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Ignition Coil possible cause of stall or vapor lock? '41 Buick


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Car: 1941 Buick Roadmaster, model 71, dual carb., large straight eight.

 

I recently had my first case of what appeared to be vapor lock. After a trip of 50 miles, mostly heavy traffic, the car got real rough at a stop light and then stalled. I could not restart it. I checked the front carburetor fuel bowl and after removing the observation plug and gasoline leaked out. It was full. The float was up (I nudged it too in case it was sticking). Within 40 minutes I was able to restart. About 15 minutes later I experienced what appeared to be a loud backfire while backing up in a parking lot.

 

Most of my friends think my carburetor and/or fuel line overheated and caused vapor lock. One friend says I should check the coil since it may cause such a situation when very hot. He wants to give me a spare coil to carry around so I can swap it if this happens again. If the car starts right up with the new coil then the coil is  probably at fault. He also said a faulty condenser could cause this.

My friend has a coil with an internal resistor and one without. He asked me what kind I have. I don't know.

 

Does anyone know the specifications on the coil for the Model 70 Roadmaster (large straight eight) engine? 

Thanks.

 

(and yes, I have since covered some of the fuel line with reflective tape. I have not yet acquired spacers to place under the carburetors)

Edited by Roadmaster71 (see edit history)
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I had "vapor lock"on my 1933 Dodge for several years. Mine would run until I shut the engine off and then would not start until it cooled down or I had someone pull me with a chain. I finally tried a known good coil. Miracle of miracles, the vapor lock was cured. Who knew that gasoline ran through the coil? Zeke 

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18 hours ago, zeke01 said:

I had "vapor lock"on my 1933 Dodge for several years. Mine would run until I shut the engine off and then would not start until it cooled down or I had someone pull me with a chain. I finally tried a known good coil. Miracle of miracles, the vapor lock was cured. Who knew that gasoline ran through the coil? Zeke 

Zeke, exactly! So far I am thinking of taking the one with the resistor with me and getting ready to swap if something happens.

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I'm sure the coil is most frequently the culprit, but not always.  I recently cured a problem like this with the MG by replacing the rotor.  When warmed up, it would run ok on the throttle, but miss and splutter and eventually shut down at idle.  When I tried to restart, it would spin like a top on the starter but never a huff or puff until it cooled down, like 20-30 minutes.  Then it would act like nothing was ever wrong.

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I recently went through a similar type problem with my 1947 Buick Super.  It started shutting down while I was driving and even though I had never experienced the problem before I suspected vapor lock.  It would sit and idle just fine for extended periods of time and has never run hot.  In looking things over it appeared that there was some very fine stringy material in the glass filter bowl going into the carburetor.  I then began to wonder if possibly the fuel tank had maybe been sealed years ago before I had the car and was now breaking down.  The carb had recently been rebuilt and I pulled the fuel pump and rebuilt it.  It was really full of gunk so I decided to drain and drop the fuel tank.  When I opened the tank and looked inside I was totally surprised to see what looked like the inside of a brand new tank.  At that point I thought the problem was related to the internal mess in the fuel pump so I put everything back together.  It started right up and ran fine so after letting it warm up for a while I decided to take it out for a drive.  About a mile down the road it quit again.  By then I was pretty well lost and decided to shift to the coil and install the spare I had.  I'm not sure what your 1941 was originally, but on the 1947 Super the original coil only had a single terminal on the top instead of the usual two screw terminals.  The other terminal was on the bottom of the coil covered with a cap that locked to the coil.  The wire from that terminal went from there through an armored cable to the ignition switch.  I guess the purpose was an anti-theft device to prevent hot wiring.  Also on cars that came with radios there was a condenser included under the cap in the base of the coil.  If I hadn't had a shop manual to help me I would never have known how to remove the cap on the base of the coil to get to the wire.  There was actually a special tool with instructions on how to separate them.  I wired up my spare coil and just ignored the condenser since I really don't use the AM radio.  Thankfully after installing the new coil it now runs fine.  Hope you solve your problem and get back on the road soon.

Bill

 

 

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I've had a large amount to do with vapour lock with modern fuels. A clear fuel tube will let you see what's happening at temps. And if is the issue an electric fuel pump on a switch works well as you can turn on to aid starting and when in heavy traffic or heat and getting vapour lock flick it on and off you go no worries.

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Thanks for all the great suggestions. I have an order in for a high quality coil. I will pick it up tomorrow at NAPA and install it immediately.

It sure can't hurt. I've had the car about 15 years and this will be the first new coil I put in.

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On 9/8/2017 at 9:59 AM, zeke01 said:

I would switch the coil out before leaving home rather than at a stoplight or on the side of a busy road. Same results with less stress and greater safety. Good luck. Zeke

Exactly. You are of course correct. That is what I will do. Stress I already have too much of!

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On 9/8/2017 at 11:12 AM, FLYER15015 said:

Roadie 75,

Please go to "mykmlifestyle.com" for your coil.

This website is for real.

 

Mike in Colorado

Mike, that looks like a great parts source. I will look to it in the future. I've been so busy that I never saw your post until today and already ordered the part from NAPA.  Thanks for the reference!

 

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It is that Ethanol crap.  You almost can't avoid it, but that's what it is.  the steel fuel line runs between the cylinder head and the thermostat housing at the front of the engine.  Anybody knows that alcohol boils at a lower temperature than water.  Put an electric fuel pump on the car with a toggle switch and when it happens turn it on and it blows the vapor out immediately and you can go on until the next time.  I've wrapped my fuel lines and it has helped a little but not always.  I don't use Stabil.  I use a blue mixture I buy at Tractor Supply or sometimes NAPA.  It is called Star-Tron.  It helps, also, but doesn't always keep this from happening.

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