Long story short, after replacing some parts in my 1994 Coupe, the engine now wont start, even though it cranks fine. Also, the speakers for the radio dont work.


For context: the engine in my 1994 LT1 automatic has been idling a little rough for a while, but the car has been working fine (especially once you get going, save for a pretty harsh 1-2 shift) and i've been driving it for weeks. I believe the car would crank but no start if I turned the car on, then tried to start the engine, but I if I cranked the key from the off position it would start ok. But I replaced the radio with an aftermarket HU, keeping the stock speakers, and I had a few issues. The radio was working at first, but it randomly cut off mid-drive, and wouldn't work at all anymore. Also the front right speaker had a clicking/humming noise. Also the passenger power seat rail was broken. And a couple of other misc issues.

So I took the car apart to deal with all of these issues at once. I bought 4 new amps, took out all 4 speakers, and replaced all of their amps at once, took out the passenger power seat (still waiting for the replacement), and cleaned up the wiring for the stereo. So I reconnect the battery (I also installed a battery quick disconnect switch) and start it up, and the car is idling extremely rough. Also, the radio turns on and works fine, but the speakers are not working. I turn the car off, and later when I turn it back on, the car will no longer start. When I turn the key, the starter motor is able to crank quite fast, and it sounds like its working fine. But it just wont start. Not even if I crank it from off.

I measured my battery at 12.25 volts, which isnt ideal, but should be enough to start the car. And I tried connecting my battery charger to it for about a half hour or so, and starting it with the charger still connected. Same problem. I looked at the fuse box on the right side of the dash. Funny enough, I did have a fuse out, but it was fuse #6, something related to the tail lights, and even after biking to walmart to buy some fuses and replacing it, it still doesnt work. I am honestly stumped and frustrated at this point. If anyone has any suggestions I'd love to here them

 

And of course, right after posting this I manage to fix the speakers though the car still wont start, and thats the bigger problem here.

For the speakers it turns out it was good old fuse 37 after all, which is crazy, because I would have been a bucket of money that I went through and checked each and every fuse with a multimeter last night and they were all working. But today I do that all over again, and realize fuse 37 is blown...but in a weird way. The fuse clearly blew, but in blew in a way where the connection was almost still complete, so maybe that had something to do with the weird behavior. Anyhoo, thats fixed.

Still cant start though. Just now I went though every single fuse in all 3 fuse boxes, pushed in each one to make sure it was seated properly, replaced the one fuse that was blown, there were a few fuses that were a bit higher than the amperage on the diagram on the inside of the lid, so I replaced those with fuses of the exact correct size, and tested each and every fuse with a multimeter for continuity, being extra sure I didnt miss a single one. Every single fuse is good at this point, I can say that with confidence. So at this point I have no clue why my car wont start. Here are a few more details you may or may not actually care about:
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• The security light does not come on when I try to turn the car on. This is not a VATS problem
• after trying to start it a few times (unsuccessfully) and popping the hood, I clearly smelled fuel. Idk if that means anything
• In the fuse box in the passenger side dash, I noticed fuse 15 is missing, and has no leads. But I believe thats because that fuse is only used for ZR-1 vettes (with the LT5 engine)

 

Your comment about “starting from off” sure sounds like you have leaky injectors that are flooding the car. Sounds like you are saying it wouldn’t start if you turned they key to on, waited for prime, then tried to start? I would put a fuel gauge on the rail, turn the key to on and watch the fuel pressure then turn the key to off. If the pressure bleeds off quickly you definitely have a problem there.

i would also check your oil. If it smells like gas I’d change it because leaky injectors can dump fuel and it can make its way down the cylinder walls and thin out the oil (and cause a loss of compression and worse).

After that you have some basics here, fuel, spark, air. Have you tried to pull codes? Do you have a FSM?

 

I did the thing where I jumped pins 4 and 12 of the OBD port, then looked at the gauge cluster LCD. Nothing. Not even a single code. C12, then 1. ---, 4. ---, 9. ---. A. ---. The only light in the gauge cluster is the check gauges light, and the only lights on that little square thing are a service engine light and a battery light (but my understanding was that those could come on even if the car is more or less running great, please correct me if im wrong though).

I went ahead and bought a fuel gauge on amazon (and renewed my amazon prime while i was at it...you win this round bezos), and estimated delivery is tomorrow morning (what a world we live in). So in the morning I will check that, along with the oil like you mentioned.

I have a service manual that I bought from eBay, but I dont think its the factory service manual, and honestly it hasnt been much help for me up to this point. But its something I guess

Thank you for your help by the way

 

Ok, at this point I have no clue whats going on. First of all, here's the dipstick:

I dont think this is at the heart of my troubles, but I am also a complete noob, so feel free to correct me.


Next, I attached the fuel pressure gauge to the valve below:


I turned the car on (without trying to start the engine of course) and the pressure shows around 35 PSI or so (or maybe 1-2 PSI higher, but around 35). Then I turn the car off again. After 5 minutes the pressure dropped by 5 PSI, and was sitting right at 30 PSI. After an additional 10 minutes (so 15 minutes after turning off the car) the pressure had dropped an additional 5 PSI (so it dropped a total of 10 PSI after waiting a total of 15 minutes), and was sitting right at 25 PSI. Is this indicative of fuel pressure leaking somewhere?

I then looked at the fuel pressure regulator. I sniffed it, and it didnt smell like fuel to me. Also, I took off the vacuum and the stem thingy wasnt wet with fuel or anything.

I tried cranking it a few times and then sniffing around the engine bay to more precisely pinpoint where the fuel smell is coming from. I ended up sniffing all of the fuel injectors (yes I felt like an idiot). They are in 4 clusters of 2. Three of the clusters did not smell like fuel, but one of them did. Specifically I smelled fuel when sniffing the two fuel injectors closest to the FPR (though again, the FPR itself did not smell like fuel).

After cranking it a few times I noticed it was getting rougher and rougher with each test. The cranking started getting more irregular, the interior lights flashed more aggressively, and the entire car was shaking more than it was during my early tries. I was getting concerned and did not want to crank it anymore.

Here's where it gets weird. I did all of this this morning. This afternoon I went back and tried turning the car on again (not starting the engine). Now all of a sudden I get this loud, incredibly high pitched whining noise! I could barely sit in the car it was so irritating! And it would happen every time I turned the key to run or acc...It literally was not doing this this morning. But it gets weirder. I tried completely unplugging the wiring harness for the radio (recall I was working on the radio and amplifiers originally), and tried it again. Noise gone. Ok. Then I try cranking. AND THE CAR FREAKING STARTS...granted, it did not roar to life like the tiger it normally is. Instead it more ungracefully puttered to life like an old cat starting to lose its eyesight thats probably going to get put down in a matter of weeks....but regardless it turned on!

I am just totally stumped at this point. I thought my radio work was pretty clean. And these are brand new amps I just put in the thing. Why would this cause any of these problems? I dont know what to do

 

I would not mess with the radio anymore and would leave it disconnected. You may want to pull the fuse for the Bose module in the back compartment as well. Doubt this stuff is related but just to eliminate it entirely in case something is introducing a ton of electrical noise.

I would reverify your battery connections are clean and tight (pull them off and clean them and the battery terminals before reattaching). In fact you may want to remove the cutoff switch. Check the main fuse block by the battery and make sure those connections are clean and tight. Then check your grounds, especially the main engine ground. You will then want to verify that the battery voltage matches closely the voltage at the main fuse block and fuse block in the car.

Your symptoms sound like irregular battery voltage, from a poor connection somewhere or a failing battery.

I am not an expert on how quickly FP should fall but it does sound like you could also have a leaky injector. You can measure the resistance of the injectors electrically to see if any are off. The other tests are in the real FSM if you have it if not you can buy the electronic version.

Hopefully some others can chime in.

 

This is solid advice, however my replies have been taking a little while to get approved, and in between me typing my reply and it getting approved, going up, and you replying to it, I have more strange developments.

Remember how I went and tried it in the morning, then tried again in the afternoon, and got different results? Well I tried it again last night, and again got different results. I went back to my car last night, disconnected the battery, unplugged the stereo wiring harness, reconnected the battery, and put the car in the run position. No noise. Cool, just checking for a baseline. Then, I disconnected the battery, plugged in the stereo wiring harness, unplugged and replugged the stereo replay, reconnected the battery, and put the key in the run position. No noise, the radio works fine now....then I try to start the car, and it starts.....

You mentioned I should check my grounds, and I actually have a suspicion that that is the culprit. A very strong suspicion. This was in the back of my head ever since the radio started giving me troubles, and as things have gotten weirder and weirder, that problem has seemed more and more likely to me. Especially when it comes to intermittent problems; issues that only happen sometimes, despite you not changing anything, are a hallmark trait of a bad ground. Also, symptoms that seem to make absolutely no sense whatsoever are also a hallmark trait of a bad ground. In the morning I think I will laser focus on that issue, checking connections everywhere, and getting my money's worth with my multimeter.

If this doesnt lead to a solution, im over it. The car is currently starting, so if it's not a bad ground, I will just button the car back up, attempt to drive it 4 miles to my mechanic, pray it (and I) gets there in one piece, and throw money at the mechanic to make it his headache instead of mine.

Thank you so much for your help dude, seriously. I'll keep you posted on how this story ends

 

Ok, I went and checked the battery voltage at the terminals, and checked the voltage again at different metal parts in the engine bay (such as the chassis itself and the engine) and all the voltages match. To be honest I would have gone deeper into it, but I dont even know exactly where the grounding bolts are in the engine bay, so I didn't investigate further.

Then I went to go check power at the radio and compare. With the key in the acc position, with one door open, I measured the voltage going into the radio from the wiring harness, and it was 11.65v. Then I immediately went to the battery and measured at the terminals, and the terminals were reading 12.05v. Thats a big enough difference to conclude that there is a grounding problem, right?

But then I saw something. And Im pretty sure its it. The positive terminal of the battery. Specifically, the washer built into the cable that sits between that bolt and the battery post. Both the battery and the bolt are new, so neither of them see any corrosion. But the washer thing that sits inside of the battery cable is not looking pretty. It is sitting awkward, and has quite a bit of corrosion. Not so much on the outside side that's touching the battery post (though I did sand this side as well), but the inside side thats touching the bolt. Its quite difficult to see, and really the only reason I can see it at all is because the washer, which is supposed to be attached to the cable, is kind of hanging off partially, making it sit crooked on the post.


The inside seems to have this powdery residue all in it, and it is very corroded. I forced the powder out with an can of compressed air (and totally didnt eject it straight into my eye) and did the best I could to sand it, but its a very tight space, and really I could only access half of it. I may just have to replace the cable. After doing this and retesting the voltage, the voltages were about the same (maybe the voltage at the radio went up to 11.67 or something, but same idea). So Idk.

Either way, at this point I just buttoned it up. The electronics on the inside seem to work ok, except my aftermarket stereo again wont work. Its having a problem where when I test it with the radio trim bezel off, it works totally fine, but as soon as I attach the bezel it just straight up stops working, like theres no power going to it at all. This isnt a surprise to me since its been doing this ever since I first started trying to install the radio. Its just I still dont know whats causing it (though after this whole ordeal I suspect its a ground issue involving the metal brace that goes across the back of the dash?). Either way though, that issue seems daunting enough to warrant its own thread, plus its not related to the original question anyways, so Ill leave it at that for now.

I took it for a test drive around the parking lot, and maybe it idles passably but not good, and it seemed to almost die on me at a stop sign (rpms went from like 800 to 400). Once the engine got revving it seemed as spry as ever. As soon as I started driving there was a smell of gas coming from the engine bay that was quite strong (my window was down). After parking I immediately popped the hood aaaaand a white smoke/vapor was coming from the engine bay. Specifically it was coming from around the trans fluid dipstick, like between the engine and windshield. I smelled the smoke/vapor and it 100% did not smell like gas.

I plan on driving it to the mechanic tomorrow morning (hopefully it can make it there ok) and having them do what they do best (and what I clearly dont do very well). Thanks for the help. If the mech says anything I find interesting Ill share here