1923 Firestarter

[Guest actor]

I have a 1923 Dodge Brothers Depot Hack (woody). I've had two engine fires as of late... both seeming to be the result of fumes/gas igniting from the carburator float chamber. It does have an in-line fuel pump with a seperate flow regulator/valve which is set to about 2.5. I am really stumped as to how to prevent future eruptions. I don't see in the manual where there should be a gasket under the lid, but that could be one possibility. Any suggestions?

[Guest DBtouring]

The carb float and needle valve on these cars cannot handle the pressure from a fuel pump. They will overflow every time. The pressure from the gravity flow of the vac tank is not enough to open the needle valve. Of course it can leak if it is worn, but get rid of the fuel pump and go back to the Vac Tank. It works fine. Haven't had any problem with mine since I got it working 4 years ago and it is a lot safer than an electric fuel pump.

[Guest actor]

I will definitely try disconnecting it. Can I leave it in place and simply disconnect the power supply without it interfering with the flow?

[dwollam]

I have worked on several DB's that had an electric pump inline before the vacuum pump and with the electric pump turned off they still worked ok. However, remember if you turn on the electric pump it WILL overflow the vacuum tank. As the previous gentleman stated, the vacuum tank will work great providing the seat inside that shuts off vacuum when tank is full is in place and not falling out AND you have good gaskets (2) , one under the inner tank flange and one on top of it and under the top cover AND no vacuum leaks.

[Guest lmccoll]

My dad's 24 DB has an electric fuel pump, but it takes a special kind with a special low pressure regulator. The regulator can be set in 0.5 psi increments and needs to be set at 1.0 psi or 1.5 psi. The pump and regulator are located near the gas tank in the back. I only know of one brand of pump and regulator that will work with these low pressure systems that will adjust down this low. This one has been on his car for over 25 years that we know of, I just bought a new one and put on it. If you want the brand, let me know.

[Guest actor]

Thanks a million for the responses. This 23 has had a pump and regulator on it for many years. The regulator sounds very similar to the one you described, and so I will adjust it down. My guess is that the regulator is set too high, pushing too much fuel to the carburator tank, causing the fires... I've only owned it a year, and so am not terribly familiar with the vacuum system just yet. I think I'll stick with the pump, adjust the regulator, and meanwhile familiarize myself with the vacuum system and parts. I'll study the manual a little more before digging in to it. I'm not too anxious to mess that up!

[Guest oldodgeboys]

I'm using a 2 PSI electric rotary fuel pump and a rubber-tip float valve conversion. The set-up work fine and buys me some time to build a nice vacuum tank.

Here is a link for a rubber-tip conversion. You probably will have to cut the original float valve rod. (I didn't use this kit since a rubber-tip valve came with my '25 when I got it)

Myers Early Dodge

[dwollam]

The fan belt only turns the fan, not the other way around. The water pump and distributor are gear driven, then that same shaft turns the fan pulley. The fan SHOULD actually be just loose enough to still slip so that it does not put undo stress on the fan bushings. The oil pump is bolted to the bottom of the oil pan and is also gear driven. I can't imagine an engine getting hot enough to actually catch on fire from inside and come out the oil filler tube, even if running no fan at all if the car was moving down the road. There has to be something else in the wash, so to speak.

[nearchoclatetown]

Are you sure your too high fuel pressure didn't load the crankcase with gas? Might be a good time to change the oil. Oil won't burn very easily unless it's diluted with gas. You've still got a problem as Dave said.

[Guest oldodgeboys]

Oh yeah, I agree, the problem is still there.

I don't even know what to say about the fan belt assessment of the problem...

[Guest actor]

*sigh*

There's a reason my login name isn't "mechanic".

Will change oil tonight, and check for signs of a gas mixture. Still confused as to how gas might get into the oil, but will start there.

[Guest oldodgeboys]

A few years ago I had an engine fire in my '29 Hudson. It scared the @&*!%# out of me.

Please be sure your problem is fixed before you put the car on the road. Your close to loosing a DB, or your life. Now, I dont know you personnally, but I do know that we just cant loose another DB!

[nearchoclatetown]

You suggested your friend said that the fire was INSIDE the engine. Oil doesn't burn until over 400 degrees. There HAS to be gasoline involved if the fire is coming from inside the engine. If the engine has been running too rich the extra gas would go past the rings into the oil. I'm just guessing from what you said.

[jan arnett (2)]

I have only seen engine fires started one of two ways. A back fire through the carburetor or fuel leaking onto a manifold or exhaust pipe. Normally a backfire is because of timing problems or crossed wires. It can also be the result of carbon in the distributor cap. If I were trying to find the problem here are the steps I would take.

1. Change the oil. You will be able to smell raw gas in the oil if it is loaded up.

2. Disconnect the fuel line from the vacuum tank to the gas tank. This will allow the car to run on a full vac tank to check it out.

3. Check the plugs to see if they are running rich. If they are carboned up then clean them as you probably are floating the carb needle valve.

4. Fill the vac tank and start the engine and see if you have the same problem.

5. If you do then your problem is probably not linked to the fuel pump.

You did not say if the fuel line from fuel pump is going into the vac. tank or directly into the carb.:eek:

[Guest actor]

I really appreciate the tips. After tonight's work session, I have a much more plausible theory... one which several of you have suggested.

I changed the oil, and yes, there is a distinct gas odor to it... (Jan, the fuel line goes from the gas tank, to the electric pump to the regulator (now set at 1 psi), to the vac tank, then the carburator). Previously, the regulator was at 2.5 during the fire episodes.

With the regulator at the higher psi, I think you are right, nearchocolatetown. The extra fuel must have been pushing past the rings and into the oil. When the engine became hot after 15-20 minutes of driving, that's when the engine oil was hot enough to vaporize the gas , which would then ignite the oil filler/breather like a chimney.

Tonight after changing the oil, I let it run for 30 minutes at a pretty good clip... in neutral on the garage pad... and no signs of backfire, or, well, fire for that matter.

If the problem was too high of a psi from the fuel pump, why wouldn't it flood, or otherwise show obvious signs of running too rich?

Tomorrow I'll check the plugs and carburator.

Thanks again for your input... someday I'll know enough to return the favor!

Edited August 26, 2009 by actor
typo (see edit history)

[Guest John1918]

Petrol can get into the sump. My friend had a crankcase explosion in his Standard Six, it blew out the tappet cover gasket and the oil filler cap blew off. The valve in the vacuum tank had failed to shut off when it was full and petrol flowed down the vacuum line into the inlet manifold. From there into a cylinder and down past the piston I guess, maybe even down the valve guides, older engines would have a bit of a gap there.

The vacuum tank works under vacuum conditions, so I don't know how the needle valve would cope with pressure from an electric fuel pump.

John

[dwollam]

The vacuum tank WILL NOT hold back the pressure from the electric pump. It will over flow then be sucked into the engine through the vacuum line (if it is still hooked up). That could very well account for the gas in the oil condition. If the vacuum tank is hooked up and working, there is no need for the electric, although usally it will pull through the electric pump ok (with it turned off). If you must run the electric, then bypass the vacuum tank and set your regulator to a half pound. The other issue I have ran into with electric pumps is the amount of power they require. If your generator is not putting out well, it can use nearly all the juice it can put out, leaving you with a barely charged battery.

[Guest actor]

Thanks, Dave. I will do some more experimenting with it.

[Guest silentstarter]

Hi from Australia,

Having suffered 3 carburetor fires and still have my '24 Dodge Brothers Tourers on the road, the cause was finally tracked down to a cracked exhaust manifold allowing hot exhaust gasses into the air inlet on the exhaust manifold when the engine warmed up.

Externally the exhaust manifold looked OK, it was only when I removed the manifold to replace the exhaust gaskets that the manifold separated at the crack when attempting to removing the outlet flange.

Examination of the fracture revealed that exhaust gasses had been entering the inlet path to the carburetor as the crack was blackened with exhaust residue.

To eliminate this from ever happening again I have blocked off the air inlet from the exhaust manifold and now draw air from the left hand side of the engine using a air inlet box which allows the carbi to remain mounted as intended. Photo's available on request.

Note. I use a low pressure electric fuel pump mounted under the floor at the rear of the car and since these mods the vehicle has travelled successfully from Victoria to Queensland and return as well as Melbourne to Adelaide without any concerns.

For the sake of four exhaust gaskets its well worth looking into.

[Guest actor]

Wow, that must have taken some detective work! I'll check that out this winter, however it seems now that my fires have been limited to the oil breather/fill tube due to too much fuel pressure. I've reduced the regulator to .5 psi and have had no further issus. Thanks for the scenario, and I'll check it out.