87 Deville Has Fuel Pressure to the TBI But Injectors Activate
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Cadillac DeVille 1985 to 2005 including:
1985-1992 Fleetwood, 1993 Sixty Special, All FWD Forum Discussion, 87 Deville Has Fuel Pressure to the TBI But Injectors Activate in Past Cadillac Vehicle Discussion; Friends, my 1987 Deville has a new fuel pump, filter and pressure regulator. Fuel Pressure does reach the TBI But ...
  1. #1
    calichild is offline Cadillac Owners Member
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    87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    Friends, my 1987 Deville has a new fuel pump, filter and pressure regulator. Fuel Pressure does reach the TBI But the injectors won't release any fuel. The engine will start and continue to run for a couple of seconds if a bit of gas is poured down the TBI throat.

    Please give me a list of things to check and how to check them.
    My mechanical experience is community college automotive courses back in the early eighties and a few dozen fixer uppers. My diagnostic capabilities sux but I have an excellent understanding of electro/mechanical principals, including electronics and digital logic.

    Please help Obiwan, you're my only hope.

    PERTINENT INFORMATION I FORGOT TO ADD
    I am actually starting this for my nephew, the car ran then didn't run after an alternator swap. there is a brown wire with a green end with the alternator wires that I cannot tell where it goes. Someone else took the alternator off. To me it's a basket case, I am finishing someone's job.

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  3. #2
    basscatt's Avatar
    basscatt is offline Cadillac Owners 10000+ Posts
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    Quote Originally Posted by calichild View Post
    Friends, my 1987 Deville has a new fuel pump, filter and pressure regulator. Fuel Pressure does reach the TBI But the injectors won't release any fuel. The engine will start and continue to run for a couple of seconds if a bit of gas is poured down the TBI throat.

    Please give me a list of things to check and how to check them.
    My mechanical experience is community college automotive courses back in the early eighties and a few dozen fixer uppers. My diagnostic capabilities sux but I have an excellent understanding of electro/mechanical principals, including electronics and digital logic.

    Please help Obiwan, you're my only hope.
    -------------------------
    check for Diagnostic Trouble Codes -

    if you don't know how - go here and read the ENTIRE post -

    http://www.cadillacforums.com/forums...odes-dtcs.html

    if you have any codes - post them here -
    ALONG WITH THEIR DEFINITIONS -
    -------------------

    check
    ALL the fuses

  4. #3
    98eldo32v's Avatar
    98eldo32v is offline Cadillac Owners Connoisseur
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    I'd check fuses first. Wiring harnesses, and grounds. Plug connections at throttle body and ecm. A wiring diagram will be helpful also

    ----------

    The force is with you........always

  5. #4
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    &

  6. #5
    98eldo32v's Avatar
    98eldo32v is offline Cadillac Owners Connoisseur
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    OXYGEN SENSOR

    The oxygen sensor in the DFI system consists of a closed end Zirconia sensor placed in the engine exhaust gas stream This sensor generates a very weak voltage signal that varies with the oxygen content of the exhaust stream. As the oxygen content of the exhaust stream increases relative to the surrounding atmosphere, a lean fuel mixture is indicated by a low voltage output, as the oxygen content decreases, a rich fuel mixture is indicated by a rising voltage output from the sensor.

    When the oxygen sensor is warm 392�F (200�C) The output voltage swings between 200 millivolts (lean mixture) and 800 millivolts (rich mixture). However, when the oxygen sensor is cold (below 392�F), the voltage output drops below this range and the response time of the sensor is much slower. The sensor cannot react quickly to rich-lean or lean-rich transitions; therefore, the sensor does not supply accurate information to the ECM. The output voltage may be read using a high impedance digital voltmeter.

    NOTE: The high impedance digital voltmeter must a minimum 5 mega-ohm input impedance. Digital voltmeter's with a lower input impedance may cause an inaccurate reading or force the system to behave incorrectly.

    Some 1985 FWD DeVilles and Fleetwoods may experience a lean driveability condition and possibly ECM diagnostic codes 13 and or 45. Symptoms of a lean driveability condition can cause chuggle, surge sag, or reduced engine performance. This condition may be caused by a voltage difference between the oxygen sensor ground (engine block) and the ECM oxygen sensor ground reference, circuit 413, which connects to the generator bracket. Should a poor ground exist, the voltage difference between these two grounds is added to the oxygen sensor signal, falsely indicating a rich (high voltage) oxygen sensor signal to the ECM. The ECM compensates for a high oxygen sensor voltage by commanding a lean mixture.

    If the generator stud has a black or brown single wire ring terminal on it, then the ECM oxygen sensor ground must be relocated. If the generator stud does nut have a" black or brown" single wire ring terminal on it, then the ECM oxygen sensor ground has been relocated. So proceed to the trouble code diagnosis if a code 13 or 45 is present

  7. #6
    STS_Seville_Hunter is offline Cadillac Owners Enthusiast
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    Doesn't the icm in the distributor control the injectors?

  8. #7
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    The OP commented on a "brown wire" that doesn't "have" a home since an alternator change.

    I now have given him the information needed to give that wire a home.

    That "brown" wire is a ground obviously for the oxygen sensor circuit.

    Since the circuit is now ungrounded, this could possibly lead to some of the issues encountered.

  9. #8
    Ranger's Avatar
    Ranger is offline Cadillac Owners Member
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    Quote Originally Posted by STS_Seville_Hunter View Post
    Doesn't the icm in the distributor control the injectors?
    No, pretty sure even in the '87, the injectors are controlled by the PCM or as it was called back then, the ECM.

  10. #9
    drewsdeville is offline Cadillac Owners Master
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    The injectors are controlled by the ecm, which uses signal from the ICM as a baseline trigger. They work in tandem.

    That brown wire with green connector that goes to nowhere... that's used to ground the alternator out when performing voltage sensitive diagnostic procedures - such as adjusting the TPS. Under normal circumstances, it's not plugged into anything.

    An oxygen sensor problem will not prevent the injectors from pulsing. The car will start and run without them even plugged in.

  11. #10
    basscatt's Avatar
    basscatt is offline Cadillac Owners 10000+ Posts
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    Quote Originally Posted by 98eldo32v View Post
    The OP commented on a "brown wire" that doesn't "have" a home since an alternator change.

    I now have given him the information needed to give that wire a home.

    That "brown" wire is a ground obviously for the oxygen sensor circuit.

    Since the circuit is now ungrounded, this could possibly lead to some of the issues encountered.
    ------------------------
    actually - the brown wire - with the green plug
    is used to ground out the alternator -
    typically done while setting the ISC motor and/or TPS -

  12. #11
    limo1 is offline Cadillac Owners Member
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    Re: 87 Deville Has Fuel Pressure to the TBI But Injectors Activate

    Things to check for no ECM control to the injectors.
    The 15amp fuse for ECM good should be able to go into diagnostic mode and look at things like TPS MAP
    Check the injector fuses under the dash remove the under dash covering and confirm the two 3 amp fuses in the relay center are good, do you happen to have a an alarm immobilizer this is where I would wire it into.
    . you should be able to measure 12V on the injector hot PINS.
    Remove the injector connectors and measure the resistance of the injector coils should be a couple ohms. also measure the injector coils to ground they should show very high resistance (not coil short to ground).
    You can also test the injectors when in the car with some fuel pressure by using a 9V smoke alarm battery and just touch the injector pins and it should squirt fuel try both injectors to confirm they are not clogged up internally.
    The ECM supplies switched grounds to the injectors confirm the ECM grounds are all good check them on the motor close to the alternator grounding stud. also check the O2 ground terminal at same time.
    It is possible the ECM has blown transistors supplying the injector grounds, they can be replaced if blown.
    confirm the ECM connector is good and not corroded.
    confirm the injector wires are not being pinched when you put the air cleaner on the shroud and tighten. it is possible wires are being grounded and blowing injector fuses.
    also you can confirm the oil pressure switch is functioning as the ECM will activate the fuel pump for few seconds but it is then parallel with the oil pressure switch to keep fuel pump operating as long as oil pressure in motor.
    Two wires on the oil pressure switch can be jumper-ed to keep fuel pump running with no oil pressure. the third pin on oil pressure sensor is the actual oil pressure light .
    good luck

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