Tbi swap build thread

[cjracing15]

I am going to atemped my first build thread for who ever wanted to swap in a 87-94 STOCK TBI SYSTEM. I am going to use the intake (& all the hardware),throtlebody,stock wiring harness and all the other things you need to do this swap. I am going to go pin by pin, wire by wire ,and tell you where everything goes.
I know this is a common swap now a days but when I started looking for info for this swap i had do go and find info from alot of deferant web sites. I would like for people that are intrested in doing this swap when they google "tbi swap" they come to this site (67-72chevytrucks.com). So here we go.

Here are some pics of my truck and motor.

The motor is a 90 model 350 tbi motor. I swaped this motor in last year and i used it because I had plans on doing this very swap then. The reason I did not do the tbi swap then was because this truck came stock with a 4.3 in it. I did not want to swap a deferent motor and try to swap the truck to tbi at the same time. So I rebuilt this motor and bouhgt a eldebrok carb intake for tbi heads and used a quadrajet.

I will have some more pics tomarow so stay tuned.

[cjracing15]

Ok here are all the pin outs and the color of the wires. My computer is the standard #1227747

A1- grn/wht- this wire is used to power the fuel pump-relay.
A2- no wire
A3- no wire
A4- gry- to egr-relay. This is a ground for the ECM to control the EGR relay.
A5- brn/wht- service soon light. This is a ground to turn on the light.
A6- pink/blk- switched 12v from the ignition relay.
A7- no wire
A8- ornange aldl serial data wire pin-e
A9- wht/blk-aldl pin B When jumpered to ground will set the computer to diagnostic mode.
A10- brn- VSS speed sensor signal to the computer, (This wire I will wire this to on side of a after market VSS sensor and the other wire on the sensor goes to ground).
A11- blk- MAP sensor ground.
A12- blk/wht- System ground. This wire is tied to other grounds in the harness and goes to engine ground.

B1- orn- 12v batt power ( I looked and traced down this wire on my 87 cab harness and this is fuesed I think it was a 15). I will probably use a inline fuse.
B2- tan/wht- Fuel pump signal from the relay. This one ties into several places, the fuel pump, the relay, and the ecm. When the relay is on it sends 12 volts to trun on the fuel pump.
B3- blk/red- Distributor plug
B4- no wire
B5- purple/wht- Distributor plug
B6- no wire
B7- blk- ESC signal This is the knock sensor signal to the computer.
B8- dk grn- AC signal. This tells the ECM that the AC is turned on. I am going to tie this into the ac clutch wire.
B9- no wire
B10-orange/blk- park neutral switch wire. some people say this is optional but I do not think it is because it gives a signal to the computer to give the engine a slight bump in rpm.(if you don't need it why did they put it there?)
B11- no wire
B12- no wire

C1- no wire
C2- brn- wire is not needed
C3-grn/blk- Idle air control
C4-grn/wht- Idle air control
C5-blue/wht- Idle air control
C6-blue/blk- Idle air control C3-C6 all go to the Idle air control valve plug on the TBI it's self.
C7- no wire
C8- no wire
C9- purple/wht-Starter crank signal wire. Goes to the small terminal of the starter.
C10- yel- Temp sender
C11- lt grn- Map sensor
C12- no wire
C13- dk blu- throtle position sensor
C14- gry- signal to map and TPS. ( you will see it tied together in the harness)
C15- on wire
C16- orange- This wire is tied with B1 so it is a 12volt wire

D1- brn/wht- system ground goes to the engine.
D2- blk- tied to the wires for the engine ground.
D3- no wire
D4- wht- distrbutor plug
D5- tan/blk- distrbutor bypass. This is the wire that you disconnect to set your timing.
D6- Tan- O2 sensor ground to engine.
D7- purple- plugs in to the o2 sensor
D8- D13 no wire
D14- grn- Injector plug plugs into the top of injector
D15- no wire
D16- blue- Injector plug plugs into the other injector

[cjracing15]

Originally Posted by cjracing15

Ok here are all the pin outs and the color of the wires. My computer is the standard #1227747

A1- grn/wht- this wire is used to power the fuel pump-relay.
A2- no wire
A3- no wire
A4- gry- to egr-relay. This is a ground for the ECM to control the EGR relay.
A5- brn/wht- service soon light. This is a ground to turn on the light.
A6- pink/blk- switched 12v from the ignition relay.
A7- no wire
A8- ornange aldl serial data wire pin-e
A9- wht/blk-aldl pin B When jumpered to ground will set the computer to diagnostic mode.
A10- brn- VSS speed sensor signal to the computer, (This wire I will wire this to on side of a after market VSS sensor and the other wire on the sensor goes to ground).
A11- blk- MAP sensor ground.
A12- blk/wht- System ground. This wire is tied to other grounds in the harness and goes to engine ground.

B1- orn- 12v batt power ( I looked and traced down this wire on my 87 cab harness and this is fuesed I think it was a 15). I will probably use a inline fuse.
B2- tan/wht- Fuel pump signal from the relay. This one ties into several places, the fuel pump, the relay, and the ecm. When the relay is on it sends 12 volts to trun on the fuel pump.
B3- blk/red- Distributor plug
B4- no wire
B5- purple/wht- Distributor plug
B6- no wire
B7- blk- ESC signal This is the knock sensor signal to the computer.
B8- dk grn- AC signal. This tells the ECM that the AC is turned on. I am going to tie this into the ac clutch wire.
B9- no wire
B10-orange/blk- park neutral switch wire. some people say this is optional but I do not think it is because it gives a signal to the computer to give the engine a slight bump in rpm.(if you don't need it why did they put it there?)
B11- no wire
B12- no wire

C1- no wire
C2- brn- wire is not needed
C3-grn/blk- Idle air control
C4-grn/wht- Idle air control
C5-blue/wht- Idle air control
C6-blue/blk- Idle air control C3-C6 all go to the Idle air control valve plug on the TBI it's self.
C7- no wire
C8- no wire
C9- purple/wht-Starter crank signal wire. Goes to the small terminal of the starter.
C10- yel- Temp sender
C11- lt grn- Map sensor
C12- no wire
C13- dk blu- throtle position sensor
C14- gry- signal to map and TPS. ( you will see it tied together in the harness)
C15- on wire
C16- orange- This wire is tied with B1 so it is a 12volt wire

D1- brn/wht- system ground goes to the engine.
D2- blk- tied to the wires for the engine ground.
D3- no wire
D4- wht- distrbutor plug
D5- tan/blk- distrbutor bypass. This is the wire that you disconnect to set your timing.
D6- Tan- O2 sensor ground to engine.
D7- purple- plugs in to the o2 sensor
D8- D13 no wire
D14- grn- Injector plug plugs into the top of injector
D15- no wire
D16- blue- Injector plug plugs into the other injector

This might help also if you don't have it. It is on the first page of this thread. Again good luck.

[rfmaster]

Pancake

Looks like you are digging into retrofit - full speed ahead

For P/N switch functionality you'll have to wire a small, simple circuit which requires some wire (12 AWG purple and 16AWG, 1/4" crimp connectors (female and male), BOSCH 30 amp relay, and silicon diode 1N4001 - Radio Shack.

Questions???

//RF

[pancake]

Ok...almost ready to put the tbi on my Blazer.....but have another question. I understand the wiring for P/N switch but do I NEED this for a manual tranny?

again, thanks for all the info and advice.

[rfmaster]

pancake

To get things going it is not required, but having a neutral position sense switch will improve driveability (i.e. ECM alters idle and timing somewhat (depending on ECM, other parameters as well - EGR operation, AIR) between neutral position and being in gear.

Leave B10 (orange-black) unconnected for now (this way ECM will see that truck is always in gear).

//RF

[cjracing15]

Thanks for the info and the pics. If i were to use a frame mounted pump witch one would you recomend?

[DirtyLarry]

Man, I don’t know. The frame mounted pump I had was a Summit Racing house brand. I hear good things about the Walbro pumps. I actually bought a slightly used low pressure Walbro from a board member, Rust Buster, for my ’72 C20 that I just completed the TBI swap on a few weeks ago. The damn truck is still at my buddy’s getting the exhaust hooked up so I haven’t had a chance to find any bugs with it yet. The Walbro pump is what all the TBI conversion kitters like Howell sell with their complete TBI kits.

Here is the Walbro mounted on my ’72 C20 with a TBI 5.7L. Not a very pretty install but it is not a very pretty truck either.

[rfmaster]

Hey Cj

A while back DirtyLarry and I had a bit of discussion going about EFI retrofits and engine swaps. In this thread I posted my setup details - double posting is never a good idea...

http://67-72chevytrucks.com/vboard/s....php?p=2950627


//RF

[cjracing15]

Originally Posted by rfmaster

Hey Cj

A while back DirtyLarry and I had a bit of discussion going about EFI retrofits and engine swaps. In this thread I posted my setup details - double posting is never a good idea...

http://67-72chevytrucks.com/vboard/s....php?p=2950627


//RF

Thanks for the link. That does look like a good way to go. I do have one efi tank with the pump in it. I am going to use that right now and try to go with a stock setup latter.
Thanks, Jamie

[cjracing15]

Originally Posted by skidder111

I did this swap in my 72 K5 some years back. It is hooked to the original 4 spd. My question: How important is the vss on this setup? It was never hooked up. Is it required for the ECM to go into closed loop?

From what I have read the vss is used by the computer to see how fast the car or truck is going. The vss is also used to control the egr valve the charcoal canister purge valve, idle speed, and air fuel ratio at speed.

I belive in this way, if chevy did'nt need it why would they spend the money to have it installed in the wiring harness.

How does your truck run with out it?

[skidder111]

The truck runs great. The VSS is for the electric speedometers and cruise control, but I'm wondering if it does anything else. If it is supposed to control the issues you mentioned above, but is unable to, would you get a code?

[Captkaos]

FYI you don't HAVE to get EFI tanks, just don't run the truck less then 1/4T or so if you are offroad/camber often.

Walbro is a good pump, but in the tank is the best location.

[cjracing15]

Well being that you have a 4 speed trans what did you do with your prn/nurteal wire for the computer?

[skidder111]

Park/Neutral? That's some thing I would have to check into; I don't recall. The truck has the original Muncie 4 spd.

[cjracing15]

B-10 is the signal wire # for the ecm that is you park nutreral switch wire. If it is grounded the computer thinks it is in nuteral all the time and will not throw a ses light. A-10 is the vss signal wire. it runs the the vss sensor it's self.

[skidder111]

So what you're saying is if there is no VSS signal going to the ECM, it will not run as efficiently as it could? And also stay in open loop? Now that you mention it, B-10 must be grounded because I don't get an SES light other than start up.

[cjracing15]

Are you using a stock, or a aftermarket harness?

[skidder111]

Stock harness from an 89 pickup.

[cjracing15]

Well I would re-trace the wires to see what they are doing.

A-10 is a brown wire from the ecm, and B-10 is a org wire with a blk strip on it. let me know what you find, I am just staring my swap as you can see.

[rfmaster]

Originally Posted by cjracing15

Well I would re-trace the wires to see what they are doing.

A-10 is a brown wire from the ecm, and B-10 is a org wire with a blk strip on it. let me know what you find, I am just staring my swap as you can see.

P/N line Orange/black wire is grounded by a P/N switch when in park or neutral position. P/N switch ECM input is used by ECM to compensate idle speed when additional engine loads (AC, PS pressure, etc) are present while in drive and within idle speed range. ECM commands IAC to add additional 50 to 75 RPM over commanded idle speed under such conditions. In your case (manual tranny) leave p/n wire open (i.e always in 'drive')

VSS is extremely important for complete EFI operation. It is unfortunate that many omit VSS during conversion. In your case, having 4 speed manual, it is imperative to have a functioning VSS. Since you have 1227747 ECM you'll need to have 2-pulse square pulse VSS inline unit. These are readily available (JTR, others). VSS provides vehicle speed to ECM which uses this input to accurately set fuel mixture and timing. One common problem with absent VSS and manual tranny is a severe drive train jerking during deceleration. This due to inability of ECM, which uses TPS, MAP and VSS inputs, to enter DE/DFCO mode (Deceleration Enleanment / Deceleration Fuel Cut Off).

When the ECM detects a sudden drop in throttle position and engine load, it reduces the injector pulse width while continuing to monitor engine load and vehicle speed. The purpose of DE is to produce a lean fuel mixture by reducing the amount of fuel gong to the engine. DE mode conditions are determined by ECM on a continuous bases provided that 1) Vehicle speed is above XXMPH (this depends on EPROM calibration value), 2) engine load decrease is below a limit value (this parameter also depends on EPROM calibration value), and 3) Filtered %TPS drop is <1%.

The difference between DE and DFCO parameters is that DFCO parameters are based on fixed values stored in EPROM. The DFCO fuel mode is entered after moderate to heavy acceleration then followed by abruptly releasing the accelerator. Usually ECM will transition into DE prior to entering into DFCO mode as the deceleration continues. Interestingly enough operating conditions may or may not cause ECM to command DE exit by itself. However when ECM enters DFCO mode DE is automatically disabled. Usually DFCO is a 'long' term (self resetting) duration event - coasting down hill in gear for example.

Both DE and DFCO are used for emission control, (keeps CATS from being burned up due to excess fuel during deceleration), but the two will effect drive train and exhaust longevity. There are many other ECM controlled parameters that are derived from VSS input.

//RF

[cjracing15]

I thoght that on OBD II they did not use a vss sensor, but the ecm got it's signal from the abs computer.?

[DirtyLarry]

Originally Posted by cjracing15

I thoght that on OBD II they did not use a vss sensor, but the ecm got it's signal from the abs computer.?

VSS is still used today to provide data to the PCM/ECM for engine controls, speedo, cruise, trans shifting scheduling, torque converter lockup, etc but not ABS. These days, there is actually a wheel speed sensor at each wheel to provide input to the ABS module to control 4 wheel ABS system and traction control if equipped. In the TBI days the trucks only had rear wheel ABS which the rear wheel speed input to the ABS module was read from the VSS sensor on the tail shaft of the transmission.

[GlennBrittain]

Many thanks for taking the time to post your info and progress. This will be a great help to myself and I am sure many others when I get to my drive train. Right now I have an 88 GMC for the donor but may look for the last year of TBI.

[rfmaster]

My apologies - 7747 does not have DFCO - MPH threshold, which is used in 8746 ECM found in TBI passenger cars. Also, DE is mapped to MAP and RPM threshold in 8746.

Now that I looked back at my notes I know where I got confused - in my conversion I used 16136965 from 1991 B-Body which just happens to be almost pin compatible with 1227747 (there are couple more control outputs and MAT input) which in its stock form uses speed threshold for DFCO. In the end it did not matter to me at all since I have converted to EBL which provides full control over DE and DFCO.

VSS in 7747 is used primarily for TCC control, Knock retard, Highway SA, EGR, & Idle speed compensation.


//RF