I have a 1985, that started getting hard to start cold, seemed fine when warm. It has now gotten where it won't start. I get good pressure at the rail, the injectors all test >10 ohms, the TPS is good, the IAC valve was all crappy, so I just replaced it. I seem to get good spark on my first test of the plugs. In poking around this morning I notice that I'm not getting 12v to the injectors. The service manual seems to imply that both leads to the injectors would get 12 volts with the ignition on. I seem to get consistently about .5-.6 volts at each wire on every injector. Also, the manual says to hook up a test light J34730-2 and check for blinking. Given that I don't have a J34720-2, can anyone point me to how that might be wired?

Thanks,
Rob.

 

You should 12v on side of the injector connectors. The ECM grounds the other side. Connect a test or noid light across a connector and crank the engine, it should flash.

 

The ECM pulses one injector wire to ground during cranking and running, the other wire is connected to 12v when the ign is in run and crank. You need a noid light available at parts stores or you can make you own with an LED (light emitting diode) and a series 680 ohm resistor. You unplug an injector and connect the test light across the injector plug and have someone crank the engine. The light should pulse during cranking. The homemade light must be connected with the proper polarity to work. Check both of your injector fuses with an ohmeter.

 

OK, I discovered that the ECM was not getting power.. Somewhere in my debugging, I must have knocked that loose. Fixing that put 12volts at both connectors on each injector with the key in ON. Perfect! Which got me back to where I was where it would not start. I got a noid light for the injectors, and I'm still not getting a pulse across the injector when attempting to start. Per the service manual, I touched 12volts to the 430/purple wire on the ignition module and I do get a flash to the injector noid, and I do hear the fuel pump kick on for the 2 seconds. The last step in the manual for this is to "replace the ignition module or check connections". Given that I tested this at the ignition module itself, it seems like the connections should be good. I took the module out and got it tested and it checked out ok.

I'm somewhat confused now. The only other thing that comes to mind would be the pickup coil, but given that I'm getting a spark to the plugs, that seems unlikely.

Any suggestions? The book implies that 12volting the 430 ignition wire and getting a reaction verifies the ECM is OK.

The thing that gets me a little is that this is something that came on somewhat gradually. Like something was wearing out or clogging up. It doesn't feel like an itermittent short or a sudden disconnect/breakage.

Rob

 

grab a hold of a spark plug wire, and have your significant other turn the key. you will know in an instant if you have spark.

 

Yep, I have taken a hit from a plug wire before, it wakes you up a little.

I am getting a pretty good spark now, and have been able to use a timing light while trying to start it and the timing looks pretty close, so I don't think it's a spark problem.