@Bing you are correct about the ECMs being the same except for the PROM which is removable. I borrowed one from the salvage yard down the street. (I’ve got friends in all kinds of places.) I exchanged the PROMs and plugged it in. I get the same results. It almost acts like it wants to start, but not quite. It still runs for a moment on ether.
@Cougar, where do I begin to look for a bad ground? Since the ECM is mounted to the body with a plastic bracket, that can’t have any bearing on it. If it’s under the dash, I may need to find someone younger and thinner to stand on their heads for me.
The more I look at this car, the more I think it may have sat for a long time. A ground issue is a distinct possibility. It’s an '89 showing only 127K miles. It is very dusty inside and out. It may have had this problem before it was parked and/or abandoned. I was told it was stolen, but who knows. Abandonment may be why it wound up at the police impound auction.
I’m really getting beyond my level of incompetence but the ECM is grounded by one of the wires I believe. One of the wires on one of the plugs to the ECM is the ground wire, not on the case itself. You really need the schematic to see which wire. Don’t know if they’re black or not. One thing you can do is check all the wire cavities to makes sure none of them has backed out and not making a good contact.
Is this a throttle body injection or the standard injectors to each cylinder like an 89 V6 would be? Is it a Pontiac or the Chevrolet version if that makes any difference.
As far as grounds for the ECU go there could be and most likely is several ground wires going to the ECU. I don’t have details on your model to tell you where they are at. You could try cleaning any engine grounds you come across to see if that helps. @knfenimore has been very helpful in providing wiring data digrams, perhaps he can get one for your ECU.
@Bing brings up a good point about bad gas and I can’t remember now if the fuel pressure has been checked but I do seem to remember you stated that fuel was getting to the rail and you have verified the injectors are getting power but not turning on due to some unknown reason the ECU is not turning them on by completing the ground return for them and a replacement ECU didn’t correct the problem. Hopefully that is a recap of the current situation. Please correct any errors if I made some. Along with the ECU grounds the power inputs to the ECU should be checked also.
@knfenimore if I’m reading the diagram correctly, the ECM ground is a black & white wire at position A12. Right?
The wire bundle appears to go through the side of the car and then up over the right fender area. Where would the grounded end of that wire be? I don’t think it is very near to the ECM. Can I simply splice into that wire anywhere along it and provide a good path for it to reach ground?
I’m not sure if A12 is the ground for the injectors. Looks like its the ground for the fuel pump. You need the whole schematic for the ECM me thinks. At any rate you should be able to just go to A12 on the plug with an ohm meter and the other to a ground to see if you have continuity. If so, I don’t think that wire is the problem.
@knfenimore In answer to your earlier question, it has 43 PSIg of fuel pressure. I was so interested in seeing the diagram that I didn’t see the question. The fuel was new after I replaced the non-functioning fuel pump. I got most of the OLD gas out of the tank and put in premium to augment the small amount of low calorie stuff left in the tank. I’m pretty sure that IF I can figure out why the injectors aren’t triggering, I’ll have a running '89 Firebird Formula 5-speed.
The oil pressure pumps up to 30 PSIg while cranking, so I think the bottom end is probably good.
To see if there is a bad ground connection on a wire just measure the voltage on the wire with the meter reference lead tied to a good chassis ground point. If there is a bad connection to ground on that wire there will be voltage on it. A good ground connection will have no voltage on it since there is no resistance for voltage to drop across it when current is flowing.
The middle drawing shows a couple of injectors tied to the ECU. It also shows a VATS system and I now am wondering if that system has anything to do with shutting down the injector operation. I don’t know for sure if it does control them but I suspect that it might be causing this problem.
EDIT:
After doing a search about the VATS operation it does look like the injector operation is controlled through the VATS system along with the starter operation. Since the starter circuit is woking okay hopefully the injector operation is okay also. In the first diagram it shows ECU pin C9 is tied to the starter solenoid wire by a fused wire for ‘crank sense’. Check that pin for power while trying to start the engine. Check the fuse if the voltage is low on that pin.
@Cougar Since it will run on ether, I don’t think I have a VATS induced spark or starter issue any longer. Do you? VATS was my initial suspicion for ALL of my car’s problems, but I have the right key now. I’ve already checked all the fuses.
@knfenimore, I hope to find time to check the wiring with the diagrams you graciously provided this afternoon. Thanks. Maybe I’ll be posting about a running car later.
I think Cougar was saying that the VATS could be causing the injectors (fuel supply) not to work not that VATS was causing spark not to be supplied. So it makes sense that spark is still there but VATS is not allowing the injectors to operate, thus causing the fuel issue and the ability to run with starter fluid-by-passing the injectors.
Best concentrate back on the whole VATS key issue which was the original issue which makes more sense than the coincidence of two problems at the same time.
But I have the proper VATS key now. Can VATS still be an issue?
The key was not a coincidence since the car was stolen. The key was simply missing, and the ignition switch had been drilled out. I also think ground issue theory may be correct as I think the car sat for a long time either prior to or after the theft.
Even though you have the proper key I am now thinking the issue you are having is related to the VATS system rather than a ground wire connection problem to the ECU that is used for the injectors. Here is a link to a site that explains the GM VATS system. Carefully read the explination of the ‘NORMAL’ operation that involves the starter and the “fuel enable” of the injector circuits.
Make sure pins A6 and C9 of the ECU have power on those pins while in the START mode. The drawings show they are fused leads. I assume pin B6 is the connection point that the description talks about sending a pulse width signal code to the ECU in order to turn on the injectors. Since the starter circuit is working it may indicate that the VATS system is really okay but it seems strange to me that the injector portion of the circuit is having trouble. Perhaps there is something going on with the code signal that allows the starter to work but not the injectors.
So I’m wondering, with the VATS, how did the guy get it started that stole it? Drilling out or punching the lock shouldn’t have been able to overcome the module.
I always hate it when I get a used car and don’t know what the heck the guy before did to it. It’s save a lot of time if they’d just leave a note.
Might be time to just let someone look at it.
Edit: I have a 95 factory manual but not an 89 and even though it is the Passkey II system, it is very similar to the above information. One thing it said in bold was that it was very important for the wires from the new ignition cylinder to be properly routed. Didn’t say why. The other is that there is a separate chart for “Starter Cranks but No Start”. Essentially it is checking for voltage at A3 as Cougar said and checking that dark blue wire for opens or shorts. So it is possible for the Passkey system to allow the starter but not command the injectors. Outside of wiring or the ECM problem though it is a defective Passkey module.
Thanks for the good info @Bing. I would guess the wire routing is important to help keep external noise from getting picked up on the wires and effect the system. It sounds like your info has some different wiring than the other info posted here but the VATS output wire is dark blue. I can’t say which one really matches the OPs system for sure. Investment in a factory wiring diagram would really be a good thing to have and help solve this problem.