Hi all,

I swapped a 90 TPI SD system into a 1990 TBI car over the winter. I purchased the engine with the computer and harness as one unit. Since then I have not been able to get the injectors to fire. In tracing the wiring I found the connector to the ECM does not appear to be correct. Example, C11 should be an injector wire, however it does not exist. C12 is the other injector, however mine is a different color. C16 is yellow when the diagrams state orange. Also the harness has a yellow, black and green connector, the books show yellow and 2 black. Everything hooks up OK and the connectors are fine. The ECM is the correct #. Is this a wrong harness? Anyone have any advice to save me from going nuts?

Thanks for all of your help

Shawn

 

Yes that is the wrong harness. I cant remember what computer goes with that harness but its not the 127730, which is the compuer number you should have for a 90 tpi set up. I work for a business that makes TPI, TBI, LT1 LS1, ect.. ,harnesses, and have came across this issue before with customers. The harness you have is simmular but not the one that you want.

 

That is the computer that I have. Do you have any suggestions on where to get a good (cost effective) harness to put this all together?

Thanks again
Shawn

 

Larryselectricsite.com give him a call. These harnesses have all the emissions removed and no pass key system so your chip/eprom will need to be reprogrammed but they are a lot cheaper than buying a stock repalcement from gm. Other than that check out ebay. I can help you out with a chip if you go with one of larrys harnesses or you can buy one from him. btw i think that the tpi harnesses are on sale this month, but I'm not sure.

 

I got a another SD harness from the salvage yard in town. Everything is hooked up (again)
I do not get a ground to the injectors, but my check engine light now comes on.
So far....I checked the ECM and do not get a ground from C11 or 12. The engine cranks. I checked the VATS and the resistance at the wires matches the key. The engine does crank. I checked the continuity between the injectors and the harness plug at the ECM and it is good.

I checked B6 and I did not get any voltage (5v I believe it is suppose to be)

Would this be a VATS issue? I would assume if the engine cranks the VATS is OK. I disconnected the system and the starter shut down for 4 minutes like it should. Could this be related to having a VATS module from the original car and an ECM from a donor??

Thanks again

Shawn

 

the vats module must match the key that you have if you didnt change that then vats should not be an issue. The injectors should have 12 volt ignition on the pink wires and the other is the ground pluse made by the computer. Use a node light or an analog volt meter to check that the computer is pulsing the injectors. They sould make a ground if not then threre should be some ground wires on the harness that attach to the rear of the heads, check and make sure none are broke. They sould be ok if you say that the ecm is powering up. This would be where i would start. To my knowledge there are two components that the vats controls the vats starter realy and the injectors. Hope this helps.

 

possible bad ignition module. I have seen them spark the coil but not send the ecm the dref pulses. Mike

 

First, thank you for all the help.

I found a ground problem and corrected it. Here is where I am at:
The injectors pulse and I have good fuel pressure.
I have no spark from the coil. I checked the coil, replaced the ICM (it was kinda crappy looking) and checked the pickup-it is at 800ohms (and I did replace it when I rebuilt the distributor a bit back). I have 12v power to the coil and the connections to the ICM are good, power and ground to it as well. I checked the wires and they all have continuity to their respective ECM positions. The tach is not working, so this combination makes me think that the signal is not coming from the ICM to the coil. The ECM grounds all appear good. I checked C7/8 and D8/9 but I am not getting any power reading, my guess is because the car is not actually running....
I have 2 chips for the ECM and have swapped them both out with no change.

So, anybody have any advice which direction to head now? This is making a great book writing experience.

Thanks again
Shawn