1951 desoto hot starting problems

[bifda]

I have just put my 1951 desoto custom on the road and am now having starting problems when hot. I have tried cleaning the points, another coil, I have cleaned the carb, cleaned the plugs etc, but to no avail. I have just been out in the car and after 10 miles she stalled at a junction and refused to start, I tried a couple of things like putting the old coil back on etc but the battery soon ran flat. I jump started with a 12v battery 30 minutes later (the car is still 6 volt) and away it went.

I am going to tidy up the wiring as some are fraid, but apart from this does anyone have any suggestions.

There is a junction box which the shop manual calls a circuit breaker and resistor unit, which appeared to have the IGN and BAT leads the wrong way round, so I have now swapped them which maybe the problem but as yet I have not tried as the battery now needs charging.

Is there anything obvious that I am missing, or any common fault with these cars.

I should mention this is the inline 6 cylinder engine, and the carb is the one with the electronic connections to do with the kick down for the transmission.

Any help grately received

Wayne Smith

[bifda]

I am going to try and find some asbestos string to wrap around the fuel lines, the car does have the heat shield on top of the fuel pump. I have just fitted new battery clamps to the leads as they were badly corroded, but may actually fit new leads now as well. The earth lead goes directly to the engine block.

When the car wouldn't start yesterday I did try the main HT lead to the block and although the spark jumped a large gap it was not a nice blue spark. Can I fit a condenser made for a 12v system? I am no electronic whizz and so don't under stand the info supplied but will ask around.

As for the 6 volt system I have two studebakers a 1928 and 1930 both of these are on the original 6 volt system with no problems, I like to keep them stock if possible,

Wayne

[bifda]

Today, I have been working on the Desoto, I replaced the carbon fibre HT leads with copper ones, the main one from the coil was burnt on the end with the carbon fibre not sticking out of the end of the insulation. I also installed new Low tension cable from the coil to the distributor. I replaced a couple of other cables that were fraid and not looking too good these were from the coil to the circuit breaker and resistor unit. I also noticed that the main battery lead to the starter was not overly tight on the solenoid so I went to tighten it only to find the copper bolts threads were stripped. I took the starter off and cleaned the very black commutator etc and refitted it with new copper bolt in the solenoid.

Then this evening I have been on a 30 mile trip with no problems. It starts and runs well and when hot I turned it off and restarted a few minutes later with no problems. I am now going to try a trip when it is hotter weather and hope all is well.

One thing I do notice is a flat spot when accelerating the engine stumbles before getting up and going. The accelerator pump seems to work as a jet of fuel squirts when the pedal is operated, is this something obvious?

Thanks for all of the helpful replies

Wayne

[DeSoto701]

Gald to see that you got the car running again. My wife is from the London area, where abouts are you located? Condensers are measured in micro frauds. Give me the information on your car and I will see about any parts you are inquireing about and get part numbers for you here in the US. I am a mechanic for Delta Airlines and also order parts with alot of suppliers.

[bifda]

Thanks for the support. I am from near Bristol, a place called chipping sodbury. The car is a 1951 desoto custom, the engine is the 6 cylinder flta head. I am unsure what the original condenser would have been.

Thanks

Wayne Smith

[bifda]

Thanks for the comprehensive reply. I love it the way that what started out as an innocent question has now taught me loads!!! One more question, if I go to my local auto accesory shop and get a modern condensor will this actually be a capacitor or do you know a source for the capacitors that you use, do they look like the old condensor, and would they ship to the UK. I actually have a few old cars, the '51 desoto, a '32 Olds, 2 studebakers (1928 and 1930) along with 3 1930's Austins (English cars) and my everyday 1948 Land rover. I regularly check the points at every 500 miles as the cars are wedding cars and need to be reliable. I would like to now fit capacitors to all of them and then that should over come the points cleaning.

Regards

Wayne Smith

[Rusty_OToole]

Capacitor and condenser are the same thing. Capacitor is the newer name.

The old ones were made of wax paper and aluminum foil. In time the wax paper would fail and burn through. The new ones are made of Mylar plastic and will last almost indefinitely.

Ignition condensers have only one lead, electronic capacitors have 2. I don't know if that accounts for the difference in name. I also don't know if condensers have to be grounded. If the old ones were it must have been thru the case as they have no ground wire.

If you get a capacitor that is a different size and will not fit inside the distributor put it on the coil. Connect it to the wire that goes to the points. It will function the same. English motorcycles were set up this way for years.

My 51 DeSoto manual says the condenser is .25 to .28 Mfd. I think the lowest voltage electronic caps are 25 volt so that should be lots. Higher voltage will not make a difference, use a high voltage cap if it is all you can get.

Edited June 22, 2010 by Rusty_OToole (see edit history)

[bifda]

The car is getting better but still not 100%.I checked the pacsalin spacer under the car which is there but no gaskets so made 2 and fitted them.

Yesterday I altered the float level as it was very low. I also advanced the timing as it was retarded, did it the way the manual says. I have wrapped the asbestos strapping around the fuel line.

I took it out to a hotrod meet 2 nights ago and when returned home it wouldn't start as the battery was flat. Upon inspection I noticed yesterday when running the dynamo (generator) was moving about so when removed noticed the bottom bolts were loose, maybe this is why the battery isn't getting charged up quickly.

When starting is it best to depress the gas pedal, give a little gas or not touch any pedal?? It has the original auto choke still installed.

I will get on top of this!!!!!

Wayne

[Rusty_OToole]

When starting from cold it is best to depress the gas pedal part way slowly then release it to set the choke.

Starting hot it should not be necessary to touch the gas pedal. But if it does not start right away it may help to hold the throttle open slightly.

[Guest Desoto Joe]

Hello, I have a 49 Desoto and have had a lot of similar issues with it starting poorly when hot.

Something you can try to do to help your 6 volt system is try running a larger cable(smaller gauge ground cable) from the positive ground side of your battery directly to the upper bolt that attaches the starter to the engine block. This will take a several foot long cable-I would tell you what length I put on, but my car is in the shop having the back brakes fixed and I don't have it at home at the moment.

You may have already done this, but if not try it, it helped mine. This is not original and may hurt you in shows. . . but it should give you more starting power whenever you need it.

Desoto Joe