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On your Weber 38/38, do you . . .

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i'm beginning to think all webers have an issue.  i have a 32/36 that wont start cold!  not an ignition issue, because i also have a 38/38 which starts no issue at all cold, one pump to get set the choke and it goes.  neither have an issue warm, but i have a cooler thermostat in my car and we dont get really hot summers in my neck of the woods.

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Wow, lots of diverse thoughts - thanks! I do have the phenolic spacer, and the carb itself doesn't seem to get all that warm. And I have enlarged the intake holes to match the carb's. Have also checked and rechecked floats. I do see a gas puddle below the carb down in the intake manifold, so it appears to be flooding while sitting. The top one of the two fuel connections on the carb has an arrow pointing out, and it has a tiny hole (flow restrictor?), so by adding a fuel return line there theoretically would allow pressure in the float chamber to lessen. I'll try holding down the accelerator pedal while starting next. Otherwise, the 38/38 works real well, giving spunky acceleration.

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I do have the phenolic spacer, and the carb itself doesn't seem to get all that warm.

Have also checked and rechecked floats. I do see a gas puddle below the carb down in the intake manifold, so it appears to be flooding while sitting. The top one of the two fuel connections on the carb has an arrow pointing out, and it has a tiny hole (flow restrictor?), so by adding a fuel return line there theoretically would allow pressure in the float chamber to lessen. I'll try holding down the accelerator pedal while starting next.

 

 

Fuel collection on the floor of the manifold seems abnormal and is almost certainly causing the hot start issue.  Full throttle, for hot starts, may be the easiest work-around, but it is not a proper fix since not all carburetor-equipped engines exhibit this symptom.

 

A certain amount of ambient heat is inescapable, but from what you describe, it may only be a part of the problem. Have you checked your fuel pressure? If it is a tad high, maybe, just maybe, the heat is causing fuel to expand and increase pressure beyond the needle valve's capability to contain it. Another scenario is a leaky accelerator pump diaphragm or there is a weak check valve/spring.  A heat-soak-induced fuel pressure increase might easily explain a dripping accelerator nozzle and the resultant puddle. I am not saying this is the issue, yet I would run the engine to normal operating temperature and then, with the air filter removed, carefully watch for this or any dipping-oozing phenomena. Once you discover the path of the fuel, e.g., the accelerator pump or auxiliary venturies, etc., it should clarify potential remedial action.

 

As alluded to, if the fuel pressure is normal (below 3.5 lb/in2) the problem could be nothing more than a weak or compromised needle valve assembly.  If, the in-line fuel pressure increases at rest due to heat-soak, it could test any needle/seat combination’s ability to resist that increased pressure. This would occur notwithstanding any float setting. The needle valve's durability is generally taken for granted. Most are constructed with a spring-loaded bearing that may not last forever, or half as long, if the fuel has contaminants. The same goes for the construction of the needle tip.  Again, this may not be the problem, but it is worth a look-see.

 

Another thought concerns the float assembly. Floats are generally tolerant of malformation and misadjustment. It is presumed that you are using the recommended settings for your specific type of floats. Even if you have the recommended settings, if your assembly is slightly off or tweaked, the floats may not operate correctly, possibly restricting full float operation or providing an unsatisfactory working fuel level. It may seem counter-intuitive, but if the float setting is off or binds, once heat-soak affects the carb bowl's fuel level, the float sticks open just enough to release the needle valve, resulting in slight flooding. This could be compounded by fuel pressure that is too high due to the pump, the lack of a high-pressure release or return system coupled by the much-discussed heat-soak. For this reason, you might want to compare your float assembly with another one, or possibly swap it out.

 

 

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https://www.youtube.com/watch?v=u5C-paKEh-Y

 

 

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Edited by percy

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(edited)

I installed the Jeep filter on my car last year and it seemed to fix my vapor lock issues until this week.

After driving the car for 30 min and stopping for lunch for another 30 min the car started, ran a minute and then died.  I pushed the car under a shade tree and put a wet rag on the fuel pump for about 15 min. My visible fuel filter before the fuel pump gradually filled up and the car started.

 

One complication may be that the Underhood insulation is reflective silver

Without air flow under the hood, my hypothesis is that the silver insulation retained engine heat and evaporated the fuel.

 

I have noticed that when I park the car in the garage with the hood closed that the level of fuel in the fuel filter is low when I start the car again. I drove the car home Friday And let it cool in the garage with the hood up and the fuel filter remained full.

 

My car has a 38/38 Weber.

 

Short of an electric fuel pump,  any ideas for a cure?

Thanks

Edited by SaharaX2
Misspelling

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