86, 4 speed, 3.4 swap. I just got the engine in and it cranks over but it does not start. It doesn't even try. Zero gas smell while cranking. With starting fluid it will fire once(not sure if a backfire or what, no muffler and inside a garage so its loud). Fuel pressure relay clicks good, fuel pump kicks on for 2 seconds, theres fuel at the pressure check valve(and its had tons of flow when I emptied the tank with it, and yes it has several gallons of fresh gas). I just swapped the ICM and no change. Theres spark when I checked it(plus it will ignite starter fluid). Checked fuses, both 5amp fuses are good. Plenty of battery voltage(12.8v while cranking). Oil pressure reads 40+ and the gauge moves while you crank. The tach is wonky, it just climbs all the way around while you crank it(not sure why). Check engine light is on while cranking. Every electrical contact was cleaned with contact cleaner when I rewrapped the harness. I have 4 good grounds on it(did a battery relocation to the frunk and it cranks over very well). Cap, rotor, wires, plugs, and coil were changed right before I got it. Fuel injectors are brand new bosch, injector harness was cleaned and checked(cold start injector was removed and capped off).
86, 4 speed, 3.4 swap. I just got the engine in and it cranks over but it does not start. It doesn't even try. Zero gas smell while cranking. With starting fluid it will fire once(not sure if a backfire or what, no muffler and inside a garage so its loud). Fuel pressure relay clicks good, fuel pump kicks on for 2 seconds, theres fuel at the pressure check valve(and its had tons of flow when I emptied the tank with it, and yes it has several gallons of fresh gas). I just swapped the ICM and no change. Theres spark when I checked it(plus it will ignite starter fluid). Checked fuses, both 5amp fuses are good. Plenty of battery voltage(12.8v while cranking). Oil pressure reads 40+ and the gauge moves while you crank. The tach is wonky, it just climbs all the way around while you crank it(not sure why). Check engine light is on while cranking. Every electrical contact was cleaned with contact cleaner when I rewrapped the harness. I have 4 good grounds on it(did a battery relocation to the frunk and it cranks over very well). Cap, rotor, wires, plugs, and coil were changed right before I got it. Fuel injectors are brand new bosch, injector harness was cleaned and checked(cold start injector was removed and capped off).
Yes, it has spark. The fuel injectors are not firing.
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Originally posted by cartercarbaficionado:
noid light
Its all the injectors. Its some fiero or GM specific nonsense keeping the injectors from getting power. I found some old threads with similar issues and checked things like ICM. My next step is a new new coil just to rule out as its only $20. It could also be the computer I supposed but I need to know how to rule everything out first.
I have been digging into this some more, the tachometer spinning all the way past redline while cranking is something but I can not find what that means.
I have confirmed I have good spark. The issue is somewhere at the ECM getting tach signal. I unplugged the filter, lost tach but no change while cranking(still no fuel). I jumped the filter plug, tach moves while cranking and move all the way past redline(just like it does while plugged in). There is SOMETHING making the tachometer climb the entire time it is cranking. I have not found a single troubleshooting tip or forum question even close to what I have. I trun the key and the tach jumps off the line like it should, as I crank it it spins up very fast and past redline all the way past the numbers, as soon as I stop cranking it drops back down to 0. Whatever is causing that is the problem on why it won't fire the injectors. I tried unplugging the TPS(no change), I tried unplugging the EGR(no change).
I have confirmed I have good spark. The issue is somewhere at the ECM getting tach signal. I unplugged the filter, lost tach but no change while cranking(still no fuel). I jumped the filter plug, tach moves while cranking and move all the way past redline(just like it does while plugged in). There is SOMETHING making the tachometer climb the entire time it is cranking. I have not found a single troubleshooting tip or forum question even close to what I have. I trun the key and the tach jumps off the line like it should, as I crank it it spins up very fast and past redline all the way past the numbers, as soon as I stop cranking it drops back down to 0. Whatever is causing that is the problem on why it won't fire the injectors. I tried unplugging the TPS(no change), I tried unplugging the EGR(no change).
yeah thats not right. is your icm or pickup functioning correctly?
yeah thats not right. is your icm or pickup functioning correctly?
ICM is new, I replaced it and there was no change between this one and the old one. Going to see if autozone can test them tomorrow. The pickup I assume is working because I get good spark. The issue is somewhere between the ICM and the ECM with the tach signal. The computer is not getting the right tach signal to fire the injectors. I have not found a single other fiero on a forum post with a tach that spins all the way around while cranking so I have no idea what to even troubleshoot. The odds of the old ICM and the new one having the same inexplicable problem are low so I suspect its after the ICM somewhere on the tach signal path to the ECM(but I don't know enough about the system and the wiring to nail it down yet). I am going to try and check wire continuity from the ICM to the ECM. I already eliminated the tach filter(does the exact same thing with the filter removed). It could be a bad ECM but damn, I do not want to spend $100-300 for a new to find out it's doing the exact same thing.
ICM is new, I replaced it and there was no change between this one and the old one. Going to see if autozone can test them tomorrow. The pickup I assume is working because I get good spark. The issue is somewhere between the ICM and the ECM with the tach signal. The computer is not getting the right tach signal to fire the injectors. I have not found a single other fiero on a forum post with a tach that spins all the way around while cranking so I have no idea what to even troubleshoot. The odds of the old ICM and the new one having the same inexplicable problem are low so I suspect its after the ICM somewhere on the tach signal path to the ECM(but I don't know enough about the system and the wiring to nail it down yet). I am going to try and check wire continuity from the ICM to the ECM. I already eliminated the tach filter(does the exact same thing with the filter removed). It could be a bad ECM but damn, I do not want to spend $100-300 for a new to find out it's doing the exact same thing.
Remember that there are two tachometer paths, one for the tachometer gauge, and one for the ECM, they are seperate. The tachometer I think is attached to the coil, and reads "spark" (one pulse every spark that the coil makes), the ECM tach comes directly from the pickup coil in the distributor through the ICM, so basically pickup coil - ICM tach out - ECM (calculations) - ICM spark in - coil - tachometer lead. What the tachometer shows is exactly what your coil is doing, regardless of what it should do, unless the tachometer board itself is dead, if you observe normal spark through a timing light (one per timing mark), but your tachometer is reading 7000 or whatever, then something's wrong between coil and needle, but if your sparks are also messed up and going crazy, then that would be between pickup and coil.
Remember that there are two tachometer paths, one for the tachometer gauge, and one for the ECM, they are seperate. The tachometer I think is attached to the coil, and reads "spark" (one pulse every spark that the coil makes), the ECM tach comes directly from the pickup coil in the distributor through the ICM, so basically pickup coil - ICM tach out - ECM (calculations) - ICM spark in - coil - tachometer lead. What the tachometer shows is exactly what your coil is doing, regardless of what it should do, unless the tachometer board itself is dead, if you observe normal spark through a timing light (one per timing mark), but your tachometer is reading 7000 or whatever, then something's wrong between coil and needle, but if your sparks are also messed up and going crazy, then that would be between pickup and coil.
Yeah, I have been going over the wiring diagrams. I have it nailed down to either the pickup coil, the coil, the wiring, or the ECM. Im going to swap the coil and pickup coil as soon as I get them. I also might try just grounding the injectors myself while I crank it to see if they at least click over and spray fuel.
Okay, so I was right, the injectors were NOT firing. It had NOTHING to do with the ECM or the coil or anything like that. I tested the coil, tested the pickup coil, both tested good. So I tried hotwiring the injectors directly through the 6 pin plug and nothing, they would NOT click at all. I pulled one plug off an injector and plugged in an injector cleaner hotwire lead and it clicked just fine on the battery. I checked the wire continuity and it was good. I pulled the intake off and found when I slightly pushed down on an injector lead it would power the injector when it was hotwired through the 6pin plug. The new Bosch injectors are just slightly too tall for the Fiero injector wiring harness to make contact with the terminals! So I dug up the firebird injector harness and it plugged in just fine and fired the injectors when hotwired. So I cut the 6pin off the fiero harness and rewired the old firebird harness and combined them, plugged and bolted everything back up, tried to start it and it got fuel, then backfired a bunch and would not start. Of course the distributor was 180 out, swapped it back around, set base timing and it fired up! It started and ran on the first crank. Theres no coolant in it yet and there a big puddle of oil under it now(I am thinking I messed up the rear mainseal install of course) but that is tomorrows problem. Today the engine finally runs! Thanks everyone!
