Log Review

[Mwtvvo]

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.

[dave w]

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

[Mwtvvo]

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

[tayto]

Not to sure what overheating has to do with the ECM, sounds like you have other mechanical issues.

[Mwtvvo]

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.

[tayto]

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*...