VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 12V fuel pump

Hi Gents,
I found a 2014 thread re electic fuel pumps but it does not answer my problem. Please help.
Elderly friends just bought a 28 Tourer with a 12 system. The new 12v fuel pump is obviously over powering the fuel system and I was asked to help.

How do I slow down the 12v pump? Could I add a reistor to reduce the power to say 6v.
Any suggestion would be much appreciated.
Regards
Chris

I would remove the 12-volt fuel pump, pack it up securely, make a trip to the Grand Canyon, get as close to the edge as possible, and chunk it.

When you return from your trip to the canyon, remove the 12-volt battery and put it in the garage on a float charger.

Remove all of the 12-volt bulbs and replace with 6-volt.

Replace the battery cables with welding cables.

You didn't say, but I suspect it has an alternator. Well, we are too late to wrap it up and take to the canyon. Anyway, reinstall the generator and cut out.

Give the engine a good "tune-up", and let's go for an extended drive.


PS: No! Charlie did not write this.

Hi Ray,
TKS for the advice, but no can do. We are if South Africa and a trip to the Grand Canyon is out of the question.

The deed is done and we have to live with the 12v system for now. Unfortunately the best I can do for these people is to somehow slow down the pump.

Any other ideas please.

Regards
Chris
Cape Town

Hi Chris,

Why don't you fit a vac tank, they were original and lasted many years.

Too many people don't have the patience to restore a vac tank, and cant replace with a fuel pump quick enough.

I have run a vac tank for most of my 42 years with a 28, fitted a fuel pump, nothing but trouble, straight back to the vac tank, no issues.

Regards

Ray

TKS Ray,
I'll have to go have a look if this car still has it's vac tank. Where does this tank live? Where can I find out how it is supposed to work.
Cant I just drop the power to the pump down to 6 to 8v and voila, fixed?
This is not my car and I am looking for a quick fix.
Regards
Chris

Chris,
There are two things to try. First a resister to lower the voltage. Don't know the current requirement. Expect a resister like used on early 12volt ignition systems would work. The second is a pressure regulator. A few have good luck with them but the majority that I have worked on (probably because they were not working well) weren't reliable at the low pressure required to keep the carburetor from overflowing.

I only use vacuum tanks. I learned to rebuild them so I could ensure I always had a working one. Supplied them to several friends.

Tks Chip,
I suggested a resistor but fortunately it is not my car or my problem, although I would like to help if I can. I went over to have a good look at the setup and low and behold, the vac tank is still there. It is half bypassed and unfortunately one of the connections on top has been broken off. They have a mechanic helping them but he is not an old car guy.
Lets see how far they get. I'll step in if they ask.
Thank you very much gents.
Regards
Chris
Cape Town

These cars are out of my wheelhouse, but I think can offer some thoughts. I would not mess around with the supply voltage to the pump that will contribute to early pump failure. I know Holly sells a fuel pressure regulator, installed with a fuel pressure gauge you might be able to get control on the problem.
I would only guess that the original fuel pressure needed if any is less then a pound? So you would need to find a real, real low pressure electric pump if they even make a 1-3 pound PSI pump. Another way to decrease pressure is to increase the diameter of the fuel line on the supply side of the pump, while keeping the feed side of the pump the same diameter that you have. This would be trial and error and maybe a clear filter might be more helpful then a gauge so you can see what is going on. I think getting the fuel delivery down to a trickle might be what you need in this case.
Good luck

Chris, I highly recommend that your friend get a copy of the shop manual. Many vendors sell reprints.

I also vote for putting the original vacuum tank into service. I've been running my '27 with a vacuum pump for over 20 years with few problems. AND, I don't think it was ever opened up.

Inside the shop manual, you'll find a lot of info on the vacuum tank system. For additional information, see this document:
http://www.hudsonterraplane.com/tech/1927/StewartWarnerVacuumTank2-11-27.pdf

As for the broken fitting on the top of the tank, a quick fix might be JB Weld or similar product. If needed, there are vendors that sell new tops or you can buy a reconditioned one from one of the VCCA members that restore these units.

I know a couple of folks that have the electric fuel pumps and they are constantly having problems keeping the pressure low enough so as not to overwhelm the carb.

All my best, Dean

I'm no expert by any stretch but you could try a simple fuel return system so the excess fuel and pressure return to the tank and have less chance of overwhelming the float in the carburetor.

It is a simple process to correct. Go to almost any auto part store and ask for a inline fuel pressure regulator. You can cut into your fuel line and place in the regulator and easily control the flow so to not over pressure the fuel into your carburetor.

I do agree with most of the other posts, going back to a simple original vacuum tank is best since neither the pump or the regulator have a long life. Most always carry a spare with them and the tools to replace them when they tour.

Hi Chris, I'm in Johannesburg and rebuilt a '28 tourer about 6 years ago. It was a basket case that I got in Barkly East. It came with a vacuum tank that had no internal mechanicals and the tank itself was perforated from the rust.

I converted to 12v by changing the field coils in the generator and left the original cut out. I put a resistor in the hooter and that works fine. I have a 12v pump without a pressure regulator, instead I focused on the needle and seat. The hole in the seat is slightly smaller so it requires less force from the float to close, but with a higher pressure the fuel flow rate is the same. The needle is also one of those rubber tipped ones. In the 6 years that I have driven the car, I've never had any flooding problems.

As you can understand, parts availability in South Africa is not the same as the States so "'n boer moet 'n plan maak". After 6 years I'm still on the hunt for roof irons for the canvas top and can't find any. I just don't go out if it is going to rain.

Please contact me via PM if you need any help.

Australian Hood Irons can probably help you with a top assembly for your 28 tourer.

Gentlemen, thank you very much for you suggestions and advice. Your imputs are much appreciated.
My friend is not a car guy, he loves his old Chevy but cannot fix it himself. He has a mechanic helping him by the hour, if you catch my drift. I dont know for how long though.

I dont know the 28( I have a 29) but I'll help if need be. In the meantime I can share my newfound 28 knowledge and you advice.

I'll study the operation of the vac system in the mean time.

Dankie DaveT. I think thier problem lies with the float and needle sticking because of the high pressure.
Thanks guys
Regards
Chris

Hi Chris,
The original Carb was designed to operate on a gravity feed from the vacuum tank on the cowl. The needle valve float was not designed for more than 3 PSI. Someone may have purchased a fuel pump for a Fuel Injected vehicle. They run 45 - 60 PSI.
Lowering the voltage will not reduce the pressure but it may not operate. (Automotive electric fuel pumps are designed to run at a constant pressure. They build up to a pressure and shut off.)
I suggest checking the pressure to be sure you have the right fuel pump for a carb.

Hey,

I agree with Lou, the original Carter carby was not designed for an electric fuel pump.

How about this for an idea, take off the fuel pump that the car was not designed for and get the vac tank working.

Pretty simple, and the results are worth the effort.

Cheers

Ray