GM TBI No Start Jeep 4.0 I6

Hello everyone,

I just swapped a GM TBI from a 4.3 V6 to the 4.0 in my AMC Eagle and I am at my wits' end with this. I put the wiring harness together myself, and I intended to control fuel and spark. EGR, Knock, and VSS have been left out (at least for now).

These are my main setup specs:

-1995 Jeep 4.0 engine with 4.2 intake
-Rebuilt 4.3 GM throttle body
-GM 8 pin ignition module triggered by Duraspark magnetic pickup
-Stock Duraspark distributor with mechanical advance locked down
-MSD Ford style TFI ignition coil
-E2000 fuel pump
-1227747 ECM
-APAB-$42-4.3-Manual.bin from here, stock 2732 chip programmed with GQ-4X programmer
-Custom wiring harness modeled after the IH one at the link above (did not connect A4, A7, A10, B10, C2 or C7)
-New heated 3 wire O2 sensor, CTS, IAC, and TPS (set right around .51v)
-Bluetooth ALDL reader using Tunerpro RT v5

All grounds are made to the engine block, which has a good cable to the battery, good strap to the frame, and good strap to the firewall. The only sensor that is not new is the MAP sensor.

This was running pretty good with the carb and MSD cdi box immediately before the install, but got poor gas mileage and was a pain to warm up in cold weather. It did however start instantly.

When I initially finished installing everything, I did actually have it running for a little bit. At the time, the computer was for a 5.7l. It would rev up to between 1000 and 1800rpm and the idle was all over the place. The pedal was not responsive, and after about 30 seconds to a minute it would stall. After a few starts, it began to backfire out the carb, and at one point it was backfiring out the carb and popping out the tailpipe at the same time. I got to see it with a timing light then and it looked like it was about 10-20 degrees ATDC...knock retard maybe? moving the dist would not change it, and disconnecting the bypass wire still would not let me set static timing to 0.

For the past couple weeks I haven't been able to get it to start at all. The distributor is definitely in the right spot, rotor pointing at #1 plug wire on compression stroke, and it is not 180 out. Wire positions did not change. It has spark, coil is getting 12 volts, and the pickup coil in the dist checks out. It might be giving a little too much fuel, but the injectors fire a good cone shape and don't drip. Plugs are clean and gapped to .045"

There are no error codes being shown, and as far as I can tell everything looks OK in Tunerpro. I might be able to take some screenshots to post soon.

Would I need a completely custom .bin file for this setup? Do spark tables need to be modified? Maybe I missed something with EGR/Knock/VSS wiring? I would think it should at least start as it is... I've gone through just about everything I can think of. The only thing that comes to mind now is rotor phasing, but since it ran before I don't want to mess with that yet.

Any help would be greatly appreciated! This is an awesome forum and you guys have been a big help to get me this far.

Attachment 8479Attachment 8480Attachment 8481Attachment 8482

Maybe your ignition module has taken a dump? Do you have it attached to a heatsink? Is it getting hot with the ignition on? I've seen similar problems because of a failing module and the fact that you can't adjust the timing tells me it's probably an ignition issue.

Ignition module should be fine. I had one BWD module from Advance Auto go bad instantly. Then I used a junkyard GM module, which is what I had it running on.

Now I have a Duralast module from Autozone. It is bolted to a metal plate with two 12 gauge ground wires going to the block in different places, and has Radio Shack specialty heatsink compound on the back. While the spark isn't quite as strong as my cdi was, it does spark and should be good enough to start.

I have another on the way from Rockauto that I'll be able to test with soon. I can't stand these little modules...always seem to be trouble. I may end up ordering a Delco OEM replacement when I actually get it running.

I was thinking about hooking up the cdi as described at the bottom of the page here just to give it a shot

It has spark at the Coil? Do the Injectors pulse or spray fuel while cranking?
If No Injector Pulse, I would do this:
Using a Scan Tool or your Tuner Pro and an ADX file, connect to your ECM with the key on, engine stopped. Look at the TPS and move the throttle to insure you are viewing LIVE data. Then watch RPM and start the engine. After a second or two, you should see some RPM on the variable. If not then you need to do some diagnostics.
With a wiring harness diagram, find the "REF and REF LO at the 4 pin connector @ the Ign Module. Test the BAT + At the 2 pin on the module. (You stated your Ign module grd had 2 wires and a heat sink. Alum plate 1/4 think bigger than the module. Silicone grease works well as a heat sink grease.)
Find the correct ECM Pins for the Ign Module REF and REF LO wires and disconnect the ECM and Module connector to measure the resistance. Insure the Correct pins on the Module AND the ECM.

Use the Scan tool or ADX file to insure your MAP is close to 4.80 volts. Higher altitude will be lower volts. Watch TPS for 0.50 to 0.80 aprx and the volts increae with throttle opening. No Diag Codes.

If you plan to use the Knock sensor with the 4.0L engine, the knock characteristics will be different than the 4.3L 90 degree V-6 GM engine. You could get false retard and a poor running engine. Use your ADX file and watch for knock. If none, advance the timing using Tuner Pro in an area, and drive. Record the drive and look for knock in the advanced spot.

If you've ruled out the ignition module, then you need to check the rest of the ignition system and the ECM. You should be able to adjust the timing to 0 once you disconnect the bypass. Since you can't, there has to be either a distributor or ECM problem (or something I'm not thinking of). A couple of weeks ago, I had a no start issue. I had spark and sometimes could get it running, but it was very difficult. I replaced the coil and it fired right up, but I never had problems setting the timing.

The injectors do pulse and seem to spray a nice cone shape as they should.

IIRC, the MAP sensor read at exactly 4.8volts- pretty close to sea level here. TPS is set at .51volts, and does increase with throttle movement (live data through tunerpro with key on).

I didn't plan to use the knock sensor at all. I had read somewhere about using a resistor in place of the knock sensor wiring, but I didn't know if this applied to me. I may use a VSS someday, but the Eagle has an odd mechanical speedo gear and cable, and I have plans for a digital gauge cluster in the future.

I tested coil resistances, which are still within tolerance, and it is getting 12 volts. I also swapped in a different coil just for testing, and still nothing. Cap and rotor are good, and the plug wires are a good set of make-your-own MSD wires.

I will have to triple check that the ignition wires from the module are going to the right pins on the ecm. Otherwise, everything I can think of in the ignition system is good, except for MAYBE rotor phasing.

I had noticed that the ecm thinks it's in Drive while starting. Would this have an effect on it without the Neutral safety switch hooked up?

What about the pickup coil wires? How are they connected to the ignition module? I assume its a good stock (or stock replacement) pickup coil with a orange and purple wires? On the GM ignition module, there are two terminals, P (positive) and N (negative). The purple wire on the pickup goes to the pos terminal and the orange wire goes to the neg terminal. Also make sure the black wire coming from the distributor has a good ground too. I grounded mine to the same heat sink I have my ignition module on.

Also, I had a problem when I first installed my tbi system years ago. I had installed a new distributor pickup in the distributor (cause the one that was in there, the plastic was cracked) It was a advance auto pickup. Anyways, it would barely run and backfire, sputter and thats about it. I ran around in circles forever chasing my tail swapping out everything and the last thing I did was replace the pickup cause everything wanted to point to that, but I kept dismissing it because it was new. Anyways I installed the most expensive one napa had and my problems were solved.
Cant say thats your problem, but just wanted to put the idea out there. But it does kinda almost sound ignition related to me.

Thanks for the reply! I have tested the magnetic pickup and gapped it .008" from the reluctor, it was also known working before the swap. The wires to the module are all good, redone with audio grade connectors, and it gets the same voltage readings at the module as the pickup sends immediately from the distributor connector. All my ground wires go directly to the engine block with good 12 gauge wire to where the battery connects.

It does get good blue spark (tested with an HEI spark tester), and it also has good fuel cones spraying from the injectors (no drips). I'm thinking it's a timing issue, as it sometimes backfires while trying to start. However, the mechanical advance is locked down, the rotor points to #1 plug on the compression stroke, and it is not 180 out. I also tested a different, brand new distributor I had for kicks- same result.

At this point I will probably need to set the rotor phasing to rule that out. Just strange that it was running before and not now. Still no engine codes. Only other thing I can think of is the MAP sensor might be bad.