GM TBI conversion on a 304 CJ-7

[Texasdave]

Went to the Junkyard yesterday and pulled what I hope is everything I need to do this conversion. The donor vehicle was 1989 Sierra GMC pickup. The ECM was an 1227747. The BCC is still to be determined. I did not see any where I thought they should be. However on the ECM with all the information it had ASKF. I believe that is the BCC ID. I'll have to check when I get home to confirm the order of the letters. When I did a BIN search those letters did not come up. Anyone know anything about this chip? I will be going through this step by using the information found on this site. The help here has been tremendous especially david w and Eaglemark. I will keep you posted as to my progress from time to time and seek advice. I am putting it on a 304 AMC bored to .30 over. I will check with the fellow that redid it to find the cam he used.

[Texasdave]

Okay, basic question. My Jeep did not come with a check engine light so when I'm wiring in the TBI conversion do I need to wire in some sort of light?

[dave w]

Yes.

The computer will supply the "Ground" to the check engine light when there is an error. The other wire of the light is connected to the ignition switch ("On").

dave w

[Texasdave]

Working on the wiring harness and and I am unsure of which wires I need and which I don't. I have two multi-port plugs in the wiring bundle that connects to the wiring bundle inside the vehicle (1990 Chevy Pick up donor vehicle). DO I cut these out? I think I should but I'm unsure what they connected to inside the cab. I feel like a bomb tech do I cut the pink wire or do I cut the green/black wire. Only good thing, at least I won't blow myself up.

[dave w]

Figure out the ECM wiring first, here is a link to the 1227747 wiring schematics: http://www.gearhead-efi.com/Fuel-Inj...Information-42

dave w

[Texasdave]

When I removed the wiring harness it had a bulkhead connector, or at least I thought it was. In reality the wires go straight through and are covered by this plastic goop. I heated the goop and it melted allowing me to separate the wires. This makes it easier to work with them. BTW I was careful not to get it so hot that it melted the wire coating.

[fastacton]

When I removed the wiring harness it had a bulkhead connector, or at least I thought it was. In reality the wires go straight through and are covered by this plastic goop. I heated the goop and it melted allowing me to separate the wires. This makes it easier to work with them. BTW I was careful not to get it so hot that it melted the wire coating.

Yep, that's the fun part!

[Texasdave]

Because I cut the wires short to the ALDL I am going to have to add some wire to be able to mount it. What is the preferred method? Soldering and shrink wrap or unpinning from connector and crimping new wire?

[lakedrifter]

hey your in my neck of the woods:)

I'm not at expert at ECMs and programming, but I have worked in wiring a couple years now. When these guys mention re-pinning you usually see it when upgrading to a new style of ECM. They are basically moving the wires around to the corresponding pins for that ECM. Some may re-pin for looks. Some may simply wack and soldier the wires where they need to be. The only time I can see actually having to "re-pin" is if you may some how degrade the quality of the circuit. I know that some wire pairs are twisted and some wires have to be shielded. I'm not sure how I would handle those if I came across one that I needed to cut.

In my case, I'm doing a direct swap. I cut my entire wiring harness from the doner and all my wires are soldiered and shrink wrapped for the ECM.

Heath

[Texasdave]

Okay after some thought and consideration of time and quality I am leaning towards buying a pre-made wiring harness. I was talking with a sales person and he voiced concerns about tuning with a performance cam. Something about trouble with the vacuum values changing and the engine wouldn't idle correctly. Couple of questions: 1) Is this really a problem 2) Can you program the ECM to compensate for this anomaly?

[dave w]

1) Is this really a problem?

Yes, depending on the camshaft. Usually "Computer" friendly cams are a good option. Computer friendly Does Not mean "Stock Chip" friendly!

2) Can you program the ECM to compensate for this anomaly?

Yes, the fuel table (Volumetric Efficiency - VE Table) needs changes based on information from a TunerPro RT data log.

dave w