VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc Vacuum or electric fuel pump?

Hi folks, I'm hoping someone can help.

I have a '28 Coach, I have 2 original carbs for it, both of which need attention, and the original vac tank and float are beyond repair. I'm in the UK and these things are super rare here.

So I'm running it with a Zenith14991B carb fed by an in line electric pump, this setup works very well, the motor starts first turn and runs very smooth and reliably, I'm tempted to keep it.

I am aware of the dangers involved in using an electric pump in our old cars without an engine oil pressure cut off, but the carb specs says it needs a pump, not gravity fed.

I would much prefer to use a vac tank as they seem more reliable and the safer option, and have now obtained another one that seems OK.

So my question is this:

Has anyone used a similar Zenith carb fed by a vac tank (in effect gravity fed) without any fuel starvation or weak running problems?

Bernard

The fuel valve in the 14991 is Zenith number C81-1-40. If you go to vacuum tank/gravity feed you will need to replace with C81-1-55.

CAUTION: If you drill it out, you cannot "undrill" it should you wish to go back to the pressure pump.

Jon.

Thanks Jon, I hadn't thought of that, seems a simple fix, I'll get one ordered asp.

Bernard

Most vacuum tanks will interchange irrespective of make (may not necessarily correct for that car) but should operate.
Tony

Thanks Tony, I have looked at a few, some are more complicated that others, but the end result is the same.

Mountings are the big problem when you dont want to drill more holes. There are really 4 requirements that cannot be changed 1) mounting (several options) 2) a supply line from the tank 3) outlet to carb and 4) is a vacuum scource. The internals can vary greatly but all have the same result, it is only the complexity that changes.
Tony

The ones fitted to '28s seem to be the simplest of the lot, but the floats split because of the constant pressure changes, mine had so many soldered up cracks that to was too heavy.
I cleaned off the solder and wrapped it in a thin layer of glass fibre, it worked fine until the modern fuel turned the resin to mush!

Have you thought about coating it with fuel tank sealer?

Despite claims to contrary I have not found a fuel tank coating that will not begin to flake off after an extended period. I must admit I haven't tried any in the last few years. Just rebuild a Steward 8 screw tank that was coated with something. Finally had to physically scrape of as much of the coating as I could from the inside of the outside tank and outside of the inside tank. It was flaking and bubbling. There was a layer of rust and polymerized gasoline between the coating and metal. Since I don't know the history don't know what the coating type or brand.

I have used several reproduction floats. They work just fine.

A word to the wise: While on the VCCA Tour in Riverton WY, I experienced fueling problems with my '28 Coupe. After I got home I replaced the fuel tank, vacuum tank and carburetor. The internal vacuum tank looked like Swiss cheese. The bottom of the carburetor was severely corroded and the gas tank coated with brown crud. I tried to clean the tank by rinsing with lacquer thinner and acetone without much success. Tumbling with crushed gravel, drywall screws had moderate success. I now drain the gas tank, carburetor and vacuum tank if more than a few months between use. Car performed flawlessly in Altoona, IA this past month. Oh, yes! If at all possible I use ethanol free gasoline. Been using that in my small engines as well. Though it costs more it pays back in less problems. Though I have electric booster pumps on several of my vehicles I use the stock type pump on all of them when driving. They are MUCH more reliable. Heard two more stories just this week about problems with pressure regulators and/or electric pumps over-pressuring needles/seats in carburetors.

As an demonstration try putting a shallow dish with an inch or two of gasoline with ethanol in an outside shady spot. Check every few minuted. How long does it take to form beads of water in the bottom of the dish? Yes, those clear beads that form are water! Happens here in only a few minutes dewpoints in the 60s-70s. Might take longer in the desert. Where that water bead sits is the next rust pit!!!

I put gas tank slosher sealer in my 35 coupe tank 30 + years ago from BILL HIRSCH. Its still in there.

mike lynch

Chipper
As I understand the story, that is why most modern cars have plastic tanks, because of the water absorbtion ability of ethanol in the fuel.
Tony

Hi Jon, despite exhaustive searching I'm having trouble locating a C81-1-55 valve, are you able to point me in the right direction, do you have a link?

Bernard