I hsve an 89 Iroc-z and it wont start. Has a new fuel pump and ignition coil, and it does have spark. Problem is I think that its not getting gas because the injectors arent getting power to them. What gives the power to the injectors and what could cause this?

ECM gives the command for the injectors. A fuse gives power to the injectors. Look on the fuse block(s).

Ignition power supplies Relay power energizing the injector power. This power goes through the injector coil and ends up at the ECM. ECM commands a LOW signal, this event causes the injector to open and fuel sprays out.

All driver side injectors are from the same ECM driver and all pass side injectors are from a separate identical ECM driver. I think one side, the wire color is black & green, the other side is Black and purple.

Welcome to the Club!

Hopefully others here will emit their knowledge and correct me if I'm wrong, I have been told this, ask my wife.

Security Light on? If so welcome to the wonderfull world of VATS.

Is there any way to test the PCM to see if its bad?

A dealer can, but they like money so....

There is a 3rd generation website out there (I don't know the link, but I am sure you can search for it here on this web site) that maybe able to help you out with an after market vendor who can check out your PCM. I don't think new ones are terribly expensive anymore and should be available at a parts store. So compare the cost of a new one from NAPA to what the dealer wants to charge and take it from there.

When I worked for the dealer our "test" was to plug a new one in.

The only way I know is to get the service manual, a digital VOM, and check every input and output for the ECM.

Obviously, that could take a long time. That's why if you've eliminated wiring (including grounds), ignition module or sensor failures, you could throw a $75-$100 ECM at it. As posted above, Reman aftermarket ECM's aren't that expensive. Another option is a boneyard part, they can be had cheap.

BTW, how did you determine the injectors weren't getting voltage?

[ 11-11-2004, 07:45 PM: Message edited by: ZZ430DropTop67RS ]

I unplugged on of them and put the leads from my dmm in the connections and cranked it over.

I unplugged on of them and put the leads from my dmm in the connections and cranked it over. With the connector unplugged, IGN on, at least one wire should have battery voltage to ground. The other wire should have something less as it comes from the ECM.

Now, plug the connector onto the injector, battery voltage should be seen on the wire from the ECM as bat/volt would go through the injector coil to the ECM to complete the circuit.

If you have a good DMM and it has analog scale at the bottom of the display, this scale reacts faster than the numbers showing. You can place the DC Volt meter leads across both wires of the plugged in injector connector and have an assistant crank the engine over, the analog scale should be going from 0.5 volts to battery volts. If this happens, it signifies battery voltage is getting to the ECM through the injectors and the ECM is commanding the injector(s) to open.

But only if the fuse is good and relay is working and its contacts don't have carbon buildup.

Well i tested the injectors the right way this time. (I put the positive leed in the injector connectors and put the negative to ground and cranked it over.) And i got power in both conections. So...it could be not getting enough spark, could be clogged injectors or intake (we had a big dust storm like a month ago and got crap all over my engine since i didnt have a hood on at the time.)I did get it started a couple days ago after i moved the wiring around a bit looking for shorts and i took off the air cleaner and it fired right up, but it had like no power, i dont think it was firing on all cylinders that time. So here is what i came up with that could be the problem...

-Timing (Bad timing could cause it to not start or run really rough with very little power, right?
-Clogged injectors/intake
-Bad fuel relay (when i turn the ignition on i can hear it prime the system, from there on i dont know what its supposed to do if anything.)
-Fuel pressure regulator (may not be getting enough fuel)
Ignition module (spark may not be hot enough)

Originally posted by fourtwozero:
Well i tested the injectors the right way this time. (I put the positive leed in the injector connectors and put the negative to ground and cranked it over.) And i got power in both conections. Not the correct way.

The pink/black wire to the injectors are switched ignition 12V. Should read 12V with key on.

The light green and light blue are the the wires that the PCM "grounds" to pulse the injectors.
You should not have seen power present on those wires. I am guessing that You only unhooked one injector for Your test and the "power" reading that You got was feeding back through the other injectors that were still hooked up.

If You don't have a "noid light" You can just jumper a regular test light across the terminals and see if it blinks while cranking the engine over. The PCM can handle it for a quick test.
Unless You have a DVOM that saves readings, the light is the best way to check this since the injector pulse is too brief to get a good voltage reading.

I'm with Mark....is the security light on???

nope security light is not on. thanks for the tip 18436572, ill go do that right now.

The results are in, the injectors on the drivers side have pulsating power, however the injectors on the passanger side do not. I also noticed that they require a 10 amp fuse and there is a 20 amp fuse in there for both of them. Still no spark on either side.

I had the idea to test the spark control module, and i found that it has no continuety between and of the connections. I tested it by disconnecting the plug from it, and tested all the connections for continuety and got nothing.

[ 11-13-2004, 04:44 PM: Message edited by: fourtwozero ]

Good third gen site is:


www.thirdgen.org (http://www.thirdgen.org)

I found the problem, the place i got my sending unit gave me one for a TBI which flows about 15psi, i have a TPI which needs about 35-45 psi. It took me like a month of trying to troubleshoot this till i gave up and towed it to a shop only to pay them 80 bucks to tell me i had the wrong pump in there. Now i have to buy a new pump, filter and strainer, AND pull the tank again to replace them. Aint that some ****.

Man, I feel your pain. I've got a visual of those Viking guys bumming out over a Capitol One card. I hadn't thought about the different fuel pressures. That's a good one for the archive.

graemlins/thumbsup.gif

Thanks for taking the time to post the results! I wish more People would do so.

Glad Ya got it figured out.