Tbi swap build thread

[manimal]

Module tested fine. So I picked up a reman ECM. I replaced it 2 yrs ago this month...wife reminded me it was doing the very same thing. SO I will replace it in the morning.

[manimal]

FIXED!Turned out it was the ECM. put a new one in this morning and she runs great.

[rfmaster]

Originally Posted by manimal

FIXED!Turned out it was the ECM. put a new one in this morning and she runs great.

Based on this posting - our wife's know everything and they remember everything!

Darn - sorry to hear that it end up being ECM! They were designed to handle surges, but if enough sparks fly one is asking for it..

//RF

[MAX85C10]

Hello all. My TBI swap build is about to commence in about 2 weeks, one basic question i have while i am gathering parts is, can i use the harness out of a 89 c20 van with the 1227747 ecm? Will the harness out of the van be the correct length to reach all of the sensors since it will be going into a squarebody c10? The one in this van is the only one i can find in the local boneyard that is intact and untampered with. Will this harness require extensive modification in order to work in my squarebody? This is an awesome thread BTW!!!

[rfmaster]

Welcome to the thread Max

In the past I have looked at using VAN harness for conversion. I have looked at Astro van and later 94-95 full size vans as a possible source of harness's as they tend to be the last to be looked at by JY marauders. The van harness and 1227747 ECM from the same van should work, but expect to spend time going over each circuit as they tend to run longer than usual C/K harnesses. The 89 C20 van EFI harness should be more a less stand alone harness with few extra circuits tied into the main bundle. The later, post 1990 harnesses were fully integrated with the rest of the engine bay circuits and require extensive 'skinning' (just like a deer) to extract EFI only circuits. It generally takes couple of hours, plenty patience to clean and extract needed EFI circuits. See photo's posted earlier in the thread. Make sure that donor has the same engine type (V8) and CID as the transplant recipient. If it is a direct swap - it should be a straight forward operation. There are couple of gutcha's but there are easy to traverse.

//RF

[MAX85C10]

Thanks for the reply! im hoping to find a c/k harness but they are all torn apart, connectors missing/ broken. Thank you for the input, im sure i will have more questions once the build begins.

[MAX85C10]

okay, I ended up finding a 87 c10 to pull the haness out of and a 1227747 ecm. Im going thru the harness now and I found a vacuum sensor that ive never seen before. it was mounted on the intake manifold on the passenger side. It is not the standard MAP sensor for these trucks, it has 3 vacuum ports and a 2 prong electrical connector. But the harness also has the standard 3 prong plug for the standard MAP sensor. Im confused as to if i need this weird vac. sensor. Wish I had a pic but i cant find anything like it on the web and am unable to take a picture at the moment. Any help would be greatly appreciated!

[MalibuSSwagon]

Originally Posted by MAX85C10

okay, I ended up finding a 87 c10 to pull the haness out of and a 1227747 ecm. Im going thru the harness now and I found a vacuum sensor that ive never seen before. it was mounted on the intake manifold on the passenger side. It is not the standard MAP sensor for these trucks, it has 3 vacuum ports and a 2 prong electrical connector. But the harness also has the standard 3 prong plug for the standard MAP sensor. Im confused as to if i need this weird vac. sensor. Wish I had a pic but i cant find anything like it on the web and am unable to take a picture at the moment. Any help would be greatly appreciated!

Sounds like it may be the EGR solenoid or something for the AIR system. Post a pic.

[rfmaster]

Originally Posted by MalibuSSwagon

Sounds like it may be the EGR solenoid or something for the AIR system. Post a pic.

It is probably mounted on the back side of this bracket (you can see light gray and pink/blk wire sticking from connector - upper right) MAP and ESC modules are visible.



and looks something like this:


It is called EGR solenoid.

//RF

[MAX85C10]

I found out what the switch was, it was the EGR solenoid. the MAP and ESC was missing so i will have to track one down. One question i have is, how do i merge the new TBI harness with the original harness? i pulled the entire harness from the donor truck, fuse box and all. What wires will i have to tap into to merge the two harnesses? Thank you

[MalibuSSwagon]

Well if you have the entire truck harness, check it over real well and replace your entire harness.

[rfmaster]

Originally Posted by MAX85C10

I found out what the switch was, it was the EGR solenoid. the MAP and ESC was missing so i will have to track one down. One question i have is, how do i merge the new TBI harness with the original harness? i pulled the entire harness from the donor truck, fuse box and all. What wires will i have to tap into to merge the two harnesses? Thank you

What year is your square body??

The 89 donor harness will require some work. Generally, I leave original engine bay harness intact. The EFI harness will require two separate IGN-on connections (in run and crank) - both should be fused, one direct battery connection - fused, park neutral switch, VSS input, fuel pump supply, starter cranking circuit, SES light and ALDL connector (I hope you grubbed that). The donor harness is reworked to remove unneeded circuits, but that depends on several factors - AC, TH350 or 700R4, etc. It would be a good idea if you post what you have and what you are planning to install. Also list ECM broadcast code (BCC) - four letter ID code on the tag. All of these connections have been previously described and schematics are posted in this thread.

//RF

[MAX85C10]

my truck is a 85 c10 305. and 700r4.the ecm i have is a 1227747, BCC is ARJT out of a 91 burban. i got the entire harness out of a 87 c10 and would like to retain cruise and AC idle compensation. i have the fuse block and bulk head connector but i dont know what will be necessary. will i just use fusible links to fuse the few circuits that need power? I would like to make the TBI harness completely standalone if possible and leave the truck harness original. I am all about original and factory options operable. Thank You all!

[rfmaster]

To start

Lay down 89 harness flat on the garage floor and take a photo

//RF

[critict1gc]

Ok i am about to pull my hair out, I have been going at this for a year and cant get my truck running. I have traced down every wire and down continuity tests umpteen dozen times. I am getting 12v everywhere i should, grounds are good, I have a couple diferent ecu's.

I found a flow chart on chevy thunder and used it. One thing it told me to do is to unplug the harness that goes to the distributor and give one of the wires 12v. I did and the fuel pump turned on and the injectors started to pulse. That tells me that the wireing and ecu are good but the ignition module are not.

With a new dizzy, cap, and coil I still have no spark.

Thoughts???

[rfmaster]

Make sure that dizzy (pink wire) gets +12 volts during cranking - very common oversight. Also, make sure that injector supply circuit (two red wires) is ON (eg +12 volts is present) when ignition key is in cranking and run position!!!!

//RF

[critict1gc]

The pink wire that goes to the coil, is that what you mean because yes it has 12v.

[critict1gc]

and yes the injector supply has 12v also.

[critict1gc]

Is there any way to test the distributor

[rfmaster]

Originally Posted by critict1gc

Is there any way to test the distributor

I am going to assume that you have an external coil, small hat HEI.

An HEI distributor, as a complete unit, together with ignition coil - must provide spark during cranking (under 400 RPM) and send DRP signal to ECM. Individual components in the HEI distributor can be tested => ICM can be tested at better auto parts stores, HEI coil can be checked with DVM, reluctor coil (inside distributor) can be checked with DVM. Another often overlooked item is a two wire harness between dizzy and coil, as well as electrical grounds. All of these may contribute to no start (no spark condition).

//RF

[critict1gc]

What about the electronic spark control module. What does it exactly do. If its faulty will it cause no spark. Also if I got the esc off a vehicle with vats is the vats incorporatded into the esc

[rfmaster]

Originally Posted by critict1gc

What about the electronic spark control module. What does it exactly do. If its faulty will it cause no spark. Also if I got the esc off a vehicle with vats is the vats incorporatded into the esc

Lets take a step back... Can you provide a complete listing of your setup?
ECM - service number and broadcast code, distributor type, donor vehicle information, etc.

The ESC module - the black square module



acts as buffer-filter between knock sensor and ECM. Its presence or absence will not affect engine starting.

On the the other hand ECM (Pin B6) presence or absence of VATS signal from the VATS decoder enables or disables the ECM to operate the fuel injectors during cranking. An extensive discussion of how VATS system operates can be found here:
http://www.thirdgen.org/vats_passkey_system

In general if ECM has an EPROM with VATS enabled a VATS system (or VATS emulator) will be required to allow normal starting sequence. Naturally, a custom EPROM can be sourced with VATS function disabled.

//RF

[critict1gc]

My ecm is the 7477 from a 305, not sure what its out of exactly. I got it off a guy that just had the motor and complete harness sitting on the floor of his garage. My distributor is this one
http://www.jegs.com/i/Proform/778/66...d=#moreDetails

this is my coil
http://www.jegs.com/i/MSD-Ignition/1...d=#moreDetails

I have the painless vss, I also have a 3 wire O2 sensor and I wired to a relay from a digram that was in this tread.

Is there any thing else you need to know. I appreciate the help.

[critict1gc]

Also egr has been deleted.

[rfmaster]

Originally Posted by critict1gc

My ecm is the 7477 from a 305, not sure what its out of exactly. I got it off a guy that just had the motor and complete harness sitting on the floor of his garage. My distributor is this one
http://www.jegs.com/i/Proform/778/66...d=#moreDetails

this is my coil
http://www.jegs.com/i/MSD-Ignition/1...d=#moreDetails

I have the painless vss, I also have a 3 wire O2 sensor and I wired to a relay from a digram that was in this tread.

Is there any thing else you need to know. I appreciate the help.

The Proform 66938RC and MSD Ignition 8226 should provide spark in TBI system. As a sanity check I would double check the MSD coil winding resistance: Primary should be less than 1 OHm and secondary 5.8 kOhm. It is not unheard of to receive a defective coil! There is a two wire harness running between distributor (ICM) and coil (white and pink wire). Do yourself a favor and make sure that it is in a good shape and circuit continuity is there. A broken wire or intermittent pin connection will render ignition coil or ICM inoperative. Use DVM to check both circuits. Other commonly overlooked problem is to make sure that harness plugs makes contact with module socket pins - paste tiny amount of dielectric compound on each pin of the plug - insert and remove. There should be an indication of a contact between socket contact and plug pin.
//RF