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 we go I got all the pins labeled today was able to take two pics before the camera batt's played out (got new ones tonite), will show the labeled harness tomarow. Here are the two I got off today. It's the engine after I striped all the top-end off. I am rather proud of how clean my rebuilt engine is after a year of daily driving (and a little off road stuff).

[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 Damien

It helps to have a wiring diagram for the donor vehicle. It will take about half a day to sort out and remove all the unneeded circuits. The harness on the newer style trucks comes through the fire wall on the passenger side near the heater box, so some of the wires may be too long or short for a factory appearing installation. Good luck. This should be helpful for a lot of people.

The harness I am using came from a 87 truck (thanks beater c-10), I also had a 90 suburban I bought for parts and I have that harness also to save for anouther project. Anyway I will show everybody tomarow where the stock suburban harness came out of the truck. It is in the same location on this 86 truck because it had the esc distribitor from the factory. I am going to use this hole.( It's on the pass side also)

I looked at a 92 today and they would probably have a little extra wire if you use that harness but not so much that you could not make it look factory if you wanted to.

[cjracing15]

Originally Posted by D13

I'll be following along for ideas on my TBI 250 conversion! What trans do you have? And do you have cruise with VSS like the 1990?

I have the stock 700 in it. I will probablly hook the cruise up later down the road but not this time. And I am going to use a vss sensor from jag that run.
Stay tuned.

[rfmaster]

Part numbers of interest
Part Description Part #
TBI ECM 1227747 BCC ASDU: 1227747
Heated O-Sensor 4-wire: 25312184; AFS75
TBI Overhall Kit: CK1081
Injectors (350) Orange Black: 17112493; 217-344; 5235206
Coolant Temperature Sensor (CTS): 12146312; 25036979
Throttle Position Sensor (TPS): 12116257; 17111787; 17111471
Manifold Absolute Pressure (MAP): 16137039; 2131545; 16017460; PS10076
Idle Air Control Valve (IAC): 17111460; 25527077; AC102
EGR Control Solenoid: 1997111?; EVS30; 17112193
VSS (from JTR): 2PRS
Knock Sensor (350): 10456288; SU154
Engine Spark Control Module (ESC): 16128261; 16131231

[cjracing15]

Well I did not get to my truck till late today. But I did get rid of all the wires I do not need on the harness. What you see in the first pic is the harness all labeled and sorted out. As you can see it is kind of in two parts. Tomarrow I am going to take apart all the tie points in the harness and that will untangle the last of the wires and then i will recrimp all the tie points like the factory but hopefully a little less of a spaghetti mess. I will take pics of before and after i do this.

The second pic is where i am going to run my wires in the cab. It is the rubber grommet for the esc brain. It is the same size hole that was in the 90 suburban, so it should work real nice.

In the third pic you see the factory oil presure unit and switch adapter, in the last pic is the one out of the suburban that I will have to use because the tbi oil switch adapter has a different thread size than the carb model. I think I will just drill and tap the 90 model adapter for for the stock gage sending unit. You have to use this stock tbi switch to tell the ecm that the engine has oil press. because the fuel pump wire is run through this switch.

I will try and post here again tomarow. stay tuned.

[rfmaster]

You may want to temporarily drop dizzy back in to check for interference between dizzy body and oil pressure switch. I have a spare SB sitting on engine stand - this gave me ample opportunity to check interference.

[cjracing15]

Originally Posted by 68c10owner

Can anyone tell me if there is a single external fuel pump that will work wit hthe TBI? I have dual tanks so i would need 2 fuel pumps if I went with internal pumps right? Would I have to change my tanks or just the sending units?

If you use in tank pumps you will have to get a FI tank. The fuel injected tanks have baffels in them to control fuel slosh so the pump will not suck air if the tank is low of gas. Plus you will have to get the sending unit and pump.

I am just going with one tank right now because that is what i have. I will get both tanks working in the futrue.

I have talked with "Dirtylarry" about what he did and it sounds real good.

He swap the one primary tank on his truck with the in tank pump, and then monted a transfer pump so he can just pump gas out of the spare tank when he needs it. It will be cheaper I think than making every thing work like stock. (unless I can find a donor parts truck cheap)

[cjracing15]

Well I got to work on the old truck today. Got a little done before I had to quit.

First I untangeled the harness a litle more. I cut all the tie points on the harness and re soldered them so they are all untangeled, and i can route the harness some time this week hopefully. THe first pic is what you will find with a stock tbi harness with all the tie points. They are crimped and covered with tape from the factory. The pic has a sample of both.

Second I got the oil sending unit and switch fixed. I went to the parts store and got an brass adapter to adapt my oil switch to the tee threads. Problem sloved.

Third I instaled the intake on the motor I to use anouther intake than the one in the pic above because I found a crack in on of the back bolt holes. So I was thankfull that I had a spare. You can see in the last pic of the oil switch and sending unit instaled on the block. Stay tuned.

[68c10owner]

Originally Posted by cjracing15

If you use in tank pumps you will have to get a FI tank. The fuel injected tanks have baffels in them to control fuel slosh so the pump will not suck air if the tank is low of gas. Plus you will have to get the sending unit and pump.

I am just going with one tank right now because that is what i have. I will get both tanks working in the futrue.

I have talked with "Dirtylarry" about what he did and it sounds real good.

He swap the one primary tank on his truck with the in tank pump, and then monted a transfer pump so he can just pump gas out of the spare tank when he needs it. It will be cheaper I think than making every thing work like stock. (unless I can find a donor parts truck cheap)

My truck has dual tanks but I only use one so I guess it doesn`t matter. I`ve only used the other tank when I was running low on gas and was worried if I had enough to get to the station.

[DirtyLarry]

This is going to be a nice and informative thread!

With TBI, I think you guys will probably be fine running a frame mounted pump to pull fuel through the dual tank switch valve however you may need to figure out a way to pause the frame mounted pump while you switch tanks otherwise you will stumble the engine momentarily. As far as the pump, just mount the pump as low as you can below the tanks and switch valve and on the engine side of the switch valve.

The problem I had running a frame mounted pump with my 8.1L was twofold. First, 8.1L requires 60 psi fuel pressure but on my marine controlled 8.1L it only requires 43 psi. None the less, the return side ports on the OEM switch valve are little bitty 5/16 ports and restrict the high pressure fuel return flow back to the tank causing the fuel pressure to run around 100 psi at the fuel rail! Once I bypassed the switch valve the fuel pressure ran normal. This would not be an issue for TBI as TBI only runs around 12 psi and what little fuel goes back to the tank is very small compared the later model sequential EFI engines. GM used that exact switch valve on TBI trucks anyway so again, the fuel return through the switch valve won't be a problem.

The second issue I had with the frame mounted pump was mainly off-road where you are crawling along on the trails at 2 MPH for hours on end without any wind blowing over the pump to keep it cool. Once I would stop for a minute to take break or something then try to restart the truck it would only crank as the fuel pump was too hot and cavitated the fuel inside. The pump would scream like crazy when it was warm too! Being my truck sees more off-road than on, I wasn’t going to be able to live with that so I swapped to a ’87 TBI tank, ’87 TBI sending unit with a Corvette fuel pump to feed the 8.1L the pressure it needs.

GM and AC Delco pn for the switch valve 14029228


Here is how I had my frame pump mounted. Protected by the cross-member from road debris and also shielded from the exhaust. This contraption is gone now that I have converted to an in-tank pump and a transfer pump to move fuel from the secondary tank to the primary.

[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.

[DirtyLarry]

Originally Posted by joe231

Hey DirtyLarry, what kinda pump do you use for a transfer pump?TIA

Mr. Gasket #12D. Summit Racing pn MRG-12D. It is a low pressure/high volume pump. The pump is actually labled as diesel fuel but it will work as a gasoline transfer pump per Mr. Gasket tech line. I am happy with it so far with only testing it in the garage a few times. Moved 1/4 tank of fuel in less than 4 minutes from the secondary to primary tank. Will be making a run to the mountains in a few weeks so I should have real world results soon.


Mounted on a fabricatedcross member between the frame rails. Operated by Painless Wiring electric fuel pump harness kit PRF-50102 (Summit Racing pn) and a toggle switch.

[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

[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]

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?

[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?