'41 Cad. Hard to start when hot.

[Kevin]

My '41 Cadillac starts perfectly when cold and runs very well. After switching off when at normal operating temperature, it will not restart although it is spinning over fast. It seems to be weak spark. A NOS coil has been fitted, points, condenser, rotor and cap are new. Wire lead from coil to distributor, plug leads appear to be relatively new but they are the resistor type. They all measure about 6,000 to 7,000 ohms which is correct but is this too much for a 6 volt system ? Should I fit wire leads ? All battery cables and engine earths  are good as are the solenoid wires. I have read somewhere that hot starting was a problem with these cars. True or false ? Any ideas ?......Kevin.

[homeonprunehill]

09-02-08
To answer your question, Yes,KEVIN, It's TRUE. they are hard to start when hot. NORMAL operating temperture will cause them to be hard to start. NO, it sounds as if the starter does not have any rust preventing it from starting.The "Resistor"Pluegs are to prevent "radio" from being noisy. Don't change them. Search flat-heads over-heating. Good Luck,JIM

[baxterculver]

I think you don't have an electrical problem.  Your problem sounds like fuel.  Do you have an electric fuel pump?  Modern gas boils at a lower temp than 1940's gas and I'll bet you need to push fresh gas into the carburetor when the engine has been sitting spiking up the temp in the gas line and carb.  My '39 frequently has the same symptoms.  I switch the electric fuel pump on for about 5 seconds and it fires right up.  Sometimes I have to leave the electric pump on thru the start sequence and a bit longer to "clean" out the vapors.  Search this site for electric fuel pumps for install recommendations.

[Bill Ingler #7799]

Baxter has a good point on using the electric pump to help start a hot engine but in addition to the pump I would experiment with different ways of starting when the engine is hot. Starting a cold engine calls for a rich mixture which is the function of the choke. Starting a hot engine calls for a lean mixture and no choke. I would check to see if the choke is fully open when the engine is hot. If the choke is fully open then very slowly push and hold the accelerator half open to draw in more air to lean out the mixture. Maybe you only need to depress the accelerator just a little to find the proper air /fuel mixture to start the hot engine. I use this method to start my 41 which has a Stromberg carb but touch the throttle just a little on the 47 which has a Carter and I end up with a flooded engine.Then it is push and hold the accelerator to the floor and crank to draw in air. 

[John Washburn CLC 1067 Sadly deceased.]

Kevin,

My belief is that one should never ever put resistors plug wires on these old 6 Volt cars. I changed out a lot of resistor plug wires on CLC members cars here in the Rocky Mountain Region and they all start better when hot and have better performance.

Resistor wires are ok for 12 Volt applications not 6 volt.

My opinion.

John W

[John Washburn CLC 1067 Sadly deceased.]

Kevin,

Forgot to add that I use Packard Cable Spark Plug Wire, no resistance. Napa sells a kit for boat and off road applications of spark plugs wires that will work, but the wires are blue.

I think the feds mandated that cars had to use resistance spark plug wires in the late 60's. So you have to improvise or use one of the old car vendors who still sell the old type wire spark plug sets.

John W

[Kevin]

Thanks to all the people who have replied. I had checked out the carb, the choke is open when the car is hot and if you push the pedal there is a full stream of fuel from the accelerator pump. When it does finally start it fires on all cylinders unlike a flooded engine. I had ordered an electronic ignition kit which arrived today so I will fit it and let you know how I get on.
Kevin

John W

[TonyZappone #2624]

No one addressed the positive and negative battery cables.  Replace them with 00 size cables, or welding cables, and your problems will probably go away.  Moreover, many of these starters need rebuilding, and by that I don't mean snapping the brushes and putting oil on the bearings or bushings.  If all else fails, on my '47 convertible in Florida, just to be sure, I resized the battery box and installed a group 4 bus battery.  My 41 and 47 start, hot or cold, all the time.  Both of them have resistor wires, by the way.  TonyZ

[STEVE CLC #16187]

Kevin, check your compression, that is one of the biggest problems for hard starting when hot. Low compression in one or two cylinders will make a difference.

steve

[Fred Zwicker #23106]

Overkill, but two (2) Optima 6-volt batteries connected in parallel will start the car, hot or cold. This will give you 6-volts at 180 cold-cranking amps.  An auxiliary 6-volt electric fuel pump is also helpful, primarily for a cold start after engine has not been run for a long time. (Hide the switch for judging).

To see specs on the 2-battery setup, see the following link:

http://www.fzoldcars.com/Page_8.php  (Full explanation of this setup at this web site).  Or go to my web site at www.fzoldcars.com and click on "Technical Stuff".

Then arrow down to section showing this installation.  Picture of this setup has been posted in the past, but is also shown below.  The smaller black wire in photo leads to the 6-volt Battery Tender (also highly recommended when a car sits a lot).

1) Original ? - No (but in my 1939 LaSalle, batteries are under driver's floor so do not show.
2) Overkill ? - Yes  (I like overkill when needed, and older Cadillac flat heads need all the help they can get.)
3) Does it work ? - Always.  (There is nothing worse than a beautifully restored car that will not start).
4) How fast does it start? - 1 to 2 seconds at most. (I don't need or carry jumper cables).
5) Cost ?  About $200, including the cables that I purchased at NAPA.
* Note - In addition, be sure to install all new cables in 00 size, or 2/0 gauge.  (Available at J.C. Whitney and other sources).  If you buy cables at most auto stores, you will get the lighter grade cables used for modern 12-volt cars and even with the above setup, car will probably not start easily. Al;so clean all connections and an extra ground cable from starter ground to frame isn't a bad idea.

I also have a 1966 Cadillac (12-volt) and previously had hard-starting with the standard cables, so I ordered (at NAPA) a set of heavier cables that really did the job.  These are not in stock, but available from NAPA at extra cost.  Never skimp on batteries or battery cables, or you will pay the price.  Also I recommend molded cable ends, as the type of temporary ends that attach over the cable with two bolts will eventually corrode and your troubles will return.


Fred

[domer]

I just recently purchased a 1952 Fleetwood from Maryland and had it transported to Colorado.  The caddy is doing the exact same thing as mentioned above.  It starts with no problem when it is cold and runs fine.  Today,  I let the car idle in Drive with the parking brake while I added some air to my tires.  The car just died on me and would not restart. I could see the gas in the fuel filter bowl bubbling or boiling. I didn't have a flashlight so I couldn't see if the carb was taking any gas.  I removed an aftermarket fuel filter and added a little gas to the carb. The caddy started right up. I thought I had the problem corrected but it did it to me again later on in the day.  It started right up while cold but did not start up while hot.  A guy walked up to me while I had the hood up and noticed the gas boiling in the fuel bowl.  He said that I probably had vapor lock and that I should insulate the fuel line going into the carb.  Would this help me out?  Being in Colorado with the high elevation,  do I need to make some major adjustments on the carb.  I will definitely purchase bigger battery cables based on the info above.  I am hesitant in adding an additional fuel pump as I really wish to keep the car as original as possible.  Any thoughts or additional suggestions are greatly appreciated.
Thanks, Dominique

[Glen]

Domer, first check to see if the fuel line gets close to the exhaust system at any point along its length.  Check under the hood and under the car. 

It does sound like vapor lock.  At the altitude you are at gas will boil at a lower temperature so you will be more prone for that problem. 

I’m a little surprised the fuel is boiling in the fuel bowl.  IIRC that is on the output side of the fuel pump so should be under pressure and less likely to boil. 

You wouldn’t happen to be still running on Maryland gas would you?  Maybe a fresh tank of gas formulated for the altitude might help. 

Glen

[domer]

Well I'm not positive if the gas is actually boiling in the glass bowl but is certainly makes all sorts of bubbles. I loosened the glass bowl and moved it around and the bubbles got even worse.  I did add a full tank of Colorado gas as soon as soon as I received the car.  I did a thorough inspection of the fuel line underneath the car.  I didn't see the fuel running near the exhaust.
Not sure what else I can look for.
Thanks
Dominique

[Otto Skorzeny]

One of the problems that those of us who drive our cars regularly are facing now is the gasoline sold today isn't the same as it was 20,30,50 or 60 years ago. It's not even the same as it was last year.

Modern fuels are now formulated for modern cars with pressurized systems and fuel injection. They are more volatile than the fuels designed to run in our old vehicles. Cars which may already be prone to vapor lock are even more susceptible to it with today's fuels. Even if vapor lock doesn't occur, modern gasoline doesn't burn the same in our 50+ yr old carbureted engines.

Modern fuels can cause a host of problems that are sometimes impossible to diagnose when everything is in perfect order and meets factory specs. The gasoline, however does not meet factory specs for our cars and should be taken into consideration when trying to solve a problem that seemingly has no answer.

Ethanol is a big problem. I've been driving my 1956 CDV for 7 years as a daily driver. I've driven all over the Southeast on trips of over 2000 miles. I've never had a problem until recently. Many stations around here (Atlanta) now have signs saying gasoline may contain AT LEAST 10% Ethanol. That means it might contain more.

Ethanol is known to deteriorate, weaken and soften rubber. I have had to replace two fuel pumps this year because the diaphragm had been "stretched" and couldn't pump the volume required. One was a brand new pump, the other was a rebuilt unit.

On the '56, the pump arm travels only about 1/2". That doesn't allow for much error if the diaphragm is even slightly compromised.

I am now trying to find a brand that uses little or no ethanol. I may have to just bight the bullet and install an electric pump.

The point of all this is that the fuel you're using has to be considered as the source of any fuel related problem you may be experiencing. People who only drive their cars a few miles a year may not notice these problems but if you use your car for more than the occasional show, you will begin to see these problems.

Another poster in this forum asked why his '75 Caddy ran rough at idle when "everything is perfect and within specs". The answer could very well be that the fuel, not the car is to blame.

[domer]

I see your point exactly.  I just hope there is pemanent solution because I really don't want to install an electric fuel pump.  Solutions, ideas, tips are greatly appreciated.
Thanks
Dominique

[John Washburn CLC 1067 Sadly deceased.]

Domer,

In Colorado we put electric fuel pumps on the cars to stop vapor lock, it is the best way to ensure trouble free driving at altitude. It is a standard modification and no points are deducted in judging for this.

Come take a look at the 53 bumper and I'll show you the electric fuel pumps I've in stalled on the 53 and 56.

John Washburn
Elizabeth, Colorado

[Bill Ingler #7799]

After reading all the replies to your posting and then going back and reading your initial post it seems to me it all points to vapor lock in the engine pump. I had a friend stop yesterday with his 47 and we took a short drive to take a look at another 47 parked a few blocks from my house. Yesterday here in Scottsdale it was about 100. When my friend tried to start his 47 for the trip back, the hot engine would not fire. The engine turned slowly but still fast enough to start but no start. He then turned on the aux electric pump and the car started. Today`s blends of fuel are not going to change so we who drive the old cars need to adapt our cars for today`s fuels. I like to stay original as possible but I like to drive my cars so each has a aux pump. The 41 has a perfect place to install a pump, on the cross member above the differential. You can`t see the pump unless you crawl under the car. The picture below shows the pump on my car. Have fun and enjoy your car.

[Fred Zwicker #23106]

Bill,

I am not sure if it was necessary, but after installing my newly rebuilt engine, I insulated the fuel line leading to the carburetor from the fuel pump.  Since it passes over the exhaust manifold (black shiny surface below this insulated line in picture), I felt it was a good idea. The other line (also insulated) is the line from the exhaust manifold heat shield that supplies air to the automatic choke for sensing purposes. 

However, I also installed a concealed electric fuel pump back at the gas tank (with concealed switch for judging) and have a dual Optima battery setup as previously described in my earlier reply to this post.  * Note, I have never needed to use the electric fuel pump except after the car has been sitting for several months, and for this purpose alone is well worth the expense.  (Too much trouble to remove the air cleaner and manually prime the carburetor).

Since the lowest priced fix is to install the insulation to the fuel line, feel that this is a good place to start.  Cooper's also sells some type of insulation for the starter motor which I purchased, but did not install, as never had any starting problems, hot or cold.  Hopefully you have the correct size (00) battery cables with molded ends and clean connections everywhere and that you battery is new and the largest and heaviest type available.   

Fred

[Bill Ingler #7799]

Hi Fred: I have OO cable on both cars with ground back to bottom starter bolt as well as using the Optima battery and a good strong starter. I never have had problems with the starter spinning a hot engine. I will still can get a vapor lock on a hot day out here or on a tour in a long climb to high altitude. I had the 41 up in John Washburns country several years ago on a tour and the electric pump was used on several of the climbs over the 12,000ft passes. I never saw the need to insulate the line from the fuel pump to the carb as that line already is under at least 4 lbs of pressure from the engine pump.

[Fred Zwicker #23106]

Bill,

Sounds like you are already doing everything right.  Luckily in NE Ohio we do not have elevation problems - just cold weather, snow and ice in winter!
I guess my last post should have been directed to Kevin, as many of us "old timers" have already figured how to be sure that our Cadillac engines always start!  Being aware of the potential problem, I did all of the "fixes" at time of car and engine restoration and so far, so good. 

Fred