Hi everyone. New to the forum and my first time posting. I have owned a few fieros over the years, but this is my first swapped. The engine is from a 92 deville. It ran fine for awhile, and then just wouldn't start one day few months ago. It would start but shut down after just one second. I have replaced the isc motor, fuel pump, filter, hall effect sensor, icm, tps, and the plugs, and still no luck. I cant get any codes to read off the dash before, but I just replaced the throttle position sensor, and the check engine light is off now but still doing same thing. If anyone has any insight to what may be going on would be greatly appreciated.
You said it was running before? How did you bypass the VATS? Did you have it programmed out, or did you install a small frequency generator circuit? If you had it programmed out...did you have any additional ECM programming done since? If you are using the frequency generator, then maybe it has failed?
Changing everything is a bad troubleshooting methodology, since it is not uncommon for new Fiero parts to be faulty out of the box. You could be injecting more problems before the faulty part gets changed and then you'll never know you fixed the original problem. It's like a dog chasing its tail.
Im not sure about what all has been done. I bought the car this waywhile back. I am not a great mechanic by no means just know enough to keep afloat for most part. But he had receipts where he bought parts for the swap clear back in 2002. He said he completed in 2005. Sorry i dont know more about this stuff. Thats why i am kinda on here.
Changing things out was kinda my only option for awhile as noone else i knew knows anything about this. Until i seen this sight and thats why i am here now. Where would the frequency generator be located.
Changing things out was kinda my only option for awhile as noone else i knew knows anything about this. Until i seen this sight and thats why i am here now. Where would the frequency generator be located.
If you have one, it would likely be right next to the ECM. The ECM is located at the firewall under the "storage box".
Here's a link to a common one you can buy on eBay. It'll give you an idea of what it probably looks like.
You are either using a small circuit like this one to bypass the VATS (vehicle anti-theft system), or the ECM has been reprogrammed and had the VATS turned off.
EDIT: I don't want to take you down a rabbit hole by focusing on the VATS bypass, but it fits the symptom of running for a second and shutting down.
[This message has been edited by Neils88 (edited 06-11-2015).]
I have already been in the ecm and i dont remember seeing anything of that around it. I will check tomorrow though. Any ideas are better than no ideas man. Cause thats where i was at before you replied back and thank you for that also. If it not there any other ideas?
You need to use a systematic approach. Try spraying some starter fluid into the throttle body. If the car starts and runs for longer than a few seconds then you know it's a fuel problem, otherwise your problem is likely electrical.
If it was a Fiero Factory swap, it probably has the VATS bypass module installed. It'll probably be about a 2 inch "pigtail", just below the PCM. At least that's where mine was. (That's what it sounds like to me, too.) Also check the wiring where it plugs in to the PCM.
------------------ Raydar 88 Formula IMSA Fastback. 4.9, NVG T550 Praise the Lowered!
[This message has been edited by Raydar (edited 06-12-2015).]
Ok, just went over whole wuring harness inside cab that go into pcm. Took out whole center console so had more room and didnt see a resistor or anything wrong with any of the wiring.
Starter fluid is first thing i tried, was trying to see jf had weak spark and plugs needed changed anyway. It was idling little rough when cold and ran rich so started trouble shooting from there from what i thought could be. But swaps are little out of the normal for me though.
Ever since i installed the new tps, the check engine light has went off. Sorry im not giving all info at once. Not used to asking for advice and explaining. With your all's help, hopefully we'll get there though. Oh and no it still has the fiero controls by the way.
No problem...we will go through this systematically.
First of all, ignore the fact that you've changed lots of parts already since as you will see going through the many other troubleshooting threads, new parts are very often bad out of the box. If you want to change a part to see if it is the cause of an issue, you are better off swapping parts from a properly running Fiero since the parts have been proven themselves to work. The downside is you could damage the part that you swap if there are other issues...better have a really good friend to lend you parts!
It sounds like the VATS has been programmed out of ECM. (and we haven't ruled it out as a problem yet)
Your description of the results of starter fluid was a little confusing. To clear things up, can you confirm that without starter fluid the engine starts and then dies after about 1 second. However, when you use starter fluid it idles rough for a bit and then dies. (correct me if I'm completely wrong)
No it will not run on starter fluid. Before it quit running, it was idling low at about 450-500 rpms, and ran little rich. What else exactly could i look for on the vats to check it. I have never dealt with this before. Learning process for me
No it will not run on starter fluid. Before it quit running, it was idling low at about 450-500 rpms, and ran little rich. What else exactly could i look for on the vats to check it. I have never dealt with this before. Learning process for me
Since it won't run on starter fluid that basically rules out the fuel system as a cause (unless you have bad luck and have multiple problems...)
The VATS cuts off the fuel injectors, but you'd still have a spark so if you use starter fluid it should still start if the VATS is the problem. I would guess that VATS is not your problem.
Does your tachometer move when you are cranking the engine?
I wonder if the ECU is commanding the relay to fire after startup.
If your VATS is bypassed with a frequency generator, your ECU will have a dark blue wire on the green 32 cavity ECU plug at location F10. If you have the wire, follow it to find the signal generator circuit. If no wire, your ECU has had it programmed out.
FYI, its not uncommon for the circuit to have problems, mine acts up occasionally. I open the console door and flip the shrink wrap 'finger' covering the circuit and it fires up and runs.
I need to get that programmed out......
[This message has been edited by olejoedad (edited 06-12-2015).]
Yes the fuel does kick on when key 'on'. I will have to look tomorrow to see about the wire. But i looked like crazy hoping it had one anyways. Guess i was hoping one would appear anyways, lol. Would've solved so much frustration.
I just checked the connector. No wire in f10 slot.
F10 is the feed from the Passkey system. I wouldn't expect anything there, since we've concluded that your VATS was likely programmed out of the ECM.
Have you replaced the ECM (chip) by any chance?
You'll need to determine which system is causing the shut down. You should confirm that you have and maintain fuel pressure with an inline fuel pressure gauge. You should also confirm that you are maintaining spark, and that your injectors have power and are firing.
Kept pressure gauge on it right after started having probs. Keeps at 44 lbs when key on. Drops to about 34 lbs while cranking and back to 44 after starts for those 2 seconds.
This may sound stupid, but are you sure there's fuel in the tank? And not years old fuel, new fuel, and your car isn't sitting on an angle that the pump won't pick it up?
Dont have a spark tester. I changed fuel pumpand put some new fuel in it. Has about 6 gallons in it. If it fires up for 2 seconds, shouldnt be a spark problem though should it. Could there be something else that shuts injectors down after it fires up?
Not stupid question either, i have seen couple guys before go through troubleshooting before and it was just no fuel. Lol. Frustration can block train of thought and make me miss over some simple stuff to though
Dont have a spark tester. I changed fuel pumpand put some new fuel in it. Has about 6 gallons in it. If it fires up for 2 seconds, shouldnt be a spark problem though should it. Could there be something else that shuts injectors down after it fires up?
I was just systematically eliminating possible causes. I doubt it's a spark problem, but putting a spark tester inline of one of the cylinders could eliminate a great many possibilities. They only cost a few dollars from many auto parts places.
Right now everything keeps pointing back to the VATS, which would likely mean you'd likely need to replace the ECM and have it reprogrammed for the 4.9. However, you obviously should to be 100% sure of the cause before going that route.
In addition to checking the spark, you should check that you have power going to the injectors (and not being cut off). A noid light would tell you if the injectors are firing properly.
You are looking for what stops working at that 2 second mark, that is ultimately going to point to the cause of the shut down.
And what else would shut injestors off after start up? I know its not fuel pump i can hear it run and kick off few seconds after it shuts down. I do know my tps was bad, cause it wasnt activating my isc motor before and now it is, and my check engine light has webt away since.
Here the logic probe is used on a 3800 to see the injector pulses. It is hard (impossible) to see the injector pulses on the video but it is easy to see them in real life. Note the pin is inserted past the seal on the non-Pink wire of the injector. You will know it is the right one if the lights come on on the tester. Red = +12v and that means the injector is not being fired at that time. A quick green flash indicates the injector is being fired.
Of course the injectors won't be fired once the engine stops running. The key will be to see if the injectors stop firing before the engine stops rotating.
[This message has been edited by phonedawgz (edited 06-14-2015).]
The downside with troubleshooting is that you do need to pick up some basic diagnostic tools. Fortunately, the basic ones don't cost too much. Do consider picking up an OBD I cable from phonedawgz. I have that one and it works great.
Yeah i understand with the troubleshooting. If it gets to costly though thought about ripping it out and starting from scratch with new harness and everything. I always wanted to do it myself but got this one for 3200 running smooth, one year house of kolor paint job and interior redone so i just jumped on it
It's possible you have a bad ground for the ecu. Check all your grounds, and sand the one for the ecu down to bare metal. Test for power 12v switched at the ecu, because if it's not low on fuel, maybe your ecu isn't getting power, my northstar will fire and run for 1-2 seconds with no power to the ecu. Trust me, it just happened to me not that long ago. Figured it out when my laptop couldn't find the ecu. Sure enough, bad ground.
Picked up spark tester and a logic probe. With the logic probe, i dont have manual for this engine or anything. Which pin # would i check in the ecu connector that goes to injectors?
Picked up spark tester and a logic probe. With the logic probe, i dont have manual for this engine or anything. Which pin # would i check in the ecu connector that goes to injectors?
You won't need to check them all...just have to check one and see if it stops firing while the engine is still rotating. It's a bit tricky, so you'll want a helper to be cranking the engine while you are checking.
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