Dodge Brothers 1926 Stewart carb problem

[DB25Touring]

Mine is one of the last of the 12 volt DBs. Any help very greatly appreciated:

 

So, the metering pin in the valve of the Stewart carb detached from its washer, as they are known to do. Resoldered it to the washer, think I did a very clean job. Set the pinion shaft per Stewart instructions. Also tested floats with water test. Reinstalled all.

 

Cranked engine for a few seconds, and heard a loud pop. A neighbor yelled over and asked if I was OK. I assumed it was a backfire and always assume backfires come from the exhaust. But can't be sure. Tried cranking again and same thing. 

 

Adjusted the adjusting screw in both directions--leaner and richer. Same response. Removed the adjustment clamp and tried adjusting the pinion shaft in both directions--leaner and richer. Same thing--"back"fire.

 

One difference I noticed is that when adjusted richer, there were more pops, leaner, fewer pops. So, under some circumstance some kind of gas seems to be getting ignited.

 

Has anybody ever had these symptons? I've read about other backfires but they didn't seem to be quite the same thing. I've had the carb off four times and done the adjustments as required.

 

There are a couple of thoughts I've had for what to do next:

 

1. I realized that the part of the carb I never opened up was the metering valve. I wonder if it could have been clogged with varnish or other debris when the metering pin broke loose from its washer and got sucked up into the valve? I do recall seeing instructions somewhere for dismantling the metering valve but don't remember where. Can anyone help with that? Or another way to make sure the valve is clean? Solvents? I know you shouldn't stick metal into it.

 

2. I may recheck the float. After reading many comments in forums it appears there could be fine cracks? Also, I'm wondering what the sound of liquid gas in the float sounds like? I thought possibly I heard some veery fine debris very quietly rattling around, as if left over from the production process. But I did not hear any liquid sloshing. On the other hand, I'm half deaf. 

 

What I have done: replaced condensor and coil, adjusted distributor points, and checked plugs for spark. All OK. 

 

The car was running beautifully before the pin dislocated. I don't like the idea of ethanol in a car not designed or it so I only fill with the non-ethanol expensive stuff. Defeating myself?

 

I'm not a professional so if I missed something obvious, don't be afraid to tell me. I like learning from my mistakes. In fact, that's usually the only way I can learn! But I will never forget it.

 

Thanks.

 

John

 

P.S.: I know I am probably politically incorrect, but I have an electronic fuel pump on it and it runs beautifully at 1 1/2 pounds, as others have observed. I did have a rebuilt vacuum pump but have not had time to install.

 

 

 

 

 

 

 

[Lahti35]

1 hour ago, DB25Touring said:

Mine is one of the last of the 12 volt DBs. Any help very greatly appreciated:

 

So, the metering pin in the valve of the Stewart carb detached from its washer, as they are known to do. Resoldered it to the washer, think I did a very clean job. Set the pinion shaft per Stewart instructions. Also tested floats with water test. Reinstalled all.

 

Cranked engine for a few seconds, and heard a loud pop. A neighbor yelled over and asked if I was OK. I assumed it was a backfire and always assume backfires come from the exhaust. But can't be sure. Tried cranking again and same thing. 

 

Adjusted the adjusting screw in both directions--leaner and richer. Same response. Removed the adjustment clamp and tried adjusting the pinion shaft in both directions--leaner and richer. Same thing--"back"fire.

 

One difference I noticed is that when adjusted richer, there were more pops, leaner, fewer pops. So, under some circumstance some kind of gas seems to be getting ignited.

 

Has anybody ever had these symptons? I've read about other backfires but they didn't seem to be quite the same thing. I've had the carb off four times and done the adjustments as required.

 

There are a couple of thoughts I've had for what to do next:

 

1. I realized that the part of the carb I never opened up was the metering valve. I wonder if it could have been clogged with varnish or other debris when the metering pin broke loose from its washer and got sucked up into the valve? I do recall seeing instructions somewhere for dismantling the metering valve but don't remember where. Can anyone help with that? Or another way to make sure the valve is clean? Solvents? I know you shouldn't stick metal into it.

 

2. I may recheck the float. After reading many comments in forums it appears there could be fine cracks? Also, I'm wondering what the sound of liquid gas in the float sounds like? I thought possibly I heard some veery fine debris very quietly rattling around, as if left over from the production process. But I did not hear any liquid sloshing. On the other hand, I'm half deaf. 

 

What I have done: replaced condensor and coil, adjusted distributor points, and checked plugs for spark. All OK. 

 

The car was running beautifully before the pin dislocated. I don't like the idea of ethanol in a car not designed or it so I only fill with the non-ethanol expensive stuff. Defeating myself?

 

I'm not a professional so if I missed something obvious, don't be afraid to tell me. I like learning from my mistakes. In fact, that's usually the only way I can learn! But I will never forget it.

 

Thanks.

 

John

 

P.S.: I know I am probably politically incorrect, but I have an electronic fuel pump on it and it runs beautifully at 1 1/2 pounds, as others have observed. I did have a rebuilt vacuum pump but have not had time to install.

 

 

 

 

 

 

 

Perhaps take the float cover off and verify fuel in the bowl?

 

I have a '23 I was trying to get going last month and turned out the carb bowl was dry from a plugged up vacuum tank. I know you said you have an electric pump, but I would be inclined to check the carb bowl visually to verify fuel is present. If I had never serviced the whole carb I would take it apart and soak it in Berryman chem dip.

 

I just did the carb on my '20 a few months ago to and it was a little gummy, specifically the check balls in the bottom part were stuck. I verified my float was good by shaking it and listening for any liquid inside sloshing around. You can also submerge it and look for bubbles and again shake it to listen for liquid. 

 

Have you messed with the engine timing? 

[Mattml430]

Back firing is normally a timing issue. Start fresh from the beginning, get it to ign Before TDC and do a static time and see where it’s firing on number 1. 
Make sure also your leads haven’t been accidentally swapped around. 

Edited 14 hours ago by Mattml430 (see edit history)

[DB25Touring]

Checked there is fuel in the bowl. No, I haven't done anything to the timing. I did tighten up the distributor points a little, but after the first try.

 

But maybe I'll have to check the engine timing. 

 

That said, Lahti35, you did get me thinking. When I tried to start, there was no gas leaking from the float bowel. But it was coming out of the carburetor proper, and, if memory serves me right, from the bottom half. That makes me think once again that something might be clogging the metering valve stem when the metering pin disconnected and shot up the valve, perhaps pushing gunk into the valve. So I'm going to focus on that, first.

 

But if anyone knows how to clean out those metering valves or remove them to be cleaned I would appreciate hearing.

 

Thanks for your suggestions. Open to any and all.

 

John

 

[Mark Gregush]

Souldn't be coming out the carb itself unless the float is not shutting off the fuel when the bowl is full. 

By any chance are you running the electric fuel pump without a regulator? 

 

Edited 12 hours ago by Mark Gregush (see edit history)

[DB25Touring]

Aha! So maybe I do have a problem with the floats. But I do have a regulator set at 1.5 lbs pressure, if by regulator you mean setting the pressure. Or am I misunderstanding?

[DB25Touring]

But it occurs to me, what other way can a float be checked except the water immersion?

[Minibago]

The Dodge Brothers Stewart Carburettor is designed to work on gravity.

The float shuts off the needle on it’s seat when the desired level is reached.

No pressure.

Fitting an electric fuel pump even one set at 1 & 1/2 Psi is easily able to push fuel past the seat.

The original needle and seat are brass to brass leading to a wear groove around the needle.

A worn seat will allow leakage leading to the electric pump continuing to supply.

Myers early Dodge offer a soft seat insert to help with this.

Many Dodge Brothers owners can tell you stories of cars catching on fire due to fuel spillage caused by electric fuel pumps.

Just my ten cents for what it is worth.

[Minibago]