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Thread: 8747 ecm running out of injector

  1. #1
    Carb and Points!
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    8747 ecm running out of injector

    Have been playing with this off and on for over a year. The combo 1968 396/325hp big block, 1228747 ecm 2" tbi with 80# injectors. solid 15 psi fuel pressure. Have the truck running ok without a cel at idle and about to 50% throttle and 2600-2700 rpm then goes lean and backfires. Have a wideband o2 wiith af ratio gauge (separate from normal o2) mounted about 6" down from exhaust port. On the fuel map from dead center down and to the right the fuel is maxxed out at 99+. Tried another complete 2" bb tbi with known good 80# injectors and same thing. Dave at Moates said to adjust the BPW in the VE table. Don't seem to be able to locate this. Found bpw vs coolant temp? Could use a little help. When I get this one going I have another to do also with similar setup. Anyone close to Omaha?

  2. #2
    Fuel Injected!
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    What tuning software. In Tunerpro the BPW is under the Fuel category first item using $42-1227747-V5.9.3.xdf.

  3. #3
    Fuel Injected!
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    I think this is the one you want... http://www.gearhead-efi.com/Fuel-Inj...Information-4F

    BPW is in the scalars...

    Provided you have excel, you can calculate bpw with this spreadsheet: http://www.gearhead-efi.com/Fuel-Inj...BPW-Calculator

    I'm not sure if you started with a 5.7 or 7.4 bin but those would have bpw of 135 and 134 respectively in the stock bin. For a 6.5 bpw would be less like 117 so if you indeed have 80# injectors and 15 psi and running with the stock bpw setting as mentioned, I would think you'd run rich on a stock tune.

    Your VE1 + VE2 should not add up more than 99 and it's my understanding TPRT won't let you save it that way.

    Are you aware that the BBC throttle body came with different injector sizes? Can you verify with injector part number?
    http://www.gearhead-efi.com/Fuel-Inj...d-part-numbers

  4. #4
    Carb and Points!
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    Thanks for the response. It all sounds confusing. I do have 2 of the early 89-90 tbi units. #1 was taken off of a unmolested truck and #2 I got replacement injectors for a 90 7.4l. I have not been able to find that bpw table in tunerpro. Looked again tonight. Yes started with a 7.4 bin file and ran rich at idle but goes lean with throttle and load. Have fuel table maxed out at 99.61 for most of the map. a/f goes into the mid 15s then backfires. There is no esc or egr on this setup also. Will see if injectors still have part # on them.

  5. #5
    Fuel Injected!
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    In Tunerpro key stroke Ctrl+F type "BPW" click "Search"

    Yanno...idk if I'm understanding this BPW thing correctly. I'm kinda experiencing the same thing helping someone tune his truck. Perhaps BPW is a good place to start. With this person's vehicle, kinda dealing with some unknowns i.e. injector size I started to mess with the BPW until I had a good idle, logged and massage VE tables. Once all that was dialed in...mash the go pedal and like yours near the same rpm "POP!" Dealing with a Holley but gonna get the number off the delphi style injector and hopefully identify it's flow rating. Punch it into Dave W BPW calculator, set it in the bin and forget it.
    Last edited by stew86MCSS396; 04-28-2018 at 02:18 AM.

  6. #6
    Carb and Points!
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    Ok. Verified injector #5235231 80pph. Found bpw in scalers and was at 120. Changed to 135 and went rich and still popped. Changed to 127 and is closer but still pops. Tried another ign coil with no change. What I have noticed now is it doesn't want to run in open loop. Very rich and low idle like 350 rpm. Patience running thin about to sell both systems and go Fitech. May have to find local dyno shop that can help.

  7. #7
    Fuel Injected!
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    Myself and a friend have big blocks (454) and had problems with pops as throttle was applied (only certain times). Our fix was to cut out all the spark retard and increase wot timing similar to what you would find in and old performance non electronic dist. For me it has been over 2 years with no pops. In the begining I fooled with mixture as it sounded like a lean pop but as I said turned out to be retard.
    Last edited by myburb; 04-28-2018 at 03:35 PM.
    6395, BHDF, 7.4 BBC lightly modded now 6395 BMHM back to BHDF

  8. #8
    Fuel Injected! S.O.B.B.'s Avatar
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    Something to check.in the truck bins the small blocks all have injector bias setting is set at .396 and the BBC bins that is set at .276 if I remember correctly. Also the BBC spark latency setting for large cap distributor is different than the small cap.compare BBC bin to yours.the spark latency gives more advance with a larger number.the injector bias gives more injector open time with a larger number.I'm still new to this so I hope I got that right.lots of reading on here to help. hth20171220_014325.jpg Screenshot_2017-12-20-01-47-59.jpg
    First one is sbc truck and second is BBC truck.more advance in BBC. If u read about latency this can be 10 degrees of difference.
    Last edited by S.O.B.B.; 04-28-2018 at 09:28 PM.
    Jeeper
    87 sjimmy 4.5L /nv1500/ 8.8 3.55 rear/disc brakes.

  9. #9
    Carb and Points!
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    3 more night of work and no improvement. Reinstalled esc module and wiring thinking no timing advance. Didn't help. Played around with blm some more. Didn't help. Tried another distributor. No change. Realized have 7.4 bin without esc so went to download 5.7manual bin and laptop crashed. Solution: Holley Carb and HEI.
    I AM DONE. Have 2 systems for sale. 2 early 454 rebuilt throttle bodies with 80pph injectors and oe adapter plates, 2 1228747 ecm with chip adapters installed, 2 wire harness, 2 distributors with caps and rotors, 2 coils, 2 coolant temp sensors, 2 o2 sensors, 2 map sensors, 1 inline fuel pump, Moates autoprom with cables zif adapter and 2 chips. 1 of the throttle bodies has kickdown linkage added to it at the correct ratio. Anything else I can round up in the shop for tbi goes with it. $1100. May separate 1 system from the other, not interested in 1 piece at a time. Thanks to all who took time to help me along the way. I'm sure someone can do this its just not me.

  10. #10
    Carb and Points!
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    Make a reasonable offer with shipping from Omaha ne. 68112. Thanks

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