I'm in the process of going HSR to carb and will retain the intank pump. I still don't understand a few things however...

The dizzy wiring I think I have down.

I'm already assuming I will have to rewire the fuel pump and disable VATS...I've got a vague idea how to accomplish this.

1. Can I unhook the tranny wiring or does that need to stay intact??

2. Will the Alt continue to function properly when the ECM is pulled? I'm pretty sure they are tied in somehow.

Right now the alt charging lead is wired to the ECM connector and if thats removed how will it work?

3. DO I HAVE TO LEAVE THE GROUNDS FROM THE HARNESS TO THE BACK OF THE HEADS ON OR ARE THOSE USELESS NOW???

4. Will the starter wiring remain functional??
More to come....

 

Have you ever studied a wiring diagram?

 

Do you have one?

 

http://www.austinthirdgen.org/module...howpage&pid=22

Bookmark that, give it a good study.

 

yes, grounds from the rear of the heads need to be there.
Starter should be fine as is.
leave the tranny wiring, that should only be the reverse light right? (or a digital speedo in your year?)

 

May I ask what you are doing with the stealth ram?

 

As badly as I don't want to I'm probably going to sell it, recoup some money and loose some frustration. I really don't want to, plan is to get the carb running to check the rest of the shortblock and car and then go back to HSR and get it running...BUT I have a feeling if this carb thing turns out okay (which I'm sure it won't) I defenitly won't get the HSR running
/rant



I've studied that wiring diagram and am still confused BUT what I plan to do is hook up everthing I might need and leave the ECM hooked up.
I'm in the process now of removing the harness to organize everything.

 

Yea, those wiring diagrams are confusing.
Any specific woes that haven't been addressed yet?

 

Nah...I just still don't understand what needs the ECM to function but it seems to me everything does so I will have to cut and splice my harness again and hook up the following (from the factory harness)...

Alt (Alt Charging Lead)
Dizzy
(2) Tranny Connectors
Fuel Pump Relay
Oil Press Sender
Water Temp Sensor
Starter Wires
GNDs to heads
(I think thats it)

Of course the Lights and Horn will stay hooked up with the rest of the body wiring, and my Fan Switch, and eventully my 6AL again
MAN I'M CONFUSED!

 

i thought that you would only have to get power and tach to the dizzy and maybe TC lockup and everything else could stay as is the ecm would freak out and give you a ses light but i dont see why that wouldnt work

 

alt - charge sensing wire. That (I think) comes from your ignition wire in your steering shaft, and through the "charge" light in your dash. Shouldn't go through the ECM at all.

dizzy - You'll need a vacuum advance unit. Then you only need it wired up to power, and tach. The same plugs (I think) can be used, you just omit the plug that controls the advance curve.

fuel pump relay - you'll probably have to re-wire that one to an ignition wire.

OPSU - that's just for the gauge, I don't think it goes to the ECM.

water temp - drivers side just goes to gauge, leave that be, passenger side goes through the ECM to control fan turn on temp. That's a tricky one, try hot wiring it to go on with the ignition for now. If the carb is a route you'll stick with, there is a standalone gizmo you can set up to turn on one, or both fans, at specific temps.

starter wiring shouldn't have to be touched at all.

GNDs to heads should be left alone.


2 tranny wires? Find out what they are. I think one is to light up your reverse lights, the other...? Speedo sensor?

 

oil pressure sending unit is actually used as a FP switch keeps the pump running as long as the engine is seeing 4 psi of oil pressure thats why you wouldnt need to rewire the FP relay the fuel in the bowls will fire the engine then the opsu will turn on the pump

 

Except I would still run power through the relay.

 

Damn I have to type this again...
Completely tore into the harness last night. Cleared a few things up. I wish I had a pic of before I got things organized!

Most of the stuff I need connects on the drivers side by the booster away from the ECM but some still doesn't.

The starter wires, alt wires, water temp sensor, brake fluid indicator, one tranny connector (reverse lighhts I think), and dizzy wires all run to the drivers side.

However, the oil press sender, fuel pump relay, the second tranny connector (VSS?), and of course the connector that powers the ECM all run across the motor to the passenger side.

So, I'll still have to do some wire cutting, splicing, and hiding but the remainder of the wires I'll bunch up and leave be until the motor starts then more than likely cut um off!
I don't think I'll go back to EFI unless I buy a new harness anyway since mine isn't in the absolute best shape.

 

The dizzy wires from the drivers side are the coil positive side and the tach signal.

 

YOu need to hop on AIM sometime. I've dug up all the schematics I used when i re-wired my car bumer to bumper.

 

I would go at it from the other direction... Start at the ecm and work your way through the engine bay Just seperate the wiring out as you are doing... You shouldn't need any of the wiring that leads to the ECM...with the exception of your Fuel pump (tan ith right stripe) which actually goes right past the ecm Through a connector to the rear of your car. Don't forget that you will need to regulate that fuel pump down to around 5 PSI...

 

Yea, I'll be ordering an AFPR from Summit when I get my carb and find out the last few things I will need for the conversion. As far as AIM I don't think I even have an account anymore!

I have running to the ECM...
1. Green w/White striped wire running from ECM (pass) side to the fuel pump relay.

2. One grey wire from ECM that splits and runs to the fuel pump relay, oil press sender, and the drivers side bulkhead.

3. One Purple wire and one Yellow wire running directly to the tranny from ECM side.

4. One Blk w/White striped wire running from ECM side splitting to a GND, the fuel pump relay, and the drivers side bulkhead.

5. And two other GND's from the ECM side (one has two Blk w/White striped wires and one has a Blk w/White striped wire and one tan wire).


Also, there is one orange wire running from the ECM connector (stock its found near the battery and unplugging it kills the power to the ECM) that leads to nothing. Still trying to figure that one out...(the other wire from this connector runs to the fuse and then splits to power the oil press sender, fuel pump relay, and has two splits going to the ECM). Heres a pic...wheres that orange splitting wire supposed to go?

I know I said a lot but if anyone knows what these wires specifically do I'd love to hear it. If I can bypass this ECM altogether (and run these wires elsewhere) I'd also love to do so. I just don't know what I would do about my speedo...

 

could that be the fuse for the fuel pump?

 

First off, go to this site: http://www.chevythunder.com/fuel%20i...%20pinouts.htm . This will give you all the info you need to identify every wire running off the ECM. He also has detailed schematics and alot of other useful info.
1. the green/white wire will (when 12V is applied) throw the pump relay and turn your fuel pump on. If you are going to use the oil pressure sensor to turn on your pump, you can cut this wire or simply remove the relay all together.
2. The grey wire is the power wire to your fuel pump. This wire needs to remain intact from your oil pressure switch to your fuel pump. You can cut the section that runs to the ECM.
3. The purple and yellow wires are running to your vehicle speed sensor. I suggest unplugging these from the tranny- you wont be needing the VSS. Note: THis may or may not be part of the cruise control. So you may want to look into this if you want to retain your cruise.
4. Disconnect the black/white grounds
5. This is the main power to your ECM. I use the fuse as an easy way to reset my ECM without disconnecting the battery. This wire can be removed.

Hope this helped... Good luck
-KS
----------
Dont forget to regulate that fuel pump!

 

Yea that sheds a little light, thanks! I totally forgot I had that chevythunder site bookmarked.

If I cut the grey wire from the ECM that runs to the oil press sender, fuel relay, and drivers bulkhead will those still function properly or does that still need to be connected?

And if I remove the VSS wires how will my speedo function? (Don't have cruise so I won't worry about that!)

And addressing that orange ECM power wire...there is a red wire that runs from the connector (with the orange wire) to the fuse then an orange wire running from the fuse to power the oil press sender, fuel pump relay, and to the ECM. What I don't understand with this is if the orange wire that runs to the connector goes to nothing how are any of those items listed above getting any power?
The pic above shows the orange wire from the connector that leads to nothing and the red wire that leads to the fuse then to an orange wire going to the above listed items....I hope I'm not confusing anyone as much as myself!

 

Oh, BTW...If I want to run the fuel pump relay (I'll keep the relay for safety) off the oil press sensor what wire would I need to connect the Green w/White Striped wire to from the relay on the oil press sensor?

And I guess the pump not priming when the ignition is on wouldn't be a problem with a carb?

 

The fuel in the bowls is enough to start the motor.

Powering the fuel pump relay off of the oil pressure switch is kind of backwards. They're designed to be seperate of eachother.

Keep the OPS as it is, power the relay via something else (I run mine with a fuse tap off of the main block).

 

but the fuel pump is directly connected to the oil pressure sensor so.... why change it

 

Ok,
First road block to converting from TPI to Carb with an electronic speedo... Looks like you will need to find a VSS buffer... Check this thread out: https://www.thirdgen.org/forums/thir...er-needed.html
Take that red and orange fuse you have... Run the Red wire to an "always hot" connection. Splice the orange end to the orange wire comming out of the oil pressure switch. The fuel pump relay will serve no function without the ECM to trigger it. If you absolutely have to have this relay working, you can do one of a few things. 1. Run the green/white wire to a toggle switch so you can toggle the fuel pump off and on. 2. Run the green/white wire to ignition hot so that the pump is running when ever the key is in the on position. 3. you could build a custom timer circuit to run the fuel pump for a specified number of seconds whenever the key is turned on. The only time you would ever need the relay is if you ran out of gas, obtained some gas, poured it all in the tank and forgot to pour any in the carb to get the car started. I that situation, you could flick your toggle switch to fill the bowls on the carb then flick it off once the car started.
Good luck,
-KS

 

OK...

1. So ALL the wires running to the ECM and the GND's running to the ECM I can cut off and do away with correct?

2. I need to wire in a buffer box for my speedo to work so for the meantime I won't have a speedo.

3. The orange and red fuse wires and connector (ECM power) I'll leave since thats connected to the alt charging lead and that will give all the things power.

4. And I need to run the green and white wire from the fuel pump relay to a switched power source or a switch???? I don't really want the pump running all the time when the ignition is on unless the car is started.
Example...if I run the green and white wire to a switch and flip it on to 'prime' the bowls what will keep the pump running when the car is started (but the switch is off)???

5. Finally...I see there is a connector in the car right next to the ECM that some wires from the harness run to. Here's a pic...what exactly do these function as???
Please give me some feedback

 

Anyone? Really need help here....

Turned on the kill switch and got NO power to anything. My headlights are still connected like normal but are not working...not making any sense.
I didn't hook up any engine wiring but the lights should still work.

Something isn't adding up.

 

Wow! Who hooked thirdgen up to a dial-up modem?
Anyway, Your oil pressure switch will keep the pump running as long as your oil pressure is above 4PSI. Do you have a multimeter? If so, Lets make sure you are getting voltage from the battery to the fuse block. Touch the black lead to a good ground on the chasis and see if you have 12V on the fuses. You dont have to remove the fuses to test the voltage, if you look closely, you will notice two small metal leads on the top of each fuse. Touch you probe to these and let me know... Also check the battery and see what voltage you have... Did you disconnect the chasis ground from the battery by accident? Nothing has power? THere should be a 4 guage wire going from your battery to the engine... That connector you are holding in your hand is your "under dash terminal block" Check this page out: http://www.chevythunder.com/fuel%20i....%20pg%20C.htm
Some of those wires need to be connected for your speedo and your fuel pump. looks like a gray wire for the fuel pump (comming from your oil pressure switch) along with a yellow wire and a purple wire (comming from the VSS) to run your speedo and cruise.
Let me know...
-KS

 

Man, I'm not getting notification emails...

Anyway, I got the car fired up finally! Everything SEEMS to be working properly (or as much as I could hope) and I left the pass side dash connector un-hooked.

Speedo doesn't work since I need the VSS buffer box. The rest of the gauges work fine with the exception of the oil press gauge (which was working fine but now is jumping around erratically) but I have a mech gauge hooked up in the front of the car. I don't have cruise...

O yea...I didn't have power earlier because I forgot to hook up the MAIN battery cable to the starter from my distro block

 

LOL, I knew it had to be something simple... You must have a bad connection to that oil pressure gauge... i would guess down by the sender where i had you cutting and splicing stuff. Check the output voltage coming off your sender and see if it is steady or eratic. Has this car been siting long? I know i had many problems with the guage cluster in my 86 and was always taking it out to repair broken traces. Once you get your buffer box, both your cruise and speedo will work again... Keep me posted if you need any more help...
Good luck,
-KS