1924 Tourer fuelling

[Guest thetservice]

Hello all,

I am trying to get a '24 Tourer running but seem to be having a problem setting the carb up.

I drained the stale fuel and put in some fresh unleaded and eventually got the car to run using the autovac. However, now the car seems to run incredibly rich (puffing out black smoke from the exhaust and not running smoothly).

I tried adjusting the screw that acts as a stop for the choke lever as it seems to be the only form of mixture adjustment but it made no discernable difference. Any suggestions anyone?

It was suggested that modern unleaded is too "hot" for the car and I may need to add paraffin or kerosene to "cool" it a little. Has anyone had to do this on their car and if so, what sort of quantity are you using?

Many thanks,

Richard

[JayG]

I don't think it's a gas issue. I run regular unleaded and I'm sure many others do to. Where is your spark and choke set? These would cause what you're describing.

[Pete K.]

My 1925 tourer runs fine with modern crap gas, regular unleaded, with only a few ounces of Marvel Mystery Oil in tank too. You need to adjust the bellcrank on bottom of carb where choke wire is fastened to on the shaft that controls the fuel metering piston. I have no idea if your carb is either rebuilt or in "Known good condition". There could be an internal problem. The tall , ribbed screw on that is for fine tuning only.You shouldn't be carboning up that bad. If the smoke is all black, that's gas you're burning. blueish/white is oil burning. That engine won't have a big problem with fresh gas, it's not burning "too hot" with modern gas. You need to pull plugs and clean them, adjust them, they may be carboned up. Your spark lever is down for starting car, up when she's running. It has no effect on your fuel/air mixture. Only the dash control for mixture is your choke button.

Edited March 8, 2013 by Pete K. (see edit history)

[MikeC5]

Yea it's not the gas. I suspect it is a carb issue. These carbs have a floating piston that regulates the fuel/air mixture and if were to get stuck it could cause your problem. The dash cable goes to a small 'rack and pinion' gear set up which is used to richen the mixture for cold starting. This could be maladjusted or stuck. These carbs are pretty easy to take apart and there is some technical information on them available on the web. Here is a link to some info:

Stewart Carburetors reference book from 1927 especially for Dodge restorers.

[Pete K.]

Some internal problems I've seen with the Stewart carb in question are; Stripped teeth on pinion gear, Metering pin broken loose from piston, clogged passages in piston and metering head. Bungled up metering pin seat, Carbon crud build up on metering head and stem (this has to float freely up & down). Mis-adjusted choke lever arm to rack & pinion assembly. Air leaks at main body and throttle shaft. I'm not even getting into the float chamber.

[Pete K.]

One thing I missed in your post Richard; I hope you don't refer to the modern gas you are using, otherwise known as E-85. Don't ever put that crap in your old cars.

[Guest thetservice]

Yea it's not the gas. I suspect it is a carb issue. These carbs have a floating piston that regulates the fuel/air mixture and if were to get stuck it could cause your problem. The dash cable goes to a small 'rack and pinion' gear set up which is used to richen the mixture for cold starting. This could be maladjusted or stuck. These carbs are pretty easy to take apart and there is some technical information on them available on the web. Here is a link to some info:

Stewart Carburetors reference book from 1927 especially for Dodge restorers.

That's great, thankyou!

I set the carb with the metering valve head fully open when the choke is closed, maybe I have set this wrong. I'll have a good read of the info you provided and hopefully get somewhere with it.

[Guest thetservice]

Pete,

I have regular unleaded. That ethanol is a killer for any car, not just our "oldies". Sadly, our government plan to allow the 10% ethanol content fuel to be sold here soon.

Regarding the spark advance/retard, I am starting the car as you say with the lever down and the hand throttle part way up, then advancing the spark once she's running (same as on the Model Ts I'm used to).

The rack and pinion assembly is working in the carb and is lifting the metering head (piston) but maybe I have set this incorrectly? I would assume that with the choke off the piston should be fully lifted? It seems logical that the piston is acting like a butterfly on a conventional carb?

Thanks for the advice Pete and Mike.

[MikeC5]

Glad to help getting another DB on the road. The way the choke is supposed to operate is when you pull out the dash knob, the pinion gear rotates to move the metering pin down relative to the piston (at rest in the down position). As a result, the tapering part of the needl;e opens a larger annulus between needle and jet thus richening the fuel to air ratio. From your description it sounds like you may be doing the opposite. The idea behind the piston is to maintain a constant f/a ratio and not simply metering the mass air flow (as a butterfly valve does). The piston responds to changing load (vacuum) and meters fuel via the tapered needle appropriately. If you ever seen S.U. carberetors on British cars, they use this principal also except the needle is connected to the piston and moves instead of the jet.

[platt-deutsch]

Be sure the float is not full of Gas. Put it in a can of gas and be sure it floats..

[MikeC5]

Good point PD. The old brass floats have a tendency to develop small cracks. I bought a new repro from Meyers.

[Pete K.]

Yes, Those old floats do develop leaks. I test mine in a bowl of very hot water in my kitchen. Once submerged, the hot water expands the air in float and you'll see a tiny air bubbles at a leak. Have a marker pen at hand to circle the area leaking. Don't hold it under long, so as you don't let water into the float. If water gets in the float, you need to drill a tiny hole, usually at the soldered seam (I do anyway), to drain water out. You can carefully heat the float to "steam-out" water. Sometimes I let float sit for a few days with a tiny wire set into the drill hole facing bottom. Then solder up your drill hole using a minimum amount of solder. I've had success doing this on a few old car floats and it saves a lot of bucks!

[Guest thetservice]

Yes, Those old floats do develop leaks. I test mine in a bowl of very hot water in my kitchen. Once submerged, the hot water expands the air in float and you'll see a tiny air bubbles at a leak. Have a marker pen at hand to circle the area leaking. Don't hold it under long, so as you don't let water into the float. If water gets in the float, you need to drill a tiny hole, usually at the soldered seam (I do anyway), to drain water out. You can carefully heat the float to "steam-out" water. Sometimes I let float sit for a few days with a tiny wire set into the drill hole facing bottom. Then solder up your drill hole using a minimum amount of solder. I've had success doing this on a few old car floats and it saves a lot of bucks!

Yes, I have checked the float. It's a fairly common thing with the floats used in Model Ts and I test them in the same way. I suspect it is more a setup problem so I'll start with that when I get a little time.

Thanks Guys!