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DA vacuum pump issue


Dodgenz
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At the risk of people having to repeat themselves, I have a problem with my Stewart vacuum pump on my '29 DA. Used to be quite reliable, even if left for some time, but the last couple of times i've had fuel starvation issues. I've disconnected the tank fuel line and tried to draw fuel from another source to eliminate the fuel tank and line - it briefly sucked a bit up then stopped, but when i stopped the motor the fuel bowl filled with the bit it had sucked up. On re-starting it wouldn't suck much at all.

 

I haven't dealt with one before, so wonder if anyone has any suggestions before i pull it to pieces? (A couple of photos - one with the first engine start with some sucked up, then with the second run and it only pulling a little up the pipe).

 

Thanks.

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49 minutes ago, Dodgenz said:

At the risk of people having to repeat themselves, I have a problem with my Stewart vacuum pump on my '29 DA. Used to be quite reliable, even if left for some time, but the last couple of times i've had fuel starvation issues. I've disconnected the tank fuel line and tried to draw fuel from another source to eliminate the fuel tank and line - it briefly sucked a bit up then stopped, but when i stopped the motor the fuel bowl filled with the bit it had sucked up. On re-starting it wouldn't suck much at all.

 

I haven't dealt with one before, so wonder if anyone has any suggestions before i pull it to pieces? (A couple of photos - one with the first engine start with some sucked up, then with the second run and it only pulling a little up the pipe).

 

Thanks.

20220115_171911.jpg

20220115_172132.jpg

I just bought the manual for these, if you want me to email all the pages to you send me you email. 
 

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If you have even a tiny air leak it will play up.

Maybe dried out gaskets.

A point of issue with these are the fittings into the top, they can crack and cause a vaccum leak (suck air)

Some tops are pot metal and can just disintegrate.

Overhaul kits are available as are the booklets show by Matt.

All in the USA.

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Look for leaks around the intake manifold to block gasket and carb mounting gasket. When the engine is running, does it seem to want more fuel/richer mixture than normal at idle? That could indicate a leak in those places.

 

Edited by Mark Gregush (see edit history)
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1 hour ago, Mark Gregush said:

How does the oil pump affect the engine vacuum, with the vacuum line being connected to the intake manifold?

It doesn't.

I was pretty medicated when I wrote that ;) , plus I was multitasking trying to be somewhere. 

I meant to point out the lines that run from the area of the oil pump to the tank need to be checked for leaks. That's ultimately where I'd start and work my way up. I had changing oil on my mind from another question I was answering for someone else earlier and my thoughts were mixed up. My mistake @Dodgenz

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Thanks all. Will email you Matt. And it acts like it could be blocked, so i'll try that filter on top before i remove the top itself; plus will check the manifold pipe.

 

So have checked the above, there is no filter (anymore!), but reasonably clean inside; and manifold pipe is sucking well. BUT if i understand the operation correctly, the air valve is not opening when the top tank is full, therefore not dropping the fuel down. It rattles up and down happily enough but doesn't move whether the float is up or down. These are the two float positions...

 

Any thoughts on what might have happened ? I can't see what is broken or missing, it looks fine, as if it's always been like that. But if i blow through the air tube nothing comes through in either float position (unless i manually move the valve).

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10 hours ago, Dodgenz said:

Should there be something below the little brass collar here? (To make it push the valve higher).

air valve 1.jpg

One of the problems with these vacuum tanks as they age is the  vacuum cut off needle  and seat where the  "brass seat" becomes loose in the diecast vacuum tank top.  The brass seat in your photo does not appear to be "seated" in the tank top possibly because it is loose.   Not sure if this could be the source of your fuel starvation problem  but it is something I would check.

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Just returned from about a 5 mile run in the DA (its longest run yet!!!) and because I did not run out of fuel, assume the vacuum tank working OK. But, my only other experience with vacuum tanks was on an Essex, some years ago, hence my comment on the filter above. It was the only problem I ever had with it in the years I owned the car. When sucking fuel into the vacuum tank, there was a very audible sucking noise, which was kind of reassuring, as you knew the vacuum tank was working. With the DA, I have heard no noise. Should I, what is normal?

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It seems as if Stude was on the money, having tapped the seat back in we seem to be in business. Didn't have much petrol so didn't go far, but went ok. Thanks!

I can't hear mine sucking on the DA either so now it is working again I'd say that is normal.

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