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Vacuum Tank Problems


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Hello all,

 

I'm having what I think are vacuum tank problems on my 1930 Packard 726 that I have yet to find an answer to. It's a pretty typical 8-bolt Stewart Warner type. I've scanned through all of the threads on here about others with vacuum tank troubles, but my problem seems distinctly different than almost all of those. The closest I have found was in this thread here. The situation described there is very similar to mine in that

 

1. There is no problem getting fuel into the vacuum tank. I have had that problem before, but I've fixed leaks and the like and it pulls fuel very well into the tank as can be seen through an inline filter. 

2. There doesn't seem to be a vacuum leak. The car idles very well, and especially when idling, the slight vacuum drag (I guess you could call it that) that the vacuum tank puts to the engine when the tank starts to draw fuel is only sufficient to cause a slight dip in the idle speed, which picks up immediately again after the valve closes.

3. The vacuum valve seat is not slipping. A few years ago I was shown a trick to use a punch to preen a bit of the pot metal over the brass seat, so it can't slip out. Before then I  had the problem where the valve seat slips out, keeps the valve from shutting off, and fills the tank to the point that gasoline dumps into the vacuum line, but that fix solved it.

4. The lower tank is full of gasoline. Even after I start to run into troubles, when I remove the vacuum assembly and inner tank the lower tank is full of gas.

5. The atmospheric vent for the lower tank is not plugged. 

6. The flapper valve on the inner tank seems to seat well. I've done the test where you press it to your face and try to breathe in to check the flapper action, and it seems tight. I've ordered a replacement just in case, but while once I was confident that might be the problem, I'm not so confident anymore.

 

The trouble goes like this: The car starts and idles very easily from a cold start. After warming up for a few minutes, and starting the drive, the car will run excellently for about 5 miles, cruising easily at 45 and pulling up hills nicely. Then, quite suddenly, when running at speed the car will start to act as if it is starved for gasoline. It will rapidly lose power and it will cough and backfire when throttle is applied. The sediment bowl appears, when this starts, to have a pocket of air in it it, and bubbles can be seen running through it, seemingly coming up from the carburetor line. I've taken a couple vidoes, which I put together here (https://www.youtube.com/watch?v=pWD68lHuAyg). The car does not stall though, and will idle seemingly quite happily once pulled over. Recently, when trying to get to the bottom if it, I was able to repeat the process of driving about 5 miles before hitting that power wall again without shutting down the engine for longer than a couple minutes to fiddle with things, so I don't think it's related to heat. The other tricky thing is that it seems somewhat intermittent. I ran into this problem in October, replaced the gaskets for the tank, and it seemed to run fine. Then I ran into this problem again, and afterward filled a crack near the fuel inlet on the top piece, and replaced the gasket for the sediment bowl. I then drove it for a few hours, and a couple days later the problem came back. 

I don't think it has anything to do with the ignition, though I could be wrong. 

Has anybody had a similar problem before? Any clues as to what might cause it?

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37 minutes ago, DavidMc said:

Whoops! Should be fixed now   So what was the problem and the solution

 

I think he's saying the video link is fixed and it should now be viewable. I don't think his vacuum tank problem is solved yet. 

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28 minutes ago, Matt Harwood said:

 

I think he's saying the video link is fixed and it should now be viewable. I don't think his vacuum tank problem is solved yet. 

I believe you are right. 

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Had that same problem with a customer's car. Starts and runs fine until a few miles down the road and then starves for gas and gets worse the more I pressed the pedal down. Pull over it would idle fine and then same thing would happen after a few miles of starting out again..

 

Check the vacuum tank and lines and all was good. Turns out it was the driving motion shaking up rust scale from the bottom of the tank and partially blocking the fuel pickup tube every time the vacuum tank cycled on and was pulling fuel from the tank.

 

If the the car was pulled over and idling before it could completely stall, it would start to run fine again. Without the motion of driving, as soon as the  vacuum tank would cycle off, being no suction to the gas tank, the rust would fall back to the bottom of the tank until more driving stirred it up again to be sucked up enough to cause the engine to starve for fuel.

 

Dropped and cleaned the tank, sealed it with Hirsch sealer, and no more fuel problems. 

 

Paul

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1 hour ago, PFitz said:

Had that same problem with a customer's car. Starts and runs fine until a few miles down the road and then starves for gas and gets worse the more I pressed the pedal down. Pull over it would idle fine and then same thing would happen after a few miles of starting out again..

 

Check the vacuum tank and lines and all was good. Turns out it was the driving motion shaking up rust scale from the bottom of the tank and partially blocking the fuel pickup tube every time the vacuum tank cycled on and was pulling fuel from the tank.

 

If the the car was pulled over and idling before it could completely stall, it would start to run fine again. Without the motion of driving, as soon as the  vacuum tank would cycle off, being no suction to the gas tank, the rust would fall back to the bottom of the tank until more driving stirred it up again to be sucked up enough to cause the engine to starve for fuel.

 

Dropped and cleaned the tank, sealed it with Hirsch sealer, and no more fuel problems. 

 

Paul

 

100% this. Junk in the gas tank masquerades as all kinds of other ailments. Even if you think your tank is clean, I bet it isn't.

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Watching the fuel level in the filter bowl, I wonder if the flapper valve on the inner tank is leaking allowing some suction into the outer tank and therefore the filter bowl.   If this is happening it would also be affected by the opening and closing of the carburetor float valve .  The suction from the engine is very strong and could easily cause some leakage around the flapper valve but with the other influences its hard to be certain what is happening.   It will be interesting to know what happens when you replace the flapper valve. 

Peening  the brass valve seats might stop them falling out but may not prevent leakage.   I would be more inclined to seal them with Loctite or better still fit a new top.  

I hope you post your findings.

 

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Thanks for your input everybody!

 

I think the idea of junk clogging up the sending unit is pretty plausible. The only thing that gives me pause is that when I've had the problem before my first thought was that was happening, and even blowing air through the line didn't seem to do much to rectify it. Sometimes it's been literally blowing by mouth back through the line, and nothing really changed. It might be that so much junk is floating around that it immediately clogs up. When I first started working on this car in 2017 the tank got some attention, but mostly in the form of throwing a bunch of nuts and acetone in it and swirling it all around to get rid of some of the rust, but it probably really needs to be opened up and blasted, if only to just remove it as a possible point of failure and help with peace of mind there. 

I'm also intrigued by the possibility that the vacuum intake valve on the vac tank might leak a little. It certainly didn't feel totally tight when I tried the the "close of the vent and try to suck through it" trick. I didn't think about the possibility that air might simply go around the edges of the seat, so I'm thinking I might put a little JB weld or superglue around the edge of the seat, just to be sure. I bought another tank assembly off eBay, which needs some serious cleaning but otherwise is in good knick. If all else fails I might try to fit it, but I need to try some other things first. 

Unfortunately, in the last few weeks I've started to hear a very slight knocking sound at startup and at high speed. I'm hoping that maybe it's just piston slap from some weak piston rings, or maybe just built up carbon. I did the "hold a brromstick to the engine and your ear" thing to listen to the sounds, and the closest I could find that sounded like the knocking noise seemed pretty high in the engine, so I'm reeeaaalllyyy hoping it's not any of the main bearings. I gapped the plugs a few days ago, some of which were pretty far out of spec, but I noticed a lot of carbon on top of the pistons and, presumably, around the valves. Gapping the plugs will help but I also adjusted the metering jet on the carb, which is adjustable. I think it was just way too rich. I'm also going to adjust the valves, which haven't been touched in who-knows-how-long, and I'll probably pull the head to do it, giving me a chance to look at the seats. And, having gone that far, I'm going to drop the pan, too, and double check to see if there's anything noticeably wrong on the bottom end. At the very least I'll get a chance to get rid of all that accumulated carbon, and make sure the valve train, which is pretty noisy, is to Packard specs.

All that will take some time, as I'm on a shoestring budget and I've got to save up a little bit to purchase replacement gaskets. I'm hoping I can get to that in the next few weeks, but I'll be sure to update this thread later so this might help somebody with a similar problem in the future. 

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When you have a fluctuating level in the glass filter bowl , if that is caused by junk in the tank or fuel  line then it implies that the vacuum tank is completely empty and receiving only a trickle but you have stated that the lower tank is full so even if there is a problem at the tank once  the vacuum tank is full then fuel feed is simply gravity to the carburetor and the problem is confined to the vacuum tank /carburetor area      Vacuum leakage past the flapper valve might be creating  partial suction in the outer tank especially if the lower tank vent is blocked or restricted.  There are vents to both the inner and lower tanks.  Make sure the lower tank vent is clear, and not blocked by the gasket between the top and outer tank

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For what it is worth I would recheck the brass vacuum valve seat in the diecast metal for looseness.  I do  not think that "peening" with a centre punch or whatever on the diecast metal to hold it is any real or lasting fix.  I would also check your oil to see if it is diluted with fuel.

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Hardest fuel supply delivery problem I ever had on an early car with a vacuum tank.......a small hole 2/3 the way up the pick up in the fuel tank. over 2/3 full the car was perfect, driving down the road as the level dropped in the tank we would get intermittent fuel supply problems. Tank was very clean and showed no obvious reason the line would have the issue...........Now on every car I buy I just pull the tank, cut it open to sand blast and seal it. The few extra days work is worth it. I have had too many cars with too many fuel issues to play fix the one component. I go through the entire system every time.

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Interesting but not relevant to this issue.    The OP says the lower vacuum tank is full . So why is the level in the filter bowl going up and down, it can't have anything to do with the fuel supply to the vacuum tank.   The fuel tank could be empty and the car should run fine until the fuel in the vacuum tank runs out.  

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One suggestion to help diagnose issues.  Install a vacuum gauge on the fill port plug and just let the car idle. You can watch the gauge for level of vacuum and how often it cycles.  If vacuum is really low or it takes a really long time under vacuum to fill or it cycles too fast or it is completely inconsistent, then you know something is wrong and that information will at least help you think through the mechanics of what is going on and help you solve the issue.

 

20181001_200935.thumb.jpg.6d6c40c9c16420c391f4e6cc98357a42.jpg

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I have had two problems with loss of power when driving.

1.  Shortage of fuel due to a worn out rubber vacuum line under the dash between two copper lines from the vacuum tank & the wiper motor.  Strange but it fixed my problem.

2.  On a 1953 Willies Aero after about 4 or 5 miles, the car lost power & would not get over 30-40 mph.  An 85 year old mechanic recommended the diagnosis.   The exhaust valve stem would get hot expanding and not closing the valve.  Had a shop do a compression check identifying the valves not closing.  A valve adjustment fixed the problem.

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If after all the recommendations above you are still having problems, keep in mind that on that era Packard the vacuum tank sits right above the exhaust manifold. Back in the 1960s we had a '29 Super 8 club sedan that would starve for fuel going down the road. We addressed it by insulating the vacuum tank, thus eliminating vapor lock. When I bought my '29 Super 8 roadster about 12 years ago, I had a metal shop match the shape of the vacuum tank with sheet aluminum, but leaving a half-inch or so of clearance on the sides and bottom (it did not extend over the top). I installed this shield, separating it from the vacuum tank with a layer of insulation (don't remember what type). And with that, plus other work to clean up the inside of the vacuum tank and ensure the flapper valves were clean and smooth, I can cruise that car any speed I want even in Texas summers. I even ran it at 75 for about 10 miles once when I got trapped among trucks on a freeway. Normally cruise 50-55. It has 4.07 rear end gears and 700x20 tires. I've read that today's gasoline boils at 160 degrees, so that could be something to think about if the above suggestions don't work.

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If we are to resolve the problem raised in the original post by DavidN1930 we need to address the surging in the glass filter bowl under the vacuum  tank, as clearly shown in his attached videos.  Why is the fuel level going up and down and why are there large bubbles ?  The fuel enters this bowl from the top and exists from the top so when ever the level drops the supply to the carburetor is interrupted and the the car will stall or at least loose power all as described in the initial question.

Vapor lock is a possibility and I have had to fit heat shields to my 1920's Packards but unless it is at least warm weather that is unlikely to be the problem.    A heat shield is essential for hot weather with these cars.

Incidentally fuel does not have  a single boiling point.  It is made up of a number of  liquids with varying boiling points and the lowest of which boils at around 40 Deg C . 

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