2G Injector Drive Troubleshoot?

ok_opie · Apr 30, 2006

OK, Here is my question, to my injectors I have 12v+ 12+ on both sides with key on. Key off it is dead on both sides. I first figured ECM. I cut pin 1 wire directly from ECM (injector wire for Cyl. #1) dropping 12v+ from one side of cyl. #1. Testing directly from ECM it has 12V+. I figured ECM Bad considering per wireing diagram it goes 12+ from EFI relay to Supressor Resistor to one side of each injector, leaving ECM to pulse ground to operate them. I installed suposed good used ECM and same response, do I have another bad ECM or is my problem elsewhere? I have placed a noid light to the injector wires and it does pulse it does not appear to pulse properly to the eye but it could be right. Engine is in a no run condition, good compression all across, good fuel pressure, and good spark.

Just for a lil history this is a 6 bolt swap I have never actually heard car run it had a thrown rod in it when I got it, and someone decided to syphon all fuel out of it prior to me picking the car up and I burnt the fuel pump up trying to start it with the bad 7 bolt. Yes I installed new fuel pump and tested pressure the main thing is why is the ECM's pushing 12+ to the injectors.

luv2rallye · Apr 30, 2006

ok_opie said:
I have placed a noid light to the injector wires and it does pulse it

The pulse to ground is so narrow on the ECU side that your voltmeter isn't even going to notice it (so it will read 12+). Noid light blinking (or even dimming) is a good sign they are working. Pull a plug and see if fuel is getting in the cylinder.

ok_opie · Apr 30, 2006

So the ECU will send 12V+ when not pulsing. I just know in general (GM ford Isuzu all that I have needed to test) ECU injector drive is dead when not pulsing. The noid light does blink. I am going to run another Fuel pressure check and verrify any leak down. The tester I used leaked down itself and verrify the fuel pressure. I don't believe Chiltons book told me the required pressure. I will research to find it, surely its listed in the forums somewhere. I found a minute fuel leak last night and I am going to test the injectors for spray today. I will update.

Thankyou

luv2rallye · May 1, 2006

ok_opie said:
So the ECU will send 12V+ when not pulsing.

No but close. The ECU side becomes an open circuit (and so it floats) when not pulsing. You read +12V there because you're reading it through the injector which has +12V on the other side. The ECU side floats to whatever voltage is on the other side. Think of it as a wire that you just cut off which has +12V on the other side. You will always read +12V on this side no matter how much resistance is in the wire since no current is flowing so there can be no voltage drop across it. The injector in this scenerio is the resistance.

ok_opie · May 1, 2006

That is what I thought you might have been refering to. I get +12 with out the injector hooked up, and when wire is cut 3 inches from ECU I still get +12V out of ECU and killing the power to the injector that I cut.

I appreciate your help from what you have said and my past automotive exp. I have a set of bad ECU's

ok_opie · May 2, 2006

Update -- Per Dave @ DSMlink.com the ECU will send +12V when an injector is unplugged. It is a portion of the monitoring of the ECU.

Currently the car is changing by the minute, I had Noid light all across now only Noid on Cyl 1 & 2, 3 & 4 are dead. Receiving power from resister/MFI relay just no signal, they receive +12V from ECU when unplugged.

I physically checked injectors/wiring its all good except no signal from ECU to shoot injectors 3 & 4. I then rechecked my 1G CAS and found I had the Cam and Crank sensor wires swapped them and rechecked all other wiring.

And I get nothing, the MFI relay is not getting any power like it should to power coil/inject/ECU/etc. I can not find any blown fuses in either engine compartment or under dash. Any body know where it is so I check injector fire.

Well I found the fuse and the problem was a loose connection in the distribution box. However still only injector 1 & 2 are shooting fuel. Anybody have any idea, I am still leaning towards the ECU I wish I had another GST to test my ECU's on I just hate to buy yet another ECU.

ok_opie · May 4, 2006

Well I finally got it the whole time the problem was in the CAS. I don't know why the 97 cam/crank sensors didn't work originally or why the 94 GST CAS didn't work it was out of a running car but I got one off of a 91 N/T and it is running now a lil mis and stall but I don't have alo of shit hooked up yet just enough to run nor have I set the ign. timing yet.

Thankyou for everyones help especially Dave Mertz @ Dsmlink.com

hypnotized24s · Jun 8, 2006

i am currently having about the same problem. i just bought a 90 laser.. and the guy said the only thing wrong wtih it is the computer. so i got a replace ment computer off ebay but im not completely sure the ecu is working in perfect condition..but it didnt crank.. it will crank if i spray ether in it but will not start. i am getting good spark and fuel pressure. but no gas to the cylinders i think... im getting 12v to the injectors but i dont think that they are firing. any one know where any wiring diagrams are of this on the net? or do i need to buy a owners manuel?

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2G Injector Drive Troubleshoot?

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