carmover Posted July 22, 2018 Share Posted July 22, 2018 What is causing the spark plugs to get black and sooty?I am trying to track down the running rough problem in my 25 Buick.I installed all new ignition parts and pulled the manifolds and checked everything out and cleaned the carb and checked it over and reinstalled everything and checked the timing and it was right on the money.I adjusted the valves to 008 hot.I also checked the distributor insulation to make sure it wasn't arking and I found the metal strip from the points was not in the holder where it is supposed to be.It was high up enough that it could surely cause arking so I fixed that.What I forgot to mention was when I started it this morning after reinstalling the manifolds it started to run decent until it got hot and then started to running bad and shut off and would not start again.I pulled the plugs and all 6 are black and sooty.I had the carb adjusted the best it would run but could not get it perfect by the way it was running. Link to comment Share on other sites More sharing options...
Matt Harwood Posted July 22, 2018 Share Posted July 22, 2018 (edited) Black and sooty is a rich condition. If it happened that fast, probably VERY rich. It tends to become a cascading effect--as more soot builds up, it's harder to get a spark, so more soot is created until finally the car won't run. You might have to adjust jet sizes to get it right. The adjustments on the carburetor are typically only for starting and idling, whereas the mixture at speed is largely controlled by the size of the jets. They should be reasonably easy to change and probably somewhat standardized so you can tweak them to suit the conditions. It's possible that you've got a weak spark which is causing the cylinders to load up, but I don't really think that's the case. I think it's just rich. Do you smell fuel at the exhaust? Edited July 22, 2018 by Matt Harwood (see edit history) 3 Link to comment Share on other sites More sharing options...
carmover Posted July 22, 2018 Author Share Posted July 22, 2018 Matt It Started to smoke out the tailpipe like it was running rich and I kept giving it more air but couldn't get it to lean out.It has a good strong spark.As I mentioned I found a couple of things I didn't like and fixed them and also found a couple of valves a little tight and got them adjusted properly so I am hoping that new plugs will fix it. Link to comment Share on other sites More sharing options...
Leif Holmberg Posted July 22, 2018 Share Posted July 22, 2018 It looks like your problem are the vacuum canister,the fuel goes stright in to the inlet manifold becuse of some leakage in the needles or you have fuel inside the float.A common problem on our 1920s Buick.Open upp the top of the vacuum canister and take a real look at the parts there. (and just remember use the original measurment on the vacuum tube beytween the canister and the inlet.As wider tube as more fuel goes stright in to the inlet manifold if anything got wrong in the canister!) Last year I saw a Swedish 1928 Buick with a 3/8" tube and a not working vacuum canister,and I can tell you that was really BLACK SMOKE comming out in the rear end! Leif in Sweden. 1 Link to comment Share on other sites More sharing options...
Terry Wiegand Posted July 23, 2018 Share Posted July 23, 2018 Ronnie, If I were a betting person, I'd put money on the vacuum tank. I had the same identical problem(s) that you are having with our 1920 K-46. I had John Wolf out in Ohio rebuild the vacuum tank for me. To make a long story short, the two springs in the lid were not shutting off the vacuum from the manifold once the tank was full and the float would rise. The result was that raw gasoline was being sucked into the manifold above the carburetor. The springs were changed out with ones that were of the proper tension and that problem went away just like that. Please understand that I am not telling you that that is what your problem is - but, it sounds awfully suspicious and identical to the problem(s) that I experienced. You might check that out and let us know what you find. Terry Wiegand Out Doo Dah Way 4 Link to comment Share on other sites More sharing options...
carmover Posted July 23, 2018 Author Share Posted July 23, 2018 I am not running a vacuum tank I have an electric pump and regulator.I used to have the problem that you had but I gave up on it.I couldn't get the canister to shut off and it kept putting fuel into the intake.The carburetor seems to be doing its job.I am a little confused that the owners manual says to open the fuel valve one turn and stop with the notch lining up with the post.Problem is that when the valve is closed and the needle is seated the notch is on the opposite side from the post and using the post as a marker if you bring it around to the post I would think that is a half of turn and if you open it up one full turn it would go back to where it started and wouldn't be lined up with the post.I may of had the fuel needle open to much.I am going to get some new plugs Monday and see if any of the improvements I have done today helped it.I also found a possible short in the distributor that could have caused all sorts of problems. Link to comment Share on other sites More sharing options...
dibarlaw Posted July 23, 2018 Share Posted July 23, 2018 Ron: I wish we could be together while troubleshooting. My car would do the same things you are describing and I went through all that you have done. Except now I am waiting for the return of my rebuilt engine and pray I do not experience the same issues you are having upon its being restarted after 11 months. The carb can cause all sorts of mischief if not adjusted properly. The notch on the Idle needle valve is only a reference point. The setting to get enough fuel for an initial start. Once started it is to be adjusted open until the engine rolls from running rich, then turning in to lean out mixture until the engine also starts to stumble. Just like setting the old B&S lawnmower engines. Once a happy medium is found then the air vane is adjusted to check throttle response. As you are turning the large air vane knob you should notice a difference. If it does no good then the air vane valve and the venturi block may need file fitted for proper tail clearance. I believe a .009 clearance. I did this 3 years ago and all seemed fine. When I removed the carb when the engine was pulled I noticed that the tail gap had changed...swollen closed .. got to love that die cast! I followed the Marvel carb rebuilding instructions exactly except for the parts that state "go to your Marvel service shop and replace this part and that part and get a new spring and etc"...all made of UNOBTANIUM. Also the high speed jet is a bit too large for modern fuel. It will always run rich. The recommendation on the forum was to solder the tip and re-drill with a smaller drill. Or you can contact your Marvel distributor and get a new jet.... Not. 1 Link to comment Share on other sites More sharing options...
25 Buick Posted July 23, 2018 Share Posted July 23, 2018 Smell your oil. If the fuel is too rich and getting into the oil it can very quickly destroy an engine. 2 Link to comment Share on other sites More sharing options...
Terry Wiegand Posted July 23, 2018 Share Posted July 23, 2018 25 Buick, A very good point. After I had all the trouble with the vacuum tank I changed the oil and lubed the chassis points while I was under the car. Terry Wiegand South Hutchinson, Kansas 1 Link to comment Share on other sites More sharing options...
carmover Posted July 23, 2018 Author Share Posted July 23, 2018 2 hours ago, 25 Buick said: Smell your oil. If the fuel is too rich and getting into the oil it can very quickly destroy an engine. You are right about that and I am keeping a good eye on that too. Link to comment Share on other sites More sharing options...
Fred Rawling Posted July 25, 2018 Share Posted July 25, 2018 Terry, The springs on my vacuum tank float are brittle and broker off., Now they are a bit shorter than they are supposed to be. Please let me know how to contact John Wolf to see if he has springs. Fred fred.rawling@live.com 1 Link to comment Share on other sites More sharing options...
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