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1921 Dodge Brothers Starting Problem


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Hi I'd like to ask assistance for an issue that's left me sitting  few times.   If I turn my 1921 Roadster off after running for more than about 10 minutes, it fails to start again.  It'll crank till the cows come home, but won't fire.  I initially thought possible vapor locking, as I live in the Phoenix Metro area and its been well over 100 degrees when I've driven it.  I no longer believe this is the case per below.   

 

Basic stuff: fuel, spark, timing. 

Fuel: I have plenty of gas.  The vacuum tank has been bypassed and fuel is being delivered to the carburetor via an electric fuel pump and variable regulator, which adjusts from 1 to 7 lbs. It's set at 2.5 Ibs.  I disconnected the fuel line to the carb and it has a lot of pressure, perhaps too much for the Stewart carb? I have a good strong battery, and plenty of spark to the plugs.  Timing must be good.  Starts first time, every time when cold, but when slightly warmed up, if I shut it off, it could be hours before it starts again.  

Sounds like carburetor to me, but I have limited experience with fuel delivery issues.  I also adjusted the regulator from 1 to 7 lbs, but with little luck.

 

Any reason shutting off the car after such a short amount of time would not allow it to fire?

 

Thank you,

Dave

 

 

 

 

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Try putting some fuel into a spray bottle and as your turning it over spray a couple of squirts into the air intake. That will prove either way if it’s fuel or not. 
If it still doesn’t start Pull the plugs and see if they are wet. If they are you may have to much fuel pressure or a bad needle and seat. They don’t like to much fuel pressure. 
After that with no change do a compression test on each cylinder. 

Edited by Mattml430 (see edit history)
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Are the plugs wet after cranking? You don't need to spray gas into the intake (would be hard as the air is pulled thru exhaust manifold preheater down through the valve chamber into the carb with a fresh air intake for warm weather down between the cylinders), unless they have been removed, 21 would have priming cups. If it runs for 10 min. my vote would be to check the condenser or maybe the coil. I think 2.5 on the fuel pressure might be too high. It would only be gravity feed from the vacuum tank which would hold less then a qt with the bottom only a few inches above the bowl on the carb., so not much head pressure.

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Thanks for additional responses.  It'll be next weekend before I can run it again.  Am hoping it's something simple, as it's starting to drop below 100 in Phoenix, and we'll have good driving weather in a month.  

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  • 2 weeks later...

All, so I've finally had a chance to play with my '21 Roadster.  I've not been able to fully verify why my car wouldn't start after running a short while, but have some ideas and findings.  

 

Based on the suggestion that fuel pressure to the carburetor is only gravity fed, I reduced the pressure from the fuel regulator from 2.5 to 1 psi and it's been running fine.  The other suggestion was that most ignition problems are  electrical and nature, so I replaced a very old and used battery with a new one. 

 

 I found however that if my ignition key is not perfectly aligned in the ignition and lighting switch, the car won't run at all.  Additionally, when I tried turning my headlights on, any movement of the lighting switch will to shut the car off as well. It seems the ignition switch is bad. I'd appreciate any leads on finding a new or replacement.

 

Thanks in advance.

Dave

 

 

 

 

 

 

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If the switch is similar to the one on my '25 (Clum), you may be able to take it apart and try to fix it.  It has bendable tabs that allowed me to disassemble.  Worth a try.  Otherwise try Myers Early Dodge or Romar and see if they can source a good used one.

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Thanks for the suggestions.  I left a message for the folks at Myers Dodge, and then spoke with the gentleman at ROMAR.    Apparently this is an ongoing problem with these old switches, and they're hard to come by. I'll try to fix the switch, but may end up using toggle switches under the dash for my lights and/or ignition. Would be an easy solution if I can't fix or get parts.  Again, thanks.

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Ok, so I've bypassed the ignition and light switches, and everything's now on toggle switches.  Starts fine, lights work, but after running for about 10 minutes I turned it off, and unable to start again.   It's got to be the carburetor or the coil.   I've ordered new spark plug wires and a distributor cap nonetheless.   Can't hurt. It's getting to be nice touring weather in Arizona, so am anxious to try look at  new thing to figure it out.  Will give it a go in another few days.

 

Dave

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I melted a modern coil once after forgetting to turn off the ignition (I was running it out of gas for the winter).  The points happened to be closed when it stopped and it probably had power to the coil for 5 - 10 minutes before I noticed.  It's easy enough to put a DVM on the coil and see if resistances check out.

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It appears my electrical problems may be resolved regarding the battery drainage. Toggle switches seemed to have worked. However,  I'm left with the problem of a car not running.   I suspected when it gets warm the condenser may be failing.  Typically, after running it for 10 minutes or so and shutting it off, I can't start it for hours afterwards.  I tried again this morning.  It started with ease snd I let run 15 minutes, shut it off, waited five minutes, and haven't been on able to start it since. It'll fire but then immediately die.   Remove the distributor cap, manually operated the points, and verified a fairly good spark from the coil, although I don't have a comparison for the size of spark.  I'd like to change the condenser, but don't know how to remove it (see attached picture).  I understand an exact replacement isn't available, so what does everyone use,  and how would it be installed? Any other ideas?

 

 Thanks in advance.  

IMG_1047.JPG

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These condensers are available from Cindy and Tom at Myers Early Dodge (I think as a changeover). They open the old housing and fit modern internals then seal it back up as I understand.

good luck.

 

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Or any condenser will work. I have put several modern condensers on DBs, they don't care. Next time it won't start just disconnect the condenser wire. If it runs that will prove it is bad. It won't hurt to run it a few minutes without a condenser. 

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I believe the condenser case has studs attached that go through the bottom of the distributor with nuts holding them.  I used a modern capacitor that fit inside the distributor.  I don't have the specs on hand but will look it up tonight.

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Here's what I installed a few years ago.  I think maybe I bought it on-line from Fry's but it shouldn't be hard to source something very similar.  The thread link below may be of interest too.

 

https://forums.aaca.org/topic/255556-replacing-condenser-and-cutout-with-modern-equivalents/?hl=capacitor

 

 

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Edited by MikeC5 (see edit history)
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22 hours ago, in2antiques said:

I tried again this morning.  It started with ease snd I let run 15 minutes, shut it off, waited five minutes, and haven't been on able to start it since. It'll fire but then immediately die.

 

Have you tried spraying starting fluid or gasoline in it to see if it will start and keep running to rule out it being a fuel supply problem?

 

Edited by Ronnie (see edit history)
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  • 2 weeks later...

 I appreciate everyone's advice. I had several problems with the car. The ignition/light switch was draining the battery. Turning the lights on at any time would  kill the ignition.   I bypassed both of those with toggle switches and it now holds a charge and starts easily even with the lights on.   I also purchased a condenser from Myers Dodge, and my restarting problems disappeared.  We drove the car 50 miles on Saturday with no problems.  

At the end of our drive it stalled at an intersection.   I couldn't believe when I wouldn't restart, but then found a broken wire under the dash (from the floor starter switch).  Fixed, and on my way.   The carburetor is running very rich and I believe it's stalled after flooding. One way or another the problem with not being able to start when hot has been fixed.

 

Many thanks to all who posted on the site,

Dave 

 

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