That's a very good call. I'm planning on including that in my search for problems. I can't imagine the issue being anything besides the VATS or a damaged wire or wire connector. It's really seeming electrical.

 

I only mentioned that because I recently saw another thread where someone had that issue and the car wouldn't run. Honestly before I saw that thread that didn't even enter my mind.

 

I asked about the relay because it provides power to the pump for prime and for crank. Once the engine is actually running, the oil pressure sender provides the pump power, bypassing the relay altogether. U said it will only run if you apply throtle, so maybe I should have suggested the oil pressure sender instead, now that I rethink it. What does your fuel pressure do during cranking, and then what is it doing while it coughs and sputters?

 

I've already got the VATS bypass module so I'm going to put it in soon regardless. I've done research and found that most of the time when a third gens VATS goes bad, the security light flashes a lot or stays on. Mine just flashes a few times when I try to start it & then it goes away. The car cranks too, but it struggles to start like its starved for fuel, air, or spark.

I guess my main questions are: Does it sound like my problem is the VATS? Is it a possibility that VATS is the issue even though it cranks strong and doesn't constantly run the security light? Does anyone have experience with VATS only controlling the injectors?

 

Well I guess I should be looking into this also. I haven't checked my fuel pressure under cranking. I think I might even look into this before I cut up my wire harnesses to put in the VATS bypass. I'm not sure I want to dig into the VATS project yet so the oil pressure sender would be cool with me. If I find that my fuel pressure cuts out during the choking and sputtering, should I also change my oil pressure sensor as well as the oil pressure sender?
Also: If I find that the fuel pressure is good even up through the choking & sputtering, does it sound like this could be the VATS?

 

the sensor and sender are one in the same

 

Sweet! That's even better... I've had a rather busy schedule this last week so I haven't had too much time to work on the car. I took a few minutes this morning thinking I would ground the fuel pump slot in the ALDL to test if the oil pressure sensor was cutting the pump off. I found that my ALDL doesn't have a slot for the fuel pump. The rabbit hole just keeps getting deeper and deeper with my red vert headache.
I'm going to research on a different way to test the oil pressure sensor to make sure its functioning properly. I'll also bite the bullet & install the VATS bypass when I get a chance too. From there, if its still not running, I'll keep researching and testing different stuff and looking for grounds and shorts. But one things for sure, I'm definitely done throwing parts at it until I reeeeeeeally think certain stuff needs to be replaced.
I'm tempted to either sell it or rip out the engine and all engine management and put a crate engine in it with all new engine management when I can afford to. There's also a 68 Nova 4 houses down the street rotting away in somebodies front yard. I'm thinking about maybe getting rid of the TA and asking that guy what he wants for the paper weight in his driveway. Ha!

 

This may be a dumb question, but my '89 IROC has a fuse in the fuseblock for the injectors, have you checked that? IIRC its a 10A fuse. I hope you figure this out soon, its frustrating when you run into something like this

 

I wish I could say that was the problem. The fuses were one of the first things I checked. I made sure they were all there, in properly, and still intact. I checked again yesterday when I was poking around. I get frustrated but I really like the TA. I'd be more likely to keep at it until I finally fix the issue or throw a crate engine in it before I would sell it. It's not hurting anyone by sitting in the driveway so I'm just going to stay diligent and keep testing stuff until I find the problem. I'll be happy with it once its purring again.

 

in the harness on the passenger side i believe near the EST connector should be a red wire with a single blade connector just sort of hanging out. that is a fuel pump testing connector. Supply 12 volts to that connector and the fuel pump should come on

 

I keep learning new stuff about my car everyday. Thanks for the heads up. I will check it out next week when I get home. I'm excited to get testing. I'm hoping I check it out, and it fires up with the pump grounded. Then I'll change out the oil pressure switch and hopefully be right back on the road. I'll keep my fingers crossed.

 

makes it easier to bypass the circut and kick the pump on while working under the hood. as long as 12 volts is to that wire the pump should run continuiously with the key on or off. If it doesn't come on than you know you have some sort of issue somewhere

 

Thanks. This is majorly helpful. After I test the pump with the connection, I'll know for sure if there is an elecetrical issue in that system or not. If the pump runs, then I'll know I most likely need an oil pressure switch (or maybe a new oil pump), and if it doesn't run then I know I need to look deeper into the electrical side. Either way, your tip is putting me on the right track.

 

Ok, I have an interesting update today. I supplied 12V to the fuel pump and it ran. So since the oil pressure switch and the fuel pump relay were collectively $47, I decided to change both of them. The oil pressure switch was BAD. It seemed to have oil coming from the edge where the plastic meets the metal fitting, plus it was so bad that the electrical connection was actually saturated in oil. I dried out the harness connector as best as I could and put the new switch in. Then I put in the fuel pump relay.
The pump wouldn't prime with the new relay in, but would prime when I put the old one back in. It still wont start. I didn't test the fuel pressure yet. I know that is important info so I will do my best to check it before, while, and after cranking. Depending on what I find for fuel pressure, I'll see where to go from there.
So my questions for the day are: Would the electrical end of the oil pressure switch and harness connector being completely saturated in oil cause some sort of a short somewhere that I might now need to fix?

Also, is it probable that Autozone sold me the wrong relay or a faulty one? Or could there be some sort of system issue that the new relay is bringing to light?

 

you can most definatly get handed the wrong or a faulty relay. As long as you you wiped the connector up good it should be fine. Mine is also showing some age with some wetness around it. I am going to be swapping it out next oil change

 

Yeah, I brought the relay back to Autozone this afternoon & when the guy looked at it, he said it isn't even a part they sell. But I got my money back & I'm not thinking I need a new one anyways since my pump primed with the old one. Now I need to check my fuel pressure during cranking to make sure I don't need a new relay at all.

I guess what you're saying is good news, but that still leaves my TA as a paper weight. I'll test my fuel pressure and install my VATS bypass and see where I'm at. If its still not running after that, I'll go get a compression check tool & check both left and right banks. I'll keep testing stuff and looking for shorts and grounds. So far, everything seems to be checking out electrically sound. To be honest, I still haven't used my spark test tool. I've replaced every single ignition component so I didn't think I needed to check it, but I probably should.

 

Alright, I've been doing some research. I feel like I might have found the holy grail of electrical issues. I found the symptoms of a bad IAC valve to be identical to the problems I've had (listed in posts #1 and #9). From the stopping dead on the highway to the inconsistent running problem all the way up to not starting at all & the struggling to run while I apply gas. So now I'm going to attempt to adjust it & see if there's a way to test it for volts or ohms to see if mine has gone bad. I'm going to keep my fingers crossed on this one.

I really hate to throw more parts at it so I'd really like to see if I can prove the IAC to be bad before I replace it, but it reeeeeeeally seems like it could be the issue. Let me know what you guys think.

 

I have to say reading your thread has been painful, for a fraction of what you've paid in "shotgun" maintenance you could have bought a scan tool and had this problem corrected 6 months ago. Trying to work on and Diagnose one of these cars without being able to read real-time data from the computer is as good as working on it with your eyes closed and one hand tied behind your back I cannot stress this enough, get a scan tool and not just a code reader either, you need something that will display real-time data. It will tell you if your IAC valve is working, if your TPS is good (and set right) if all your temp sensors are working correctly, and ultimately if your computer is any good (which i suspect it might not be because its pretty much the only thing you haven't changed!)

 

Even if the IAC was no good you should be able to get it running by opening the throttle up a little. I have has IAC's die on my before and you can usually limp the car home. I don't think the IAC is the issue. You can change it for your own peace of mind but I don't think you will see a result

 

Alright so in order to prevent throwing anymore money at it without it running, I will aquire a scan tool. I didn't even know I could get one for OBD 1, I thought they were just for OBD 2. I've only ever seen code readers for 3rd gens. I'm used to older cars where there is no scanning, u just trouble shoot with reasoning & replace what really seems to be the issue. Apparently that's the wrong approach for anything with a computer.
What scan tool do you suggest? Which one do you use?
Oh, and I replaced the computer too. I've got a HUGE list of parts that are new.

Well alrighty then. I read some symptoms that lead me to believe this could be the issue, but I think a scan tool is the way to go. I guess reading symptoms online and throwing parts at it has been my problem. I don't have too many sensors left to replace before I have an all new engine management system!

 

Ok I don't know what scanner you are using but the only ones I know of that support OBD1 and datastream and ones made by snap-on, MAC, MATCO etc. those are not cheap. I believe we are talking about a $1200 scanner. I do not know about this cheap OBD1 datastream scanner so if you could let us know what it is and where you got it and how much it was so I can go get one for me?

I am not saying that it's good but the purpose of the IAC is to bypass air into the plenum for idle with the throttle blades closed. so If the IAC was shot in the "closed position you should in theory be able to to start it but opening the throttle blades up

 

I tend to have to agree with this. I love the fact that you are replacing parts that prob will need replacing in the near future, but to be doing all of this and not know exactly what the problem is, is silly. If your goal with the car is to keep it and have it as a reliable DD, then you are on your way.

I also think its the VATS. I thought that to be my problem, but I have an 85 and I found out that I dont have VATS.

 

Although Its been several years since I bought my scantool I believe it is an "autoxray" brand and at the time cost me about $150.00-$200.00 Having said that I just went to their site and it appears they don't sell cheap ones anymore their MSRP is 650.00 now but it does do OBD 1 & 2, Still if that's too steep there are other alternative handheld devices, just a few minutes with google or a search on this site will bring them to light. Or, If it were me I would just go over to craig moates site (moates.net) and for $80.00 get the ALDU1 and cable1 product in the GMobd1 section then download a copy of "tunerproRT" I think It's about $40.00 but well worth it, load it into your laptop and go interrogate your cars computer and find out whats really wrong with it. This solution is by far the most powerful and will let you learn a great deal about what the computer controls on your engine. And if you get really ambitious you can use this same software (with some additional hardware from the same site) to program your own custom roms.

 

I checked out your suggestion about Moates and Tunerpro. It seems interesting, but how hard is it to read the results? Will I need a course in engineering to decipher the info? I'd really like to get the information from the computer to track down problems. Let me know how hard or easy it is to use this system. Thanks

 

what if you don't own a lap top? Than that wouldn't work. It seems most cost effective over all to use a multi meter and OHM things out and check voltages and what not. This is a fairly simple fuel injection system. I understand that this thread is long and has numerous possibilities of what the problem could be. the OP has been good about getting information back to us and I have been very active in trying to help the OP figure the problem out. I know I am not always right and I have been proven wrong but I don't think spending 650.00 on a scan tool, or spending 650.00 on a laptop to spend more money for a cable+software is very cost effective at the moment. The OP has replaced a lot of parts yes, but he has not replaced a lot too because of good old fashioned testing and asking for our opinion. Just my .02

 

I've attached a screen shot from the tunerpro RT ALDL realtime data page, this shows just some of the parameters you can monitor, Most of them are self explanatory.The rest you will learn with a little reading. keep in mind this is what the computer is seeing so if you see a sensor that is reading out of whack you will know there is a problem. It makes diagnosis very easy.

 

I would find it hard to believe that in this day and age he either doesn't have a laptop or at least cant borrow one from someone for a day or so. These tools are invaluable for anyone that owns one of these cars and works on it themselves. "Good old fashioned trouble shooting" will very often have you running in circles on a computer controlled vehicle, Does he want to drive his car or spend 8 more months changing parts and playing with a volt meter? He doesn't have a 70's F body And he shouldn't be diagnosing it like one. As for this being a "simple" fuel injection system, actually no it is not the computer in the op's 92 is surprisingly capable and if you played around with software like tunerpro you would be amazed to see all the calculations that are going on inside that 20 year old dinosaur.

 

Thanks for the picture. I can see that there is a lot of info on the readout. Is there a list of what the correct parameters should be to compare the actual numbers to? If throttle position is .53 volts as shown in pic, how does one know if that is within tolerance? The information is great if one knows what the readings should be compared to actual. Thanks for this info you are being very helpful.

 

Your best source for that information is the factory service manual, Or by searching the boards, All the information is in here somewhere.......... the faqs in the DIY prom section are very informative too.

 

Cool, thank you for the advice. I will look into the software and cables for the computer. Between $100 and $150 for some serious computer diagnostic equipment sounds like a good deal. My major questions with it are: Will it work if the car isn't running? If so, what kind of data will/could it pull to point me in the right direction with it not running at all?

I appreciate your .02, AAAALLLLL of it to be honest. I really appreciate all of the help and tips you have given me. You have definitely been the most helpful with the problem. I will be continuing to test sensors and connections next week and I will also be installing the VATS bypass I recieved, just to be sure. I'm planning on installing it, and if that doesn't fix the issue then I will check all plugs for spark and check my fuel pressure at the rail before, during, and after cranking. From there, I will test the TPS and possibly replace the IAC for piece of mind. I do happen to have a laptop so no worries in that department. I'm interested in the computer diagnostics route, but I want to know more about it before diving in. I fully believe in testing sensors and going back to basics with fuel, air, and spark because no matter what kind of computer is on it, it's still a car.

I'm lucky enough to have a laptop, but I still would like more info on this program. I will do some research myself online, but mostly I just need to know would this software help me right now without having the car running? Plus, the ECM and PROM are new, so I don't know if that would have anything to do with the softwares' efficiency right now either.

Thank you to everyone who has given me any advice. You guys are keeping me going on this interesting (but slightly painful) road to get this beast ripping up the roads again. I greatly appreciate all the help and can't wait to post up a video of it running like new!

 

Yes you will still see the same data as illustrated in the pic above with just the key on and engine not running the values will of course reflect that. For instance, lets say you are looking at the monitor page with the key on and engine not running and your voltage at the fuel pump is showing 0v, well that might indicate your fuel pump relay is bad, Or lets say your coolant temp sensor is indicating 220 degrees but the engine is stone cold, well you wont get any start up enrichment and that could cause running problems, These are just a couple of the many possibilities, And if you manage to get the engine running at all, even poorly it will really begin to tell the tale. Does that give you a better idea of how valuable this might be?

 

I am not doubting that these values are important to know. I have borrowed a MAC scanner in the past but only when I am really stumped. I just don't have the money to be spending on a scanner. I am sure I am not the only one.

 

Yes it does. That is extremely helpful. Thank you for all the info. I'm definitely going to aquire what I need to trun my laptop into a diagnostic dream. I don't think I will be getting it any time extremely soon because our baby is due in September so I have a lot of things to do to get ready for him and my money is better spent elsewhere for the time being, but I will be getting the software and cables. That will make my life way easier with the TA!

I can't agree with you more. I don't believe I would be buying a scanner in upwords of $650, but I will aquire the software and cables seeing as how I already have a laptop. I won't be buying it too soon though so next week I plan to install the VATS bypass I already have and if it still doesn't run then I'll keep testing sensors and checking for electrical issues as I go. As far as being stumped goes though, I'm sure you can tell I am as stumped as stumped can be right now.

 

Here is a link to a different thread, Check out the last post. It looks like you can get into this for well under $100.00 https://www.thirdgen.org/forums/dfi-...i-scanner.html

 

I have read this entire post front to back. I feel your pain in trying to figure this no start problem out.

Perhaps it might me the ignition lock cylinder that is keeping the car from starting? Isn't this where the sensor is for the diode that is in the key? Just a thought and maybe i'm wrong.

 

from reading your posts, you have spent a TON of money already. Whats another 80 bucks to pinpoint your exact problem??

Sorry, thought you where the original poster!

 

I know you don't believe it may be the problem, but I had the same problem on my 350 TPI. On your throttle body, take a few seconds and unhook the throttle position sensor and try starting it. I did this and it started right up. See if that may just happen to be the problem.

 

Oh wow, thanks A TON. I will definitely grab the cable and the program after my son is born. I checked out the TunerProRT and I like it. I think that will not only save me with my TA, but really sway towards picking up another third gen for my oldest son.

I wish I could say that was the problem. I already inspected the connection in the steering column and then I did the Ohm check down at the harness connector at the bottom of the steering column. I got the exact same Ohms as when I checked the key directly so the ignition lock cylinder shouldn't be the issue. I appreciate your input though. At this point I'm thinking it has to be something easy like that.

Ha! I agree with you though. I'm down for getting the software and cable and scoping out all the sensors and feedback that the ECM gets. I just need to take a financial break on the car for a little while until after my son is born. I can still mess with it though so I'm going to do some free stuff and tinkering for a while.

At this point, I'm open to ANYTHING being a possible cause, besides the stuff I've already changed or checked. I'm leaning heavily towards the VATS and since I already have the bypass I'm going to wire that in when I get a chance. But before I do that, I will definitely take your tip and try unplugging the TPS and see if it starts. I'm also going to try unplugging the IAC and try starting it too. I've been suspecting either of them of being the problem, I just hadn't thought to simply unplug either of them and try to start it. Thanks for the idea! This will probably be the first thing I do to the car once I get home.

 

Check your fuel pressure regulator vacuum line. Pull it and and if it drips gas or smells strongly of gas, the diaphram is torn and you're pulling gas into the intake manifold and essntially flooding the car like and old carburated car. Had the same problem on a '95 Olds Achieva.

 

For the record, I put a new TPS on and I don't even get a service engine light anymore.

 

I think that might have been part of the problem to begin with, but it's fixed already. I changed the fuel pressure regulator and cleaned the vacuum hose. The regulator was really bad and needed to be changed for sure.

Nice. I'm going to play with it when I get home and see what I can come up with. I hope I find the TPS or the IAC to be the problem and then I can just change out an easy to access part and be on the road again. We'll see though, because it hasn't been that easy so far. LOL!

 

How did the IAC/TPS check work out?

 

Unfortunately it didn't happen yet. I don't get to go home until Wednesday afternoon. I plan to work on the car probably Thursday or Friday. I'm in the Navy so my schedule usually sucks. I'll post my reuslts as soon as I get done though. I'm keeping my fingers crossed. After the IAC and TPS, I don't have too many sensors left that could be the problem. HA!

 

yeah it looks to me like you are almost at the point where you are going to need to dig into the harness....which is always fun

 

Well I didn't have too much time today for the TA, but I did get out there and tried starting it with and without the TPS and the IAC. No progress so we'll see what happens when I get a chance to wire in the VATS bypass. I'm really not looking forward to going through the harness, so I'm really hoping for the VATS TDM to be the issue. I guess we'll see.

I did notice that when I first attempt to start it, it feels like its going to fire but then it just returns to cranking, like the fuel or the air got "shut off". Maybe that's a good sign that its the VATS.

 

Maybe one of the more experienced guys can answer this, but would this guys issue have anything to do with open or closed loop?

 

With the IAC unplugged you might want to open the throttle plate up. If the IAC is jambed up in a closed position and you unplug it and dont open the thottle a little you have no air going in. Also check your MAP sensor connections.

 

Here's my update. I wired in the VATS bypass and it didn't fix the problem. I know that I wired it in right because I tried to start it and it cranked but didn't fire up, so I tried adding the extra wire from the bypass in so it would change the signal to 50 hz and it wouldn't crank or anything. Then, I removed the 50 hz wire and it cranked again so VATS was working correctly in the first place.

Yesterday I syphoned out all of the gas and put in 5 gallons of fresh 91 octane. Still cranking but no start so the problem wasn't bad gas.

Now I'm getting to the point where I'm just going to completely take it apart and start looking for faulty wiring. I'll trace out ever electrical system starting with ignition and fuel and I'll just keep going until I find the issue. I'm determined to get this thing on the road. I'd really like to restore this car back to its luster and eventually get more third gens and restore them to pass down to my kids.

I had a minor lapse of sanity last week. I got really frustrated with it and put all the interior back together, took more pictures of it, and posted it on CL. I was 100% ready to get rid of it over something that I'm positive is easy and dumb that I'm missing. I even had listed in this post that I was going to sell it. I have restored my motivation to get this bird flying again. I'll keep updating and letting you know what's going on with it.

I still have plenty of tools to aquire, including the ALDL cable and TunerPro, but I will continue on and either find the problem, or throw a crate engine in it. Ha!

 

I saw your giving up post the other day and thought it was a shame, glad youve come to your senses. Do yourself a favor and spend the less than 100.00 to get the cable and software, with it you will get it up and running in no time.

 

DON'T GIVE UP!!! You've learned so much about the car already and they really are lots of fun... If it was a VATS problem, chances are it won't start. VATS controls the starter relay and the injectors. So if VATS is faulty it won't start or send fuel to the injectors... It doesn't do anything else... if you got fuel, you got VATS. Should be able to check fuel by sticking your nose in the exhaust or I'm sure there's other reasons.

hmm ps. I have that same engine and am pretty happy with it. Stock, 270K kms on it... oil rings are shot but the compression is still good.