Weber Carb Woes - Cold Start

[CCM911]

Hello:

Still in the process of waking up the 1973 Targa. Car is equipped with Weber carbs. All rubber fuel lines replaced, and fuel pump is now a lower pressure Facet.

When cold, I have to spray starting fluid into the throats, and then it will run. I can run it at idle, and it runs perfectly. Once warmed up, I can start the car easily, and again, it runs fine. However, if I let it cool down, I once again need to use starting fluid to get things going again.

There is no choke installed. Yet on my Ducati with FCR flat-side carbs, there is an enrichment valve, so I could just turn the throttle a few times and it fires right up. And in the case of the 911, the hand throttle has not been hooked up, so I am at a loss as to how to enrichen the mixture for cold starts.

Any weber experts out there?

Thanks so much for reading.

[jpnovak]

two full pumps of the pedal. Then wait about 20 seconds for fuel to start to evaporate. Then start the car using pedal to squirt additional fuel as necessary. Once running, pull hand throttle so that idle is 1500 rpm or so. You will likely notice the car starts on 4 cylinders, then a 5th will hit, then the 6th will hit and you have to adjust down the idle speed.

Typical of carbs in my experience.

[kfosburg]

When it's cold, before even energizing the fuel pump, look down in the barrels and see that fuel is being squirted from the accelerator pump jets when you open the throttles. You should see quite a bit of fuel. The float bowls contain enough fuel to do this repeatedly. If you don't, you may need to refurbish your accelerator pump gaskets and/or check for float bowl leakage.

These Webers don't have a choke and pumping the accelerator is how you enrich them for starting. My hand throttle is broken and I generally have to lightly blip the throttle for about 15 seconds and then it's fine. The hand throttle does nothing to enrich the A/F, just runs it at a higher RPM.

Karl

[CCM911]

Thanks Karl!!!

Yup. That is the problem. I see the jet on the left rear barrel squirting fuel, but nothing on the right side.

Awesome! Now I know what to repair.

[CCM911]

I am going to start by ensuring that the diaphragm is intact, and that the circuit is clear. Can I remove the cover, the diaphragm and the spring while the carbs are still mounted to the car? Or do I have to remove them?

[Trackrash]

Originally Posted by CCM911

I am going to start by ensuring that the diaphragm is intact, and that the circuit is clear. Can I remove the cover, the diaphragm and the spring while the carbs are still mounted to the car? Or do I have to remove them?

Yes, you can R&R the diaphragm covers with the carbs in place. However to access the accelerator pump nozzles, you will probably have to remove the top of the carbs. They have check valves in their mounting screws.

[kfosburg]

Originally Posted by CCM911

I am going to start by ensuring that the diaphragm is intact, and that the circuit is clear. Can I remove the cover, the diaphragm and the spring while the carbs are still mounted to the car? Or do I have to remove them?

Either way works. They're not that hard to remove the entire carbs from the car though - 6 nuts, fuel hoses, linkage ball joints, and air filters.

Use some carb cleaner with the nozzle attached to see if the path to the jet is clear.

There are a lot of very knowledgable Weber people on this forum and I've learned a ton over the years from their experience. You'll find dozens of threads on troubleshooting and tuning them.

Good luck,

Karl

[rbogh901]

Mine start fine cold. I have no worries even driving to 9000 feet, skiing, and coming back to the car. As mentioned, push a little fuel into the carbs with a couple of bumps on the throttle, wait briefly then fire away. Catch it with your gas pedal and it Smooths out almost immediately. Below freezing is no problem. Just like an older motorcycle only you don't have to kick-start it.

[rbogh901]

By the way, best thing is to drive it gently right away. I can usually head off in 15 to 30 seconds. Better for the motor then sitting and trying to warm up at idle. Keep it easy for a few minutes, mostly only idle circuit, 3000 RPMs. Or less.