Me and my father have been working to install a TPI system from an 89 Camaro into a 77 Vette.

We worked with the harness, which was hacked up pretty good. After many hours with a multimeter and wiring diagrams, we were able to restore the harness to a working state..So I thought

I am currently having a problem with getting the injectors to fire. We can get the pump running and can get fuel pressure at the rail. Spark has even been verified and it is there!

So when reading the ECU pins, I get the following:

I get a good circuit from the injector signal wires to the ecu, along with a good signal from the injector fuses to the injectors

Now here is the weird part, injector ground through the ecu is Pin A10. If I plug in all the injectors, and give them power, I can get 12 volts from pin a10 to another ground. However if I remove the injector plugs, this goes away. This goes to tell me that there is a ground crossed with power or something of the sort in the mx.

Anyone want to throw out any ideas?? I cant find any crossing wires in this circuit anwheres!

 

What that readign indicates is that the injectors are getting their 12VDC supply from the harness (as they are supposed to) and that the ECM is not switching the injectors ON. The ECM switches the ground, not 12V positive, so until the ECM's transistors bias forward and conduct that 12V from the injectors to ground, you'll read the voltage through the solenoid coils of the injectors at A10.

 

Could it be a VATS problem? Or fuel pressure?

 

The ECM grounds the injectors to fire them, as Vader mentioned. It will only ground the injectors when it receives a reference pulse from the distributor. I suggest you look into that.

 

I thought that A10 on the ECM was for VSS and the injectors were grounded though D15 and D16.



Kat

 

Kat,

Good catch, but I believe he mentioned using an ECM from an '89 TPI, which would be the 1227165. It appears that the diagram you posted is for an '85 TPI, which used the 1226870 ("electric abacus") ECM. The connections are different between those two. Still, A10 should not be grounding the injectors on either ECM.

Maybe this will help:

 

Actaully Vader it is from a 86. I snagged it off of Mike Davis's web site a few years ago. About the only differenace between the and the 89 is the VATS which goes to B6 iirc.

Kat