I have a 67 122s with a B20 fitted with a webber carb,, the electric choke version.. If I start it everyday or every second day or so it starts great..But,,if it sits for a week or more it is a bear cat to start..It seems as though there is no gas in the carb.. I do not see any leaks where it has drained out.. I put a new mechanical fuel pump on already but I was thinking maybe a electric low pressure fuel pump may help the situation.. Anyone else have any ideas ?? Thanks in advance !!

Robert;

...obviously sounds like an empty fuelbowl in the carb, which the pump has to charge up before you will have any chance of starting...is the fuelbowl on the Weber vented somehow?...that would explain a lot...I just have to question other posters suggestion that fuelbowl is syphoning*...it seems to me that if you were to open the bowl after a week and see it empty, that would confirm the condition...then its just a matter of explaining why fuel is leaving/evaporating(?) so fast...and my explanation of why it takes a mechanical (low pressure/low volume) pump so long to recharge the bowl is simple: In normal operation, the pump is replacing the consumed fuel and taken from bowl...topping it up as it is used by engine, which is a lot less volume than having to fill it from empty.

* siphoning is only possible when there is a continuous column of liquid...and I just fail to see how that can be the case when there is a bowlvalve (a CLOSED bowlvalve) in line with the column, and in the case of the SUs, fuel FALLS through the airspace below valve into bowl.

Cheers

This afternoon I went out and tried to start it.. It has sat for a few days.. I turned it over for a second or two,, then went out and took the air cleaner cover off the webber. The choke was closed properly.. Then I removed the gas line from the carb and there was no gas at all in the line.. My only thought is that it must be siphoning back some how,,surely it can`t evaporate that quickly in a few days when in a cool garage.. I put a new mechanical fuel pump in it a few months ago.. I have never had a webber carb before but I do not understand how it can siphon back gas out of the bowl and down the line.. A inline check valve would probably work if I can get a small enough one.. Anyway,,it is a mystery for now.. Thanks for all the input..

You could take your checking one step further with the filter off. Hold the choke open so you can see down the carb throat and operate the throttle linkage a couple of full strokes---you should see a good stream of gas from the accelerator pump discharge nozzle. You are giving it a few pumps before starting, aren't you? If there's no discharge that would be one more bit of evidence that fuel is not staying in the float chamber (without taking the carb top off). This isn't a fix or an elegant solution -- but if you kept an oil squirt can loaded with gas handy were the car is parked for days at a time you could give a squirt down the throat to get it fired up without having to do a lot of cranking. Maybe the float level is set too low, with just enough gas evaporating to not be able to feed the accelerator pump? -- Dave

The feed to the pump nozzle is from the bottom of the float chamber and a couple of easy pumps should be enough to start the engine from cold but it will likely need some choke to keep it running. We've all seen someone frantically pumping the pedal when trying to start a car and that will empty the float chamber pretty quickly and also flood the motor. Even SU owners do it thinking it adds a boost of fuel.
Non return valves should be available from any marine supply company. I'm in the UK and this is an example. You shouldn't need it but if it cures your problem that's what matters.
http://www.thornycroftparts.co.uk/product207754_422910.aspx
Note also the electric pump on the same site under best sellers. It would be fine for use back close to the tank and "pushing" fuel as designed. Not for under hood use.
Slightly of the wall but make sure that the fixed fuel line that comes in through the inner wing cut away points up as high as possible. That along with a curved rubber feed pipe to the pump that also arcs upwards will reduce the chance of syphoning. That should at least leave some fuel in the pipe either side of the pump.

I would suspect the choke before i would think it was fuel pump.I have a '66 122 with original twin su's and manual choke and have no trouble starting eveen in winter after sitting for several days. At one point i put an electric pump back near the tank and bypassed the mechanical one. My su carbs don't need more than 3-4 psi from the tank.

I also have a Webber with the same 'problem'. The fuel will flow back to the tank after a week or so, or evaporate? I can tell because the clear fuel filter will no longer have any gasoline in it.

So I just crank the starter for about 10-15 seconds. Starter button required for extended starting :>)

Klaus
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Always willing to listen, just not able to take direction.

That is interesting Klaus.. This is exactly the same situation for me.. Crank for 10-15 seconds to get it to start.. If it sits for a day or two,,no problem,,it fires up on the first couple of cranks.. The good thing is that I put a geared starter in so that helps a bit.. I have the glass filter as well.

The mechanical fuel pump only delivers 2-3 psi. I doubt you can find an electrical pump with so little, most are 20+psi.

The gas line from the tank to the pump is pretty close to gravity feed, so do not run out of gas and put air in that line. The engine driven pump is not capable of pumping air at starter speed.

Klaus
--
Always willing to listen, just not able to take direction.

I have a Weber 38 DGAS. I used to have electric solenoids on the carb but found that they stick sometimes. Before I removed them, I tried disconnecting the fuel line to see if it was a fuel pump issue. It ran fine on the gas in the Weber fuel bowl. You may want to open your carb and check the fuel bowl and float. That might be your problem. It should run on the fuel in the bowl until it gets more gas from the pump.

I am deathly afraid to drop the fuel bowl/float on my Weber. I know it hasn't been done in at least 10 years, parked for 8 months each year. There could be worms in there! Or a lot of rust and shellac. The carb throats were bad enough.

Klaus
--
Always willing to listen, just not able to take direction.

Thanks for all the feedback.. I have not gotten too serious about figuring out the problem yet as I will soon get it up to the brother-in-law`s garage for a bunch more work,, front seal,,petronix ignition, etc. so will get it working properly then.. At least I have a few ideas now!!! Thanks for all the info !!! I just bought a new Mazda 3 today for the wifey.. Kind of like light years ahead of the old 122s ,actually 43 years.. lol Cheers!!

here's a stupid trick to check the fuel pump as a culprit. Park on a slope nose down, if the fuel was syphoning out of the bowls before it shouldn't if you are on a decent slope, you can jack the rear as well.

I don't think it is the pump either.
Are you sure your float valve is not sticking shut?

Before considering an electric pump, none of which I like, diagnose the issue. After the car sits for a few days, yank the discharge fuel hose and place it in a container and crank the engine. See how quickly fuel appears and that may confirm your suspicions. It may very well be a weak spark or the choke valve not closing fully instead.

I have this problem as well but only after sitting a month or so. to me it seems the valves in the FP are a little leaky and the carbs get siphoned dry . to my mind a check valve might be all it takes to stop this from happening. If you put it between the FP and the carb the carb stays full, the pump won't have trouble pushing by it. if you put it between the FP and tank you might have problems as pumps like to push more than pull. Personlly I would avoid the 'lectric pump, but I have SU and they are very low pressure and the stock pump works so well I would not want to mess with it.