Fuel or carb problem?

[Guest 97welter]

I have a 1926 Buick 27 Standard. I removed the carb, it wasnt gummed up at all. I cleaned it out and replaced the gaskets, and sealed the cork with Crazy Glue. I then got the car running with the gas line to the gas tank disconnected and the vaccuum line to the vaccuum tank disconnected. I also opened up the vaccuum tank and it wasnt gummed up, but I cleaned it out and replaced the gaskets. The float was fine too. The car would run for a few with the fuel that was gravity draining into the carb from the vaccuum tank. I had to use starter fluid into the intake manifold to get it started though....

I cleaned out the gas tank and hooked everything back up. I still have to use starter fluid to get it started, and it dies after running for less than a minute. The fuel filter remains full of gas and I took the fuel line of the top of the vaccuum tank and it appears to be wet. Any ideas what the problem is? Maybe the carb? Or the tank?

[Fred Rawling]

My first thought is how long has it been since the fuel filter was changed.

The next thing that I would do is fill the vacuum tank and see if the car runs for more than a minute or two. A full vacuum tank should be good for a 7 mile drive.

If it runs for a while on the full vacuum tank, the next thing would be to place a very small piece of paper on the vent tube opening while the engine is running. If the paper sticks there, the vent valve is not closed.

That valve should be closed when the float in the inner tank is down so gas can be sucked in from the gas tank.

[Guest 97welter]

Yes, it runs a few minutes on a full vaccuum tank. The only fuel filter is in the bowl under that tank right? I have cleaned that. I will check the vent line

[Fred Rawling]

Originally, there was a filter screen inside the filler plug on the top of the vacuum tank.

If this is a new car to you, check the fuel line under the floor boards for an in-line filter. That is a good place to install one. You can do it from above and not have gas running down your arm while working on it.

When screwing things into the die cast tank top, do not use teflon tape. Teflon is a lubrficant. You can ovder tighten fittings and crack the tank top.

Another place to check is the pick up tube in the gas tank. There is a screen on it that can get pluged up.

When I replace the plugs in the vacuum tank top and the pick up tube in the gas tank, I put a little permatex #2 on the copper gaskets to seal them.

Fred fred.rawling@live.com

[Bob Atkinson]

If it still has the original fuel filter, this would be a round brass screen affair you can see in the glass settling bowl below the vacuum tank. This should be the only fuel filter. You should be able to clean it off with a brush and carburetor cleaner (or gasoline) and put it back in.

Mine will run over 30 minutes on a full vacuum tank with the feed from the gas tank disconnected so it sounds to me like you still have a mixture problem or vacuum leak.

A silly question (maybe) but you are using the choke when starting it cold and leaving it mostly out for the first few minutes the moter is running aren't you?

[Guest 97welter]

Yes, all the filters are clean, there is no aftermarket one. I havent used any teflon when I reassembled it. I am using the choke for about a minute, it starts to die, so I push the choke in. What are the setting for the carb? I have the air mixture screw set to where the tab is right at the bottom of the screw head. The fuel screw is like 2 turns out. Is there anything to check when I open the carb? I believe the vacuum is sucking gas from the tank.

[carbking]

Are you getting black smoke while running?

Once the engine dies, are the plugs wet or dry?

Jon.

[Guest 97welter]

There is no smoke when it is running. The plugs are dry, have some black carbon deposit, they are new plugs. I set the fuel mixture knob one turn open and the air knob screw head bottom flush with the end of the tab. Ive tried adjusting the fuel some and it will pop a little bit and die. When I opened the carb, I didnt adjust anything inside. What else should I try?

[nickelroadster]

You may have a bit of a problem with modern gas which needs to be run a little richer because of the alcohol. If you are getting backfires it is probably because it is too lean. Two suggestions. Check and see if you have any room to raise the float level but keep it beneath the main jet) or add about two drill sizes to the main spray nozzle. There is pretty good material on these marvel carbs in quite a few of the Dykes manuals which are easy to find. If you have trouble finding one, let me know and I can post a short article from an old Skinned knuckles magazine.

[carbking]

The reason for my questions was to attempt to determine if the engine was starving for fuel or flooding. Sounds like it is starving.

The first thing I would try would be to totally disconnect the vacuum tank; borrow a portable outboard motor tank or some other suitable container; and try running the engine on the different container. This should tell you if you have a carburetor issue or a fuel delivery issue.

Jon.

[Guest 97welter]

I have tried to find some info, but have not had any luck. So, how do I raise the float? Where is the main jet? Im not too familiar with the updraft carb. Adjusting the fuel mixture screw wont help enough? I dont want to drill a hole in the jet.....

[Bob Atkinson]

Your adjustment to the fuel mixture valve sounds about right to me. But try adjusting the air valve to a point where the top of the tab is even with the TOP of the screw head (you said earlier in this thread you adjusted the screw with the top of the tab even with the BOTTOM of the screw head) - at least that is where mine is when the carburetur is in adjustment. It may not hurt to turn the screw in a little more than this until you get the engine running and warmed up. At least this is what I do. Then I turn the air screw out until the engine starts to idle rough and back in until it smoothes out.

This air valve operates a restricter plate in the air flow out of the carburetor. Its purpose is to accelerate the air flow pulled over the needle valve in the carburetor to assure enough fuel is sucked out and vaporized properly at lower engine speeds. If it is not working the engine will starve out.

If you haven't taken the air screw out and cleaned the sliding surfaces with fine steel wool and checked the spring, this would be a good idea too. I have had the occasion where these sliding surfaces have gotten gummed up and stuck.

Edited December 13, 2010 by Bob Atkinson
Correction to above: The fuel valve should be turned out ONE turn, not two. (see edit history)

[Guest 97welter]

I have had the air valve out and there was no gum at all. The spring is fine and I checked the operation, which was smooth. I will try to adjust the air valve in more. im just not sure where and how the float should be adjusted to. Also what else needs to be adjusted........

[nickelroadster]

Do find a Dykes manual that has this carb in it. You need to get an understanding of how the carb works in order to diagnose your problem. Your float level should be about an eighth of an inch below the level of the high speed jet nozzle. Measure the heighth of this nozzle and put a little mark on the outside of the carburetor of where it comes to. You can pull the plate off of the float bowl and see where the gas comes up to. This should be about 1/8" below the level of the high speed jet. If this is ok, then you need to enlarge the size of the high speed jet. Get a set of numbered drill bits from 61 to 80 and find out the size of the hole in the high speed jet. Usually if you enlarge this two or three sizes it works pretty well. If you drill the jet out too much, than silver solder and redrill to a smaller size. Of course this last davice assumes that you have ensured that the carb is getting adequate gas. The air valve doesn't adjust the mixture very much and the alcohol in modern gas needs to be richer than straight gas. Make sure you understand the operation of this carb!

[michaelod]

There is a manual online for the 1929 Buick Marvel carb at:

www.1929buick.com Photos :: 1929 Marvel Carb

This is pretty close to the carb you have and should be useful.

Thanks,

[ROD W]

If the vacuum tank is full, the motor should run for about ten minutes. If your only getting a couple of minutes running, its only running on fuel in the carburetor bowl. when I turn off the vacuum tank mine runs for a minute or so. Sounds like

fuel isn,t draining properly from vacuum tank

[Guest 97welter]

Yes, the fuel may not be running correctly from the vaccuum tank. I am going to remove the cover from the float and watch while it is running.Any other suggestions?

[Guest 97welter]

Why will it only start on starting fluid?

[Mark Shaw]

Send me a PM with your email address and I will email a pdf of your vacuum tank system.