by pass vacuum tank?

Can I by-pass the vacuum tank on a 1927 Studebaker by adding a 6 volt electric fuel pump? At cruising speed (45mpg) the engine seems to be starving for gas. Maybe not enough vacuum to fill the tank. As when the vacuum wipers quit while accelerating.

Yes, you can bypass it. However, be sure to use a low pressure fuel pump. This is what I use in my Model T's http://www.amazon.com/Airtex-E8011-Electric-Fuel-Pump/dp/B000DT7Y70/ref=sr_1_1?ie=UTF8&qid=1423602827&sr=8-1&keywords=airtex+fuel+pump+6v

Yes, you can bypass it. However, be sure to use a low pressure fuel pump. This is what I use in my Model T's http://www.amazon.com/Airtex-E8011-Electric-Fuel-Pump/dp/B000DT7Y70/ref=sr_1_1?ie=UTF8&qid=1423602827&sr=8-1&keywords=airtex+fuel+pump+6v

Ok, I've seen those electric fuel pumps before. Can I use it in line with the vacuum tank? i.e to keep the vacuum tank full when running at cruising speed or at low vacuum while accelerating?

No, you really should take the vacuum tank out of the system if you're using the fuel pump. Otherwise, the fuel pump will completely fill the inner & outer tanks of the vacuum tank and eventually push raw gas into your intake manifold through the vacuum line. Doesn't mean you have to remove the vacuum tank of course, just change the plumbing.

OK, got it! Thanks.

A better solution might be to repair your vacuum tank. I have a '29 Packard with a 385 cubic inch engine fed by a vacuum tank. Once I diagnosed the vacuum tank and did some simple repairs, I've driven the car thousands of miles, including in the mountains of Colorado, without trouble. The only time I starved for fuel was on a 10-mile continuous climb in Colorado, with full throttle much of the way. I pulled over and let the tank catch up for a few minutes. Odds are that your tank is more than adequate if it's in proper order. First thing to check is make sure that the inlet screen, if there is one, is clean. There is a reason that fuel pumps replaced vacuum tanks -- but in normal antique car driving, you're unlikely to ever hit the limit if your tank is working properly. Once you achieve that state, a vacuum tank causes less trouble than an electric fuel pump -- and it doesn't require electricity.

I fully agree with James... "a vacuum tank causes less trouble than an electric fuel pump -- and it doesn't require electricity".

Can I by-pass the vacuum tank on a 1927 Studebaker by adding a 6 volt electric fuel pump? At cruising speed (45mpg) the engine seems to be starving for gas. Maybe not enough vacuum to fill the tank. As when the vacuum wipers quit while accelerating.

I note that you say "seems to be starving for gas", so my first reaction would be, find out if that's true before messing with anything.

Can I suggest you pick a quiet piece of road and run it at speed until you encounter the problem; at this point, given its safe to do so, turn the engine off and coast to a suitable pull off spot, now see if the vac tank and carb have any, or correct levels, of fuel in them by lifting the top off either, assuming all this is achievable without too much difficulty.

Like others, I have motored many miles with vac tank vehicles, not without problems, but have managed to make repairs without having to resort to electric pumps, pressure regulators, wiring, re plumbing etc.

Hi,

I've also done many miles on a vacuum tank with no problems, if your tank is in good working order there should be no problem. You can plumb a 6v pump in line with your vac tank, but have a switch close by, so that you can turn it off when needed.

I would look first at your gas cap, is the vent on the cap clear? If not your vac tank is sucking against a vacuum in the gas tank. Secondly look at your carb, is the float level right and are the jet sizes right? Lastly check out your ignition condensor and coil, they could be breaking down under load and can often give you a fault that appears fuel related.

Regards

Viv.

May I say that hchris (post number 8) gave the best advice.

I quote

"I note that you say "seems to be starving for gas", so my first reaction would be, find out if that's true before messing with anything.

Can I suggest you pick a quiet piece of road and run it at speed until you encounter the problem; at this point, given its safe to do so, turn the engine off and coast to a suitable pull off spot, now see if the vac tank and carb have any, or correct levels, of fuel in them by lifting the top off either, assuming all this is achievable without too much difficulty.

Like others, I have motored many miles with vac tank vehicles, not without problems, but have managed to make repairs without having to resort to electric pumps, pressure regulators, wiring, re plumbing etc."

First determine if the fuel is starving, then choose a plan of repair. Check for vacuum leaks in the engine manifold, vacuum line and fittings, and all around the tank itself. Tanks commonly leak around the top of the tank where the top mechanism bolts on. Make certain the drain flapper valve fits properly and seals off the back-flow (very important). Make sure there are no pinholes or cracks in the inner chamber part of the tank (also very important). Also make sure all the fittings and all the lines in both the fuel lines and the vacuum lines are not plugged a little (or even a lot). And do make sure the fuel tank or cap is properly vented, otherwise you will develop a vacuum inside the gasoline tank and a vacuum to vacuum tug-of-war will begin, and pull very little gasoline.

I, too, have run several cars with vacuum tanks. Yes, I have had my share of trouble from them. Once I got them working right, they mostly have been very reliable and I like them. Just like a timer and coils are part of the heart and soul of a model T Ford? A vacuum tank is much the same to many non-Fords.

One other nice thing about a vacuum tank. Even if it fails. A small can to drain gasoline from the main tank and transfer to the vacuum tank can get you home. Most vacuum tanks hold more than a quart, if your car gets about 20 mpg, you can drive in roughly five mile jumps between refills. I have done that.

I also had a vacuum tank fail in an unusual way for which there were good reasons and a long story that I won't clutter up this thread with. The float failed most impressively, and sank. This resulted in the engine sucking raw gasoline straight into the intake manifold. This was a car in need of a lot of work yet, and we had taken the challenge of an endurance run with it. Among the extra "tools" we carried that day, was about three feet of rubber fuel hose. I cut it into the vacuum line near the vacuum tank. Looped the hose through the firewall where it could be reached by the passenger, then cut the hose in a convenient location. We manually controlled the vacuum air to the vacuum tank by connecting the cut hose for a ways which allowed the tank to fill. When we felt the tank was full enough, we disconnected the vacuum line and plugged the hose going to the intake manifold with a spare bolt. In this way, we kept going for many miles and up steep hills.

Could you do that if an electric or mechanical fuel pump failed? Huh?

I have had four cars (including one model T Ford Boat-tail roadster) that used vacuum tanks and I drove all of them quite a bit. By far, most of those miles have been virtually trouble free. The few times I had trouble? I was always able to get it home without a trailer or tow.

Drive carefully, and enjoy, W2

Hi Again,

We also had a problem on a chev, running a Stewart autovac with the diecast potmetal top. It took ages to find the problem. The 2 valves attached to the float have brass inserts pressed into the pot metal, we had one that had become loose and every now and then it would drop out of position upsetting the vacuum from working properly with a shortage of fuel. Once I found the problem it was an easy fix, just use bearing locktite to bond it into place. The car has never missed a beat since.

Viv.

I have had exactly the same experience as viv w with one of the brass seat inserts coming loose causing loss of suction. I replaced the top with a reproduction one. I have covered about 30,000 miles in 1920's cars with vacuum tanks with no other problems with the vacuum tank.

I would consider an bypass electric pump only to overcome vapor lock problems otherwise fix the vacuum tank, they are a very simple device with lots of information available on the internet.

Let me add my 2 cents. ( I may get chastised, but here goes) I also had a Studebaker with a vacuum tank, 27 Big Six President. I had the same problem with starving for gas at higher speeds. It seems that the vacuum tank has one problem, it needs to deliver maximum volume of gas at minimum engine vacuum. At lower speeds, say 30 - 40 MPH, I had plenty of volume and never ran out of gas. When I hit 50 MPH, I ran out of gas every time. Each time, I would simply fill the vacuum tank with about a quart of gas and then move on. I plumbed a low pressure pump into the system, bypassing the vacuum tank and never had the problem again. The original vacuum tank was left in place with all of the original plumbing blocked off and it was hard to see the plumbing from the pump. Never looked back....

Frank

Frank,

The high speed fuel starvation problem you experienced is not uncommon. The fix is also quite simple. Either the fuel line from the tank is restricted, or there is a vacuum leak in the system. A dent, kink or solids build up in the fuel line are typical restrictions. Leaks in the vacuum system are also easily diagnosed by spraying starter fluid or WD-40 around all vacuum connections while running at idle. If the engine speeds-up, you found the leak. Be sure to spray the lid of the vacuum tank to detect any micro-fractures (cracks) in the pot metal lid especially around threaded connections. These too are easily sealed with Crazy Glue or gas tank sealer which is resistant to modern ethanol fuels.

I might add that in case of a vacuum tank failure it was possible to fill the tank manually and drive 5 - 10 miles before filling it again. You can't do that with a fuel pump, if it fails you are stuck.

I rebuild stewart warners for a hobby I have a Full time job.I just restored one for a Mercer,he wanted 2.One for the electric hidden in the tank.He is running on 1 tank,the one we restored,I talked him out of the fake tank.There is now way I would put a electric pump on My old car without a fire truck close behind.We also sell the rebuild kits for the stewart tanks.

Hi Again,

We also had a problem on a chev, running a Stewart autovac with the diecast potmetal top. It took ages to find the problem. The 2 valves attached to the float have brass inserts pressed into the pot metal, we had one that had become loose and every now and then it would drop out of position upsetting the vacuum from working properly with a shortage of fuel. Once I found the problem it was an easy fix, just use bearing locktite to bond it into place. The car has never missed a beat since.

Viv.

I had that exact experience with mine and fixed it the same way too!.......

I have a 1928 Chevrolet and a 1929 Chrysler that I gave up of the vacuum tanks and I am using electric pumps. I have installed low pressure pumps and also used a bypass in the carburetor gas intake to collect any excess of fuel and return it in an independent fuel line to the tank. In other hand, I have 1929 Dodge-Brothers that runs perfectly with the vacuum tank. Currently I am having deep issues the vacuum tank of my 1929 Hudson SuperSix, and I believe is vapor lock. Differently of the other cars, the vacuum tank of the 1929 Hudson is in the firewall opposite side of the carburetor, so the fuel line passes behind the engine. To add an additional difficulty, I live in Brazil, where most of the time we have warm and hot weathers, and the gasoline has 27% of ethanol (Brazilian law requirement, unfortunately). I have wrapped the fuel line with heat insulator, but with weak results. When I increase the speed the engine suffers of starvation, despite the fact the vacuum tank is full. I have checked twice already, that when the engine starts to lack of power I had more than 2 liters of gasoline in the vacuum tank. So apparently the vacuum is working well in the aspect of getting the gasoline from the fuel tank to the vacuum tank reservoir, however, it seems the gasoline is not flowing with the right pressure to the carburetor. Any chance to escape from the electric pump in this 1929 Hudson?

Regarding the Old Car Fan comment about have a fire truck following the car with electric pump. What kind of measures should be taken, when using an electric fuel pump, in order to reduce risks of fire?

Thanks,

JRA

Hi...JRA,,,Have run many miles on vac tanks,,,they'r OK

Re ,Gett'n the gas to the carb,,,is there any COILS in the pipe

from tank to carb,,,Sometimes there is a AIR bubble in the line

that will act much as a vapor lock,,,If you suspect something like

this Make up a substatute tube of clear plastic so you can see

the flow,Test the hose in gas to be sure it won't get soft,,,,,Hope

this helps,,How hot are your summers,,

I'm in North-East US its rarely hot here,,Cheers,,Ben

Thanks for the Reply, Ben. There are no coils in the pipe. It is descending and straight. Summer temperatures goes from 80F to 100F. The gasoline has 27% ethanol and I live and drive in a city about 950m (3116ft) above sea level.

Thanks

Julio

Hi,,We are about 10f degrees cooler,,elevation around 500-1000 ft

If you still seem to get blockage without the block,,,still try plastic

clear what ever,,be sure its gas resistant tho,,,

Alternate trial would be larger line,,,easier for bubble to navagate

the pipe,,,

Look the whole thing over,,,most complicated problems turn out simple

stuff not noticed the first time,,,Good luck,,Ben

One of the daingers of both electric and vacuum tank together,,,

if the tank gets full,,then gas may be forced out the VENT line,,

this is a short [4-5"]small tube in lettr Ushape,,would spray out

an down,,prolly right onto the hot manifold,,!!

NOW,,,IF,,,,the flat flapper valve on the bottom of inner tank

was leaking on the vac cycle,,,it might pull a vacuum on the

lower chamber thus starving the carb',,,Just sayn,,

Is the land hill/flat,,what speeds are we talking,,,

Here we have interstate,,an' back roads all hi gear

well mostly,,,Cheers,,,,Ben

Hi JRA,

Your temperatures in Brasil are probably similar to the USA in summer, so I don't believe that is your problem. I'm in Southern Africa and drove my old Chrysler in similar and even hotter weather, particularly Kariba and Victoria Falls when temperatures were in the mid 40's centigrade, this was when we had no ethanol in our fuel and I had no problems, so I don't believe warm weather to be the main factor.

In Zimbabwe we now have mandatory 10per cent ethanol and it is causing all sorts of problems. I have been on the net looking at sites related to problems with ethanol and unleaded fuel. One of these sites had an article about vintage vehicles and the engines running hot. In the old days fuel was not so good and the octane rating was probably at best 65, the engine compression ratio was much lower.

The article explained that with todays fuel, with 87+ octane (and ethanol making it even higher) these low compression motors do not burn the fuel properly, with the result that the burning fuel is pushed out the cylinders into the exhaust and resulting in the engine running very hot. I had this problem with my Chrysler 4 where the manifold and exhaust would get red hot on a long run and literally glowed at night. It wasn't until I saw this article that I came to understand why it did this. The article recommended putting some diesel or even paraffin into the fuel to reduce the octane level of the fuel.

We have been considering adding water to our fuel, let it sit 24 hours to absorb the ethanol and then drain off the ethanol at the bottom, before using it in our cars, will let you know if we do and the results.

Another article, I saw in The Chev Car club of America magazine recently, they recommended enlarging the main jet in the carb by several sizes if you are using blended fuel, this they say will make the car run smoother.

I welcome input on this from other members.

regards

Viv.

Vapor lock is usually formed in the suction side of a fuel system. Like from the fuel tank to the fuel pump, or fuel tank to the vacuum tank. The low pressure in line allows boiling or bubbles to form at lower temperatures.

On many older cars, the fuel line from the tank needs to be relocated as far away from the exhaust system as possible.

For a Vacuum tank car that is having running problems but the vacuum tank is full, that rarely would be vapor lock. since the fuel from the vacuum tank to the carburetor has a slight pressure from gravity.

I would look into the temperature of the carburetor itself. Is there a way to control the heat from the exhaust manifold that was necessary when the car was built, due to lousy old fuel? Modern fuel, especially with 10% and more ethanol does not need much if any carb or manifold heating. I've figured out ways to isolate and insulate the exhaust manifold from the intake manifold with great results.

The message stating the need for larger jetting with ethanol mixed gasoline is also a good point. With 27% ethanol, a low compression engine with only a gravity feed fuel supply from the vacuum tank to the carb's needle and seat, might be starving for enough fuel flow. But not vapor locking.

Another thing to try: use steel fuel line from the Vacuum tank to the carburetor.. Steel will absorb or conduct heat slower than copper. Then slide a length of woven 'loom' over the steel fuel line before the last flare nut and rolling the flare on the end of the line.

Make sure your float and needle and seat mechanism is not hanging up, and not allowing fuel into the float bowl. This mechanism can be affected by heat.. and it d*** well be affected by the cleaning effect that ethanol has on metal parts.. Too clean and not enough lubricity in the ethanol fuel will cause float mechanisms to stick.

If your carburetor is too close to your exhaust pipe, wrap the exhaust with the woven fiberglass insulating wrap, often called 'header wrap'. this will greatly reduce the amount of heat radiating from the exhaust pipe.

Hopefully one or more of the above suggestions will help with your poor running situation.

GLong

Does this starvation occur when the car is first out,,as in 3-5 miles

Or after a longer heat up time,??

If the engine gets really hot,,the valves,,especially the exhaust

will grow in length from the heat,,,AND NOT seat,causing the

engine to heat and valves [ex] to burn and loose their seal,,

My packard floorboards got so hot my feet felt to be on fire,

I found a non ''formulated'' filling station,,tanked up ,,all back

to normal,,,old times,,I increased the valve clearence from

,002-004,,,to,,,,008-,016,,,I'LL reduce this by trial and error

after I lap the valves again,,,But for now its safe,,

Cheers,,Ben

The "fuel starvation" starts after the 2nd mile. And you are right to say it is running very hot. I have already checked the timing, following the instruction book, and it is ok. The tube is already wrapped with fiberglass whool, so I will try to cover the exhaust manifold too. The carburetor has just received a new repair kit from Carburetor King. I believe enlarging the carb jet could be an interesting thing to try. If I use a electric fuel pump, what kind of pressure should be delivered at the carburetor inlet? 2 psi? 3 psi? Thanks, Julio