Should Cold Start Injector always receive signal?
 

Newbie here.....Hello everyone, I am trying to work on an issue with my a 1986 22re. When the cold start injector is unplugged truck runs fine when I plug the cold start injector in the truck stalls. With the engine running I checked the connector going to the cold start injector and with a test light found that there was still signal. Should the signal not be there when the truck is running? Is this an ecu issue. I have checked the sensor for the cold start injector and it is good. I dont think it would be an issue with the coolant temperature sensor as that sensor feeds the ecu and not the cold start injector.

Any help would be greatly appreciated.

I believe it is. The cold start injector timer that is mounted in the coolent manifold beside the temp sensor controls the duration of operation. It provides the ground/power (cant remember)but only for a few seconds if the coolent temp is cold enough. These units are known to fail.

When you're cranking, CSI gets positive 12V. However, ground is controlled by CSI timer switch. On 1986 22RE ECU does not mess with CSI.

See schematic and test points/readings here.
When coolant is cold - when CSI timer switch as low resistance- it provides ground to negative side of CSI. After a certain time / temp contact IN CSI timer it disconnects ground to prevent CSI from running too long.

Please make sure you are checking the correct Temp sensor. Disconnect the connector from the CSI Timer instead. IF you still have the problem, you probably have a short in the ground circuit.