MarksmanB

Hello, I am new to this site. If anyone could please help then that would be awesome. About a week ago I drove through a canyon for about 15 miles and I pulled into a McDonald parking lot to get food. Keep in mind that the car was running perfect, no engine light, staying about 180°F. I shut off my 1990 firebird to go inside but they were closed. So I walked back to my car to drive away. The dang thing won’t start!

I have a 1990 firebird formula with 350 TPI and a 5 speed WC-T5. About 170k miles on it. When I was stuck in the McDonald parking lot, it wouldn’t even try to crank over. So I tried push starting it and nothing. I bypassed the starter relay and then it would crank but no fire. I was messing around with it in the parking lot for about 4 hours and it would kind of start with starter fluid but would have a nasty misfire of some sort, and wouldn’t stay running at all. So I got it towed home.

here’s where I’m at, i couldn’t reach every spark plug, but I tested #1 and pulled it out and plugged the spark wire into it and grounded it. It was getting spark just fine. So I took part the intake to get to the injectors, one of them Ohmed out to 12, so I replaced it. But none of the injectors were leaking. It has 4 new injectors and 4 original. The fuel pressure was at 42 psi and would slowly drop after priming it. Making me think and injector was leaking but they were all fine. So I replaced the fuel pressure regulator and fuel pump hoping it would help. But nothing changed. Also the fuel filter is less that one year old. But the car is acting like it’s not getting fuel more than anything else.

then I replaced the distributor wires, cap, rotor, and ignition control module. Nothing changed. I can’t get the car running at a steady rate to pull the spark wires to notice a drop so that won’t help. When I plug in the cheap $30 OBD1 scanner, I’m getting a CODE 12 and CODE 46 (because I bypassed the VATS so that doesn’t matter).

I have a code 12, what does that mean? Someone said the pick up coil could be back, it measured out to 881 ohms of resistance. Which I believe is fine. Timing seams fine as it revs really high when on starter fluid. I haven’t tested compression yet because it seems fine when it has starter fluid again.

I need to check the spark plugs and compression still even though I don’t think that’s the problem. It’s just that most of the cylinders are so hard to access.

it could also still be one of those other injectors but I have no way of further testing it.

can anyone help? Any thoughts? Anyone with similar problems? I’ll venmo anyone who can help me find the problem!

MarksmanB

also, knock sensor I replaced like 4 months ago, oil and coolant are perfectly fine. Sometimes the engine will backfire out of the throttle body. Once There was a ploom of black smoke that came out of the exhaust. Starter, and alternator checked out fine, brand new battery. Vats light doesn’t stay on, I don’t think there’s any performance mods on the car. I’ve only had it one year. New coolant temp sensor, I cleaned the throttle body and intake really good. I used a noid lite and checked that each batch of injectors were getting a pulse. I’ve checked for any sort of vacuum leak and we are all good there. Throttle position sensor is working. New MAP sensor. There is no MAF sensor on this car. People say it could be out of time. But there’s no way it could have skipped gears or jumped out of time in the 1 minute that the car was parked. But my grandpa will help me next week to check the timing with hai timing light. Also fuel is clean, no contamination in the tank, fresh E91 gas. I cleaned the EGR Valve and it’s channels, and the diaphragm seems to work just fine.

Only time this car has ever misfire before was due to bad injectors. But I could verify that they were in fact bad. I don’t trust my cars with mechanics due to previous experiences. Also I feel like I am capable of doing most of it.

Komet

You say you bypassed VATS, but I didn't read the part in the story where you either burned a chip to disable VATS in the ECM, nor installed a bypass module to replicate the square wave from the VATS module. If you have only bypassed the relay, I would expect the car to crank and never pulse the injectors, pretty much exactly what you're seeing.

Also if that's the issue, save the venmo and buy yourself a complete set of injectors to install.

MarksmanB

Thanks for the quick response. I got a wire to bypass the starter relay. And I bought a new starter relay but then it wouldn’t crank over, then I put the old relay back on and pinched the terminals together and it would crank but no start. I haven’t done anything to the ECM. And the injectors are getting a pulse that I’m seeing with the noid light. So what are you thinking?

Komet

I'm thinking your VATS went out, which you should be able to verify by checking for a ground signal with IGN on Start at the small GRN/WHT (could be different color, that's what I had for my '89) wire that goes to the starter bypass relay. If it's not there, your VATS isn't working as that's the control signal to the relay.

So, in addition to bypassing that relay, you will need a chip in the ECM that has VATS disabled, or you can install one of these boys and then you should have fully bypassed VATS.

MarksmanB

so I’m a little confused, so with the ignition on, I need to check for a ground? On a grin/wht wire? What wires? And how exactly do I check for a ground? And how do I know if the ground is there or not? Sorry I’m just trying to understand how to do that. And would the vats bypass work even though the engine isn’t an lt1 or ls1?

vorteciroc

GM OBD Code 12 has two meanings (depending on the situation, and vehicle):
-12 =ALDL/ PCM communication operable.
-12 =No Engine Ignition-System/ Distributor reference pulses received by PCM.

How was the VAT-System disabled/ bypassed?...
Because with GM OBD Code 46, the Engine is not supposed to crank, start and run.

The VAT-System uses a Starter-Motor Circuit-Relay to prevent the engine from cranking, when an error code is present.
The VAT-System also prevents the PCM from pulsing the Engine Fuel Injectors properly to run the Engine.

Komet

Ignition in start, specifically. On whichever wire that is small and doesn't have +12v on it at the starter bypass relay. Since the car cranks when you bypass the relay, and it doesn't when it's installed, either the relay never activates because it's not getting the ground signal or it's not getting the +12v it needs to complete that circuit. Use a multimeter, instructions are in the manual.Yes, read the description and installation instructions.

MarksmanB

so I ran a wire between the 2 ends on the plug that plugs into the starter relay. So it just completes the circuit and let’s it start I guess. But if it’s not supposed to start, then why do the injectors get a pulse and mostly run but with a misfire.

MarksmanB

okay so there are 4 wires on the relay plug. The 2 on the ends are bigger and those are the ones that I run a wire between to bypass it. The 2 wires in the middle are smaller. So what wire am I checking a ground for?

vorteciroc

You have essentially bypassed the Starter-Motor Enable-Relay for the VAT-System.
If that is the ONLY modification that you have made...
Then you have NOT actually bypassed the VAT-System.

I do not know why the Fuel-Injectors were previously being pulsed by the PCM...
I do not know the history of your Vehicle, nor what modifications have been done to it previously.

MarksmanB

okay so what do I need to do to fully bypass it? Do I need to bypass the PCM as well? And how do I do that?

vorteciroc

I realize that you are a new member, so I am going to throw you a bone...
The Search function of this Forum, is a great tool.
So in the future, give it a try.


Read the Link below:
Link

vorteciroc

When I used to do this regularly (many years ago)...
I would solder a resistor (that matches the key + circuit resistance) directly at the VATS Module, and remove the Starter Relay from the System to ground it full time.

If the VATS Module becomes a problem, then a PCM + Wiring from a non-VATS Vehicle can be used.

MarksmanB

thanks for your help. I was reading the thread that you sent me and the guy said that method A, he puts a resister in the key cylinder plug thing that matches the resistance in the key. So if I put a resister in there to bypass the key cylinder, will that work to bypass vats? Or is it just a maybe and that I might have another issues with vats?

MarksmanB

so I ran a ground wire from the small black/yellow wire that runs to the relay and now, with the starter relay plugged in, the engine will crank over but not fire. So this what you were talking about?

vorteciroc

FML...

Komet

Not really; what you've done there is found another way to bypass the starter enable relay. I was saying to verify that it's not being grounded as a means to determine whether or not we can assume the vats module is faulty. That diagnosis isn't strictly necessary, as we can simply eliminate the vats module altogether by keeping whichever way of bypassing the starter enable relay you like, and (i.e. both of these things must be done) installing the bypass module. Note: it has multiple modes, I believe mine needed 50hz even though the instructions said the car was supposed to use 30hz so you'll just have to try out the combos.

OrangeBird

iTrader: (1)

If this is actually true, if you really ARE getting a proper flashing of the noid light on both injector banks*, then VATS ain't your problem.....

* You do know that there are two sets of "batch fired" injector circuits, yes? If you only checked one injector with the noid light you could have missed the other set of injectors not being pulsed. What you should do here is to 100% verify that BOTH injector banks are in fact flashing the noid light, as one bank out will certainly keep it from running. If, in fact you are missing one bank of injector pulses, the first check will be to check the fuses "Inj 1" and "Inj 2" to verify whether they are blown or not. If, perchance one of the fuses IS blown, the most likely culprit is a failed injector whose resistance has gone very low (shorted injector, a common problem).

MarksmanB

thank you for your input. Yes I am aware of the batch firing on these cars. I can 100% confirm that both batches are firing. I even went as far and testing EACH injector plug for a pulse. They are all getting the pulse. I also checked every fuse and done of them are blown. Do you think I should look into my injectors more?

OrangeBird

iTrader: (1)

OK, So, at this point you say your 100% sure your getting a proper injector pulse on both banks, you say your 100% sure you've got a good fat blue spark at the plugs, and you say you've got 42 PSI at the fuel rail. You say it'll start but run badly on starter fluid, am I correct? And that it occasionally backfires out of the throttle body? With all that being true, and given the sudden onset of the problem, yes indeed the next step should be to do a proper compression check to see if the timing chain has jumped (jumped chain will cause low compression which the compression test will either reveal or rule out).

Of troubling note here is the conflicting reports of the symptoms. You say you have a code 46, which indicates a VATS fault and yet you say your sure you've got an Injector pulse on both banks, one of those two are in direct conflict with each other and only one of the two can possibly be right, as the ECM will not generate an Injector pulse with code 46 present. I'll ask again just to verify, are you 101% SURE your getting a nice bright flash of the noid in a very defined interval while cranking it? Not a weak feeble little blink?

MarksmanB

yes I am 101% all of that is true. Since I have grounded my starter relay, I’m the code 46 has gone away anyways. I can check the the timing but I highly doubt the the timing chain would have skipped a link during the 30 seconds that my car was shut off.

yes the noid light is very bright. And the injectors are 100% getting the injector pulse because the engine will slightly run so we know for a fact the at least a few of the injectors are firing. No questioning that. I am indeed getting 42 psi to the rails. I am seeing a proper arc to a couple of the spark plugs as I am not able to pull every plug. Everything you said was correct. Also if I spray a good amount to starter fluid into the engine it will rev up super high for a quick second, sounding just fine and feeling just fine, so that convinced me that the spark and the compression and timing are fine, though I could still check those things. It feels like it’s lacking fuel and causing a misfire. But I really don’t know at this point that’s why I hopped on here.

you seem to be wiser than me so take that information as you will and tell me what you think I should do. I’m picking new injectors up today or tomorrow so I can give those a try first.

OrangeBird

iTrader: (1)

What I keep coming back to is the fact that the car ran fine till it was shut off for a few moments and then turned up DOA on the next starting attempt, and yet your sure it's got both a good spark and injector pulse. I just can't see the injectors themselves dying that way, almost as if something had broken, which is what caused me to wonder about the timing chain. A loose chain that finally ends up jumping a tooth or two could do exactly that, run fine one minute and then on the next startup it jumps a tooth and now it takes something way more flammable than gas to get it to start for a second or two (the starter fluid).

Now to be sure, with all of the uncertainty here, the last thing I'd do is to go taking anything else apart or replacing anything else till the problem has been diagnosed down to what's exactly gone wrong. So long as you haven't tried adjusting the timing, checking that to see if it's somewhere close to where it oughta be or not will be a good first step, with a compression test being a good step #2.

vorteciroc

I tried to stay out of this after things just kept not making sense...
+ OrangeBird has been doing a great job.


So the only thing that I want to so right now is...
I second, the recommendation to perform a cranking compression test.
Pull The Spark-Plug for a Cylinder and thread-in the Pressure-Gauge for all 8 Holes.

That will establish if the Valve-Events are relatively in order.

Code 46 though...
I really feel something is being overlooked.

MarksmanB

I really appreciate your help. I will get the timing done this week. If it checks out then I will do a full compression and spark plug test. And I will keep an update. I’ve got those injectors and I might as well replace the 30+ year old ones anyways so I’ll find out if those were the problem too.

MarksmanB

so I should have mentioned this earlier but I totally forgot. I think The reason code 46 was showing was because the starter relay was unplugged. That’s why I earlier stated the I wasn’t too concerned with the code 46. Now that I have the starter relay plugged in and I ran a ground through the relay plug, Code 46 has since gone away

vorteciroc

Forgive me...
I have to but in again.

DTC 46 (OBD and OBD-1) is ONLY set when an invalid Key (resistance value) has been detected.
This DTC is intended to prevent Fuel-Injector pulsing.

Absolutely nothing to do with the Starter-Motor Enable-Relay Circuits.

Most of the time; with an unmodified VAT-System...
Cranking without Injector pulsing, will be cause by an intermittent or bad connection to the Lock-Cylinder...
or a malfunctioning VATS Module.

OrangeBird

iTrader: (1)

Thank You VortecIroc, I really appreciate your kind words

I too am troubled by the code 46, I know from personal experience that disconnecting the VATS starter inhibit relay will not set a code, so I have no data/experience to explain what the OP is reporting here. I do believe something's being missed, especially since the OP reports all external indications are that the engine should run(has spark, has injector pulse, has 42 PSI fuel press, etc) .

MarksmanB

hmmmm, I bought some resistors a while ago. Should I try that trick where I run a resistor that matches the key between the wires that run to the lock cylinder?

MarksmanB

i have 2 keys and they both ohm out the same. Is there a chance that they or both bad?

Lumpello

iTrader: (3)

I had something similar happen to me (87 TPI GTA) car shut off while driving though, would try to turn over but wouldn’t fire, took it in and we thought it was a grounding issue, fixed that, car ran well for a bit, then same thing happened. I was thinking plugs/wires,cap/rotor etc, nothing would fix it. Let it sit for two years, took it back in, finally found it was the control module in the distributor it’s self (wires inside were fried). New distributor, runs like a champ. Don’t know if this will help, but parts of us sounded all to familiar. And some of the tried diagnoses and parts swapping sounded familiar as well. I wouldn’t have thought to dig deeper into my distributor, it seems the first time things went bad, it was just on its way out, not totally dead. GOOD LUCK!

MarksmanB

Thank you for your response. I Replaced my ignition control module that was underneath the distributor cap and it didnt make any differance. So i put the old one back on and returned the new one. So i dont think that was the issue

vorteciroc

The Ignition Key is almost never the issue here.
The two very small gauge Wires that connect the VATS Module to the Lock-Cylinder for the Ignition-Switch...
are the most common issue.

As I stated in an earlier Post:
I remove those two Wires from the VATS Module, and solder a Resistor (of the same resistance as the Key + Circuit) to the Contacts of the VATS Module.

Please re-read the information, in the Hyper-Link that gave to you in my previous Post.
Most all of the information that you require, was available via that Hyper-Link (also use the "search feature", as there is a Ton of VATS information on this Web-Site).

MarksmanB

you were right. It ended up being the VATS and after installing the vats bypass module it’s then started and runs. Only problem is now it likes to idle at 3,000 rpms. I’m not sure how to fix the idle

MarksmanB

so it ended up being the vats system. I wired up the vats bypass module and now it starts and runs. But now it idles at 3,000 rpms and causing it to get really hot. Any ideas on that?