chime in and put this one to bed...i would like to know for my own knowledge too! Thanks
     
    #14
  15. Mike85000

    Mike85000 New Member

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    Ok, Im still not 100% sure, but im reading that SD Stangs are bank firing whereas MAF Stangs are sequential. Can any experts confirm this?
     
    #15
  16. HISSIN50

    HISSIN50 "How long does it take to get help in here?
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    87+ should be SEFI.
     
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  17. txstang347

    txstang347 Member

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    Ok, I tired to get that pesky TFI out for testing. I was able to get one of the bolts out but the tool that I bought at Autozone won't fit in the area so I can get the last bolt out. I really don't want to pull the distributor out because that scares me. I don't want to disturb other areas if I don't need to that way I don't cause anymore problems by diggin' around. Any suggestions or other methods?

    Joe
     
    #17
  18. Fox8950

    Fox8950 Member

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    If you had spark why suspect the TFI just outta curiosity? ... hearing MANY accounts of people having problems with fuel pump being stuck on and injectors not pulsing ....
     
    #18
  19. txstang347

    txstang347 Member

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    Well several people have told me that the TFI factors in on when the injectors open and I'm assuming that's my problem. I really didn't want to mess with it but I figured if I could get it tested fairly easily and rule it out, why now.

    Got any insight as to what the problem was with the other people who were having similar problems?
     
    #19
  20. Fox8950

    Fox8950 Member

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    Can probably pull quite a bit up from search not sure if/how others have fixed it just know I have seen the question posed alot (constantly running FP and wont start but has spark/fuel pressure) . I've been wondering for a while now if the EEC cuts injector pulse when the fuel pump relay shorts to ground (which to me the code 95 suggests) and sticks in diagnostic mode (always on) but dunno might do a little test some day, those 2 things sure seem to happen a bit together.
     
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