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Thread: 1991 Fox Body Spark Woes

  1. #1

    Default 1991 Fox Body Spark Woes

    Hi all. Now that I can create a post, I'd like the get some feedback on what my issue could be. I installed the Holley Terminator X in my Fox body and it went smooth. Very straightforward and fairly easy comparatively. I was able to do the initial start easily, on the first try. I hear cycled the car a few times and decided to cleanup some wiring for the stock gauges. I very stupidly (after having battery out of car for four months doing many other upgrades & work) neglected to disconnect the negative battery terminal and grounded out a wire from the starter relay onto the coil. This caused the TFI module to fry and I melted the small ground off the negative battery terminal. I replaced everything in the ignition system and repaired the ground.

    My issue is I'm getting no spark. My TFI intermediary harness has continuity and all appears to be in good shape. The white signal wire is good, and all is getting the correct 12V where needed. When I unplug the main harness input connector (J1A) I get spark! I have checked all grounds on the harness and have checked continuity from the ignition plug back to the J1A, all good. When I switch on the ignition, the handheld fires up and loads fine. I get a BLUE LED on the Cam Signal on the ECU. I'm getting NO RPM SIGNAL not to the handheld, and not that I can see on the factory tachometer.

    I'm not sure where else to go from here. The ECU has been swapped out for a known good one, and it has the same issue. Could it still be in the Holley EFI Main Harness? Should I replace that? Is there anything else I can test, or any direction I should go? Thanks for helping! This is starting to get a little frustrating, of course my own fault, but still. I hate it when I can't figure something out.

  2. #2
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    Dec 2009
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    https://forums.holley.com/showthread...540#post239540 (Check Ford TFI ignition adapter connector.)
    http://forums.holley.com/showthread....5760#post45760 (Scroll down to "Typical No-Start Checks".)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  3. #3

    Default

    I'll need to put it all back together to check to see if it's bad connections in the TFI harness. We did notice some "bent(ish) pins in the harness itself and did some work on it, but it's still not right. I'll go back to check it all when I get it all plugged back in. Most of the typical no-start checks are good to go besides the ignition ones I've listed above. No RPM signal being the main one. I'll check each & every power and ground to all sensors again too, but all were good before.

  4. #4
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    Quote Originally Posted by AaronFtWorth View Post
    No RPM signal being the main one.
    No RPM signal is why it doesn't start. Check the crank sensor (TFI distributor based in your case). The Ford TFI distributor's Hall-Effect PIP sensor is the crank sensor, and the TFI module transmits crank & cam sensor signals. Since RPM is derived from the crank sensor, I'd investigate that first. Replace the ignition module with a genuine Ford Motorcraft TFI ignition module. Also, ensure the Switched +12V red/white wire is powered in the "Run" and "Crank" key positions.
    https://forums.holley.com/showthread...3-No-Spark-TFI (Related Forum Thread)

  5. #5

    Default

    10-4, I'll check the +12V in cranking and keyed on positions.

    This ran fine with the DUI TFI module. The PIP was replaced as well. This is a brand new DUI Hot Forged distributor as well. But I get spark when the ECU is unplugged, so to me that means the ignition outside of the Holley system shouldn't be the issue. I'm not even sure I can get a genuine Ford Motorcraft TFI module these days. But I'll try.

    Yes, agree, the RPM signal is why I'm getting no spark, and no injector fire either.

    It's worth noting that the very first 2-3 starting tries after the electrical fubar, it *tried* to run (terribly, chugged and never stayed started), then went into this no spark at all issue.

    The TFI module is tested good. The PIP has been replaced, the ECU has been swapped for a known working unit, still no change.

    After I get it together, I'll check the power +12V on the red/white wire and be sure it's getting +12V with ignition on, and when cranking as well. I'll also check the seating of the TFI harness, and report back.

    I also read that last forum link, that's pretty wild that could happen. I'll also say each & every time I tried to start, but got no spark I'd redo the TPS calibration, and go through the initial handheld setup, and ignition cycle before trying again. Maybe the handheld is playing tricks.

  6. #6

    Default

    OK, so I put it all back together today to try and troubleshoot some more. I started with the baseline of "will it start", and went through a TPS setup and initial startup Wizard again. Tried to crank, cranks well, but I get no start. Popped the coil wire off the top of the distributor and put in a spare plug and I get no spark while cranking.

    I messed with the TFI harness female plug to be sure everything was right and tight and making contact. To my knowledge, it is and looks fine. Also tried to "play" with the plug while cranking and nothing changes, still no spark/start.

    I stabbed the red/white wire (that in the instructions says to wire into the positive side of the coil) and verified that it's +12V, but it has a drop to about 8-9 volts while cranking.

    I've yet to hook it up to a laptop and make sure the settings in the handheld are "holding true" and not mysteriously changing. But I'll do that shortly.

    Starting to get pretty frustrating though.
    EDIT: Also, not getting RPM signal on tach, or on Holley handheld. Nothing at all in either place.
    Last edited by AaronFtWorth; 05-08-2021 at 02:46 PM.

  7. #7
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    Quote Originally Posted by AaronFtWorth View Post
    EDIT: Also, not getting RPM signal on tach, or on Holley handheld. Nothing at all in either place.
    Read post #4 above.
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS T/W 11R 205 heads, 232°-244° duration/.623" lift/114° LSA camshaft, 12:1 C/R, TFS R-Series FTI ported intake, BBK 80mm T/B, Holley Dominator MPFI & DIS, 36-1 crank trigger, 1x cam sync, 200A 3G alternator, Optima Red battery, R134a A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans, Frostbite 3-core aluminum radiator, Pypes dual 2.5" exhaust, off-road X-pipe, shorty headers, -6AN fuel system plumbing, Walbro 255 LPH pump, S&W subframe connectors, BMR upper & lower torque box reinforcements, LenTech Strip Terminator wide-ratio AOD, 3000 RPM converter, B&M Hammer shifter, Stifflers trans crossmember & driveshaft safety loop, FPP aluminum driveshaft, FPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 M/T Street Comp tires.

  8. #8

    Default

    The TFI is good, tested on a test machine. If I can figure out the no RPM then I'm sure this will work. So far, I can't figure it out. I've read all the posts and linked posts you supplied. I appreciate the help too sir.

  9. #9
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    Since RPM is derived from the distributor's internal crank sensor, I'd investigate the distributor and its wiring to the Sniper EFI.

  10. #10

    Default

    Can you try to explain why I'm seeing spark with the ECU unplugged? Then with it plugged in, nothing? Outside of the Holley system to me that means the spark/ignition system should be in working order.

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