84 Z28 5.0 L69 H.O. engine. The car went to paint two weeks ago and started flawlessly EVERY time. They did something to cause the battery to drain, so I bought a new one since the old one was from 1995. It also came back covered in dust inside and out. I started it yesterday and it ran rough at idle, put out a bunch of smoke, and wouldn't reach the high idle it normally does once it warms up and you then have to hit the gas pedal to knock it back down. I shut it off and since then it won't start. The following is a link of the video of it not starting:

http://s282.photobucket.com/albums/k...t=e1d8a777.mp4

 

Pour a little gas down the Carb and crank it if it starts then dies it's a fuel problem.

 

What color was the smoke? The video suggests to me an engine with fouled spark plugs.

 

When he left it for paint it, "started flawlessly EVERY time" can't get better than that. I don't think 2 weeks of not running would foul the plugs.
I wouldn't change the plugs until fuel, strong spark, and proper timing are verified.

My dad had a '71 Gran Torino. He had just return from a short trip of less than 200 miles, parked it, the next day it wouldn't start. I found no spark, I verified 12v to coil, coil was good, removed distributor cap, visually all was Ok, but on cranking to verify timing, the distributor shaft didn't turn. Timing gear to cam retaining pin had sheared off.

My brothers '75 GMC Sprint/Caballero sat for 3 years because of a missing coil-on-distributor metal ground strap causing the coil to burn out.

My sister's '99 Chevy pickup wouldn't start, no luck finding the problem, mechanic said it was a bad ECM, then bad motor (HUH?), they replaced them both, still no start. When my sister asked me to help I checked for spark, no spark, 12v to ignition, none found. I traced it to a missing OEM security module that requires a resistor pack plugged in to start. My brother-in-law said he was positive he had plugged it in. Finally one of the kids admitted to removing it while playing around in the truck.

A neighbor was moving out of state had a '87 GMC he couldn't get started. His father is a mechanic he adjusted the timing, it started, but back fired, and die out. He gave it a tune up, all new ignition parts, still backfired, then wouldn't start at all. Neighbor couldn't afford to tow it with him, I bought for $250, the new rotor his father had installed had a piece of metal buried in it just below the surface giving the spark a ground path to the distributor shaft and shorting out. I replaced it, it ran but still backfiring, it had jumped time, replaced timing gears (cam gear had plastic core) and chain. I parted the truck for a total of $2500.

While I don't think any of those are your problem it shows that more than one thing can cause the same symptoms. Verifying fuel, spark, and proper timing is the basics.

 

For the record, I didn't suggest changing the plugs. I said that the way the engine behaves in the video suggested an engine with fouled plugs.

If you listen carefully, you will hear an occasional firing as the engine is cranked. If the plugs are fouled, it will behave this way. It's very easy to just remove one of the plugs and check it for fouling. If it is fouled, the way in which it is fouled will suggest the reason for the plugs being fouled. Obviously, all plugs would need to be removed in order to properly assess the problem.

2 weeks of not running by itself is obviously not a cause of fouling, but if the plugs were borderline to begin with, it could well be that sitting for two weeks contributed to the cause, for example, a sticky float. The OP said the car started up initially, and smoked a lot. If the carb was dumping fuel, the plugs would then become carbon fouled. This fits perfectly with this scenario. Bottom line, always troubleshoot the easy stuff first. Pulling a spark plug seems easy enough.

 

Hope the shop didn't beat up on your car while it was there...

 

Thats what I was thinking... joyrides... until they blew up something.

 

A couple of weeks sitting up will cause my '86 Silverado to smoke alot and run rough for a little while, but it does clear up. Still that doesn't explain the no start thereafter.

Ternandes,
My post was not directed at you If I had I would have quoted your post, or used your name. I did not say you suggested changing plugs anymore than I suggested replacing, ignition, timing parts, ECM, or motor.

What I did suggest is to do basic diagnostics.

Believe me I've heard that exact same sound many times and it's almost never the same cause for it.

Because we are not there to see all that's going on the best we can do is generalize.

 

The smoke was somewhat blue and white. Judging by the amount of smoke that came out of it, they didn't drive it for the two weeks. There was a bunch of it; that always happens when it sits for a long time and it clears up. Is it possible some dust got in somewhere? It seems way to coincidental to have been running fine before and now it suddenly does not. The car had been in storage for 17 years and occasionally ran, so I know it needs spark plugs (just haven't got to those yet).

And yes ternandes, you heard correctly, there was an occasional fire and it occurred when I hit the gas pedal. I had depressed the pedal twice while attempting to start it and it coughed. However the day before when I did it too much, the car flooded and I could smell gas.

 

Ok so I went out there to try it again. I poured gas in the carb and it didn't start. However, while I was cranking it I kept hitting the gas pedal and every time I did, it coughed like it was about to fire but never did.

 

Have someone spray some carb cleaner in the intake. If that doesn't work... It's not fuel-related. Have you pulled a plug and checked for spark? Make sure the plug is grounded against something while you watch it.

Just looking at them should tell you a lot about what's going on inside the engine. Pull as many plugs as you can easily. See if they're covered in oil or steam cleaned or anything like that.

 

Ok so did the carb cleaner in the intake and no go on starting. Didn't change what you see in the video at all. When I first went out to it today, it was the first time trying to start it since Sunday (Wednesday today). It coughed several times right away and then went back to just turning over with no firing from the engine. Now it is doing a new thing while starting, see attached video. I haven't had time to pull the plugs yet. I feel it has to be something simple since the only change over two weeks was being at the shop. I know I have to check those other things, but I find it much too coincidental it started before paint and now it doesn't.

http://s282.photobucket.com/albums/k...t=361b5c72.mp4

 

You need to pull the plugs.

Sounds like the battery is dying. If the battery is fresh it sounds like the engine is getting harder to turn. That could be REALLY bad news. That's why I'd look at the plugs.

 

I had posted to all a week or so ago that my L69 5.0 H.O. Carb wouldn't start after coming back from paint. Then it started once on a new battery, idled rough with smoke and wouldn't turn over again.

So today, I spent 3 hours changing spark plugs (PITA BTW) with brand new spark plug wires. After changing all of them gaping them .035 (Champion Copper) with Duralast wires, I put the key in and....WALLAH the engine comes roaring to life, sounds better then it ever did, and ran until it was doing the high RPM idle telling you its all warmed up and ready to go. A bunch of smoke came out at first as always, but cleared up and I let it run 5 minutes. Excited by this, I get in the car to move it 6 feet (all I'm trying to do before winter), hit the gas pedal, and the thing dies.

So I turn the key, get a slow turn, then it starts turning but won't start. I hit the gas pedal twice and she came back to life. It ran for about 4 seconds and then BOOM!!!!!!!!!!!! I hear a loud bang from under the hood and see a small amount of smoke coming from under the air filter. Tried starting it again and no go. Just turns over and over and over without firing.

I have a new distributor cap and rotor I have not put in yet, but will do tomorrow. My mechanic said the boom I heard was gas burning in the carb and my rotor may be bad and not providing enough spark to keep it running off the choke.

I guess I'm seeing if anyone else has any input or has experienced this problem. I obviously have fuel and spark, am I missing something else here?

 

Bang might have been a backfire through the carb. When it was running it sounded fine? Didnt make any weird noises while it was running did it?

When it does this you need to pull a spark plug and see if you're getting spark. I told you to pull the plugs to look at them, not replace them. Might have been a good idea nonetheless, probably were gas fouled, but you really need to look at em real close when it does this, as the plugs are the best way to learn what your engine is doing on the inside. You cant look inside your engine but you can look at your plugs. It could be you're dumping way too much fuel in and fouling your plugs in a matter of minutes, but Im grasping at straws. If it ran fine for the few minutes it ran, then I'd suspect something wonky in the ignition, like the ignition module.

But again, you need to verify what it's doing by pulling the plugs, seeing what they look like, and seeing ifyou get spark.

 

InfernalVortex, I know you said to look at the plugs, however they were the original plugs from 1984. When I removed them, they were black and smelled of gas. Every time I pulled a plug out, I could smell gas. I assume this was normal since that is where gas and air mix to operate the engine. Since everything on this car is 27 years old except for the alternator, battery, and master cylinder, I'm replacing the items you have mentioned. I posted this as kind of a step at a time thing so people with expertise may assist me rather than just throwing on all new stuff and hoping for the best. I do appreciate your help though. What is an appropriate grounding point on the engine to look at a plug? I'm always by myself when I'm working on these things.

 

Oh and it ran perfect while it was running. No strange noises, hums, shimmies, or anything strange. I was surprised on how well it ran compared to before.

 

Thats something you really need a helper for. You need someone to turn over the ignition while you watch the plug. You can hold them up to anything metal, preferably something unpainted of course. Strut tower bolt/stud maybe? Just needs to touch. If you get spark when the engine is turning over that tells you something important. Should be fairly steady too.

 

How old is the timing chain? wonder if the plastic teeth cracked if its stock, or just stretched.

 

The whole car is almost original parts, so 27 years. It started this morning twice and ran fine. I was even able to move it where I needed to. It's still got a lot of work to go but at least it's running now

 

As was mentioned earlier, inspecting the plugs is the key here. You stated that the plugs came out black and smelling of fuel, and you smelled fuel every time you pulled a plug. This is NOT normal. It means that fuel is being dumped into the engine. If you pull your new plugs and they look the same, you need to look for a cause of excessive fuel in the intake. Since your engine is carbureted, I'd be looking at the float (sticking) as a possible cause. It would appear that you have cured the symptom, but not the disease.