Considering a TBI Swap

[Six_Shooter]

AKSB is from a 1227747 but a V6 Auto. So it will have the wrong Netres/small chip in it for LHM.

I've come across info recently that indicates that the NETRES in a '7747 can be either V6 or V8 in origin and have no effect on the way the engine runs. It was indicated however that IF LHM were induced using a V6 NETRES on a V8 engine, it may not run as well as using a V8 NETRES.

[MrGiggles]

I've come across info recently that indicates that the NETRES in a '7747 can be either V6 or V8 in origin and have no effect on the way the engine runs. It was indicated however that IF LHM were induced using a V6 NETRES on a V8 engine, it may not run as well as using a V8 NETRES.

So in relation to me I should try the AKSB chip and see how it runs?

What does LHM and NETRES stand for?

[dave w]

What does LHM and NETRES stand for?

LHM - Limp Home Mode
NETRES - Network of Resistor that provide the LHM with default fuel setting.

dave w

[Six_Shooter]

So in relation to me I should try the AKSB chip and see how it runs?

What does LHM and NETRES stand for?

I was talking about the NETRES, not the EPROM. The EPROM should be as close to the application as possible.

[MrGiggles]

I was talking about the NETRES, not the EPROM. The EPROM should be as close to the application as possible.

I'm not completely familiar with the ECM and it's components. I'm confused.

So the EPROM is the small removable chip under the cover with AKSB on it? Then where it the NETRES? The real question is, what do I need to change to get this ECM to run somewhat decent with my engine?

[EagleMark]

The Netres chip is the little one next to the big one with the AKSB on it.

To run somewhat decent you need a chip that matches your engine.

[MrGiggles]

I will be going back to the junkyard tomorrow to grab some plugs and a couple other things.

Is the NETRES I need specific to the 1227747 ECM? Like I said those are really hard to come by out there... I'm pretty sure that I covered most of the trucks but there might be some V8 cars that still have an ECM. There was also a 92 Suburban that still had the computer, if that could work. I hate to spend 30 bucks on a set from ebay and have my ECM be bad or something. A new ECM is only 60 bucks from the parts store, and only 30 bucks for a used one on Ebay.

Shopping list for tomorrow.

1. Injector plugs (one of mine is broke)
2. IAC, TPS, ESC and a couple other plugs
3. NETRES chip
4. See if I can find a fuel pump.
5. Coil and distributor wires that I am missing.

[MrGiggles]

If I could get some help on this issue before I head out this afternoon, it would be awesome.

I've done some research and have conflicting answers on whether or not you can swap the NETRES from an 8746 car ECM to my 7747 ECM. The reason I ask is because I found a relatively untouched 3rd gen Camaro V8 that probably still has the ECM in it. But I don't know if I could swap the chips between them.

[dave w]

There is the option of using the '8746 ECM, instead of the '7747? There might be a few wires to move in the '8746 / '7747 connectors. I'd have to check the schematics to figure out which wires get moved, if any. The advantage of the '8746 is the the Intake Air Temp Sensor. The '8746 VSS might be 4,000 Pulses Per Mile, I can't remember.

How to swap wires in the connector: http://www.dynamicefi.com/RePinHowTo.php

dave w

[MrGiggles]

There is the option of using the '8746 ECM, instead of the '7747? There might be a few wires to move in the '8746 / '7747 connectors. I'd have to check the schematics to figure out which wires get moved, if any. The advantage of the '8746 is the the Intake Air Temp Sensor. The '8746 VSS might be 4,000 Pulses Per Mile, I can't remember.

How to swap wires in the connector: http://www.dynamicefi.com/RePinHowTo.php

dave w

I had considered it but was leaning towards a 7747 because it already matches my harness and the IAT isn't that beneficial according to what I've read.

I will go to the yard and see what I can find, and see if the ECM is even still there. If I do get it I will snip the plugs out of the car so I have both connectors to compare. I see that most of those cars are 305's, is that a big deal? Will it run okay with my engine? I will have it tuned but I want to get it running first.

[EagleMark]

I'm not sure if Netres is interchangable?

As mentioned in these ECM it is more important for the Limp Home Feature then anything to do while running on the big chip.

A 305 chip may run if it's from a 7747. But to be close it needs to be a 350/5.7L chip for auto or manual depending on what you have.

Swapping in a 8746 is a plug and play, no wiring changes needed except add wires for IAT sensor.

[Nasty-Z]

I had considered it but I didn't know that the tanks were the same. That and I don't really wanna drop the tank on mine, and since my parts are coming from a scrap yard that means I would have to drop the tank on the donor as well. Do you know if the sending unit is the same for the gauge?

Yep I am still running that flywheel. She still spins true.

Tanks are the same , sending unit for the gauge is the same , you will need to do a bit of rewiring as the diesel sender only uses two wires in the connector and the gas unit uses three , the fuel pump wire will need to be lengthened from the place on the frame rail where the Diesel lift pump was to the sender area .

Really , I know it is a chore to drop the tank (possibly twice) but it is the best way to do this . I tried the frame mounted pump on mine when I first did the conversion, I did the sender swap in short order ........

I would personally go straight to the '7427 PCM , run it with a V8 Memcal , Should be plenty of those in the salvage yards. I tried mine with the 7747 when I first did mine , granted mine is an '80E truck , but the '7427 is heads and tails above the early ECM's .


TOM

[MrGiggles]

I'm not sure if Netres is interchangable?

As mentioned in these ECM it is more important for the Limp Home Feature then anything to do while running on the big chip.

A 305 chip may run if it's from a 7747. But to be close it needs to be a 350/5.7L chip for auto or manual depending on what you have.

Swapping in a 8746 is a plug and play, no wiring changes needed except add wires for IAT sensor.

I ran out of time today and was only able to glance at the Camaro. The glove box and dash on that side was still together (if that's where they put it on the cars), so I'm assuming the ECM is still there. If running an 8746 is really that easy, and tunes as easily as a 7747, then I will go back and pull it out. If anything I can throw it on Ebay and double my money on it.

I got the right TPS connecter, un-broken IAC, CTS, and MAP sensor plugs. Also the two coil plugs I was missing. Gonna start putting the harness together tonight, and get it ready to bench test. I'm still needing a knock sensor and O2 however.

Are the TBI injectors pretty reliable? I don't know the miles on mine, and if they have soft parts that wear out, I will rebuild them before I put it on. I did check the color codes and they are Orange/Black for a 350.

Tanks are the same , sending unit for the gauge is the same , you will need to do a bit of rewiring as the diesel sender only uses two wires in the connector and the gas unit uses three , the fuel pump wire will need to be lengthened from the place on the frame rail where the Diesel lift pump was to the sender area .

Really , I know it is a chore to drop the tank (possibly twice) but it is the best way to do this . I tried the frame mounted pump on mine when I first did the conversion, I did the sender swap in short order ........

I would personally go straight to the '7427 PCM , run it with a V8 Memcal , Should be plenty of those in the salvage yards. I tried mine with the 7747 when I first did mine , granted mine is an '80E truck , but the '7427 is heads and tails above the early ECM's .


TOM

There is a 92ish Suburban out there that still has the wheels and tires on it that shouldn't be very difficult to get the tank off of. I will see what they charge for it and maybe pull it this weekend. You know off hand if I can power the pump from the fuse box to see if it runs?

Which models came with a 7427? The above Suburban still has the PCM/ECM in it, and there are a couple of others that may have it. What benefits does the newer PCM give? I won't be doing the tuning, just the process of getting it running.

[Nasty-Z]

There is a 92ish Suburban out there that still has the wheels and tires on it that shouldn't be very difficult to get the tank off of. I will see what they charge for it and maybe pull it this weekend. You know off hand if I can power the pump from the fuse box to see if it runs?

Tank and sending unit are different between pickup and suburban , Pump will work if you needed it to though , I would use a new pump no matter which way I went , cheap insurance. You will need to find any 88-95 LB gas pickup for the sending unit.

TOM

[dave w]

Which models came with a 7427? The above Suburban still has the PCM/ECM in it, and there are a couple of others that may have it. What benefits does the newer PCM give? I won't be doing the tuning, just the process of getting it running.

Most all 1993 ~ 1995 GM light truck applications with an electronic overdrive automatic transmission will have the TBI PCM with Red / Blue connectors. There are three different service numbers used for the Red / Blue TBI PCM ~ 16168625, 16197427, & 16196395.

I strongly recommend using a VSS with a TBI PCM!!!

dave w