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Old 09-28-2020, 01:51 PM   #1
kcsodafiz
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Default 1939 ford flat head wont fore after a rain

Have a 1939 ford sedan with a 46 flathead v8, seems like after a rain it just wont fire. any ideas????
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Old 09-28-2020, 02:31 PM   #2
rockfla
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Default Re: 1939 ford flat head wont fore after a rain

Since your complaint is "only" when it "rains", its not a compression issue. Now your down to spark or gas delivery issue. Have you checked at the point when this happens to see IF you're getting spark to the spark plugs??? Quickest and easiest test!! IF no spark then you have your problem area to search......... IF you have spark, then you have your problem area to search!!! Hard to answer without more information on what exactly is or is not happening and when it is or is not happening. IF it is a "spark" issue the initial point after it rains you "might" look at your distributor cap and see IF you have condensation building up from the humidity/rain.
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Old 09-28-2020, 02:33 PM   #3
kcsodafiz
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Default Re: 1939 ford flat head wont fore after a rain

no i havent checked plugs, just seems like after a rain it wont fire, today it fired up??
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Old 09-28-2020, 02:34 PM   #4
Mart
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Default Re: 1939 ford flat head wont fore after a rain

Hello and welcome to the forum.

Just a guess but I'd be looking for some sort of water leak that may be dripping onto the ignition leads.
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Old 09-28-2020, 02:40 PM   #5
rockfla
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Default Re: 1939 ford flat head wont fore after a rain

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Originally Posted by kcsodafiz View Post
no i havent checked plugs, just seems like after a rain it wont fire, today it fired up??
NEXT time it happens, pull a plug wire and spin the motor and see IF you have spark.......Then you'll know which area to start looking Again at first "blush" you're having a condensation/moisture issue inside the distributor cap would be my first look IF no spark!!!!


Does the car sit outside, or in a damp garage????
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Old 09-28-2020, 04:36 PM   #6
Bill OH
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Default Re: 1939 ford flat head wont fore after a rain

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Could be a cracked coil case.
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Old 09-28-2020, 04:58 PM   #7
drolston
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Default Re: 1939 ford flat head wont fore after a rain

Even without rain getting under the hood, high humidity can condense on the spark plug wires. If they are old, the moisture can penetrate and spark will jump to ground in the wire loom instead of through the plug.
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Old 09-28-2020, 05:24 PM   #8
Kurt in NJ
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Default Re: 1939 ford flat head wont fore after a rain

What distributor/cap?
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Old 09-28-2020, 05:37 PM   #9
tubman
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Default Re: 1939 ford flat head wont fore after a rain

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Originally Posted by Bill OH View Post
Could be a cracked coil case.
I had this happen to me as well, and it was a crack in the coil tower, I only found it because it happened at night and I could see the spark "leak".
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Old 09-28-2020, 06:08 PM   #10
Ggmac
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Default Re: 1939 ford flat head wont fore after a rain

Use a spray bottle mist and at night , spray the engine lightly . Have someone try starting the engine . Look for sparks , have it as dark as possible. If it starts continue checking for spark or the sound of arcing .
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Old 09-28-2020, 06:59 PM   #11
joe 1950
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Default Re: 1939 ford flat head wont fore after a rain

with the engine running Spray the dist cap slowly and then move to the coil and wires my brother had a 50 ford when we were in high school (around 50 years ago )and as soon as the clouds got dark it would die then a old timer mechanic told us to try this and sure enough it needed a cap and rotor good luck
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