Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
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Hi. I've got an 86 Camaro Z28 with the 305 TPI motor that will not start. It was running fine until I shut it off one day, then it wouldn't start after that. I have verified that we have fuel pressure (holding at 42 psi) and spark. It does not look like the fuel injectors are pulsing.
So far I have replaced the cap, rotor, wires, plugs and fuel filter. These part were all just old and needed replaced, not because it wouldn't start. I have no codes in the computer, although the computer just keeps flashing the number 12 over and over again. Is this supposed to happen, or do you think the ECM is bad? Where should I start checking?
Ohm test your injectors. If they all check out ok, try a different ECM. The 12 is normal when the engine isn't running. The ECM will shut down the injector drivers if there is an overload. You can give it a puff of starting fluid and see if it takes off. That would pretty much narrow it down to the injectors not firing IMO.
I believe the injectors are OK as it was running fine until it was shut off. I also tested the injectors with a noid light and they are not pulsing. I tried the starting fluid thing at it almost ran, but then it backfired through the TB and burned all the hair off my arm. I stopped trying after that.
Should the computer keep flashing the number 12? I counted 21 times after the initial 3 sequence, then I turned off the key. I thought it was supposed to flash 12 three times, then any codes, then 12 three more times, then stop. Am I wrong on that?
I am currently looking for another ECM, but I hate to throw money at a problem. If the computer is not bad what should I check next?
Well, there you go. It's pretty much down to a short, no output from the ECM or no 12V supply to the injectors.
First make sure you have 12V to all the injectors when the key is on. If not, find out why. The injectors are "hot" all the time, the ECM fires them by switching the other lead to ground (it's a transistor thing). If the 12V is not there (with respect to ground, not the other injector wire), then a bad fuse or fusable link is likely.
Next, you could unplug the ECM, unplug all the injectors, and measure the resistance between the two wires of any connector. With everything unhooked and key off, it should be an open circuit (infinite or at least millions of ohms). If it shows a short circuit, find it and fix it.
While you are here, measure resistance of each injector and make sure that each one is over 10 ohms. Any that are measuring very low resistance have shorted windings and will overload the ECM driver transistors.
Sorry, one more thing I forgot to mention. I do have power to the injectors. Solid 12 volts. They just aren't grounding out. The noid light was only lighting up when I stopped cranking the engine. No light while it was cranking. Someone mentioned it could be the ignition switch, but I do not know how to test that.
I will ohm test the injectors the next chance I get.
Make sure the pickup coil in the distributor is functioning, and that the signal is getting to the ECM. That is what initiates injector pulses.
If you would use the SEARCH feature of the board, you'd find that when everything is normal with the ECM, the code 12 will flash forever, or until the battery dies. You might find a lot more useful information, too.
i had the same problem ith my 83 camaro but min eisnt tpi its cfi injected and it came down to 2 fuses that was blown under the dash cheack all of them and see if any where blown
If the INJ1 or INJ2 fuses had failed on a TPI, there would be no 12V supply to the injectors. The OP already mentioned that voltage was measured there.
Turns out the pickup coil was bad. We replaced it and it ran for a while. We took it around the block and it seemed to run OK, but not great. When we got back to the house we noticed smoke coming from under the hood. It looks like two spark plug wires on the right bank were smoking, and all of the wires were hot, like they were overheating. Any ideas on this one?
Well, my friend and I threw in the towel and took it to a shop on Saturday. After replacing the computer and the ignition switch and still no start we decided we were in over our heads.
Supposedly the shop found a bad temperature sensor that was telling the computer it was 40 degrees below 0. They said this sensor was located near the starter. We had replaced the sensor near the water pump but we did not know there was another one near the starter. Does anyone know anything about it?
The shop said they might be able to get it done today, so we'll see.
Well, it's been a while and I am still messing with this thing. The shop replaced the faulty temperature sensor, and now says the computer PROM is incorrect for the car. Supposedly the chip is for an 87 Camaro with an alarm system and is throwing codes related to the alarm system. This car doesn't have an alarm system. I don't have the number off the chip with me but I did cross reference it to an 87 Camaro.
Can anyone tell me what the correct PROM number I need is? I think I need #1228291, according to the cross reference on this site. I'm having a hard time finding one.
I don't think this is the problem as the car ran before with this chip, but I should have the correct one in it anyway.
