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8.1 swap Wiring

M

Mountain_man

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In the process of doing my swap and question came up. My fuel pressure is regulated on the fuel rail with a vacuum line, Ive seen info that ones like mine do not require the corvette fuel filter since it's regulated on the rail. Can anyone confirm this? It's going in my 91 burb and the fuel sender has the outlets to hook up to return line.
 
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No need for the vette regulator. You'd only use it if your engine did not have a return line back to the fuel tank. If that is the case, then use the vette filter, dual regulators won't hurt anything.
 
Thank you, thats what I had thought. I'm using a fuel filter out of a truck around the same range so I dont need to fully re run the fuel lines I bent. do you know someone who does harness work other then companies talked about around here? Was planning on using a guy from pirate for both otherwise. Thanks again russell
 
I would love to, just I look at diagrams and get all googly eyed trying to understand which wires to pull and which to leave. I see diagrams but nowhere says which wires to pull based on diagram talk. Care to help a guy out? I'd love to save 250 on the harness work.
 
Sure! I'd love to help ya out!

Now, the key on what to pull, and what not to pull depends entirely on what you are going to be keeping on the engine, and what you will be removing.

If you plan to drop that engine into your truck exactly as it was in the donor truck, then you really have very little to do as far as wiring modifications go. Particularly if you re-use the factory under hood fuse / junction box. In that case, it literally turns into supplying constant hot, ignition, ground, starter feed, park / neutral status, and the VSS signal to the fuse block and PCM. Outputs include your fuel pump, SES light and the serial network wiring to the ALDL connector. Everything else is from the engine or transmission straight to the PCM with no interface to your truck's factory wiring.

Say you want to delete the rear oxygen sensors, fuel tank pressure sensor, EVAP canister and EGR systems from the engine. You'd simply locate the pins for them on the PCM, remove them, and follow them back to their connectors on the other side of the harness and clip any grounds / ignition feeds that go to the other side of the connectors.

Really nothing more than that to it! If you wish to delete the factory under hood fuse / junction box, then it does become a hair more complicated, but not by much. All that means is that you must supply a starter solenoid feed back to the PCM, and install your own fuse block & relay center to power all the injectors, coil packs, PCM etc as well as provide a relay to operate the fuel pump with.

If you can come up with a list of emissions equipment to be deleted, the year of your engine and whether or not you are re-using the factory fuse / junction block, I'd be happy to give you a hand determining what needs to be removed.
 
Ok the engine is a marine spec 8.1 I'm running a 12200411 computer, 4l80e trans behind it. I would like to get rid of all the emissions I can. I have full harness but no under hood or dash fuse box from a donor. I do have electronic pedal and tac module to go with it. the suburban already has the vss and came stock with the 4l80 so yay me for no moving as much around. What else do you need? Thanks again russell.
 
Alrighty, so we want to erase the following emissions / accessory equipment:

EGR
EVAP
Fuel Tank Pressure
AIR Injection
Rear O2 Sensors
Coolant Level Switch
A/C

C1 = Blue PCM Connector
C2 = Red PCM Connector

EGR:

Remove the following pins from the PCM:

C1 Pin 47 - Grey (5V Reference)
C1 Pin 41 - Purple (Low Reference)
C1 Pin 55 - Brown (EGR Valve Position Signal)

C2 Pin 41 - White (EGR Solenoid Low Control)
C2 Pin 7 - Red (EGR Solenoid High Control)

EVAP:

Remove the following pins from the PCM:

C2 Pin 45 - White (EVAP Canister Vent Solenoid Control)
C2 Pin 34 - Dark Green / White (EVAP Canister Purge Solenoid Control)

Remove the following ignition wire:

Pink wire running from Red under hood fuse block connector C3 pin E3

Fuel Tank Pressure:

Remove the following pins from the PCM:

C1 Pin 23 - Black (Low Reference)
C1 Pin 46 - Grey (5V Reference)

C2 Pin 64 - Dark Green (Fuel Tank Pressure Sensor Signal)

AIR Injection:

Remove the following pins from the PCM:

C2 Pin 36 - Brown (Air Pump Relay Control)

Remove the following Relay:

Secondary Air Injection Relay

Remove the following Ignition Wire:

Pink wire running from Black under hood fuse block connector C2 pin D9

Remove the following Battery Feed Wire:

Red wire running from the under hood fuse block connector C7 pin A

Rear Oxygen Sensors:

Bank 1 Sensor 2

Remove the following pins from the PCM:

C1 Pin 28 - Tan (Bank 1 Sensor 2 Low Reference)
C1 Pin 68 - Purple / White (Bank 1 Sensor 2 High Signal)
C2 Pin 72 - Black / White (Bank 1 Sensor 2 Heater Low Control)

Remove the following Ignition Wire:

Pink wire running from Black under hood fuse block connector C2 Pin E8

Bank 2 Sensor 2

Remove the following pins from the PCM:

C1 Pin 25 - Tan (Bank 2 Sensor 2 Low Reference)
C1 Pin 65 - Purple (Bank 2 Sensor 2 High Signal)
C2 Pin 75 - Red / White (Bank 2 Sensor 2 Heater High Control)

Remove the Black ground wire from the ground network.

Coolant Level Switch:

Remove the following pins from the PCM:

C1 Pin 30 - Light Green (Coolant Level Switch Signal)

A/C:

Remove the following pins from the PCM:

C2 Pin 17 - Dark Green / White (A/C Request Signal)
C2 Pin 43 - Dark Green / White (A/C Compressor Clutch Relay Control)
C2 Pin 33 - Dark Green (Recirculation Door Control)
C2 Pin 55 - Dark Green (A/C Low Pressure Switch Signal)
C2 Pin 11 - Dark Blue (A/C High Pressure Recirculation Switch Signal)

Remove all ground wires from the grounding network.


Now as far as wires that must be connected to your truck's factory wiring is concerned:

Ignition power:

C1 Pin 19 - Pink
C1 Pin 75 - Pink

Injectors (Pink, 1 fuse per bank),
O2 sensors (Pink, 1 fuse per bank)
Coil packs (Pink, 1 fuse per bank)

Battery power:

C1 Pin 20 - Orange
C1 Pin 57 - Orange

Ground:

C1 Pin 1 - Black / White
C1 Pin 40 - Black / White
C2 Pin 1 - Black / White
C2 Pin 40 - Black / White

As required for the O2 sensors and Coil packs

VSS:

C2 Pin 20 - Light Green / Black (VSS Ground)
C2 Pin 21 - Purple / White (VSS Signal)

Speedometer and Tachometer:

C2 Pin 50 - Dark Green / White (Speedometer Signal Output)
C2 Pin 10 - White (Tachometer Signal Output)

Note that the speedometer and tachometer signals are a pulsed ground signal. Your factory gauges and many aftermarket gauges require a 12V square wave to operate. To get around this, you must install a pull up resistor between a 12V ignition source and the pulsed ground wire. Hook the gauge up to the PCM side of the resistor to generate the required signal.

Also note that the factory tachometer signal is the same as you'd find on a 4 cylinder engine in conventional terms. You will either need to have the PCM re-programmed to output an 8 cylinder signal, use a 4 cylinder tachometer or a signal converter such as offered by Dakota Digital.

Service Engine Soon Indicator:

C2 Pin 46 - Brown / White (SES Indicator Ground)

ALDL Connector:

C1 Pin 59 - Yellow (Class 2 Serial Data)
C1 Pin 58 - Dark Green (Class 2 Serial Data)

Also requires an ignition feed wire and a ground for most code readers and scanners.

That really about covers it! The hardest part of the whole thing is getting started. Once you start taking the loom off the harness and start locating individual pins etc, you'll quickly find that the wiring really is not as bad as it looks. Most of the wires run from an individual sensor, solenoid or module straight to the PCM or vice versa. Most of your time will be spent installing and wiring up the aftermarket fuse block to power everything, or to splice them into your factory wiring if you are so inclined (seeing as your truck is TBI stock!)

Let me know if you have any other questions, or if you run into trouble along the way!
 
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So the dash fuse box had about a million wires going into it from engine bay, should I locate each wire and splice them in? All the info you posted above is perfect btw, looks a lot less complicated laid out that way. Thank you. Just needed to begin tomorrow and I'm sure I'll look for more info. Again much appreciated.

The tach signal output doesn't affect the rpm seen by the computer just to a gauge correct? Haven't installed a tach yet anyway.
 
Yup, just the gauge.

With the under hood connector on the drivers side, you'll be splicing some of the wires and leaving other ones. There are power wires for the stock fuse block that must be left alone, sending unit wires for temp and oil pressure that need to be swapped onto the new engine, an ignition wire that was for the distributor that now goes to the new fuse block for the new engine, a starter wire that goes to the new engine, a brake prop valve and fuel level sending unit wires to be left alone etc.


The rest are wires for the front and rear lights. The wiring going in on the pass side goes to the PCM and most will be removed and replaced
 
I just noticed you have pin 41 c1 listed twice as two different colors. Any idea what the other pin should be? Thanks
 
Ah, my mistake! Sorry about that! Should have been C2 pin 41 - White... I corrected the writeup above for you
 
You refer to red c3 pin e_ followed by number. Is that the small red and white connectors? Since I dont have a fuse box yet I dont know what they go to, all the pcm wires you noted have been removed from harness though.
 
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Yup, it is the red connector. Just follow the pink wire from the evap connector back to the red connector to be sure
 
Ok Russell, I'm back in finishing up the wiring stuff and ready to pull remaining wires. I've got that red connector that appears with many wires not pink orange or anything else I need aside from one or two. These wires all get removed and discarded? What do they go to if nothing I need? I'll try to get a pic of this connector since in all the harness pictures I've seen this plug is not anywhere to be found.
 
Please do... The connector I am talking about goes into the bottom of the fuse block. I get the feeling you are talking about a different one
 
I'll get that as soon as this rain stops. There is one red and one clear. They resemble mpfi-4 plugs in a way however I've also got the standard pcm plugs as well as all the other smaller ones (c100 c152) the likes.
 
Also, any idea how I would find out if this is a marine spec engine? It does have the 42lb injectors however everything else looks just like an 8.1 regular. Casting numbers? anything? I've hunted down and found nothing on this. Thanks.
 
Huh. I've never seen a set of connectors like that before... Do you have a picture of what they were plugged into?
 
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