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'50 Ford carb leaks fuel after shut down...when "hot"


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When "hot", run the car, shut it down.  

 

~5 minutes later, fuel starts running from the main discharge nozzle, puddles on the throttle blades and runs out the throttle shaft, leaking onto the intake.  
Recent fuel pump, 

Car runs good when running

Checked for needle and seat sealing; it seals good. 

 

I watched it happen today, engine was 205* F when shut off.   What gives? 

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  • 2 weeks later...

With the top of the carburetor upside down, so the float is resting on the needle valve the measurement from the cover to the top of the float is 1.322"-1.353".

A quick check is the the fuel level should be about1/8"-1/4" below the hole for the accelerator pump.

 

Did you just rebuild this carb? Did this problem just start?

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Posted (edited)
13 hours ago, 19tom40 said:

With the top of the carburetor upside down, so the float is resting on the needle valve the measurement from the cover to the top of the float is 1.322"-1.353".

A quick check is the the fuel level should be about1/8"-1/4" below the hole for the accelerator pump.

 

Did you just rebuild this carb? Did this problem just start?

Thanks for the good reply.  No, I didn't just rebuild the carb.  Customer brought it to me with this "new" complaint.    I'm not sure how new the problem really is; he barely ever drives it and doesn't really pay a lot of attention to how the car behaves, so it's hard to get a good feel from the owner about what's really going on, and history.  I installed a Summit Racing fuel pressure regulator, set it to 2.5 PSI and still, was able to reproduce the problem once.  After shut down, pressure crept up to ~3.5 PSI or so, and the carb flooded the intake with fuel.  I re-adjusted the FPR to 1.5 PSI and was unable to reproduce the problem, but the owner took it and it flooded on him -even though line pressure at the carb remained at 1.5 PSI.  I don't think that the fuel will force past the needle/seat at only 1.5 lbs, so at this point, I'm thinking it's the float level is set too high.

 

Thanks for the float level spec...that should be easy to check. 

Edited by Tom400CFI (see edit history)
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17 hours ago, Tom400CFI said:

How about float level spec/procedure?  1950 Convertible ? 

The fact that it starts after shutdown is more likely to be associated with heat soak than float level as the other  guys have mentioned. 

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O.K.   If that is "the fact"...then could you define it a bit more clearly?  What is the heat, soaking? And how is that pushing fuel out the discharge nozzles? 

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5 hours ago, Tom400CFI said:

O.K.   If that is "the fact"...then could you define it a bit more clearly?  What is the heat, soaking? And how is that pushing fuel out the discharge nozzles? 

 

Did you read the link in Carbkings response? that pretty much explains it in a nutshell, that's the item re fuel leak from throttle shaft, commonly known as heat soak. Also more often than not it leads to the other condition of hard starting when hot.

Edited by hchris
Word change (see edit history)
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I did.  Thanks so much for that. :)

 

I'll re-set the float and see how it runs.  If it works, I'll ditch the regulator and try it again. 

It has an OEM fuel pump.  I've resisted installing an electric b/c I don't believe the car should or does need one.

 

 

 

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On 7/26/2020 at 7:01 PM, hchris said:

 

Did you read the link in Carbkings response? that pretty much explains it in a nutshell, that's the item re fuel leak from throttle shaft, commonly known as heat soak. Also more often than not it leads to the other condition of hard starting when hot.

Yes, I saw it.  I was totally "bought in"...until I did this:

"I installed a Summit Racing fuel pressure regulator...I re-adjusted the FPR to 1.5 PSI and was unable to reproduce the problem, but the owner took it and it flooded on him -even though line pressure at the carb remained at 1.5 PSI.  I don't think that the fuel will force past the needle/seat at only 1.5 lbs"

 

That pretty well eliminates fuel expansion in the line between the pump and carb.  At this point, I believe the fuel level in the carb is too high, and the bowl heat soaks after ~5 min, bubbles form, displace the fuel out the nozzle and there is the flooding.  More testing to ensue....

 

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