Hello. I'm stumped here. My 84 z28 started this problem in late summer. I kinda put fixing it on the back burner since I planned on dropping in a crate motor in the spring. The problem began out of nowhere after the car sat for 2 days in the rain. I fired it up with no problem and about 2 miles later it would bog and surge like it was running out of gas. I limped to the gas station and topped it off. Ran fine for a while. I figured maybe I had water in the tank so I added some sea-foam. The problem persisted. However each time I topped off the fuel, it ran fine. The last time it happened, it stayed that way. The exhaust note is completely different. It sounds like it's running on one cylinder bank. There is NO power. It creeps up hill at a whopping 5 mph while stacking up traffic. When I give it throttle to try to get the damn thing moving, it backfires from the exhaust. This says to me it's running rich-to the point of drowning in fuel. But why? And why the sudden onset? I'm thinking fuel or ignition are my only possibilities. Ive tried cleaning the carb numerous times and still nothing. Havent done any ignition troubleshooting yet. Some specs on the car; 305 with ecu removed (courtesy of the previous owner), 1 month old (at the time the problem began) edelbrock 1406 600 cfm carb. The vacuum advance on the distributor doesnt work. I discovered that when I took the car to have the timing adjusted because I was getting spark knock under part throttle. The tech bumped up my initial advance and said to run 93 and it won't knock. He was right. I drove the car sporadically this way for a month until the problem began. I have a new vacuum advance but havent gotten it on yet because the car is pretty much undrivable. I know that's a long story, but does anyone have any clue whats going on here? Any and all thoughts are appreciated. Thanks in advance.

 

To me it sounds like a fuel pressure problem. Definetly fuel delivery related. Check fuel pressure. When the car is off, pull on the throttle and watch the primaries. Are they spraying healthy streams of gas? Or is it kinda weak?

It could be electronic, but you saying that when you topped it off it went away and ran fine makes me think its fuel pressure/delivery related. But being it was in the rain for a while, the first thing i would check is for moisture under the cap, any corrosion/water on the posts or insidet the cap as well as on the rotor. Inspect all the distributor parts for any water or corrosion. Also check the inside of the plug wire boots on the distributor end for corrosion.

I speak from experience, my car ran fine when cold and the more i warmed up the worse it got. It bogged dow, sputtered, backfired, stalled. Turned out to be a leak in the fuel tank causing me to lose all my fuel pressure. When topped off it ran ok, but the lower on gas it got the worse it ran.

 

I had a similar problem. Sounds like your dizzy is going back. Since its dark, right now would a a perfect time to test something. Turn her on and pop the hood. Check if there are any archs from the plug wires to the frame or headers. The problem with mine was that the magnet inside the pick-up coil was cracked. To fix that, you have to pull the dizzy, remove the gear nut, and pull out the rotor shaft. It may be tough to pull out the rotor shaft so have some rubbing alcohol or a degreaser to be able to pull out the shaft easier.

 

Thanks for the advice guys! Tomorrow I finally have a day off and can take a look. Hopefully I can pinpoint my problem. Thanks again.

 

Well looks like I found the problem. Now it's just a matter of how to fix it. Following Black88z's advice, I worked the throttle and watched the primaries. First couple of times I got a good stream. After that it fizzled out to nothing more than a little spitting. I fired up the car and let it run a minute. I worked the throttle and watched again. I saw nothing coming out of the primaries. Each time I pulled the throttle, i could hear the carb furiously sucking air. It would struggle to stay running and eventually stalled. Safe to say I have a pressure problem. Now how do I fix it? I don't think a leaky tank as was suggested earlier, as the car hasn't moved in a few months now and the fuel level is unchanged. I don't smell gas coming from the car either. So where else to look; regulator, pump? These cars have mechanical pumps, correct? I'm really more well versed in working on motorcycle fuel systems, so this is a bit different for me. I open the floor to any and all suggestions. Thanks in advance guys!

 

Have you checked your spark plug wires?? Last summer I gave my car a big gulp of fuel and went squirrly on the road for a few secs. Was a very hot day too and within moments the car started acting very badly. Not as extent as you said, but it definitely felt like I dropped a cylinder or 2 even. Was running very rough and seemed gutless. I pulled over down the street and noticed a couple things. The engine twisted badly enough that it pulled the radiator wiring plug out. After sitting for an hour to let the car cool down(radiator overflow was melting hot!) I started the car back up but it still ran rough so I drove to a nearby shop and grabbed a power bar. Motor mounts were fine... I then limped home all upset because I thought I did major damage to my motor.

After throwing some stuff around in my garage for a bit I decided to open my hood and have another look. I couldn't figure it out... then out of the corner of my eye I saw a spark plug wire leaning very closely to my headers. Sure enough after turning a wire around 1 was burnt almost clean through and a 2nd had burned through enough to see the wires inside. Replaced em both and the car purred to life afterwords.


Unless you have already... I'd replace or at the least check your plug wires. If you smell gas and or car seems to be flooding out of the blue it could be that you have a cylinder that isnt firing.... or more....

 

NVM.. I didnt read down far enough into the other posts to see that you may have gotten to a potential solution cheers mate!

 

Well when you have the car off and pull on the throttle, the first few sprays will be better than say the 5th or 6th spray. By then youve used pretty much all the gas thats in the carbs' bowl, so theres no more gas to spray. When i said check it for healthy streams i really meant while it was running, or for the first few sprays. If they are strong, healthy sprays then your probably good to go, but it never hurts to do a fuel pressure test because youll know for sure that your perfect, and they can help identify fuel system problems.

I was re-reading your initial post and found this:

"The vacuum advance on the distributor doesnt work. I discovered that when I took the car to have the timing adjusted because I was getting spark knock under part throttle."

Without this working properly the car wont run right. I didnt see this before. I dont know why that mechanic didnt fix it correctly by replacing it in the first place, but ill explain what it does, in case you dont know. The vacuum advance uses manifold vacuum to advance the distributor timing to keep up with the rpms. If it was completely blocked off or not hooked up, the distributor would be at "idle" timing although your engine may be at 2000rpms. This would make your car run terribly, and if you revved it too high the timing would be so far off it would stall. Again, thats with it not hooked up at all. If its faulty or the vac. line is cracking causing it to leak, your timing would be close, but not correct. You would have backfiring thru the exhaust because the timing is slightly too retarded for the engine speed, causing it not to fire at precisly the right time. The worse the leak or lack of vacuum, the worse the timing will be off. This could cause the exact symptoms you are describling. Personally, I think we just found your problem.

I just finished rebuilding my 81 TA's engine, with it i completely rebuild a distributor with top end performance parts. That is a very strong spark in that car!! I had to put the car on a hiatus for a while because i had other things come up, but when i got back to working on the car, i got it running again and i find that it can idle fine, but wouldnt rev above about 1500, and that was pushing it. It was knocking, smoking from the exhaust and backfiring. I checked timing 3 times, carb problems, i looked at everything 3 times beefore i finally noticed that the vacuum advance on the distributor was not hooked up (like you, the P.O swapped the carb out to a non-cc, leaving me to do the same with the distributor) because i had not hooked it up before, and forgot that it needed to be hooked up still! I hooked it up and my baby revs up perfectly.

Why did it suddenly just start? Honestly, i dont know. Cars are funny things, they can just start acting up out of seemingly nowhere.

IMO, change out the vacuum advance with the new one asap. Time it correctly, back to factory standard. After doing this, see how it runs. Again, personally i sttrongly think this will fix your problem. It is still a good idea to check for arching plug wires or other ign. problems of course, but i would put fixing the vac advance at the very top of your priorities list for this car.

 

Sounds to me like a plugged up fuel filter.

If it's still the original carb, it's in the fuel inlet nut, where the line screws into the carb.

Hold that nut still with a 1" open-end wrench, then unscrew the fuel line nut with a 5/8" "tubing" wrench. DO NOT try to bust the fuel line nut loose without supporting the big one from turning!!! If you do this, you will surely twist your fuel line up into a pretzel and then have to hack-job it with rubber.

Once you get the line out of the big nut, unscrew the big nut, and the filter is inside it.

While your dist is OBVIOUSLY messed up, it CANNOT cause the problem you describe. Fix the fuel thing FIRST, then tackle the dist. Few things in life are tougher than messing with several things all at once, having something unforeseen happen, and then not being able to figure out what caused it.

 

It could be the fuel filter. definetly wouldnt hurt to check/replace. But i still think its the distributor thats the main problem.

But this should help a bit: try spraying something (starting fluid, seafoam,ect.) down the carb while giving it some throttle. If the problem goes away its probably fuel filter/pressure. If not its something else. Either way the distributor does need to be fixed though.

And as already mentioned, be very careful taking the fuel filter out, its easy to screw it up. Be careful putting it back together too, you can overtighten it and strip it out.

 

Thanks for the suggestions, everyone. I don't have the original carb. I put on a new edelbrock performer 600 cfm about a month before the problems began. The only fuel filter I have is a plastic in line one. I've changed the that twice since this began. With that in mind, I think it's something else. That was the first thing I checked. As far as spraying seafoam or similar chemicals down the carb- i tried that but not with it running. I opened the choke and dumped it in then fired it up. Seemed to maybe idle a bit higher For a moment, but mostly just made tons of smoke come from the exhaust. I'll try it as black described tomorrow. I'll also have to put that vacuum advance on. I attempted previously, but had severe difficulty getting the cap off. Couldnt get to the back 2 screws. I have next to no clearance because I have one of those accel cap mounted hei coils. I had a mechanic friend doing most of my work. He put a new trans in for me and was supposed to handle my distributor issues. But he practically fell off the face of the earth. Long story. Haha. Anyway, guess it's time to get some tools that will allow me access to the screws at the rear of the cap so I can throw that new advance unit I have on. Thanks for the replies. I really appreciate it

 

I would try using a small screwdriver for the back 2. I have always had good luck using one thats <6 in. Its a little harder to push the clamps down and turn them, but you should at least be able to get to them this way.

Good luck!

 

Yea. My screwdriver selection is poor at best. Haha. Gotta get some smaller ones tomorrow. Once I get that off, I believe it will be smooth sailing getting that on. Just to verify, I have the bell shaped diaphragm piece. As I understand it, that's all I need to replace-save maybe for the hose.

 

It should look similar to this:

http://ecx.images-amazon.com/images/...500_AA300_.jpg

I have heard of people spraying carb cleaner/TB cleaner/seafoam into the vacuum port and letting it sit for a few min and it "saving" it, but its probably a long stretch. Besides, if you have a new one just replace it lol

 

Yep. That's exactly what I have. Thanks! I'll post after I swap it out tomorrow

 

Hey guys. Didn't get that vacuum advance on yet. Busy with work. Hopefully I can tackle that in the next day or two. I'll post my findings. I didn't want it to appear as though I got the problem fixed and then neglected to offer my thanks haha. I'll let you know, as I'm sure I'll have more questions. Thanks to all

 

Hey black 88. I started on removing that vacuum advance. Got everything disconnected. I can't get it out due to that little tab that sticks thru the hole. I'm unfamiliar with the workings of the distributor so I'm not too crazy about tearing stuff apart unless I have to. Any guidance?

 

Incorrect. On a non cc dist with vac advance, main timing advance is mechanical and advanced by springs and weights, thereby increasing with rpm.

The vac advance is for fuel economy only, increasing timing at low load times like part throttle cruising, or idle if you are using manifold vacuum.

The motor will run just fine with no vac advance, but you'll get reeaaaallly bad mpg.

 

Really? Thats weird, when my trans am's vac advance wasnt hooked up it didnt want to go above 1500 and ran real poorly then, but once i hooked it up i was getting it to 4k with no problem. I guess i dont know how to explain that one.

Either way if it needs to be replaced, you have the part, and have already started replacing it, you may as well replace it if you can. The tab your talking about is on the vacc advance canistor, it pulls the pickup coil under load. You'll have to take the bolts that hold the vacc adv canistor out, then get that tab out from that whole its in on the pickup coil. After that you should be able to take it out and replace it just as easily.

Heres a pic, just for reference. Its not the same style distributor, its a large cap HEI, but for what your doing it should help you get an idea of what to do.

http://chevellestuff.net/tech/images/hei01.jpg

 

Thanks for the pic and info. That's where I'm running into trouble. I have the advance unit detached, I just can't get that tab out.

 

Got that advance done today. More of the same. Upon rechecking the primaries, if I pull the throttle with the car running, I see no fuel coming out. I pulled the fuel line from the filter to the carb and replaced it. Still nothing. I guess that leaves only one thing-the fuel pump, right? What type of pump do these cars have and where is it? In tank? Suggestions?

 

Have you followed up on your fuel observations yet?

Did you check to see if fuel comes out of the line when disconnected it from the carb? Put ign in run briefly if you have an electric pump (in-tank), or disconnect dizzy and crank a few times if it's mechanical (mounted on the block under the alternator). If you get fuel, the delivery system is fine up to that point - doesn't take much pressure to fill a carb bowl.

Replaced fuel filter as previously suggested?

Is there actually fuel in the float bowl(s)? Sounds like they are running low.

Could also be a vacuum leak, check all hoses, make sure carb is bolted to the manifold tightly etc.

 

Thanks for the pointers. I replaced the filter, but haven't checked the line in the way you described. I will definitely be doing that in the morning. It does seem like my bowls are low, if not empty. That could explain why it won't run with the choke on for more than a few seconds. If that's the case, what do I do about it? I pretty much dismissed the carb as being the problem since it was brand new and only on the car about a month before this all started. If I can't eliminate the pump as the problem, focusing on the carb itself is in order. Regarding a vacuum leak I only have the advance, PCV,and brake booster to check, correct? I'll dig in tomorrow and post my findings. Thanks!

 

I would spray carb cleaner in the carb while someone else trys to start it. If it runs it's definatly a fuel problem. As far as vacuum leaks go, It could also be leaking from a base gasket. Are you running a carb adapter? Could be leaking there also. Sounds to me like a fuel starvation problem though. Id try the carb cleaner first and check to make sure the pump is pumping fuel.

 

No,not t running an adaptor, or a spacer. Just the supplied gasket directly on the intake manifold. I'll try the carb cleaner today too. Thanks for the info!

 

Well I followed the advice posted since yesterday and I'm still scratching my head. I pulled the fuel line off the carb and kicked it over a few times. Nice, healthy stream of fuel. All vacuum lines appear to be fine. So I guess this means my carb is the issue?

 

I'm considering tearing the carb apart and cleaning it. I also noticed today that the gasket near the top of the carb, just below the edelbrock logo, looked wet, and up in the corners, there is a brownish/burnt looking residue. I have no idea if this has anything to do with my problem. This could also be from all the crap ive been spraying a d pouring down the carb lately. So, getting back to the carb cleaning. How hard is this? I've never worked on a carb for a car. I've done bikes and quads, but they are simple. Is this even worth my time, or am I focusing my efforts in the wrong place?

 

Sounds like the fuel's getting to the carb ok.

I've never worked on an Edelbrock, but it's gotta be similar maintenance-wise to any Holley or Weber I've ever worked on. All sorts of bad behaviour can arise from warped or cracked gaskets, or loose/stripped screws between main/throttle bodies etc creating fuel or vacuum leaks. Bowl float needles might stick in various positions, choking or flooding bowls. Or crap/varnish blocking tiny fuel or air passages.

If the carb hasn't had a going over for a while, maybe it's time for a gasket kit, new float needles/seat where applicable, a good soak with carb cleaner while fully disassembled, and blown thru all passages with compressed air. It's always gratifying to hear the 'thoonk' as a well-entrenched piece of crap shoots out.

Or maybe it's a tuning issues specific to the Edelbrock, either way you probably need to grab a book and start learning about your carb.

 

If your going to chase a vac leak def get a vac gauge. I have one and it's been the best thing ever. The 1406 is a Pita. I have one in my 305 and have had to tinker with it often. Still not perfect. Here are a few things that I did find. Floats were not adjusted properly ( aldo only on for a month or so) Really simple to do, jus pull the manual up on edl site if u don't have it. Also the carb mounting gasket was junk. I got a much thicker felpro and saw a 4 hg increase in vacuum instantly. Also I'm certain that u need an adaptor to mount a 1406 to a 305, u may want to look into that. Get that vac gauge it will help get timing spot on and adjust the carb. FYI I'm still chasing a small leak on mine too I'll let u know of I did anything

 

I agree, vac gauge is a basic troubleshooting tool every guy should have. I also have one mounted on the dash, to monitor general engine health.

 

Yea I was initially hesitant to consider the carb the problem since it was brand new. What makes me think something may be plugged up is the fact that I found sediment in my fuel filter. If any of that made it to the carb, it could screw all kinds of things up. Hey bigdeerock, what type of adapter do I need for that? I guess I misread the instructions when I installed the carb. I thought the intake manifold is what dictated if you needed an adapter.

 

The intake manifold does. I'm under the assumption that u have stock mani, if so u need edl adapter 2696 or similar. It turns the stock qjet mount which I believe is square to spread bore. Another issue that I ran into was PO was running PVC and oil breather on the same valve cover which I was told and read that it's counterproductive, basically a big vac leak. To check the carb gasket condition u could spray carb cleaner along the base while car is running if the idle goes up then the leak there. Short quick sprays. However I am inclined to tell you this is a potential fire hazard. However it will save u the trouble of removing the carb at least for now. How is ur choke operating??

 

I just thought u should check the plunger. U have to remove bowl to get to it. It's on the driver side and connected to the throttle linkage, it's at the top the lever has 3 holes in it. I have heard of those going bad(inner seal) and I'm sure mine is gonna fail here shortly. There like 20 bucks at oreillys. That's the only othe thing I can think wouldn't deliver the fuel if u infact have good fuel to the carb. While the bowl is off u can check float levels etc. when u manually I've it throttle does that plunger section give resistance???? Or is it just super easy??. If u need help locating the plunger lemme know ill get some pics for ya.

 

Appreciate the info. I'm running a weiand street warrior manifold. My choke doesnt work for crap anymore. It will sometimes idle at 1500 rpm for a few seconds, then drop. Other times it won't idle above 500. If I touch electric choke, I can feel that it's warm, so it's working to an extent. I'll have to get back to work on her on my day off. Thanks!

 

So I ripped the carb apart this morning. I think I found the problem. That carb is CAKED in gunk. The bowls are black. You'd think the carb has been on there years with no cleanings performed. So I obviously have a problem with sediment reaching the carb. Now, what to do about it. Can I get a better filter, or do I need a new tank?

 

I got the carb cleaned and it ran normal for a few miles. I must've plugged it up again. So I obviously need a new tank, as im getting a lot of sediment What's the difficulty innvoled on that? In the meantime, i think I'll try a high quality fuel filter, or several.

 

Is there actually 'sediment' getting into the carb? How is it getting past the filters?

 

Oh yea. Tons of sediment is in the carb. Im running just a cheap plastic in-line filter. I suppose a better one, or multiple filters would help. I should have taken a picture before i cleaned it. I was shocked. That's obviously my problem, as it ran great for a while. Gonna clean the carb again today.

 

That's odd, especially in such a short time. I use the cheap plastic ones too, never really had a problem. Obviously the filter should be trapping anything coming up from the tank, the most it should be doing is filling up with crap and cutting off fuel, not passing it on. It is full of dirt too?

Another thought - maybe the sediment source is after the filter - are you using rubber fuel hose up to the carb AFTER the filter, getting disintegrated by ethanol or old age? What's the sediment look like?

Is there a filter in the carb inlet?

And one last thought - how's your air cleaner to carb seal - stuff may be getting in that way.

 

Im using rubber hose. Just replaced it. Air filter to carb seal leaves a bit to be desired perhaps. It's definitely coming from the tank, as I can see it in the filter too. The sediment is red/brown. Im all but positive it is rust. Down the line a new tank is in order, I believe. In the meantime, I just wanna get better filtration.

 

Cleaned the carb again and blew everything out with an air compressor. Then I put on a 5 micron rated filter. Drove 45 miles to work this morning without issue. Still thinking I need a new tank though. This may prove just to be a short term fix...

 

Sounds like u may have the issue down. The better filter should help temp. I don't know if u have any other werk on your fuel lines ie pressure regulator, after market fittings etc. if u do chek the gaskets, washers etc. my hook up has multiple fittings to route my lines differently and I quickly learned that thread tape and rubber gaskets and washers get easily destroyed by gas. Otherwise I think the tank is the most likely culprit and that cheapo filter wasn't helping.

 

As the saying goes, 'suck it and see'...