Doing ECM to PCM swap

**57 Handyman** · 06-27-2017

My truck is a '92 4x4 S10 with a semi-modified 4.3L hooked up to a 700R4. The 4.3L's top side mods include '96 Vortec heads and Edelbrock 2114 intake with a carb-to-TBI 1-inch adapter. Since the Edelbrock intake does not accommodate an EGR, I need a way to eliminate the EGR. Also, because of the slowness of my 16144288, I wanted to upgrade to the faster and "tuner-friendlier" 16168625.

What I have done so far is captured in a prior thread...below

http://www.gearhead-efi.com/Fuel-Inj...168625-TBI-PCM

Last week, I installed the adapter I made which is based on information found in several threads on this site, specifically one entitled "1227747 to 16197427 Conversion PCM Swap with Wiring Pinout Directions!" With the 8625 installed, my engine will start when I prime it with starter fluid/pour fuel into the TBI but will not run continuously. It appears no fuel is reaching the TBI. Prior to swapping in the 8625, the engine ran properly.

I have run diagnostics circuit checks at the fuel pump relay and determined that the fuel pump is NOT receiving the 2 second priming and the fault is between the FP relay and the ECM. Through continuity checks, I've eliminated that the problem lies in the stock harness and my adapter. I am able to trace continuity up to pin F6 in the plug for the 8625. Based on the aforementioned thread, pin F6 should be the source of the 12V for the fuel pump.

Any help or insights will be greatly appreciated!

**ony** · 06-27-2017

I would check the wires that connect the grounds in your adapter. I made one adapter for a 427 to 288 it worked but ran rich and had a knock senser problem , I got busy and never finished it. do you have tunning equitpment? also did you change your cam. I have a 91 c1500 5 speed , before I got it some one put a 94-95 4.3 vortec in it. they are not true vortec engines,but they preform better than the 92 swill port that I replaced it with. any way the 94 vortec had a lot more ohm's on the knock sensor and 2 knock sensors. I put a 4k ohm sensor in and fixed a problem with the 288 ecm. run it probly 250,000 then burnt a valve and changed engines.i think the code I was getting is because there was not enough ohm's with 1 sensor instead of the 2 original ones. so if you run the newer pcm you may have to us 2 sensors wired up the way they are from the factory, I think they are parrall.

**57 Handyman** · 06-29-2017

Ony,

Thanks for the heads up regarding the ground. I will run continuity checks on those with my adapter. As for tuning equipment, are you referring to tuning software and the associated cables to data log? If that is what you are asking, no I haven't acquired any of those items yet.

Regarding a cam change for my 4.3L, yes, i am using a stock versin V6 cam for Marine applications.

The knock sensor is the stock single sensor setup next to the distributor...haven't done any changes. Since you've raised the need for 2 knock sensors, I will do some research on the motor setup from PCM's source vehicle.

By and large, I want to get the engine to start-up and run continuously before attempting fine-tuning in pursuit of enhanced performance.

**ony** · 06-29-2017

is your vehicle a std trans? I put a mercruiser cam in my 4.3 also, had to change the ve table a lot then add a little timming here and there. first tank of gas coming up here from tx I got 23mpg at 70 mph with 1500lbs on it, here in Indiana it runs 18-20mpg. if you post on the first thread page more people will see and might be more help. dave knows about using a single sensor with your set up.

**57 Handyman** · 06-30-2017

No, my truck has a 700R4. Wow, it sounds like we had similar performance goals for our 4.3L motors. If I remember correctly, the last time I set the timing I advanced it 2-3 degrees because it seemed to run better.

Due to family commitments, I won't be able to follow-up on checking the grounds in the PCM until this weekend. I did notice in some of the documentation I've kept that there are several. Beyond performing continuity checks, I am at a loss for how best to proceed with additional troubleshooting. Any suggestions are greatly appreciated.

Also, earlier today, I substituted another red/blue PCM (16195925 BHRJ) which I happened to have lying around. No difference...engine did not start up. That says to me the problem exists in the harness and my adapter and not necessarily with the PCM (slim chance that two PCMs would have problems sending 12V to pin F6).

Lastly, when I first began on this site, Dave W did provide some pointers which I have followed/implemented, so I am hoping he'd chime in at some point.

**57 Handyman** · 07-01-2017

This morning, one question that arose was whether it was necessary for me to have all the specifications and components regarding vehicle setup, such as engine mods, auto transmission-type, no EGR connected, electric fans, etc. already in the PROM before I can get it to even start up and/or run properly. Is it sufficient to just use (as is) whatever is already (currently programmed) in the 8625 and BCC to get my engine to run? Basically, what I am wondering is whether I am chasing my tail and will not be able to resolve my "no start and run continuously" problem due to the mismatched and modified components? That being said, how much and close do I have to be?

**ony** · 07-01-2017

it should start and run if you have a 4.3 memcal in the pcm.make a thread on the[ gm efi section] on this web sight you will get more ansers.you may have a test wire on the fuel pump relay to where you could run the pump to make sure that its the only problem. is your original ecm a 747 or a 288 ,the last 3 numbers?

**57 Handyman** · 07-01-2017

Yes, the original ECM is a 4288. Also, I googled the 16195925 BHRJ PCM and found that it came out of a 94 Bravada 4.3L. I believe in the engine bay there is a test wire which comes off of the power block and goes to the fuel pump relay. Do you think it is safe for me to use a jumper and power the fuel pump directly and by-pass the relay? What is puzzling is the relay and fuel pump circuitry functions perfectly with the 4288 installed. The only change between both setups is the adapter and PCM.

**ony** · 07-02-2017

I think I would re check the adapter wiring and make sure it matches the stamatic ,I had a wire wrong and blowed the icm modgule. I have got a pair of magnifying glasses to look at the numbers on the connectors with now. do you have a pc,if so what is it? I have got a data cord but its for a sereal port it works with a usb adapter for data loging.

**57 Handyman** · 07-03-2017

When I got to the shop today, I removed the adapter and reinstalled the 4288 ECM, removed the jumper on the ESC, and reconnected the plug to the ESC. Basically, returned everything to the stock setup. Upon turning the ignition key, the fuel pump primed the TBI, the engine started, and continued to run until the ECM switched from CLOSED to OPEN Loop. At that point, the motor began to struggle to stay running and eventually died.

With the adapter removed, I rechecked the adapter wires once again and, lo and behold, found one loose/disconnection (between old B10 and new E5) which was for the Park/Neutral Switch. After re-securing the connection and rechecking the remaining adapter wires, I reinstalled the adapter and jumped the wires at the ESC. The jumper makes a direct connection of the Knock Sensor to the PCM. Alas, the fuel pump issue resurfaced and motor would not start.

As you can see, there are no issues with the stock harness, FP relay, fuel pump, etc. until I install the adapter and PCMs.

**ony** · 07-03-2017

if you send a private message to me with your address I will send you a chip for the288 ecm that should keep it running it wont be perfect cause it is for my setup. when I change cams my idle map went from 30 up to 38-40 which really messes with idling until the chip file is tuned.