I did a ground up restoration of my 1976 Jeep CJ7 and had the 258 engine rebuilt with a Clifford racing kit by my local machine shop guru. He fabbed up his own designed sideways tbi adapter for my Clifford intake and I built a Megasquirt computer for it. Well, after 2 years of trying to get the megasquirt dialed in and having tons of problems, I'm giving up for now. My backup plan was always to put in a junkyard chevy TBI ECU anyway, since its all chevy parts in the system. I went to the junkyard and found a complete harness and ECU just sitting in the empty engine compartment of a 91 or 92 Chevy shortbed truck at the local Upullit. It was the 747 ECU, so I really lucked out. I plugged in the IAC, TPS, injectors, and coolant sensor (all propper chevy) but have not connected the O2 sensor yet and still have to pick up a MAP sensor from the junkyard. Besides the MAP, all the other sensors are brand new but the TPS. So I looked online at multiple sites, diagrams, and pics and got the basic wiring down. I'm reusing the stock fuse and relay for the fuel pump and got that figured out. The injectors weren't firing, so I read up some more and like I thought, I needed to connect the tach wire from my CRT HEI distributor to the ECU's wire to fire the injectors. Nothing happened. Well, then I did some back tracing on the injector wires in the loom and found out that the red and white injector wires go together just like my Megasquirt system, but they ended up dead ending at the ALDL cable. I patched that connection into a + 12v wire. Bam, one of the injectors started to pulse a bit and the engine started briefly. So now I have a few questions that I can't quite seem to find or figure out.
1. Should I go tot the junkyard and look for something to plug the ALDL into that will provide the power for the injectors or just spice in a power wire to it.
2. Is connecting the pulse wire from the ECU to the tach wire on my 2 wire CRT HEI distributor going to work or will it harm the ECU? I'd rather keep the CRT distributor since it has an adjustable torque curve for the vacuum advance and works so well, so if there's something I can adapt to keep it, I'm more than willing.
3. Why did only one injector come on? Maybe a ground issue? If the ECU was bad I can still take it back since I got it just this Sunday.
I have pics that I'll try and upload.
CRT HEI distributor with two wire hookup (ignition and tac)
TBI all hooked up to chevy harness
view of ALDL connection, fuel pump relay, and battery connection terminal
Close up of ALDL
Both fuel injectors work, one being brand new. I even checked out the wiring by taking off the ECU harness and grounding out the two injector pulse wires with the positive wires connected to the battery. They clicked loudly when tested. I know this has all been covered a thousand times and I did do my research for this swap and have several printed out wiring diagrams that I am using. I believe I'm very close to getting it all worked out so I can clip off the unneeded connections (but leave the wires for other purposes just in case, and then dremel in a cut out for the ecu wiring in the shifter access panel and mount the ECU. My goal is to use the chevy tbi ecu as a reliable control system in order to eventually diagnose the problems with my megasquirt system and then keep it as a backup in the vehicle in case of any system failure so I can just switch back over to it. I have had my motor in the jeep for going on 2 years now and haven't been able to get the megasquirt to work properly despite many attempts. I literally took the entire jeep apart and put it back together in a frame up rebuild, including repairing all the wiring, and made a custom harness for my megasquirt as well. I'm pretty familar with the TBI sytem, as well as megasquirt. The Chevy ECU does seem pretty easy to install, but I just want some clarification on the injector issue. A lot of articles cover the various wires, and I printed out some from this site and others regarding the 747 wiring, which the sensors were easy to plug into my existing tbi setup. I can't work on the jeep in the garage anymore since I put the 35x12.5 MT's on it, so I have to work outside after work. I'm lucky to get an hour or so on it before the mosquitos start bleeding me dry and it gets dark. If I can get the wires sorted out for sure, then I can solder the connections up and get the wiring harness routed into the jeep so that I might actually be able to drive it down the road without it coughing and weezing, sputtering, and then limping home like a crippled old mule.
And here's a youtube video of my roughly wired in setup. Keep in mind its just to make sure the injectors fire and it starts, then I'll connect everything much better with soldering and shrink tube. For now it's easier to diagnose everything with the wires spread out in the open so they are easy to trace and connect.