Injector testing

[Guest qa2]

I have a 76 Z that won't start. I just spent the past two days going over the Fuel Injection bible and did every test from the bible to my car.

1. The car passed all of the continuity and volt test for the harness.

2. The fuel pressure is correct.

3. I ohm'd the drop resister and it is ok.

4. I ohm'd the injectors and the resistance is 3 ohm's.

5. I checked for continuity between the connector at the drop resister and the inj plug, then form the inj plug to the ecu for each injector. OK.

6. The CSV, thermotime switch and the coolent temp sensor are all ok.

7. I do get a momentary start form the CSV injection.

8. The relay is working correctly.

9. Tested the ecu with number 1 and number 4 and it passed.

 

The only test that my car failed was the injector test. I can't get my injectors to click. I measure the output voltage across the inj plug while cranking the engine and only get about .6 volts on every one. I can get the voltage to go up to 1 volt when I disconnect the temp sensor. I know it should be around 4.5 volts at the plug. I can get a noid to light but still the voltage is .6 across the plug.

I have to get new plugs for my injectors since the ones I have are old and cracled and a little green in places. I cleaned up each plug and injector with contact cleaner and still no increase in voltage. Does it seem funny that I have a consistant voltage drop across every plug, this would tell me my problem is not with the inj connectors. It would have to be some where that is common to all the injectors. I get 12 volts to the drop resister, it seems my problem is with the drop resister but it ohm's ok. I am at my wits end, can someone point me in the right directon with this problem. Where or what could be causing the voltage drop or am I all wrong with my thinking? Thanks.

[Guest Drive-ability]

I am not a Z Car F/I expert I do General Motors drive-ability, but having read your post I didn't see output voltage listed past the drop down resistor. I assume it scales down the 12 to 14 volt system voltage to something the Z car is designed to need. I can only assume the .6 volt is your output voltage. I also assume you jumper the injector connector both with a volt meter and a node light and get your .6 reading. What would you get if you use the battery ground and the power feed to the injector, .6 ? again ? That’s likely the case and If so I would test the voltage leaving the dropdown resistor as close to the resistor as you can. Maybe even unplug the injector harness if you can to remove any chance there is a short to ground. Surely a fuse would blow but it depends on the resistance value of the shorted condition. I guess I would also test the voltage drop from the injector connectors to the drop down resistor. I guess since the system isn't sequential you may have a common voltage feed to the injectors hence testing that circuit would be important. All tests ok I agree the drop down resistor is looking like a skewed part.