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Fuel Boiling Out Of Carburetor
#1
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Packard 1948
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I have been having issues with the fuel being boiled out of the carburetor after the engine has been warmed up and sits for a half hour or so.

I did install a glass bowl fuel filter this time and I can tell after opening up the hood that the glass bowl is half empty (yes I'm pessimistic on this) and can even watch the fuel boiling inside the float bowl.

So to start the engine after it is hot the starter motor would have to turn and turn for a very long period of time before any fuel can get pumped into the carburetor float bowl. At least this car has an electric pump so 10 seconds with the electric pump on is the fix.

I have had issues with other cars having the fuel boil out of the carburetor. This has been the case with small block Mopars, big-block Mopars, slant six Mopars, & a Cadillac engine.

It seems the new fuel here in California has such a low boiling point that it simply boils out of the carburetor after the engine sits for a while.

Does anyone else have this issue?

Posted on: 2015/9/3 19:47
Bill,

Dedicated to keeping the man who owns one on the road!!!
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Re: Fuel Boiling Out Of Carburetor
#2
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HH56
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Yes, on the 56 and now the 47. The glass is half full on mine too. I think you have the problem nailed but with our unique (and expensive) C.A.R.B. approved California gas I don't know what the solution will be.

Posted on: 2015/9/3 19:58
Howard
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Re: Fuel Boiling Out Of Carburetor
#3
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Cli55er
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my dad had this issue on his Dart....as you say small block mopar. new carb fixed it, but it still boils in the winter with the crappy winter gas mix they have here in Texas.

my solution was to run race gas mixed in with 93 octane during the winter.....fixed it perfectly.

in the summer I run normal pump gas and it works fine.

I'm going to switch to EFI on the dart soon, which will fix it permanently.

I may go with EFI on the Packard as well, but not till later when I'm well done restoring it.

Posted on: 2015/9/3 20:53
1937 Packard 138-CD Deluxe Touring Limousine
Maroon/Black 1090-1021
[url=https://packardinfo.com/xoops/html/modules/registry/View.php?ID=232]1955 Packard
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Re: Fuel Boiling Out Of Carburetor
#4
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Packard 1948
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I installed a Holley Projection 4DI on a small block mopar about 12 years ago. OK-ish system.

If you were going to install FI on a Packard engine you will need a 12 VDC (actually 13.5 VDC) negative ground electrical system and the cooling system will really need an upgrade because the EFI will be burning the fuel at close to 12.5:1 in closed loop and that is rather hot for the old Packard cooling system to absorb.

I am running steel lines from the fuel pump to the glass bowl filter but do not have the fuel pump heat shield installed (did not have one) and on one hot day (95-ish F) after idling following a high speed cruise I could watch the fuel boiling (bubbling at least with the bowl half empty) inside the glass bowl while the engine was running. The engine was idling fine so I forgot to test if the electric fuel pump would provide enough pressure to prevent the bubbling.

And yes...the CARB fuel is not good in the carb.

Posted on: 2015/9/4 9:45
Bill,

Dedicated to keeping the man who owns one on the road!!!
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Re: Fuel Boiling Out Of Carburetor
#5
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Tim Cole
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I have an old Rochester manual that states that a closed throttle can create a partial vacuum that pulls the gas out via the idle ports. Thus, parking the car with the throttle open may help.

If the problem is in fact boiling the addition of Stoddard type dry cleaning fluid to the fuel should lower the boiling point. Although it may not work with point ignition.

I would do some lab work though. I would get an electric hotplate and check if the fuel will boil at the temperatures reached during a engine off soak.

Posted on: 2015/9/4 15:51
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Re: Fuel Boiling Out Of Carburetor
#6
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Packard 1948
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Lab work?!?!?

I'll just be happy to get this car out of my damn garage.

Can't begin to count how many times it has been up and down on the lift or how many times the wheels have been off.

Had brake drag issues yesterday... wheel cylinder was hanging up... tried to hone out some pitting... no luck... thanks to this forum listing the exact part number (the computers did not show parts available for the wheel cylinder) I was able to get it done.. this forum is a real lifesaver.

I will try the old lab test of boiling the fuel technique. If I burn off my eyebrows I'll be sure to let you know.

Thanks again its back to drinking beer after a long day of Packarding.

Posted on: 2015/9/4 20:40
Bill,

Dedicated to keeping the man who owns one on the road!!!
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Re: Fuel Boiling Out Of Carburetor
#7
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Owen_Dyneto
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Does the parts list indicate your car should have the insulator block between the carburetor and the manifold (most years and models do)? If so and it's missing, that may be the answer to your problem; if it's present you might try a thicker one. Only the 356-engined models used a carburetor heat shield but you might consider fabricating one - photo attached courtesy of one of this site's regulars.

Also, have you made sure the manifold heat riser valve is functioning properly or at the least, fully open?

Attach file:



jpg  (29.48 KB)
177_55eaeec324292.jpg 640X480 px

Posted on: 2015/9/5 8:05
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Re: Fuel Boiling Out Of Carburetor
#8
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Packard 1948
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Good thinking on each topic... Yes it has a working heat riser and the insulator spacer... no heat shield though... might consider that.

Posted on: 2015/9/5 8:57
Bill,

Dedicated to keeping the man who owns one on the road!!!
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Re: Fuel Boiling Out Of Carburetor
#9
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Fish'n Jim
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Not only an operational problem but a big fire hazard made worse if you store inside.
It shouldn't do that even with modern fuel, even if you're getting E15 or worse. So don't excuse the problem on the fuel, that's a common myth, but does not solve the problem.
Could be a vacuum leak, that's aspirating the fuel or going to the wrong place. Vacuum lowers Boiling Point. Takes a while for the vacuum to dissipate on shut off. Carb might be leaking down through the bore then vaporizing from the manifold heat and vapor bubbling back up.
It would be commonly what sounds like what O_D said, don't assume, check that's all in order underneath. Float could be stuck, dirt in the carb, vent plugged, etc. I'd tear down and rebuild carb first.
I would not run it like that and make sure the insurance is paid up.

Posted on: 2015/9/6 18:24
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Re: Fuel Boiling Out Of Carburetor
#10
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Owen_Dyneto
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Have you checked the operation of the anti-percolator valves - I assume your carburetor model has them.

Attach file:



jpg  (56.49 KB)
177_55ed88ac1860f.jpg 1280X651 px

Posted on: 2015/9/6 20:12
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