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Thread: Log Review

  1. #1
    Electronic Ignition!
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    Log Review

    Hi, I'm just starting out with 7747 platform. I have a 88 K1500 that originally came with the 305. I bought the truck with the motor blown with the intention of swapping to the 350 completely stock. It's a CA truck with 2nd Air. I bought a 130k mile used motor with 180 compression on all cylinders and replaced all the gaskets, timing chain and oil pump. I'm using 350 injectors, knock sensor, and ESC module. The entire distributor is brand new. The 2nd Air is working and back in the truck.


    My goal was to find completely stock everything, so I wouldn't have to tune the chip right away. I have 2 ECM's the original and one I got from pick and pull, but I have 3 bcc's; ADTD the original 305 with air and auto; ASDZ this came with the second ECM, but doesn't have 2nd Air; AMUS I pulled this one from a truck with a 350, 2nd Air, and Auto.


    When I first attempted to start the truck it wasn taking too long for fuel to get to the TB and it took too long to start. It was also dying under load. On some newer vehicles, this is a sign of a bad fuel pump, so I changed out to the EP381 Vortec pump (Found out later, the fuel system is supposed to depressurize after key off, turned out to be the fuel pump relay). Currently, the regulator is adjustable, and I've set it to 13 PSI as that seems to be the consensus ideal pressure. However, the truck is running rich. My thinking is the fuel pressure is too high for the stock setup, and 13 PSI is for those who have the tunning capability, (I will, but not right now).


    I've attached a couple of logs that I've run. This morning I swapped out to the ASDZ and other ECM to ensure the readings were consistent and not an ECM issue. So log 11-13a is ASDZ, and the 11-12c is the last log I ran on the AMUS and the chip I'll need to run in order to pass smog. Both logs show my BLM low. I'm comparing my log to a reference log posted under the 7747 thread.


    SO my question is, how do the logs look. Does it look like fuel pressure is my issue, if so how can you tell? If fuel pressure is an issue, is there way to use my logs to calculate the best fuel pressure for my setup?


    Also, I noticed that I have counts that spike low and sometimes high, is this normal for 7747, or is this a cable issue? I've attached a picture of my connector.
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  2. #2
    Super Moderator dave w's Avatar
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    The attached screen shot shows the BLM averages from a 1227747 TBI engine. BLM's below 128 are rich. BLM's above 128 are lean. Ideally the BLM averages between 123 to 133 are considered good.

    Adding fuel pressure generally makes the BLM's go more rich. Reducing fuel pressure generally makes the BLM's go more lean.

    Usually the stock Spark Advance Table works well with a stock engine. If the engine is not stock the stock Spark Advance Table will likely need to be optimized.

    Passing an emission test for an engine that is not stock, will likely require tuning of both the fuel table and spark advance table.

    Tuning for an emission test will likely be successful with the use of an automotive Gas Analyzer; CO. HC, CO2, O2, NO, &NO2.

    dave w
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  3. #3
    Electronic Ignition!
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    I'm back with the same truck. I have been gimping it around the country, now I'm in Texas. Short story is that I've got it running well by sound and no CEL on. I am currently using the ADSU prom, and the smog gear has been removed. I need to use this truck for towing within the next two weeks. While I was towing a trailer (Empty 16ft enclosed trailer), the truck was overheating real bad and throwing a code 43. I replaced the open circuit knock sensor and the CEL is no longer on, but the truck still struggles pulling the same trailer, the temp is going too high, and WoT feels too sluggish. The attached log shows idle, 0-70 unloaded, idle, and 0-45 loaded. It's stock except for a better fuel pump and 13 psi fuel pressure. I'm not expecting much, but hoping for more. Any ideas would be greatly appreciated.

    Happy 420
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  4. #4
    Fuel Injected!
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    Not to sure what overheating has to do with the ECM, sounds like you have other mechanical issues.

  5. #5
    Electronic Ignition!
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    That was my thought too. I don't look at logs all the time, so I'm not sure what could be wrong. Since it's all stock, I shouldn't need a tune at least not until it's running properly. I was hoping that something would be obvious on the log to give me a starting point. I hate throwing parts at a problem. Thanks for the reply.

  6. #6
    Fuel Injected!
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    did you replace the water pump when you swapped engines? What about thermostat? I replace them every 5 years regardless of milage. I would pull the rad and get it checked out/tested. I would also replace the fan clutch, Rockauto still sells GM clutches for your era truck (I just bought one). Did you set timing to factory spec? pull the EST connector and set to 0*...

  7. #7
    Fuel Injected!
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    Hi Mwtvvo, could you please publish your bins here.I have the amc304 engine in my car and would like to test these bins on it.

  8. #8
    Fuel Injected!
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    he doesn't have any bin files he has been swapping ecu's obtained from the wrecker.... why don't you look at all the bin files on this website

  9. #9
    Electronic Ignition!
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    When I did the swap, I didn't start out with a working motor, so I refreshed as much as I could. I put on a new water pump and thermostat. I recently swapped over to an 11 blade. The radiator is original to the truck, so it could be an issue. I replaced the whole distributer when I did the swap.

    Before running the recent log, I checked the timing (est disconnected) because I thought it might be the reason for the lack of power and overheating. It was at 12 (not sure how), and I adjusted it down to 0-2. The truck runs better, but lacks power. The radiator could be a weak point, but it shouldn't cause power loss.

    Any other ideas? Are logs not a good diagnostic tool? Thanks for the responses.

  10. #10
    Fuel Injected!
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    @tayto, in general you are right but I couldn`t find the ADTD nor the AMUS!

  11. #11
    Fuel Injected!
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    Is the 11 blade a plastic blade? I put one on a friend's 1992 gmc c2500 a year ago along with a new clutch. I am going to run one on my squarebody this summer. Is your clutch new or original? I would get your cooling problem sorted out first. pull the rad and get it checked out. have you done a compression or leakdown test to see if the engine is healthy? don't have enough evidence at this time but failed headgasket can cause overheating and lack of power.

  12. #12
    Electronic Ignition!
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    The 11 blade I installed is plastic: although, I think they also are made with steel.

    The original radiator failed on me. The wire to the temp sensor (near the exhaust manifold) fell off, so I the temp gauge in the dash wasn't working. Luckily I stopped for gas and smelled radiator fluid, otherwise I the truck would have overheated going 75 mph. I now have a new radiator.

    That was not the source of my lack of power though. I'm going to do a compression test and fuel pressure test today maybe that will give me more insight. (I'm new to Data Logging) I believe the fuel pressure is too high. My BLMs are very low across the range. The truck has a fuel pump in from a 95 TBI, but I think it's too much pressure still. I adjusted the regulator until it bottomed out and still had low BLMs. Also, my injector Duty Cycle is over 100, even over 1000. Do I need a custom chip to read this setting correctly ("the hack") or is this also showing my fuel pressure is too high? What is a good range for this?
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  13. #13
    Fuel Injected!
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    don't you have the wrong calibration currently? setting your fuel pressure to bring the BLMs in is a bandaid fix at best and fools errand IMO. Vortec or TPI pump is an excellent upgrade even on a bone stock setup. 13 psi, again is fine on stock stuff and where i target on stock or lightly modified.

    is your engine a 350 or 305? is a stock TBI motor or originally a carb'd engine? previously you stated you had 350 injectors. are these GM used or aftermarket?
    Last edited by tayto; 08-21-2022 at 08:17 PM.

  14. #14
    Electronic Ignition!
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    Thanks for your response. I'm really not sure what the problem is. I'm guessing at best. My blms are really low and the only thing I have to go off is my fuel pressure. I've put 305 injectors in and they made my blms too high and cannot adjust down to 128. The 350 injectors won't adjust up to 128.

    It's an original tbi 350 I bought from a junk yard said to have 180 compression on all cylinders. The injectors are also used from junk yard, all sets.

    I just finished a the compression test and the numbers are 145-150 psi. Kinda low, but consistent, and I'm not getting any smoke.

    I've been really just trying to get this thing to run in stock form. I have several logs, but I'm not sure what I'm looking at yet. The only thing that sticks out is the low blms and the injector duty cycle

    I'm open to options.
    Last edited by Mwtvvo; 08-21-2022 at 09:05 PM.

  15. #15
    Fuel Injected!
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    get the injectors professionally cleaned and tested. i have had bad injectors cause the BLMs to be low (rich). you also need to get the correct calibration and/or burn a chip with the correct calibration. re-read this thread, we discussed this already.
    Last edited by tayto; 08-22-2022 at 07:08 AM.

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