Jeep CJ7 GM TBI Conversion Help - JeepForum.com
Search  
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep CJ Forum > Jeep CJ7 GM TBI Conversion Help

Introducing MONSTALINER™ UV Permanent DIY Roll On Bed LineYear End Clearance Sale! Save 20%NEW!! HMF 50"-52" light bar mounting brackets!!

Reply
Unread 06-28-2013, 10:44 AM   #1
hoffmanuno
Registered User
1976 CJ7 
 
Join Date: Mar 2009
Location: Pacific junction, Iowa
Posts: 24
Jeep CJ7 GM TBI Conversion Help

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)
http://24.media.tumblr.com/855c1c8e7...l1seo1_500.jpg

TBI all hooked up to chevy harness
http://25.media.tumblr.com/1f88b4d57...l1seo2_500.jpg

ECU
http://24.media.tumblr.com/44a3f3ab3...l1seo3_500.jpg

view of ALDL connection, fuel pump relay, and battery connection terminal
http://25.media.tumblr.com/707aa3bb4...l1seo4_500.jpg

Close up of ALDL
http://24.media.tumblr.com/e6f23839e...l1seo5_500.jpg

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.

YouTube (Short URL)
?start=" frameborder="0" allowfullscreen>


hoffmanuno is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 01:34 PM   #2
1986cj
Registered User
1986 CJ7 
 
Join Date: Dec 2007
Location: Denver Colorado
Posts: 1,876
The tbi does not need a aldl to run. The White and Red injector wires in the GM harness connect to each other and all they need is a switched hot in the run and start position. The emc only provides a ground to the Green and Blue wires for the injectors. Find you a hot wire in both the run and start position and tap this to a relay and run your ignition and injectors from it. There are other things that have to be hooked up that the ecm looks at before it will send the ground to the injectors.
1986cj is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 01:47 PM   #3
hoffmanuno
Registered User
1976 CJ7 
 
Join Date: Mar 2009
Location: Pacific junction, Iowa
Posts: 24
That was my plan, to run those wires off a relay, when I got the system to start up and run. I got a lot of mixed messages online about whether or not I needed to use a tach filter between my 2 wire CRT hei distributor and the EMC pulse feed wire. I ordered one online today, so hopefully it will arrive next week. In the meantime I'm going to the junkyard to get the MAP sensor and will take back my EMC to exchange it for another 747 just in case it was fried in the first place. Since the truck we got the harness and EMC from had no dive train and the main power wire was chopped and then twisted and taped back together, the EMC could easily have been fried when it was taken out. finding another 747 in the junkyard shouldn't be a big deal. I'll grab a couple of relays while I'm at it as well and then use them to wire in the ignition for the EMC and injector power from the battery. This way, by the time the tach filter comes in the mail I should have everything mounted and wired up properly so it's ready to go.
hoffmanuno is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 02:54 PM   #4
james04si
Senior Member
 
james04si's Avatar
1977 CJ5 
 
Join Date: Apr 2009
Location: Arlington TX
Posts: 852
You should not need a tach filter for your CRT HEI distributor. GM did not use one with the TBI and the stock HEI. The filter is used for MSD style ignition boxes.
james04si is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 04:16 PM   #5
hoffmanuno
Registered User
1976 CJ7 
 
Join Date: Mar 2009
Location: Pacific junction, Iowa
Posts: 24
Well, that was $30 down the drain then. There were a lot of posts from people saying that they advised a tach filter because it could fry the ECM. One guy had a my style of alternator and said that the ECM hesitated at points running his two wire HEI style distributors tach wire to the pulse wire on the ECM. He put the old distributor back on with the tach filter and it worked great. A lot of other people say to put on the filter as an insurance policy against spikes as well. When I get this figured out, I swear I'm going to put this all on YouTube and narrate exactly how to do this so that everybody after me can just do it without having to go through what I did. When you read through a 100 different people's Chevy TBI builds you get about 20 different ways to wire it up and not all ECMs are exactly the same. I know you can buy a painless wiring kit to make it idiot proof, but I only want the TBI to run the fuel so that $300 is a waste of time. When I do the video, I'm going to just say "See this big ol red wire? That goes to the battery. See these injector wires? Just wire them into a relay off the ignition wire of your car, preferably the one that goes straight to your 2 wire CRT style HEI distributor. See these grounds? Mount them all to the block. See this relay that came with your junkyard harness? That gets an ignition wire to activate it as well and run this wire to your pump. Now plug in these sensors, cut off the rest, and mount that sucker because you are done!" I hate reading schematics, which is why I dropped out of electrical engineering my first year in college. I'm a visual person, so if you show me something then I can repeat it.
hoffmanuno is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 04:34 PM   #6
CSP
Registered User
 
Join Date: Aug 2002
Location: Colorado
Posts: 12,784
I'm trying to visualize this "two wire" HEI distributor. Are you meaning one wire for power and one for the tach lead?
CSP is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 04:47 PM   #7
CJ51973
Registered User
1988 YJ Wrangler 
 
Join Date: Aug 2004
Location: Versailles, KY
Posts: 2,313
It's been about 10 years but I used a ignition module from a TBI truck. It has 3 or 4 pin instead of 2 that I am assume the CRT has to get the right pulse for the ECU
__________________
Anything is possible if you don't know what you are talking about.
CJ51973 is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 06:03 PM   #8
james04si
Senior Member
 
james04si's Avatar
1977 CJ5 
 
Join Date: Apr 2009
Location: Arlington TX
Posts: 852
Quote:
Originally Posted by CJ51973 View Post
It's been about 10 years but I used a ignition module from a TBI truck. It has 3 or 4 pin instead of 2 that I am assume the CRT has to get the right pulse for the ECU
The newer HEI distributors have computer timing control. I believe they have either a 6 or 7 pins on the actual ignition module. The CRT is an old style with mechanical advance. All of this being said, you might want to pull your distributor after its ran a few thousand miles and check the cam and distributor gears. I have had 2 CRT distributors. The first I purchased about 5 years or so ago and the gears meshed perfectly, the second I bought about 2 years ago with my 258 build and the distributor gear started wearing bad within about 5k miles. That tells me that at some point CRT has changed gears at least one time since they have been in business.
james04si is offline   Reply With Quote Quick reply to this message
Unread 06-28-2013, 08:37 PM   #9
Jon In Tucson
Jesus Is Lord!
 
Jon In Tucson's Avatar
1983 CJ5 
 
Join Date: Aug 2008
Location: Tucson, AZ
Posts: 805
When I did my TBI conversion, I used the information available on www.binderplanet.com. The injection tech forum was very helpful(understatement) and the moderator, Bill-USN1 has forgot more about TBI than I will ever know. If your injector are not firing or constantly firing, it has to do with the ECM not able to figure out a spark pulse when you are cranking. I ended up converting my duraspark distributor to a GM style 8 pin spark module. Now the ECM controls spark, timing and fuel delivery just like the astro van I removed the parts from... God bless.
Jon In Tucson
__________________
Jeremiah 17:7 "But blessed is the man who trusts in the Lord, whose confidence in Him."

"The secret to a Jeep, especially a CJ, is you can't
panic." - Mike

"I may not be a smart man, Jenny, but I do know grounds."
Jon In Tucson is offline   Reply With Quote Quick reply to this message
Reply

Quick Reply
Message:
Options

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.
Note: All free e-mails have been banned due to mis-use. (Yahoo, Gmail, Hotmail, etc.)
Don't have a non-free e-mail address? Click here for a solution: Manual Account Creation
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.


Thread Tools






Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.