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Thread: TBI conversion on a Ford 400 - need help getting it to run

  1. #1
    Fuel Injected! Dr_Grip's Avatar
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    TBI conversion on a Ford 400 - need help getting it to run

    Hi guys,
    complete and total newbie here. I am trying to get a homebrew GM TBI setup running on my Ford 400 and it seems like I hit a wall by now. I really appreciate some help from you guys.

    So, what has been done so far?
    -I got a TBI system from a 1990 5.7 K-Series truck (7747 ECM).
    -Mounted it on the engine's Edelbrock Performer intake
    -A Ford DuraSpark II dizzy is connected to a brand-new HEI module (getting a perfect spark at the right time since putting the wires the right way 'round :D )
    -Fuel pump's an Airtex E8094
    -New coolant temp sensor, IAC, O2 and MAP sensor are fitted
    -I did not fit a VSS
    -Tested the TPS, it's good.
    -I used TunerPro to set the BPW to 161.5 to match the displacement and disabled the EGR (based on the ARHT bin)


    Sooo, what happens so far is that the engine starts up nice after a bit of cranking, idle's a bit high at 800-ish (but as I did not set base idle yet and the park/neutral switch isn't connected, that's not too much of a problem, I think).

    When I try to build up revs slowly, the engine will hold any given speed (1500, 2000, 2500rpm, etc) only for a few seconds before losing revs (massively leaning out?). Furthermore, suddenly stepping on the throttle leads to violent backfires through the intake. The ECU is not throwing any codes. Any ideas what might cause this?

    Once running, fuel pressure sits at .9 bar/13 psi, just as it should - but it takes about 10 seconds of cranking to build up fuel pressure at startup. Is that normal or does it indicate a problem with the fuel pressure regulator (most likely unrelated to issue above, but who knows)?

    As I said, I am a total newbie when it comes to EFI, so I am at a loss here. Any help is very much appreciated.
    Last edited by Dr_Grip; 04-25-2015 at 04:37 PM. Reason: It's ARHT

  2. #2
    Fuel Injected! mmigacz's Avatar
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    Do you have the ability to datalog? Posting the log file, and bin would help to determin what is going on.
    1986 ski centurion boat, 351W, gt40P heads, edelbrock performer rpm, 1227747 ecm, 72 lb/hr injectors (@18 PSI fuel pressure), .490/.490 lift, intake 278 duration, exhuast 282 duration, 112 lobe separation

    1969 camaro, 355ci, performer RPM intake, camel hump heads, 1227747 ecm, 454 throttle body (@18 PSI fuel pressure),

    2016 Chevy Cruz

    2014 Chevy Silverado

  3. #3
    Fuel Injected! Dr_Grip's Avatar
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    Quote Originally Posted by mmigacz View Post
    Do you have the ability to datalog? Posting the log file, and bin would help to determin what is going on.
    I attached the bin file. I'll have to solder myself a log cable and get a logfile, I think I'll be able to do that during the course of the week (the workshop's about 20 minutes from my home so it's tough to get some real wrenching time in during the week).
    Last edited by Dr_Grip; 04-25-2015 at 05:39 PM.

  4. #4
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    As far as fuel pressure goes, the regulator is normally pretty reliable provided the pump can keep up and you have a free flowing return line (more important with a high volume pump). You should get full pressure as soon as you turn the key as long as the pump is running (pressure bleeds off as soon as the pump stops). Have you watched the fuel pressure when you're actuating the throttle? It should stay right about 13 psi as long as the pump is capable. If it's dropping, then that could be your problem, but datalogs will help.
    1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
    1975 280Z, TBI 350, 700R4
    1953 M-38A1, TBI Buick 231
    1951 Ford Panel, 5.3 with 4L80E

  5. #5
    Fuel Injected! Dr_Grip's Avatar
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    Quote Originally Posted by fastacton View Post
    As far as fuel pressure goes, the regulator is normally pretty reliable provided the pump can keep up and you have a free flowing return line (more important with a high volume pump). You should get full pressure as soon as you turn the key as long as the pump is running (pressure bleeds off as soon as the pump stops).
    As I said, it takes the pump a few seconds to get up to full pressure (the short pump activity burst when turning the ignition on won't do it). I got an in-line gauge installed and you can watch the needle creep up very... very... slooooowly. But...
    Quote Originally Posted by fastacton View Post
    Have you watched the fuel pressure when you're actuating the throttle? It should stay right about 13 psi as long as the pump is capable. If it's dropping, then that could be your problem, but datalogs will help.
    We never noticed any drop once the pressure was where it should be. But I'll double-check and try to get some logs... It seems like soldering a serial cable is a piece of cake - now I just got to find an old laptop with a serial port :)

  6. #6
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    If the pump can't get it up to pressure immediately, then that might be your problem. At least with the pumps I use, I'm used to an immediate jump to full pressure, and I'd be concerned that any pump that couldn't do that would be able to give good fuel pressure much past idle. What part of Germany are you in? I spent a few years there in the Ansbach and Schweinfurt areas.
    1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
    1975 280Z, TBI 350, 700R4
    1953 M-38A1, TBI Buick 231
    1951 Ford Panel, 5.3 with 4L80E

  7. #7
    Fuel Injected! Dr_Grip's Avatar
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    Quote Originally Posted by fastacton View Post
    If the pump can't get it up to pressure immediately, then that might be your problem. At least with the pumps I use, I'm used to an immediate jump to full pressure, and I'd be concerned that any pump that couldn't do that would be able to give good fuel pressure much past idle.
    The Airtex pump is designed for the TBI systems, but maybe I got a bad one. I'll watch the pressure gauge closely and report back asap. How much pressure can the regulator take without getting damaged? I might as well think bigger in case I need a replacement pump...

    Quote Originally Posted by fastacton View Post
    What part of Germany are you in? I spent a few years there in the Ansbach and Schweinfurt areas.
    I live in Berlin now, but I went to college in Würzburg, so I know the Schweinfurt area. A nice part of the country...

  8. #8
    Fuel Injected! Dr_Grip's Avatar
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    Reporting back - I fixed the fuel pressure problem. The car now runs mostly fine. There's only one and a half issue bugging me.

    The half-issue is unstable idle in closed loop, I've seen tons of threads about this here so I guess I can tackle that on my own.

    The biggie is the spark advance: I am trying to re-create my stock dizzy's advance map as a first step and the engine starts having ignition problems as soon as the advance crosses 30°. It's clearly rpm-independent: Wherever I set the advance map to cross 30°, the ignition starts having problems, I even blew my muffler with a violent backfire!
    First, I thought I might have an arcing problem so I phased my dizzy correctly. Didn't change a thing. So I connected an engine tester and discovered something really weird:


    Yep, somehow, each plug suddenly starts firing twice.

    I then moved the P/N wires further away from the coil to rule out any interference from the discharge. Checked the signal with an oscilloscope, it's clean. The oscilloscope also tells me that the coil in fact is triggered two times per plug by the HEI module.
    How's that possible? Bad HEI module? Bad ECU? I really need some pointers here...
    Last edited by Dr_Grip; 06-20-2015 at 11:48 PM.

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    I would think it would be the module or distributor issue. The ECU doesn't tell the module how many times to fire, just how much advance is needed (as far as I understand things).
    1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
    1975 280Z, TBI 350, 700R4
    1953 M-38A1, TBI Buick 231
    1951 Ford Panel, 5.3 with 4L80E

  10. #10
    Fuel Injected! Dr_Grip's Avatar
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    Thank you for the quick reply, much appreciated!
    Quote Originally Posted by fastacton View Post
    I would think it would be the module or distributor issue. The ECU doesn't tell the module how many times to fire, just how much advance is needed (as far as I understand things).
    That's what I think, too.

    I've read on another forum that mounting the module too far away from the dizzy can cause issues, as well. What do you think about that?

    EDIT: Here's the wiring. Module is located on the passenger side fender.
    Last edited by Dr_Grip; 06-21-2015 at 11:24 AM.

  11. #11
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    I've only used HEI style distributors on my Ford builds, so your wiring setup is a bit different than what I'm used to. This is a good link for how things should be wired up(it's for megasquirt, but still applies):
    http://www.megamanual.com/ms2/GM_7pinHEI.htm
    1973 K-5 Blazer, TBI 350, TH400, 1 ton axles & 38" SSRs'
    1975 280Z, TBI 350, 700R4
    1953 M-38A1, TBI Buick 231
    1951 Ford Panel, 5.3 with 4L80E

  12. #12
    Super Moderator Six_Shooter's Avatar
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    So you mounted the ECM on the intake manifold?

    If so, stop the show and move the ECM to the interior. The '7747 is not designed for the underhood environment. The moisture, heat, vibration and other fumes/chemicals,/etc will cause you problems in time, if not very shortly.

    It seems that the Ford dizzies don't have a solid enough signal to reliably trigger a GM ICM. It works, yes, but not as well as a GM reluctor does. I've seen a few solutions used, adapting a GM dizzy to the Ford, adapting a GM reluctor to a Ford dizzy. There could be an electronic solution as well, to improve the signal, using an amplifier, but a mechanical solution seems to be the best.

    Are your wires between the dizzy and the ICM twisted? They should be. IIRC the recommended is 3 to 5 twists per inch. The twists help reduce the possibility of inducted noise interfering with the signal.
    The man who says something is impossible, is usually interrupted by the man doing it.

  13. #13
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    Quote Originally Posted by fastacton View Post
    I've only used HEI style distributors on my Ford builds, so your wiring setup is a bit different than what I'm used to. This is a good link for how things should be wired up(it's for megasquirt, but still applies):
    http://www.megamanual.com/ms2/GM_7pinHEI.htm
    Thank you for the link - but it's the manual I used anyways :)

    Quote Originally Posted by Six_Shooter View Post
    So you mounted the ECM on the intake manifold?

    If so, stop the show and move the ECM to the interior. The '7747 is not designed for the underhood environment. The moisture, heat, vibration and other fumes/chemicals,/etc will cause you problems in time, if not very shortly.
    Wait, how did you get this impression? :) Of course I didn't! It is - not ideally, I know - taped to the rear side of the driver's side fender for now. I'll rip the interior out for a rustproofing effort in a few weeks time and will move the ECM below the front bench then.

    Quote Originally Posted by Six_Shooter View Post
    It seems that the Ford dizzies don't have a solid enough signal to reliably trigger a GM ICM. It works, yes, but not as well as a GM reluctor does. I've seen a few solutions used, adapting a GM dizzy to the Ford, adapting a GM reluctor to a Ford dizzy. There could be an electronic solution as well, to improve the signal, using an amplifier, but a mechanical solution seems to be the best.
    I'll keep an eye on that, thank you for the heads-up! Right now, my problem seems to be too many triggers, not too few, but it's good to know.

    Quote Originally Posted by Six_Shooter View Post
    Are your wires between the dizzy and the ICM twisted? They should be. IIRC the recommended is 3 to 5 twists per inch. The twists help reduce the possibility of inducted noise interfering with the signal.
    They aren't. I guess that's where my problems come from. I'll switch to shielded twisted cables on Tuesday and report back.

  14. #14
    Super Moderator Six_Shooter's Avatar
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    Quote Originally Posted by Dr_Grip View Post
    Wait, how did you get this impression? :) Of course I didn't! It is - not ideally, I know - taped to the rear side of the driver's side fender for now. I'll rip the interior out for a rustproofing effort in a few weeks time and will move the ECM below the front bench then.
    From this:
    Quote Originally Posted by Dr_Grip View Post
    Hi guys,
    complete and total newbie here. I am trying to get a homebrew GM TBI setup running on my Ford 400 and it seems like I hit a wall by now. I really appreciate some help from you guys.

    So, what has been done so far?
    -I got a TBI system from a 1990 5.7 K-Series truck (7747 ECM).
    -Mounted it on the engine's Edelbrock Performer intake
    So then what is mounted on the intake?

    Also, move it inside the vehicle, the same things I mentioned earlier still apply, just being mounted under the hood. Also remember to isolate the ECM case from teh chassis ground. Grounding the ECM case to chassis ground has been known to cause ground loops and introduce noise at best, and damage ECMs at worst.

    I'll keep an eye on that, thank you for the heads-up! Right now, my problem seems to be too many triggers, not too few, but it's good to know.
    The poor triggering of reluctor doesn't mean just too few, it means poor triggering, which can include too many, due to collapsing magnetic fields.

    But...

    They aren't. I guess that's where my problems come from. I'll switch to shielded twisted cables on Tuesday and report back.
    This is where I would start, twist those wires and the triggering caused by the spark plug wires should go away.

    Also in the end using a VSS, will help with stable idle and keep the engine from stalling when coming to a stop, among other benefits.
    Last edited by Six_Shooter; 06-22-2015 at 01:38 AM.
    The man who says something is impossible, is usually interrupted by the man doing it.

  15. #15
    Fuel Injected! Dr_Grip's Avatar
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    Quote Originally Posted by Six_Shooter View Post
    So then what is mounted on the intake?
    A GM TBI unit, of course! :D The injector body itself.

    Quote Originally Posted by Six_Shooter View Post
    Also, move it inside the vehicle, the same things I mentioned earlier still apply, just being mounted under the hood. Also remember to isolate the ECM case from teh chassis ground. Grounding the ECM case to chassis ground has been known to cause ground loops and introduce noise at best, and damage ECMs at worst.
    Will do.

    Quote Originally Posted by Six_Shooter View Post
    The poor triggering of reluctor doesn't mean just too few, it means poor triggering, which can include too many, due to collapsing magnetic fields.
    On to find a GM dizzy donor, then...

    Quote Originally Posted by Six_Shooter View Post
    This is where I would start, twist those wires and the triggering caused by the spark plug wires should go away.
    Will do and report back.

    Quote Originally Posted by Six_Shooter View Post
    Also in the end using a VSS, will help with stable idle and keep the engine from stalling when coming to a stop, among other benefits.
    Any recommendations on which one to fit?

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