Trying to understand the HEI/TFI/ECM wiring

[brendan]

Okay, Bill, I was getting confused as to why there would be 2 different Ignition units running at once. I had assumed that the use of the duraspark ignition module you discussed on the binder bulletin post last week was a step used in your triggering system for the EFI.

Which style module do you use? I can't make itout in any of the pics on oyur site. I have attached a pic of the 3 HEI modules.

I am thinking that you use the 7 PIN module used with the tbi systems.

[brendan]

Here is the wiring as best I can figure. I am assuming the 7 pin EFI module. I couldn't locate any HEI pinouts, so some of this is guessing.

[Bill usn-1]

pin out

ftp://ftp.diy-efi.org/pub/gmecm/manuals/1227747/
Here is the pinout I posted to your reply yesterday.

The module is the one in the middle.

If you still think I am using the ford duraspark module with the GM ignition then you are still confused. I think you may be trying to combine 2 different posting into 1 because they discussed the ford conversion.
you can convert the holley system to a ford system and leave it at that. This is just an ignition upgrade like I was talking about on BB.
The next step I talked about was to lock down the advance and remove the ford module and wire the dist to the GM ign similar to your diagram.
the two threads were seperate discusions.
hope this clarifies.

[Bill usn-1]

Originally posted by brendan
Here is the wiring as best I can figure. I am assuming the 7 pin EFI module. I couldn't locate any HEI pinouts, so some of this is guessing.

I would add a pwr relay to the 12v ign circuit and not try to pwr the coil and ign off the scout wiring. Just use the 12v ign wire from the switch to activate the relay. It is the little black relay in my pics.

[brendan]

I understand that the two ignition systems are not in use at once. I have torn into my dist. a half dozen times playing with the mech. advance. I am pretty solid on simple distributors.


When used with the TBI you doing one of two things:

1. using the entire Duraspark system, dist. and module and just triggering the ECM with the magnetic pickup in the dist. and NOT controlling timing.

2.disabling the advance systems in the distributor and all the advance is controlled by the ECM through the adapted HEI module.

These are the two systems you have described, correct?

Which file contains the HEI module pinouts?

I think that with the TFI coil system you would need two relays, because the coil only gets 8-9 volts un the run position(resistor #8) and 12 volts in the start position. Giving it 12 volts all the time is what causes them to melt down in a few weeks.

I just reread my first paragraph in the thread starting post, and I see why you think I am still confused(Or maybe I am?).

[brendan]

Okay, I found the module in the drawing. It shows 5 pins: A through E. Are you using the 5 pin module? I don't see the lettered pins you mentioned earlier do I?

[Bill usn-1]

pins

Originally posted by brendan
Okay, I found the module in the drawing. It shows 5 pins: A through E. Are you using the 5 pin module? I don't see the lettered pins you mentioned earlier do I?

Here is the page...#6.
shows the EST hooked to the GM wiring harness. The ford pick up goes to the P&N term as described.
I suggest you print out all seven pages and really study them. It might make things a little clearer.

ftp://ftp.diy-efi.org/pub/gmecm/manu...47/747ecm6.jpg

[Bill usn-1]

Originally posted by brendan
I understand that the two ignition systems are not in use at once. I have torn into my dist. a half dozen times playing with the mech. advance. I am pretty solid on simple distributors.


When used with the TBI you doing one of two things:

1. using the entire Duraspark system, dist. and module and just triggering the ECM with the magnetic pickup in the dist. and NOT controlling timing.

no... you are still trying to mix the two. The complete duraspark ign was only used until I went to the TBI system.

2.disabling the advance systems in the distributor and all the advance is controlled by the ECM through the adapted HEI module.

Yes.. this is how I do it now. You have to have a magnetic pick up to trigger the ECM correctly. So I used the ford Duraspark pick up I had in the dist already to trigger the GM ecm.

These are the two systems you have described, correct?

Which file contains the HEI module pinouts?

I think that with the TFI coil system you would need two relays, because the coil only gets 8-9 volts un the run position(resistor #8) and 12 volts in the start position. Giving it 12 volts all the time is what causes them to melt down in a few weeks.

You can still use one.
The 12v for start can still come from the "I" term of the solenoid like your drawing.
Use the resister between the relay and the coil.

I just reread my first paragraph in the thread starting post, and I see why you think I am still confused(Or maybe I am?).

[brendan]

Bill--

Thanks for the #6 diagram. I tried to get that one to download at least a half dozen times this weekend and it just kept giving me some sort of directory page.

The module pictured is clearly the 8 pin unit in the center of the photo above.

I think I am clear now on the distributors and triggers:

Th ECM can only be triggered by using the HEI module and Durapark distributor ONLY-- no other Duraspark parts.

Thanks for your patience.

[Bill usn-1]

ONLY

I don't want to confuse you but you really can't use words like only or never or always.....There are ways to trigger the ecm with signals other than the ones we have discussed but if you are going to convert to the GM TBI system than using a magnetic pick-up dist is the best way to go, and let the computer control the fuel and the spark.

I only try to tell things the way I know them. there are always exceptions.

[brendan]

Fair enough.

I'll redraw that diagram when I get home tomorrow. I'm using the worthless paint program to do it, so I can only get it small enough to post by zipping it, sorry.

[Bill usn-1]

Sounds good.

I'll be glad to see your project under way.

[Jeff Eggemeyer]

Hey Brendan

If you want to draw it on paper, scan and send it to me, I can draw it in Autocad for you and send it back.

Jeff