Hi All,
Here is the story - just reinstalled motor after minor rebuild upon trying to start the car I have no spark! Well when motor was out
had starter wires fall and start arching so I figured may have blown fuse in MSD,it was good.
Then I figure I would check injectors to see if they fire,well both wire w/ignition on are showing power. Then I went and bought a
remanned 7730 - To my surprise I have spark! cool!,not so -
injectors still not firing so i checked inj wires at the ECM they are showing power ? so is alot of other wires along with the system ground wire...
It appears im feeding power back to the ecm but from where?
I unplugged all connectors and still get power through the inj,torque converter lock up and many others.
Now im stuck and sure i blew this new ecm,what wires would you check for power to trace back ? or where to look ? please please help.
They inj. wires should not have power right? they are controlled
by ground correct?
Ohh yeah the dash dispaly (digital) is also acting really weird.

 

Your injectors work of a ground for the pulse. The wires to the injectors "should" have power, when the injectors get a ground it opens...allowing the injectors to pulse. It sounds to me like you have a VATS (Vehicle anti theft) problem. Either that or bad injectors.

 

I dont believe that both wies should have power at the inj.
nor should the wires pins c11 and c12 have power there.
But to be safe i just unplugged all the inj. to be sure one of them is not grounding its self out.
I am getting power through a ground somewhere because the system ground (ba12)on my ecm is also showing positive?
Thanks for the effort though.

 

Trust me...both wires have power! I went through the same questions you are a year ago. They both have power. WHen the ECM tells them to pulse it sends a groun through the one wire. You either have a VATS problem or a injector problem. Effort has nothing to do with it. Facts! are what it is all about. Both wires do have power. I had to wire the TPI system to my Monte Carlo SS...it took me awhile, but I ran inot the same problem you are having now. I had power at both wires and the car wouldn't start. It was a VATS problem in my case. Try a search on "injector pulse" and see what you come up with...Again BOTH wires are to have power. Go from there.

 

Hmmm,well why does the system ground have power going to it?
Well ill burn another prom to be sure nothing happened to that
one but still can not figre why there would be power comming through the system ground.
My car was not originally equiped w/vats and its disabled in the prom but hey you never know.

 

It is hard to say when mixing apples with oranges, if you know what I mean. I'll have to look through all my diagrams again too. What year car did the wiring harness and ECM come from?? I have to step out for awhile but when I get home later I will take a better look myself. I need some more specific info on the engine and system you are using to better diagnose your problem. Talk to you then.

 

Its a 92 7730 ECM and the harness I repinned from my existing
1987 165 ECM .
Just to clear up some thing also in case you wondered the car ran fine when I tore it down and has so for about 8 months ,but sometime between the teardown and now something went bad.
Maybe i pinched a wire I don't know but its deffinetly getting power in places it should not be .
I just tried to burn a new prom in case something happened to the one that was in there,Did not work either.
Ohh yeah forgot to mention I tried scan and "vehical not responding" But I figure that would happen and Im scared to hook up the laptop in fear of hurting it.
Thanks for all the help its very appreciated!

 

I just finished checking my wiring diagrams for you ECM c11 and c12 are both fuel injector references...therefore yes both should have power if checked with a test light. The dark blue wire from c11 goes to cyl. # 1 3 5 & 7 . c12... the dark green wire goes to cyl. # 2 4 6 & 8. From there both sides use a pink and black wire. which goes to a injector fuse. All wires are hot till the ECM tell the c11 and c12 wires to ground, this casues the injector to open, or flow. Without that ground the injectors will not pulse...therefore no fuel... Now this may be a stupid question, but is the fuel pump working?? Do you here it turn on that is?? And is there fuel pressure??? What other wires have power that you believe should not??? I've got the diagrams right here so. I won't be online too much later tonight, but will be back tomarrow. Let me know.


Keiran

 

Well another one is my Torque converter lock up control(gf6)
system ground(ba12) and many other ill have to go through all tomorrow and let you know.The fuel pump is working and has pressure but it also is acting funny like when I try to start car it runs for like 30 seconds after i turn off key and does not seem to turn on when i first turn key on. and like i said the dash display is acting funny-no fuel guage,speedo reading 100,tach reading 2000
or 4000-6000 but no bar from 0-4000(digital dash)
I should be able to put a light in the injector wire and watch it pulse right? well its not doing that either.
Wonder if I didnt get a bad ECM,that would be my luck.
I change the first one and get spark back but still no injectors.
Could a relay have gone bad and causing this? Ill have to see I guess what all wires are showing current.

Thanks again.

 

First off, checking for firing on injectors is best/easiest done with a noid light. Most auto part stores have them for like $5.

You say the system ground wire is showing power. How are you using your multimeter? Or testlight.

Your torque convertor lockup control isn't working??? If you can't drive the car, I assume you are again finding voltage where there shouldn't be any?

The gauges thing sounds like a ground problem. The FP not turning on initially to prime could be related, or your ECM has a bum transistor driving the FP relay.

ftp://ftp.diy-efi.org/pub/gmecm/manu...730v8tpi-5.jpg

ftp://ftp.diy-efi.org/pub/gmecm/manu...730v8tpi-6.jpg

ftp://ftp.diy-efi.org/pub/gmecm/manu...730v8tpi-7.jpg

Those show the voltage that should be on each wire coming out of the ECM with all harnesses connected. IOW, if you pierced each wire with a really small test lead (read sewing needle) then those are the values you *should* obtain. If you don't wanna poke the wire harness, keep in mind that the ECM case has screws holding the cover on and those screws can be taken off exposing the solder pads...but I don't recommend that method because working with electricity of any kind can kill you, render you harmless to animals, require legal notification to next of kin, etc.

Pull the CTSY fuse if you are going to be doing any resistance checks to verify the integrity of your grounds to the ECM.

If I was a betting man, I would go for the ground by the thermostat housing.

 

I never said TCC is not working,I said its showing voltage (with a test light)
The noid light sound like a great idea,im going to get one.
Thanks alot for the pinout voltage maps,I just printed and am going to go check right now.
Thanks for all and any help it really is appreciated ,this is a disater right now.

 

ok here it goes. with key in on position.
connector AB,BB
BA4 BA5 BA6 BA8 BA11 BA12
11.9 11.9 11.9 10.7 9.2 9.2 VOLTS

BB1 BB5 BB6 BB9 BB10 BB11
12.2 9.2 9.2 9.2 9.2 10.4 VOLTS

CONNECTOR BC,BD
BC7 BC8 BC9 BC11 BC12 BC16
00.1 4.1 9.2 12.0 12.0 12.2 VOLTS

BD1 BD6 BD7 BD8 BD9 BD12 BD14
9.2 9.2 9.2 00.3 00.0 12.0 4.2 VOLTS


As you can see everything is showing way to many volts,
I checked connector GE,GF also with pretty much same results
I figure i will check pins showing the most volts try to trace back and possibly find the problem.
Thanks again

 

Anyone? Anything? Im really againt a wall here.
Ive tried to unplug all sensors and relays and still getting power through a ground somewhere.
I also noticed that the plug going to my alternator all three wires have power the red,and two browns and i believe that
may have something to do with it cause there are three eyelets
that go to starter the main,a single red, and an eyelet with two red wires comming from and ive narrowed it down to thoso two wires now im gonna have to split them and see which one of the two. and trace the whole length,although that may lead me to nothing but ive tried everthing else.

 

I think I just found problem I grounded the terminal to the ECM and my dash board display started showing normal so I must have pinched that ground between firewall and motor/tranny during install.
Im not sure thats the prob yet till i get everything wired back up againg from trouble shooting but it seems to be.
Thanks for help.

 

I GOT IT!!!!!!!!!
WOOOOOOHOOOOOOOOO!!!!!!!!!
I got to thinking while at work that if I was getting power to a ground wire,why is it not melting or shorting????
Because that ground was not grounded! it must have been pinched like i said.
So I ran a new ground for now and wallahhh I was rewarded with a smoke filled garage.
Time to start burning for the new cam that seems to be extrememly rich right now. 230/230 560/560


Thanks for all the help.

 

Glad to here you found the problem. Good work...Enjoy!

Keiran