1925 DB carburator adjustments?????

[astroguy]

My 1925 Dodge touring starts and idles just fine, on full choke only. Application of the accelerator pedal and the engine dies. So what is happening and how to adjust? Has a Detroit Lubricator Company carb; Stewart J2B5.

I did have the carburator out and apart for general cleaning, everything looks OK. Went out for a drive and after about 20 minutes the engine started to die, felt like it was starving for gas. Got the car back home and thought possibly was starving for fuel and checked all the lines for the vacuum tank and all looks OK there.

One item I noticed is the accelerator pedal hooks up with rods to what looks like the choke butterfly valve. The choke rod on the dashboard connects to the bottom of the carb with cable. Seems like this hook up is backwards to me, but what do I know? The connections look to be 100% correct and the car has always run well in the past.

And just to clarify, the engine always starts and runs, at idle, with full choke.

Any help please?

Thankyou!

[cahartley]

The "thing" at the bottom of the carb is the "choke" but it isn't really.

It lifts the "valve" to flood the engine for starting so it is extremely important to have a strong enough spring to pull the lifter ALL the way back or you will run in a continuously flooded condition.

The knurled adjuster causes the needle to lift, which in this case brings it closer to shutting off the supply so leans it out.

There is no need for a high speed needle as the "mushroom" looking thing inside the carburetor reacts to vacuum and is self regulating working on exactly the same principle as Kingston ball carburetors.

These carbs are pretty amazing in their workmanship and it takes a bit to get your head wrapped around them.

Once those two adjustments are sorted you may never have to monkey with it again.......that is, of course, as long as the float needle is working properly.

This is also one of the easier carburetors for which to repair a leaky seat.

Make it a habit to shut off the gas supply to the carburetor when the car is going to stand for more than half a day.

That shows the details very well >>> http://old-carburetors.com/1927-Dykes/1927-Dykes-030.htm

Edited August 10, 2014 by cahartley (see edit history)

[MikeC5]

What do the plugs look like? If it's dying due to a flooded condition the plugs should look very sooted up or even wet with gasoline. If they are light colored/whitish, then it's leaning out. If too rich is the problem I would follow advice above. If you suspect lean, the metering valve may not free to move up/down to regulate air flow and air/fuel ratio via the tapered pin attached to metering valve and going through main jet.

[astroguy]

Thank you for two excellent replies. Spark plugs look "normal", black, no soot. Will make a copy of the Carb manual and go out to look this over. Guess my next step is to figure out how to measure the timing. Need to dig around in the garage for my old timing light, probably not used in 25 years . . . .

[Pete K.]

Your plugs sound OK. These low compression engines usually show plenty of very thin black soot on base of plugs, not so on the actual anodes of the plugs. They will have a sand color to the little area right at the center electrode. A couple of things to check in that carb is the metering pin in center of the mushroom valve is not broken loose from the dashpot & floating on it's own. The bottom end of pin has a tiny pin that is slightly peened to the dashpot, not rigidly peened. In other words the metering pin should flop around a bit if you held this assembly in your hand, out of the carburetor. Also check for any broken teeth on your rack gear in carb. If you had the carb off, you may not have the choke lever back on the right place on it's shaft, meaning you need to pull the choke out to keep it running.

Forget the timing light on the '25. Time it by the book, it's much easier.

[robert b]

My 1925 Dodge touring starts and idles just fine, on full choke only. Application of the accelerator pedal and the engine dies. So what is happening and how to adjust? Has a Detroit Lubricator Company carb; Stewart J2B5.

I did have the carburator out and apart for general cleaning, everything looks OK. Went out for a drive and after about 20 minutes the engine started to die, felt like it was starving for gas. Got the car back home and thought possibly was starving for fuel and checked all the lines for the vacuum tank and all looks OK there.

One item I noticed is the accelerator pedal hooks up with rods to what looks like the choke butterfly valve. The choke rod on the dashboard connects to the bottom of the carb with cable. Seems like this hook up is backwards to me, but what do I know? The connections look to be 100% correct and the car has always run well in the past.

And just to clarify, the engine always starts and runs, at idle, with full choke.

Any help please?

How about posting a picture of the carburetur so we can all see what you are dealing with and than it will make things clear for all of us to help you. Bob

[astroguy]

A few days have passed, went out and again started the engine, seems better and went out for a short drive seemed to be OK? My next drive was about a 1/2 mile and it started to run poorly and started back firing, so much so the local sheriff had been called out to search for someone shooting a gun, yes, very loud!!! So, now my guess is too much fuel all the time? I did download and print; http://old-carburetors.com/1927-Dyke...-Dykes-030.htm . this helps a lot. Now, need to wrap my head around this whole problem again. When I pulled off the carb for a quick clean and check, everything looked OK. I did not make any changes to the little arm for the dash cable. It does appear to be running in a flooded condition even though it feels like it is starving for fuel. I also found a copy of Mechanics Instruction Manual 1914-1927 for DB motor cars and Graham Brithers Trucks. This will help a lot.

Thanks again for everyones help.

[carbking]

It is possible you are looking at the wrong suspect.

Carburetors in general have no personality. If the carb functions well for 20 minutes, it will function well for 200 minutes or 2000 minutes or.....

On the other hand, one issue with your system that CAN (and often does) cause overfueling is the vacuum valve on the vacuum tank. If (when) the valve sticks open, fuel will be drawn directly from the vacuum tank into the intake manifold, completely bypassing the carburetor. It is definately worth a looksee.

Another possibility might be the ignition system. Ignition systems that will work when cool sometimes will fail when they are heated during driving.

Jon.

[MikeC5]

Are you sure the vacuum tank is working? Did you add fuel to vacuum tank to get it started? It will run for a short distance on a manual prime. If vac tank isn't pulling fuel it will soon go lea, run out of gas. If adding another prime to tank gets it going again then the tank isn't working. If it is truly flooding it could be Jon's scenario or perhaps a carb float or needle/seat problem. I had to get a new float for mine - it had small cracks in the brass and was filling with fuel. Luckily, repro floats are available.

[robert b]

A few days have passed, went out and again started the engine, seems better and went out for a short drive seemed to be OK? My next drive was about a 1/2 mile and it started to run poorly and started back firing, so much so the local sheriff had been called out to search for someone shooting a gun, yes, very loud!!! So, now my guess is too much fuel all the time? I did download and print; http://old-carburetors.com/1927-Dyke...-Dykes-030.htm . this helps a lot. Now, need to wrap my head around this whole problem again. When I pulled off the carb for a quick clean and check, everything looked OK. I did not make any changes to the little arm for the dash cable. It does appear to be running in a flooded condition even though it feels like it is starving for fuel. I also found a copy of Mechanics Instruction Manual 1914-1927 for DB motor cars and Graham Brithers Trucks. This will help a lot.

Thanks again for everyones help.

CHANGE YOUR CONDENSOR IN THE DISTRIBUTOR

[cahartley]

The vacuum tank idea is worth looking into.

The next time it quits drain the vacuum tank to see how much gas is in it.

(To fill the vacuum tank several revolutions of the engine with your foot OFF of the accelerator, and hand throttle closed, will have gas back in the tank in no time flat.)

[R.White]

I had a problem with backfiring. It was very loud just like yours and was due to fuel being drawn down the line into the inlet manifold from the vacuum tank exactly as Jon (carbking) described.

Ray.

[astroguy]

OP here. I opened up the distributer and found a silver metal box and after figuring out how to open, there inside is a condenser, looks like it was soldered to the metal box and also looks like that solder connection was broken. So, first, need to determine the correct condenser and then find one. My mechanics book talks a lot about tune ups and timing but no mention or photo of the condenser installation.

If the condenser does not cure the problem then I must agree the vacuum tank is next possibility. This is gonna require some thinking to figure out but the book should help on this.

Thank you again every one.

[R.White]

Have you tried re - soldering the condenser? There might be nothing wrong with it and that could be an easy fix for your problems.

Robert B knows his stuff!

Ray.