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Thread: In need of advice

  1. #1
    Join Date
    Oct 2019
    Posts
    3

    In need of advice

    I am looking to gain a bit of knowledge and tech advice for my 93 SC. So with that said, I've got a few questions.

    Let me give a bit of a run down on what's going on first, to bring everyone up to speed. I Bought the car a couple months back and was told it had been sitting for 10 years roughly. The P.O. said he went out one day to start it up after it has been sitting for some time while he was out of state ( snow bird ) it would crank but wouldn't start, so he just let it sit, said he figured he would fix it one day...

    When I got it home, I put a battery in it, it cranked but no start. Noticed the shift light was staying on while cranking. I had a base line of what the issue might have been at that point. So, I decided to go through the whole ignition system. I've replaced the following --

    * Crank positioning sensor

    * ( I set the air gap properly by removing the harmonic balancer and making sure the vanes did not touch on either side. While the HB was off, it was inspected and checked over thoroughly and reinstalled with an ARP bolt with the identical OD, length, and thread pitch, torqued to spec )

    * Cam sensor and synchronizer ( TDC on compression stroke + 26 and used the little plastic tool and got everything aligned and snugged up accordingly to spec. )

    * DIS ( OK, now this is/was a new motorcraft part still like the box that my grandad had sitting in his shop for his 89 SC. This was installed with dielectric heatsink white paste. )

    * Plugs
    * Wires ( 1,2,3. 5,6,4 )
    * Coil pack

    * Ignition switch module ( This is another new in the box spare for the 89 SC we had )

    *** And just to be on the safe side, i
    * Flushed the fuel tank
    * Checked and inspected the sending unit
    * New fuel pump, strainer, and filter
    * New fuel pressure regulator

    ( I feel like I am missing something here... )

    Oh well, anyways..

    Since then, I've managed to get the car to start, idle and die and will not start back up unless I let it sit for a while, or i have it WOT, which temporarily disables the fuel injectors during cranking. ( At least this is what I've been able to gather from research. )

    At which point, the only way I am able to keep it running ( and only for a short period of time ) is, if I gingerly fan the throttle. But here's the odd thing under throttle it drops in RPM until I let off the gas. Once I let off, the rpms start to raise, then drop. It will not stay running for longer then 30 seconds AT THE VERY MOST before it just dies.

    From when I first got the SC, tonight ( 1/12 ) is the first time I've gotten the bird to show any sign of life at all. So, I know I am on the right path.

    I've gone through the no start check check list, I've verified that there is 40 +/- PSI at the rail, it has nice blue spark at all 6 wires, the shift light turns off while cranking, the tach is working, checked grounds, checked passenger frame ground, inspected as much of the wiring harness as possible, I've checked all the fuses under the hood and under the dash with a test light, I've tried to get the obd1 system to give me trouble codes but I haven't been able to get the car to run long enough, and since the battery has been removed and replaced, the memory banks have been cleared of any codes.

    SO.. Here are my questions...

    How can I test the ECU ( located on the passenger side behind the kicker panel ) ?

    How can one determine that the ECU is the issue?

    I have a known, good ECU from an 89 SC 5speed can I use the 89 ECU in the 93, it's also a 5speed?

    I've noticed, that 99% of the electrical components are identical to the 89 SC. Both of which are OBD1, and in this particular case, they are both standard transmission as well.

    I know that 94 is when the electrical had undergone major changes, If there are any differences between the 89 and 93, could someone share some knowledge with me about what changes that where made or what is different between 89 to 93?

    What are the chances of all 6 injector pintles being clogged and not allowing them to energize and deliver fuel properly?

    Have I missed any other component for the ignition?

    Where should I go from this point?

    THANK YOU!!

    Mason N.

  2. #2
    Join Date
    Dec 2007
    Location
    Salem OR
    Posts
    7,272
    Mason:

    If it sat for ten years there is a good chance one or more injectors are gummed up/stuck and not operating properly.

    Best way I know to test an EEC is to swap it for a known working unit. I'd stick with the one that matches your trans/year.

    Off hand, your symptoms could indicate vacuum leaks. Did you inspect inside the throttle body for residue on the throttle plate and inside of the housing just downstream of the plate?

    I'd cast a wide net and expect to find more than one root cause at this point, tho. If you went thru the no-start, and ohm'd out ground paths as it notes, I'd say so far you done due diligence. Be sure to cover the basics, such as a fully charged battery 12.3v resting would be nice, not below 11.8v, center bolt snugged down in the EEC. Don't just eyeball grounds, replace if older as corrosion can hide under the sheath/bolt whatever.

    About the balancer, I've heard cases where the outer ring can shift on the rubber isolator ring, causing timing issues but otherwise passing a visual check. I assume to examined the balancer for missing chunks, signs of pending failure, etc.

    Checking for vacuum leaks/replacing~securing hoses/lines is low hanging fruit compared to pulling and servicing/replacing injectors, so I'd start there. IAC, intercooler tube flanges, etc. Might be intake manifold gaskets, but those can take a bit more to deal with, perhaps at the same time as pulling injectors.

    Injectors can often be sent out and checked/cleaned and put back into service for less money than buying refurbs/new, so keep your options in mind. Search here for details on getting to them, etc.

    If you disconnect the cam sensor, can you eventually get it to fire/run? How are your electrical troubleshooting skills? Know how to use an oscilloscope?

    Where are you and the SC located, BTW?

    Ken
    Last edited by KMT; 01-12-2020 at 06:14 PM.

  3. #3
    Join Date
    May 2018
    Location
    Irmo SC
    Posts
    88
    So I had a similar issue with my 90 SC 5sp way back I'm not saying for sure this is your issue but might be worth a shot now KMT definitely knows more than I do but on mine I found that the catalic converters where clogged up I found that out on mistake I was under mine and accidentally touched the exhaust pipe and it was cold but the car had just been running so I GENTLY touched the engine side of the cat and it was scalding hot so pulled the y pipe and sure enough clogged up fixed that issue runs and idles

  4. #4
    Join Date
    Apr 2002
    Location
    English, IN
    Posts
    4,511
    As previously noted, I'd be checking hard for vacuum leaks.
    Matt Haub
    Shootouts: '09 SS 1st | '10 Mod1 2nd | '11 Bracket 3rd | '12 Bracket 1st | 2013 | '14 Bracket 3rd | 2015 | '16 Bracket 1st & Mod2 2nd | '17 Spectator | '18 Freeze-Plug Champ
    Black '89 5spd - 281K miles, MPx, Alky-Inj 387rwhp, 438rwtq (new motor) Best 1/4mi:12.521, MPH:107.23mph (old motor)
    35th Anniversary Auto 46k miles | Red '93 Auto 186k miles
    My Garage

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