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Need to upgrade prestolite ignition on 76 cj7... Advice please. :)

Need to upgrade prestolite ignition on 76 cj7... Advice please. :)
76cj7chick

76cj7chick

Old Time Jeeper
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Vehicle(s)
1976 CJ7 Jeep with a engine/tranny/wiring harness out of a 1988 s10 blazer 4.3l v6 with th700r4 automatic tranny and a cj7 Dana 300 transfer case with Novak adapter.
Complete wiring harness from the s10 blazer. Painted with HOT PINK Pearl paint with standard sized metallic halographic pink flakes. Painted by me -a newb. New rear, front and side three wire LED lights, New parts, new custom dash-by me And a lot of guidance from fellow jeepers and lots of prayers etc.... :p
Hi all!

I recently installed the GM 4.3L TBI in my 76 CJ7 jeep... It starts and everything but has the check engine light.. :( 2 codes pop up--- 42 and 43 -- meaning there is NO spark control.. I guess, cause I haven't installed a knock sensor...) :o

Since I have the prestolite distributor I hope to upgrade my system... But I really don't want to spend a loooooot of money please...;)
Ideally, I would LOVE to have the ECM/computer control timing...

I've heard I could use a 78 jeep distributor and gm 8 pin ignition module and a knock sensor that screws into the side of the engine block...

HOWEVER- if anyone has a better/more efficient and cost effective plan -- PLEASE feel free to share your thoughts.

:notworthy::notworthy:
 
GatorBate said:
I did this to my AMC 304 a while back. I went through my prestolite distributor and removed the vacuum advance and flyweights. Then tied everything, completely disabling the timing advance. I mounted the ignition module on a plate next to the map sensor. I used the pick-up coil in the distributor to drive the module.


Have you seen this drawing?


and this website
Injection Tech - Binder Planet Forums
AMC 258 DS distr conversion - Binder Planet Forums
Click to expand...


Hi Gatorbate! Thanks for the suggestion...
Do you have step by step instructions? Better yet, I would love some pics if you have them of the conversion and how you removed the parts from the distributor...:eek:
Have you ever heard of people upgrading to the duraspark/motorcraft distributor for 78 jeeps and their coils? If yes, is the vacuum advance already phased out? So I can just drop the distributor in the jeep and let the ecm (after I hook up the ign module of course) control timing? Or will the HEI distributor allow me to drop in and let the ecm control the timing? ---This will be my first time removing and installing a distributor by myself... So, any and all help would be greatly appreciated... :notworthy:

I read a few of the conversion stories on binderplanet.com... And although it is very detailed.. I'm still confused... (sorry)... Would you know if anyone sells a already "converted" distributor that will just drop in my AMC 258 i6 / 4.2l engine and work with gm tbi, (electric spark control) have a tach reference connector and don't need to change out gears? OR is that just asking for too much? :0
 
Last edited:
I have not been able to find a distributor without the vacuum advance that will work with the GM ECM and will fit our engines. Unless you shell out the big bucks for a custom build. I am running the AMC V8 AMC 304 , so I have not looked for parts for the I6.

This evening I get some pictures and I will look around and see if I still have some from when I did the conversion.
 
Thanks for your responses Gatorbate...
I phoned my brother and although he is an excellent mechanic has never locked out the vacuum advance and such on any distributor... :(

I could always buy the e-prom specifically for my CJ7 w/AMC 258 i6 / 4.2l and GM Turbo 400 from howell or affordable for $200... :eek::confused:

If you're able to find a distributor that I need, I can offer some jeep or aquarium trades or some money... :drool:If anyone has one that is already to drop in for my engine and wants to sell or trade and is located in the Seattle, WA area please send me a pm.... :o

In the mean time... Would it be bad on the the jeep or anything if I drove it with the check engine light illuminating because of code 42 and 43? :rolleyes:
 
So cj-chick this is my understanding of how the obd 1 works. Using the throttle position and the map sensor values, the ecm looks up on a table how much fuel it needs to inject into the engine for the best mixture. When your RPMs are under 400 the ignition module in the distributor controls the spark advance. Once the RPMs go above 400 the ecm takes control of the spark advance. The ecm gets the RPMs from the distributor. So without the distributor and ignition module it cannot tell how fast the engine is turning, So it will not try to take over control of the spark advance. So you can run your vacuum advance distributor without any problem.

When your engine temperature reaches 180° according to your temp sensor, the ecm goes into close loop mode. Now it reads the O2 sensor and makes adjustments to the look up table to get optimum fuel/air mixture. Also if the knock sensor hears pinging in the engine it will retard the timing to stop the pinging.

Without the ignition module and control of the spark advance the ecm cannot make timing adjustments for cold winter starts and other conditions. So, yes it will work but not to its full potential.

Modifying your distributor is not that hard and if you screw-up they make new ones for around $140. So its not like you've ruined your jeep if you can't make it work.

I took some pictures of mine. I will post them in the next day or so. So you can see how I did it.:)
 
I may have to try to convert a duraspark/motorcraft distributor then... :(

I've found other info on binderplanet.com -- Including: using a gm 8 pin ignition module with the motorcraft distributor... And I'm wondering the best coil to use with this combo..

Some sites recommend a e-core coil... But... I like the simplicity of the canister coil and I already have a mounting bracket... Will the e-core coil and/or canister type coil allow me to hook up the tach reference wire?

Anyone have a suggestion :confused:... I like the idea of using jeep parts AND gm since they are easily found and don't cost bunches of money...:o


I like pictures... :p If anyone has the setup I'm thinking about please send me some pictures or diagrams... :chug:

Thanks for your help Gatorbate... :notworthy:
 
To modify you distributor so that the ecm will control the spark advance you will need to disable the vacuum advance.


First remove the fly weights


Then weld the two parts together so the two parts move as one.


Then remove the vacuum. Then using a dremel I cut a slot in the sensor pickup plate so it can be adjusted. Drill and tap the lower plate for the set screw.
 

My donor truck had this plate next to the TBI that the map sensor was mounted on. I moved the map back (in the red) and mounted the ignition module on the plate too.( in the yellow).


next I ran a wire from the plug on the distributor to the ignition module.


I cut a window in a cap. Use a timing light to see where the rotor is when it fires. You move the sensor along the slot that you cut in its plate with the dremel so that as the timing is advanced the rotor will move from one side of the spark plug post to the other side.


Rotor phasing
rotorphasing


I filled the hole where the vacuum went with silicone to keep dirt and wasp out.
 
GatorBate said:
To modify you distributor so that the ecm will control the spark advance you will need to disable the vacuum advance.


First remove the fly weights


Then weld the two parts together so the two parts move as one.


Then remove the vacuum. Then using a dremel I cut a slot in the sensor pickup plate so it can be adjusted. Drill and tap the lower plate for the set screw.
Click to expand...



:banana::rock: THANKS FOR THE PICS! :notworthy: They will make it much easier for me...

I am thinking of buying the cardone A1 replacement distributor for 78 CJ7 jeeps with AMC 258 i6 / 4.2l engine. PN: 84-4691.... Any suggestions on this dizzy? Or should I try a HEI distributor?
I went ahead and purchased a GM 8-pin ignition control module pn: lx340... Is this the correct one? :confused:

Thanks again for your help!:p
 
By the way... This may be a stupid question.. But, I thought id ask anyway...

So-- I know that the distributors for 4.0 jeeps are computer controlled.. .So, can I use the distributor out of a 4.0l jeep engine? Or are the gears and such totally different? :confused:
 
Re: Need to upgrade prestolite ignition on 76 CJ7 with gm TBI....Advice please. :)

I don't know... The more I look at what needs to be done for the tbi to run correctly.. .Perhaps it would be better to buy the distributor already fixed for the computer?

Any suggestions on an economical but reliable distributor as such?

Thanks again in advance!:D
 
By the way... I noticed I put this thread in the drivetrain forums.. If anyone wants to put in the correct forum that would be great...:o
 
I had the same setup in my 76, but I have the AMC 304 V8. I had problems with it, so I took the ECM, coil and stock distributor out. I bought the Mallory HEI ($200)and the motor runs better now then it ever has. Only 1 wire to run the engine now. Not sure sure about the TBI set up, I have a 2 barel carb.
 
So, I've been researching a bunch on the internet on the best distributor/ignition upgrade.. Still haven't come to any "ah-ha" moments... :(
But I will keep on researching... Issue with me changing out a distributor to work with a tbi/ecm system is that I DON'T have a welder nor have I welded anything.. I have soldered and such but no welding experience... :o
I'll keep looking and thanks guys for your suggestions and help! I've printed out the pictures of the distributor change over from Gatorbate and will keep that in mind.. If I can't find a distributor that just drops in and hooks up to my ecm...

Thanks again... If anyone else would like to chime, I would appreciate it... ;)
 
I was unsure when I converted my distributor and did not want to make any irreversibility changes to it. So I removed the springs and replaced them with aviation safety wire. One of these days I intend to replace the safety wire with a permanent weld.

So whats up with the aquarium. You run a store? I was given a Redsea 250 back in November. I've been able to keep most things alive but the algae is killing me.
 
GatorBate said:
I was unsure when I converted my distributor and did not want to make any irreversibility changes to it. So I removed the springs and replaced them with aviation safety wire. One of these days I intend to replace the safety wire with a permanent weld.

So whats up with the aquarium. You run a store? I was given a Redsea 250 back in November. I've been able to keep most things alive but the algae is killing me.
Click to expand...


Huh? What aquarium? :wtf:
Are you trolling? :pissed:
No, just kidding...:p
But serious, what aquarium? :confused:
 
GatorBate said:
This
Click to expand...


:o:p OH... I see... I don't know.. Just thought a jeeper would NEED an aquarium and wanted to trade... :rolleyes:

Thanks for the suggestions... I'm a little "under the weather," so to speak... So not working on the heep for now... :barf:
 
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