UPDATE 1989 Firebird Formula, no start

You may remember this earlier thread from a couple of weeks ago. http://community.cartalk.com/discussion/2293055/what-does-the-vats-system-control-on-an-89-pontiac-firebird-formula#latest

After scratching our collective heads around here for a while, I went to a local Chevy dealer to see if his computer would tell us how many ohms should be in the ignition’s key. (There are no Pontiac dealers anymore.) It gave him the key code, but not the number for the resistor. Since I have already installed another lock cylinder in the steering column, I wanted to get a key cut that matched THAT lock, but with the proper ohms in the chip to start and run the car. Since the counterman couldn’t help on that score, he LOANED me a black box with 15 positions, one for each level of resistance, to detect which resistor was needed. I hit it on the 13th try.

So now I have a car that turns over, with the key, with the GM gizmo’s switch in position 13. This temporarily negates the need for a chip key. It will still run as long as we shoot ether into the big intake hose (up stream of the MAF sensor), but dies very shortly after we quit. So we know we have spark, and 43 PSI of fuel pressure at the rail. The 3 amp ECM fuse is good, but the engine still won’t start. I’m assuming that the injectors are not triggering for some reason.

Any ideas?

If it cranks over but doesn’t start without ether, then there’s likely no gas in the cylinder. If you crank it without ether and then remove a spark plug, is the plug wet or dry? If it’s dry, you are right that it’s not getting fuel through.

I found this on the internet. Any help? On your car the ECM is set up with two quad injector firing sequence. All even numbers and all odd numbers. It is rare that both would go out at the same time. The ECM grounds the injectors, so I would check for power going to the injectors first. This could be a fuse or a bad wire. One wire feeds power to the injectors until it reaches the engine.

I found this too. Come to find out after spending $560.00 on electric parts that were not needed, the number 5 fuel injector was shorting out causing the engine not to start. It would turn over but wouldn’t catch. I unplugged the injector and it started right up. I let it run for a bit and while running, plugged it back in and sure enough, the engine stalled. This particular engine had us going crazy. We thought if an injector went bad at least half the engine would run. Apparently this one has a safety mechanism on it.

Good luck! One of these days it’s going to fire up like it always did.

IIRC this car didn’t have a MAF sensor. Does it have the original engine?

Check to see if there is a blown fuse that may be used for power to the injectors. You always want to make sure power is good before looking further into problems like this. I would guess the return side of the injectors is controlled by the ECU.

@Wentwest I tried your suggestion of removing individual injector connectors to no avail. That would have been too easy. Darn.

I borrowed a set of Noid lights at Autozone. They proved that there is no pulse going to any of the injectors.

The injectors, or pulses to them, are definitely the problem. Do the injectors get their pulses from the module inside the distributor, or the ECM, or both? I have another distributor module, that is probably the same, out of a Camaro. I’d have to check the part numbers to be sure of an exact fit. Another ECM for that car may be hard to find, short of brand new at a high price.

The PCM provides the ground for the injectors.

Does that help.

@db4690 If the PCM provides the ground, what provides the pulse itself, or am I asking the right question? What is the difference between a PCM and and ECM? I admit I really don’t know much about how fuel injection works

Check the injector fuse as mentioned. It supplies the +12 to all injectors. You could use a DVM at the injector connector as well. The PCM provides the ground reference to each injector at the appropriate time. That’s the “pulse”.

You can give the loaner box back if you want. Simply measure the resistance, go to Radio Shack and buy an 1/8 watt, metal film, 1% resistor closest to the measured value. Then stick it in the same connector the box was connected across.

ECM and PCM, along with ECU, are essentially the same things; an engine control computer.

The schematic shows each set of 4 injectors has its own fuse as a power source with the key in the RUN position so I would verify that voltage is present at the injector plugs. The odds of both fuses being blown may be slim but it should not be ruled out.

Each set of 4 injectors is pulsed simultaneously by the ECM which makes and breaks the ground for the sets of injectors. The ECM should receive a pulse from the electronic ignition.
Have you run a code check on this thing?

@ok4450 The MIL is not on, but that could be because it has not run in some time and no codes were set when it was running. I get the impression that this car may have been sitting for quite a while. Could there be “flash codes” anyway? I drained as much of the varnishy gas out of it as possible when I installed the new pump. Then I put in four gallons of fresh premium. The problem is not fuel, it’s electrical.

Where is the ECM located on this era of GM V-8s?

Never worked on too many Firebirds and mostly on Camaros but the 3rd Generation cars are essentially the same. The ECM should be located behind the glove box or kick panel on the passenger side.
The diagnostic connector should be underneath the steering column and should be accessible without having to disassemble anything.

Yes, there could be codes present even without the MIL being illuminated.

I would double check and make sure that power is being provided to the injectors with the key on though.

The injectors are wired like Christmas tree lights. Meaning the voltage supply jumps from injector to injector.

The computer has drivers that grounds each injector at the appropriate time and amount of time.

As @ok4450 suggested, check for voltage at the injectors with the ignition key on. If there’s voltage then more than likely the drivers that ground the injectors in the computer are no longer working, or there’s a bad ground at the compuetr.


@Tester SO, if my test light is ON when the key is ON, then there is a grounding issue? Wouldn’t the noid lights have been continuously ON then too? They didn’t flash when I cranked the engine.

You plug the noid light into the injector plug, so if there’s no ground to the injector the noid light or a test won’t come on. But if you connect a test light to the power supply on the plug of for the injector and then ground the test light somewhere on the engine, and the test light turns on, you now know the injectors are getting voltage. But they’re not being grounded. And that’s controlled thru the computer.


Aha. I’ll check that in the morning.

I finally got a minute to check it with a timing light. Sure enough, the test light lights up. It must need a new computer. So I went to www.car-part.com. I see none for a V-8 '89 Firebird in my area, but several for V-6 GM S-10s and Sierras from '89 into the early '90s. Ordinarily I use carpart.com to see what fits what. Can one of these V-6 ECMs work on my V-8 tuned port injection car? Would it be “plug & play”?

Before you change out the ECU make sure it is getting power to all the lines that require it along with the grounds also.

RockAuto has your computer. http://www.rockauto.com/catalog/moreinfo.php?pk=322766&cc=1251571

Remember to remove PROM from your old computer so it can be installed into the new computer.


OK, maybe we need to go back to square one on this. At first it was a key problem. Then with the new key, it was running with 43 psi fuel pressure but only by spraying starter fluid in the intake? The injectors are firing? Or not firing because they are not being grounded? So are we concluding its an ECM problem because the injectors aren’t firing due to a grounding problem, but that would still allow it to run by squirting starter fluid in the intake, thus by-passing the injectors?
So the ignition system is ok but its a fuel delivery problem?

Its a V8 right, but with a rotor and distributor cap. It looked like that ECM though is for a V6 though not a V8. When I got a spare ECM, they told me to just make sure the ECM numbers are the same, then swap the memory chip out of the old one. But I think a V8 and a V6 would be different.

Just trying to get my head around this one a little.

The engine runs using ether. The injectors have power getting to them but
the ECU isn’t turning on the ground return to them for some reason.