I've had the inj. drivers im my ECM replaced with low impedance units. I've had this ECU roughly a year. (86 buick grand national ECM)

Recently The car started running rough. After a little trouble shooting I found the #1 injector was not firing. I'm getting full voltage at the plug. Noid light flickers just fine on the no.1 inj. lead. So I figure its an injector issue.

I pulled all injectors and set them up on my test rig. Pumped inj cleaner through them all and cycled them with 2amp 12v power source. All seemed to work fine. I re-installed them all the the car ran great.

Today (week later) the car runs rough. I went right to the #1 inj again, but it worked perfectly. Now the number 6 injector is doing the exact same thing! So I Ieft the injectors installed this time and brought my inj pulse rig over to the car. With my 2amp 12v power supply The #6 injector worked perfectly. Plugged it back into the engine harness and everything is ok again. Car drives/idles great.

I've confirmed I get bat voltage at the inj. leads. Noid light confirms they all pulse as they should.

Anyone have any ideas? The only thing I could think of is I'm not getting the initial 2amps required to open the low-Z injectors. The grounds are all ECU controlled correct? Not much I can do to help that. Can I wire in an "IGN ON" power source that I know is good to the main power going to the INJ harness? Would that even help? Are the inj drivers going bad?

Thanks...

 

Did all the injectors go back in the same hole?

 

no I moved them around, marking the previous "troubled" injector with a sharpie.

 

So #6 this time did not have the first bad one you marked in it ? sounds like you just move the one from#1 to #6.

 

Negative, I purposely moved them to help eliminate wiring issues if that was the case. As I said I marked the previous faulty #1 injector. It is not in the #6 spot it's in the #2 spot. Seems to be working fine now. I'll try hot wiring the main lead on the inj. harness with a known good bat. positive and go from there.

thanks.

 

Dirty connectors. When you unplug the dead one to check with the noid light, it scrapes off the corrosion and gives a good connection from then on until it goes crusty again.

Most times you can fix it permanently by replacing the injector pigtails and cleaning the shit out of the injectors, but occasionally it just keeps growing on the pins in the injector and just reinfects the new pigtails. It's like a virus, you have to kill every last bit of it dead or it will keep coming back.

 

I'll look into it. There is an injector sub-harness so I can completely remove it and check/clean all the pins. Thanks.