bypass

[AMCLOVER258]

So i had grabbed a detailed walk through for the bypass. my issue is it states the two wires come from the distributor to the loom through to the ICM then out. In my eagle i see the purple and yellow wire from the dizzy to a plug that its plugged directly to the ICM. what to do?

[macdude443]

What year is the car?  Can you take a picture?

In it's stock form (on most years), the orange/purple/black wires from the distributor go through a plug.  The black wire continues to the module while the orange/purple head in a twisted fashion to the computer under the kick panel.  The computer advances/delays the trigger signal, then sends the new signal out to the ICM via a light green wire.  This light green wire connects to a three wire plug at the ICM and changes color back to orange before entering the ICM.  This plug also contains the black ground wire from the dist. and a dark green wire, which is your coil (-).  The other ICM plug is usually red and white wires, for power and start retard.

The light green wire may also be orange on some.  I know the Jeeps are orange according to the diagrams I've seen.

If the orange/purple twisted wires go directly to the orange/purple wires entering the ICM, then there is no need to bypass. 




It is good practice to also splice a wire into that black wire and give it a good ground.  From the factory, the module grounds through the distributor base, which is typically pretty gross.

[AMCLOVER258]

82 and yes i have pics but cannot update until 530ish

[AMCLOVER258]

ok i think maybe it was bypassed in the past then... I will get some pics uploaded later and well see !

[AMCLOVER258]

I actually found Rafe's old video on you tube and now see what to do final question is once this is complete the ECM is now out of the mix right? so i can yank the brain and all of its wiring??

[macdude443]

Once the bypass is complete the computer will no longer "wake up" as it cannot receive a tach signal from the distributor pickup.  So yes.  You can remove it's harness.

[AMCLOVER258]

Thanks guys!

[carnuck]

Do you have the plug in the back of your carb?

[AMCLOVER258]

Alright i got around after work to get some pictures. The first pic you can see the yellow and purple from dizzy through the connectors then through to the module. so has it been bypassed?  Some of the stuff is dirty so through the last pic in so yal can see im slowly(...) working my way around to everything for cleaning!

[macdude443]

Based on your photos I would say it is in fact bypassed.  The orange and purple wires runs directly from the distributor into the module.  The distributor pickup wires are orange and purple.  There shouldn't be a yellow in that area (the orange may have faded).  Yellow should be your coil (+) feed and if I recall correctly it is a slightly larger gauge.

The other steps of the bypass would be to unplug the stepper motor and manually set it's pins so that the shoulder is 1/8" into the carb, looking down from above the air horn.  If you aren't running the stock Carter BBD feedback carb, skip the stepper step and move onto timing. 

Then you would want to set your timing at curb idle (not 1600 RPM, as the sticker indicates).  Most run there timing at around 9* BTDC, but this may vary based on elevation.  One way to set it is to advance it one degree and take it for a drive up a hill to lug the engine.  If you hear ping/rattle, retard the timing slightly, if not, advance the timing another degree.  Drive it again until you get the most advance under load with no rattle.  The rattle doesn't sound like much but it'll slowly destroy an engine.  You may know all this already.

[AMCLOVER258]

Cool, i really appreciate the info! once she's all together i will start with the timing the carb is sitting in a box so i will remove the stepper and adjust the pins after a cleaning. I'm glad we were able to get the confirmation on the bypass because i have literally attempted it 5000 times and each time i get so confused then quite and i guess that's because i was trying to do something that is already done!!

[AMCLOVER258]

So i went out and disconnected all of the harness's from the back wall of the engine bay including the ECU.. There are a LOT of wires what is the "ideal" Bare minimum wiring necessary for operation? All else i would like to remove.

[macdude443]

I've never removed any harnesses. Maybe someone else can chime in.

[carnuck]

The harness you can remove is the one that plugs into the carb and it can be followed back then removed all the way to the firewall plug.  It also goes through the firewall by the trans dipstick to the kickpanel on the passenger's side where the carb MCU lives. If you have the bypass done and the car is functioning (do it one step at a time to find out if there is a problem), then try starting the car. If it starts and runs then that harness is successfully bypassed. If not, then back up a step.

Just a note, but the best way to preset the stepper motor is before doing the other stuff, turn the key on (motor cold) and unplug the stepper electrical plug. 9 out of 10 times the stepper will be correctly positioned. The other time, the MCU is probably already dead or not powered.

[macdude443]

The harness you can remove is the one that plugs into the carb and it can be followed back then removed all the way to the firewall plug.  It also goes through the firewall by the trans dipstick to the kickpanel on the passenger's side where the carb MCU lives. If you have the bypass done and the car is functioning (do it one step at a time to find out if there is a problem), then try starting the car. If it starts and runs then that harness is successfully bypassed. If not, then back up a step.

Just a note, but the best way to preset the stepper motor is before doing the other stuff, turn the key on (motor cold) and unplug the stepper electrical plug. 9 out of 10 times the stepper will be correctly positioned. The other time, the MCU is probably already dead or not powered.

I may be wrong, but from my experience the stepper will only initialize to it's center position once the MCU senses the ignition on and the distributor turning.  Since it didn't look like the computer was giving any info to the computer I figured it wasn't going to initialize.  That is the easier way, though.