Fuel Problems -- Getting Close!

[jagnweiner]

Apologize in advance for the length of this post. I'll give a very condensed version of my saga and then get on with the questions.

I have a '25 DB Touring that for several years was a very reliable driver. About 8 years ago, I began having fuel problems which I attributed to vacuum tank problems. Car runs great for 5 minutes after manually filling the vac tank, but dies as soon as vac tank is empty.

I sent the vac tank off for a rebuild, but wnen it came back, it had cracks in the float. I eventually got an entire replacement top and mechanics (everything but the inner and outer tank).

Never quite got around to chasing down the problem over the last several years. I bought an electric fuel pump and pressure regulator a year ago to bypass the vac tank, but didn't get around to installing it either. This week, I finally got motivated to troubleshoot this problem.

I first disconnected the vac line running from the manifold and checked for vacuum. I don't have a guage, but it had enough suction to suck on my finger pretty well. Plugging that line also causes the engine to stumble and start to run rough. (Not sure if that is a clue)

I then disassembled the vac tank and checked the two valves on top. Both seem to seal fine. I put everything back together and tested it. With the engine running, but the fuel line from the fuel tank disconnected, I now have vacuum at the fuel inlet. Again, when I plug the inlet with my finger, engine stumbles and dies.

I next started working my way back to the fuel tank. I took off the aftermarket inline fuel filter halfway back to the tank. I ran it with the line open where the fuel filter was. Again, runs fine open and runs rough and dies when line is plugged. I then bypassed the filter by installing a piece of copper tube and it wouldn't run.

Went all the way back to the fuel tank and disconnected the fuel line where it exits the top of the tank. Ran fine while disconnected, ran rough and died when hooked up. I then took out the fitting and tube that go down into the tank. It was in kind of tough shape, with what I would describe as "plaque" on it. It also appeared to have some kind of attachment at the bottom (a screen?) that was corroded away. I cleaned it up and re-installed. I started it back up and running was pretty much the same. Ran very rough, firing puffs of black smoke out the exhaust. It seemed like it might have been a little better than before, but I think that could have been because I was a little more persistent in keeping it running. I ran it with the filler cap on the tank both on and off. When I put my hand on the filler hole, there seemed to be some suction there. At that point, I was ready for bed.

Any thoughts, wise ones? FYI, there is about 1/4 tank of fuel in it. I have drained the tank and added new fuel, but it has been a while, so the fuel could be stale. I also plan to try connecting tubing at the fuel filter bypass to draw fuel directly out of a gas can.

Thanks,

Scott

[72caddy]

Sounds like you solved the problem to me. If I am reading this right everytime you have the sytem hooked up from end to end the car runs poorly - when you disconnect at the vacuum tank, filter, and top of the gas tank it runs fine.

the scale (or what-ever it is)on the tube in the tank seems to be the culprit. If it is that badly corroded or sucked-up some corresion from the tank and now that it is lodged in the pipe,

Take the line from the top of the tank and then atttach a line into a clean gas can with copper or rubber - I bet it runs fine.

Good Luck. I am still fighting mine.

[Guest imouttahere]

I would disagree with "72caddy". If the problem really were caused by scale in the tank, it would make your engine die from fuel starvation. Instead, you describe black smoke coming out of the exhaust. That means it is getting too much fuel, not too little.

Does your vacuum tank float mechanism have TWO springs? I bought a (supposedly) rebuilt vacuum tank from one of the major DB parts suppliers. It was expensive. But not only was it missing one of the springs, the float leaked badly. When I corrected these problems, the car ran fantastic. It took me two years to figure it out because I incorrectly assumed that the supplier would not have sold me a vacuum tank that was FUBAR.

Did you fix your float?

Does the float and valve mechanism operate smoothly? It should. If it doesn't, figure out why not. Remove the top of the tank and the float, and then hold the top in one hand while you lift the float with the other. The mechanism should not have any "catches" or roughness, and the valves should snap into their closed position firmly and with authority, not reluctantly.

When your engine dies because it's running too rich (black smoke out the exhaust), do you have gasoline leaking out of the body of the carburetor? If so, this means that the vacuum tank is filling up too full (fuel valve not closing when it should) and the carb is sucking gas into the vacuum line. That is caused by a float/valve problem.

Good luck.

[72caddy]

Agree that the black smoke is the car running rich...but just so I follow...

If the tank is over-filling and gas is getting into the vacuum line, this causes a flooding issue and the car stumbles. The car runs fine when the gas line is disconnected because the vaccum tank does not have the opportunity to overfill or the level drops when the line is 'broken' for the various tests?

Just trying to educate myself as I may have a similiar issue with my tank. I ignored the black smoke part of the email as I was already thinking of fuel starvation.

[jagnweiner]

Billy-

Float is definitely fine. It is completely different from the one I got back "rebuilt." (I suspect your "major DB parts supplier" may be the same person that rebuilt mine, but he shall remain nameless) It has two springs and is working fine.

I see your point about black smoke indicating flooding, but it happens so quickly after hooking everything back together, that I don't think fuel is being drawn from the gas tank. The vac tank is not overfilling or overflowing (the vent tube works fine also).

72caddy, I cleaned all the scale off and the gas tank pickup tube is clear when I reinstall it, but it is possible it is picking up a bunch of crud as soon as I put it back in.

Bottom line, I think the experiment of trying to draw fuel from a separate container will give me more answers. I hope to try it tonight and will let you know what happens.

Thanks again,

Scott

[Jim Anselmo]

I am confused with:

"I first disconnected the vac line running from the manifold and checked for vacuum. I don't have a guage, but it had enough suction to suck on my finger pretty well. Plugging that line also causes the engine to stumble and start to run rough. (Not sure if that is a clue)"

I think that is a clue, under normal operation whenever the vacuum tank is full the vacuum to the tank should be shut off. Guys, why would plugging the vacuum line cause the engine to run rough? Does the engine run fine when you just gravity feed the carb and the line from the manifold is left open? I assume that's what you are doing when you have the gas line disconnected. Sorry more questions then answers......

Jim

[jagnweiner]

Jim-

I see your point. I'll have to re-check my observation on what happens when vac line to the manifold is disconnected from vac tank and then plugged by finger.

Yes, the engine runs fine when the the gas line is disconnected and there is fuel in the vac tank being gravity fed to the carb.

-Scott

[nearchoclatetown]

I'm wondering the same thing that Jim Anselo is wondering. HAve you taken any part of the carb apart? Linkage at fuel enrichner {choke}?

[jagnweiner]

This morning's update and responses to questions:

-I have not taken the carb apart or done any adjusting of it.

-I recant my previous statement that plugging the line off the manifold would cause it to die; slight change in rpm but still runs fine.

-I hooked up copper tube where the fuel filter used to be and ran it to a can of gas sitting on the floor. It ran pretty well and was drawing fuel from the can to the vac tank. Ran the engine for about 15 minutes that way.

-I drained the remaining bad gas from the gas tank (about 4 gal) and took a flashlight for a closer look to the inside of the gas tank. Things don't look great in there. It looks like someone applied some sort of sealer coating that is now starting to peal away. I suspect there is a fair amount of junk at the bottom of the tank and the pick up tube may be sitting in this junk. The drain plug is in a small indentation in the bottom of the tank. Is the pickup tube supposed to sit down in this indentation?

Ultimately, I think I need to get this tank cleaned out.

-Scott

[72caddy]

Well after getting the timing and spark issues on my car straight, turns out I have the issue as described as 'DBBilly'. When running the car idles OK, but stumbles on acceleration and eventually just floods out. Looking at the carb when this happens, dry when running, but gas leaking out when not running. Plugs are rich fouled as well.

So in reading up on vacuum tank issues I found an old article that talks about an easy test to see if your float has a hole (or not) causing the fuel to enter the vacuum line - without having to tear apart the vacuum tank.

Take a bottle and put a rubber stoppoer in the end that has two tubes. Hook one tube to the vacuum line and the other to the intake. If gas shows up, your float has a hole. If gas does not show up it is the carburator.

I can scann this and send it along if you like. Just drop me a PM.

Richard

I have not tried this yet, but will

[jagnweiner]

Richard-

Glad to hear you're getting closer too. Having had my vac tank apart, I know the new float has no cracks.

You probably already know this, but once you take it apart, you can find the cracks in the float by heating a pan of water to just shy of boiling and immersing the float. Air bubbles and gas will come out of the float at the various cracks. Use the same test after soldering to confirm that you fixed it.

Others with more knowledge may elaborate on that process a little.

[nearchoclatetown]

Jagnweiner?, if I understand it correctly your filter is between the gas tank and vaccuum tank? I'm wondering if that is interupting the flow. I'm thinking both of you should have been at Tom's tech session at Kokomo, In. two weeks ago. He covered way more about 4 cylinder carbs then I remember. I have a printout somewhere from Tom, but it won't do you any good as I don't have a scanner. If I can find it I'll reread it and try to answer if no one else knows where to go from here. JW, do the little bell shaped fremuses have flats on them from rubbing against the top of the float? Tom recommended taking the pins out and turning them over if they did. The flats affect the float level.

[jagnweiner]

You can just call me Scott. That is where the filter was; it is no longer there as I have replaced it with a short piece of copper.

If you happen to have access to a fax machine, I would greatly appreciate a copy of that printout. I can send you a PM with the number. Otherwise, maybe someone else has the material you're referring to. I'm going to get the tank cleaned out anyway, because it needs to be done.

Thanks,

Scott

[Guest Jack27]

Suggest you take the top opf the vaccum tank, do not turn it over, but hold it up high enough so you can see the valve seats in the bottom of the tank head.Sometimes these seats come loose and cause flooding. A couple of prick punches will reseat them.

[Guest imouttahere]

"W, do the little bell shaped fremuses have flats on them from rubbing against the top of the float? Tom recommended taking the pins out and turning them over if they did."

There is supposed to be a tiny curved, thin sheet metal spring, shaped like a "C", between the float and the valve hinge mechanism that prevents the float from contacting the hinge mechanism and interfering with it. If your vacuum tank doesn't have one, I don't think it would be too hard to make one out of a tin can or something similar. That was one of the parts that was missing from the so-called "rebuilt" vacuum tank that I bought.

I would like to extend hearty thanks to Ed Joyce of Florida, who sold me a vacuum tank float and valve mechanism that was complete and in very good condition, and at a reasonable price. Ed, you're a true Dodge Brother! What a revelation it was to see what parts the float and valve mechanism are supposed to contain, and how they are supposed to be assembled!

In order to mix-n-match parts, such as the float, from different vacuum tank mechanisms, it becomes necessary to remove the brass rivets in the hinge assembly. I found what works well is to carefully grind the head off the brass rivet, remove it and replace it with a 4-40 bolt and nut. Cut off the end of the bolt, where it protrudes past the nut, with a wire cutter. This distorts the threads where you cut it off, and prevents the nut from ever coming off.

IMHO, there is little or nothing inside the carburetor that can cause flooding, assuming that the choke lever isn't set 'way, 'way off. Just about the only other thing that can go wrong inside the Stewart carb is for metering pin to separate from its rack where they are swaged together, but I don't think this would cause flooding; it would cut off fuel and air together, I think, because the air valve wouldn't lift off the metering pin. I wasted a lot of time trying to find a problem with my Stewart carb until Rodger "Dodger" Hartley advised me that the carb was almost certainly not the problem.

There is a 99.9% probability that the problem is in your fuel tank, as you say, or in the vacuum tank. For example, nothing inside the carburetor can cause fuel to drip off the carb body and intake area. This is always caused by the vacuum tank overfilling and the engine sucking fuel in through the vacuum line.

[nearchoclatetown]

Sorry to confuse DBBilly. The fremuses I referred to are in the carb, not the vacuumm tank.

[72caddy]

I pulled my vacuum tank and found the the flapper valve and screw were laying at the bottom of the outer tank. That may be my problem!

Afer cleaning and re-assembly. The car is now hitting on all four cylinders - not rich fouling the plugs - and has a nice steady idle.

The next issue is the miss on acceleration which I think is the condensor or coil, but I take my gains today and hold off on that for another weekend.

Many thanks for the advice and encouragement.

Richard

[Guest ella29]

Hi Scott, laughing as this brings back memories. Sorry.

A professional mechanic convinced me to go back to a vaccum tank and get rid the fuel pump to keep the car original. I agreed since I know nothing about these cars and this was my first pre-war car. That's when all the problems started. This car normally runs unbelievably well. My fuel problem lasted for months since I either did not have time to deal with it or wanted to kill it and gave up for a while. This car died in the Halloween Parade and let me sit on the side of the road on the way home the same day. Thank God for cell phones. Here comes my Mom with a 32 oz Big Gulp full of gas, for the "BRAT", which she partially spilled in her lap, oh what a feeling! Couldn't figure it out, looked in the vaccum tank, empty. Filled it up, ran fine until she used all that fuel. I went through the exact same scenario, Smoking, sputtering, empty carb, ripping the tank open, checking all the lines, all the same stuff. I don't think there was another thing to rip apart on the car. Ultimately what it ended up being was a piece of rust stuck in the fitting in the top of the vaccum tank on the fuel side. When I pulled the fitting out of the top of the tank, I did not see a hole. Looking closer, it was rust in the tiniest hole I ever saw(paperclip diameter). Could not believe it. Apparently this tank was laying around and put together when it was needed for my car, someone just grabbed a couple of fittings and threw them in the tank and never looked. I was furious, all this for a plugged hole. There can't be any way that was ever the correct fitting. I drilled the fitting out to the size of the main opening and NEVER had a problem since. I am not worried about the rust as I have a sediment bowl on the bottom. Good luck. The "BRAT" and I are buds again and she is as peppy as ever.

Kim