olympic

vacuum tank problems

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We just had the Stewart vacuum tank rebuilt for grandson's 25 Franklin. We put it back into the car and discovered that it is not working properly. When the inner tank is full, the vacuum is still drawing fuel into the tank.  When there is still vacuum in the inner tank the lower valve is not opening properly and not enough gas is getting to the outer tank and thus to the carburetor.  We contacted the rebuilder and he says that the tank was checked with fluids and was working properly when it was shipped back to us. Well, yes, it draws fuel properly, but it won't stop. Its like the brooms in the Sorcerer's Apprentice.  The rebuilder asked us the check engine vacuum. We did this today, The 25 checks out at 16 inches of mercury. To compare, we checked out the vacuum on my 27 Franklin and it was the same. We are getting gas in the vacuum line to the windshield wiper!  I feel the problem is in the valve that shuts off vacuum when the inner tank is full. Has anyone had similar problems? Dave

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I once had this problem due to the end of the valve the opens and closes the vacuum line coming off, it had been soft soldered to the stem.  So the lever that opens and closes it could not work and the vacuum line was permanently open .  Fuel was being drawn into the inlet manifold.  I doubt you would have this problem with a newly re-built tank.

I would first make sure that the top gasket has a hole for the vent line to release the vacuum and allow the fuel to flow to the outer chamber.  That is the most likely cause from what you have described

Other possibilities:

Vacuum line valve not closing

Air valve on the tank top not opening.

The operation is very simple, when the fuel level  in the inner chamber is low,  the float drops and opens the suction line and closes the top air vent.  Suction holds the flap valve on the inner chamber closed and fuel is drawn from the main tank

Once the inner chamber fills, the float rises and that simultaneously closes the suction line and opens the top air vent.  Lack of suction allows the flap valve to open and fuel flows to the outer chamber.  

The fuel line from the tank is permanently open.

First undo all of the screws holding the tank top in place and withdraw the top with the valves,  float and operating levers .  Make sure the gasket has a hole for the vent line. Move the float up and down and make shut the two valve snap open and closed.  I suck on each to test that they are sealing remembering to hold your finger over the vent line outlet.

This should reveal the cause of the problem

 

 

 

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Sounds like the atmospheric valve is not opening to atmosphere.my guess would be a gasket or a clogged valve.and,we had 2 this year come in with the float not centered in the inner tank.

Edited by old car fan (see edit history)
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It's definitely a mechanical glitch within the tank. DavidMc is spot on in his diagnosis. Usually the problems are atmospheric as he has described above. Sometimes newly rebuilt tanks need to be limbered up a bit. If it's not solved by likely atmospheric fixes, Make sure that the float springs are mechanically "clicking" the float up and not sticking in the down position.

ron

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Check out the brass seat for the suction valve (Reference "A" in the Stewart book) as they do come loose in the die cast metal tank top.  When this happens the suction valve fails to seat properly and cut off the vacuum causing fuel to be sucked into the inlet manifold.  The seat needs to be  checked carefully as they may seem tight when they are in fact loose.

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olympic,the shop has done a bad work,to test the vacuum tank they need to test it with vacuum and a gas tank just to see if it works properly.To fill up the tank with fuel and see if it leaks isn`t enough.

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Thanks for all of the replies.  I hate opening the tank because the rebuilder might say that I caused the problem. I have to send him a msg anyway, because he wanted the readings on the vacuum. I'll keep everyone posted. Dave

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8 hours ago, olympic said:

Thanks for all of the replies.  I hate opening the tank because the rebuilder might say that I caused the problem. I have to send him a msg anyway, because he wanted the readings on the vacuum. I'll keep everyone posted. Dave

We always massage our new springs to a fast, tight click

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It  looks like to me to work better on a running car. No way could you  test this real good on a non moving car the induced vibration might make it work much better .A game beaker for sure . 

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As one of the two Old Car Fan referred to who had float centering issues I can see where that float could also have a slight chance of being stuck in a down position in the center of that inner tank. That would keep the fuel inlet constantly open. Another lesson from Old Car Fan - with the tank out of the car invert it a few times. You should hear a very distinct click when the float moves up and down in the inner tank. IF you do take it apart ensure that the float gets centered in the base of the inner tank. Take it from me - it is very easy to screw up. 

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The fuel line is constantly open, there is no valve on the fuel line, there are 2 valves, one on the vacuum line and one on the air vent line.

Centering the pin under float in its guide hole can be a little difficult but as I recall the top will not fit on until the it is centered.

 

 

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56 minutes ago, DavidMc said:

The fuel line is constantly open, there is no valve on the fuel line, there are 2 valves, one on the vacuum line and one on the air vent line.

Centering the pin under float in its guide hole can be a little difficult but as I recall the top will not fit on until the it is centered.

 

 

 

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I did not think it could happen either.but it  can.fixed one at Hershey,one at home,so it can happen,just depends on that perfect angle.We rebuild and restore these tanks as a hobby,first I've seen in years

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Ok,David is correct on.most cases.I have a tank in my house,and could not make it happen,but,I did check some of our floats,with the difference in them,it can.like I said ,never thought it could happen,but seen it twice,talked to someone once,in the past year

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Positively can happen. I had mine apart and reassembled at least six times before discovering what was wrong. It worked perfectly after finally assembling with the pin centered.

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Getting back to the original question, the vacuum tank is an extremely simple device, its not a "black box" requiring expert attention.  Understand how it works, take the top off and test that the valves are sealing and they snap open and close, make sure the gasket has a hole for the air vent, look for cracks in the pot metal top, check the for loose brass valve seat inserts, etc.  Repair kits and new tops are available.  Problems are easily detected and fixed

They are very reliable and work well.   

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The rebuilder of the tank called us today. He said to send the tank back. Hopefully he can find the problem. Dave

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I wonder whether during shipment to you the tank got tossed around, resulting in the needle becoming unseated.  You might ask the rebuilder if there is a way to secure it during shipment.  Only way I can think of is to remove the cover/lid and ensure the needle is in its proper place before installing the tank.

 

If the rebuilder fixes it, please give him credit for doing so in this same thread.  I have no idea who you used, and have no connection with rebuilders.

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Stude17 has the answer  ! It's the valve seats leaking. Not checked for proper function. But now it is back in the hands of the overhauler. Best wishes unto you......

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6 hours ago, 23hack said:

Stude17 has the answer  ! It's the valve seats leaking. Not checked for proper function. But now it is back in the hands of the overhauler. Best wishes unto you......

 

Thanks for the vote of confidence 23 Hack.

 

6 hours ago, old car fan said:

It is pulling fuel,so not that seat is not the problem.but agree,you have to look at that.seat,common problem.

 

Sorry Old Car Fan but I stand by my post.  In addition although I have never seen it happen if the float had a leak and was fuel logged that could also be the problem.  I will be interested in the tank rebuilder's findings.

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Stud17 I agree with everything you say,the only thing that bothers me is ,he said he was pumping fuel,not here to argue,fix the car's with tanks.If that seat,sometimes seats it self to the top,it. May pull,but the drop of fuel is atmospheric.hey I hope to hear back from the original poster.truth be known,I. Expect the builders reply,not problem.Let's see

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I have this style Stewart-Warner on my 1928 Plymouth for over 50 years and only rebuilt it twice. Usually is the top gasket that dries out. I have only tried it on the car after putting it back together and has always worked. It still works fine today. They are a great tank and will last for years.

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