Help Please

Discussion in 'SN95 4.6L Mustang Tech' started by Jim5208, Aug 3, 2017.

  1. I have a 1997 Mustang GT 4.6.. when i turn the key on, the fuel pump, injectors and fan keeps running, will not start fills cylinders with gas. Checked for codes all I'm getting are O2 sensors. Replaced EEC today started ran for 20 mins or so than stopped and started doing the same thing.. Any ideas of what i need to do?
     
  2. Welcome to the forums. I'll move this over to sn95 tech for you. They'll be able to help you.
     
  3. Okay Thank you
     
  4. Just to confirm. You replaced the PCM and still have the exact same symptom?

    Do all of the cylinders fill with gas or just one?

    However, if injectors are being held open and it's not a bad PCM, then the next most likely cause is a short to ground in the injector return signal wire. Do you have a "noid" style test light to confirm firing pulse across each injector?

    It's always a good idea to post the full DTC codes. There are 1,000's of them and they each have a story to tell.

    But if looking for an educated guess, for the 1996-1998 model year the O2 heaters draw their power through the PCM. Perhaps there's something going on with that circuit. Suggest disconnecting all (4) O2 sensor electrical connectors to see if this changes the symptom.
     
  5. No i dont have a noid tester, it seams to be number 4 and 6 that fill with the most gas. The rest have some but not as much. Ive pulled the fuel pump fuse, than unplugged one injector at a time. All injectors unplugged relay in bcm still clicking.
     
  6. I don't understand this. Are you saying that the CCRM in the right front fender well is clicking? If so, this is a huge symptom. Likely means a bad CCRM ground. But this could also be a bad ignition switch. More testing needed.

    FWIIW, a noid test light set can be rented under most auto parts stores "rent a tool" program. Harbor Freight has an affordable set as well.
     
  7. Yes it is clicking, can ground be fixed or do i need to replace?
     
  8. There's a black wire with a white strip that goes from the radiator core support around the battery. It connects to a round single pin connector. This is the CCRM and PCM ground. Start first there.

    There's also a ground on the right side radiator core support. It's under the intake air cleaner and easier to see with the air filter removed.

    If unable to find an obvious ground issue then try measuring the Ohm resistance from the CCRM black/white wires back to battery negative. Post. Be sure to zero the VOM before taking measurements and be sure to disconnect the battery positive to ensure there's no active voltage.
     
  9. Checked all grounds, resistants is 0.3 Ground coming from ccrm is 1.00.
     
  10. Im using my fluke 87 to check ohms
     
  11. Also tonight 1234 injectors were not pulsating. 5678 was pulsating.
     
  12. Need to test and CONFIRM key on +12 volts at each injector. Use a KNOWN good ground. There must be +12 volts at each injector with the key on. What we are trying to do is determine IF the injector isn't pulsing because of "no power' or "no firing pulse".

    1 Ohm resistance for a heavy gauge ground wire is very high. This should be a fractional Ohm.

    Here's some information on how to perform a voltage drop test. But I suspect the voltage drop test will also show the poor CCRM ground. Also focus on the CCRM connector. I have helped more than one person with a CCRM issue that the issue turned out to be bent/pushed/overheated pins at the CCRM.

    Howto perform charging system voltage drop test
    https://www.stangnet.com/mustang-fo...perform-charging-system-voltage-drop-test.56/
     
  13. Yes 12 v at all injectors
     
  14. I've checked the black and white wire at the connecter of the ccrm, its reading.06
     
  15. I picked up a new injector thought one of them might be shorting out. Pluged it into each injector plugging made no difference. I did notice that 1234 injectors that are not pulsating was warm.
     
  16. The reading at the CCRM is 0.06 what (units of measure volts/Ohms)? Is the CCRM still clicking?

    Does the cooling fan still run all the time?

    Have inspected the area around the PCM for evidence of water damage or rodent activity? How about the rest of the engine wiring harness?

    Will the PCM "talk" to an ODB2 reader?

    Going back to the original problem statement that changing the PCM did not change the symptom. So if we assume that the PCM is good and the same set of injectors are still firing all the time that implies a short to ground in the signal return lines. Might be a good idea to Ohm out each of the signal return lines back to the PCM. Measure to a known good ground with the PCM and fuel injector disconnected.

    Do you have a full set of Ford wiring diagrams? If interested in getting a set for yourself I maybe able to help. PM if interested.
     
    #16 wmburns, Aug 5, 2017
    Last edited: Aug 8, 2017
  17. Yes at the connecter it was 0.6 ccrm is still clicking. Ive checked all returns #5 im getting a reading of 0.938 all the rest are 0.0
     
  18. Yes im able to connect to pcm.
     
  19. I checked the returns at the injector plugin.
     
  20. Im using my verus scanner to connect to the pcm ran koeo only codes are o2 heaters