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  #1  
Old 03-08-2002, 01:08 PM
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Location: McLean, Virginia
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cold start problem

After my ponton, which has dual Solex carbs, sits two days or more, it takes a couple of minutes to start. When it does start then or before, it runs very nuicely at speed and at idle. The cranking and ignition systems /components are renewed and/or verified and set to spec. The fuel pump is new and produces good fuel delivery and pressure. The fuel lines are clear. So is the fuel filter. The manual choke operates properly. I find no leaks anywhere in the fuel lines or couplings. I removed and cleaned with carb cleaner every jet and hole where the jets go. I also squirted carb cleaner down the throats when the car was running.

Some pontons exhibit the same problem, others do not. I have concluded that the problem may relate to too-rapid evaporation of fuel from the carb bowls. This may derive in part, at least, from the composition of gasoline today compared with fuel of the 1950 era. The carb shown no obvious traces of leaks. Other suggestions are that the accelerator pump seals may now be defective, letting fuel leak back or evaporate. I understand that one fix would be ti install some sort of electric fuel pump. Other than that, has anyone any helpful ideas wehat is causing the problem and what could be the correction?

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Douglas
1959 M-B 220S cabriolet
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  #2  
Old 03-08-2002, 02:10 PM
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Is this an old problem, a new problem, or a slowly developing one?

Does the engine not fire at all in two minutes of cranking after it has sat for an extended period? Or does it fire and quit?

After the car has sat, can you pull the air cleaner, move the throttle and observe a squirt of gas from the accelerator pump, or does the chamber seem to be dry?

This should answer the evaporation question.

But it seems to me that in a reasonably well-sealed carb it would be hard for that much gas to evaporate even in a week's time. What you would lose should be made up by the pump in a few turns of the engine.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #3  
Old 03-26-2002, 12:15 PM
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Answers:

Not a new problem.

Once it fires, it stays running and does so smoothly.

After sitting 2 days or more, there is no squirt of fuel observable after removing the air cleaner.

I am coming to the conclsion , since these cars were originally fitted with a fuel pump that had a priming lever, that in 1959 Mercedes must have realized that the carb on this car had a basic problem of carbs not retaining fuel in the bowls after standing awhile. Am I on track?
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Douglas
1959 M-B 220S cabriolet
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  #4  
Old 03-26-2002, 02:11 PM
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Not familiar with your car, but your hypothesis makes sense to me.

If the accelerator pump chambers are dry (no squirt), then you are definitely without gas in the carbs. But it also sounds like your pump loses its prime as well because it should not take more than a few turns to get enough gas to the carbs.

Maybe a small pump on a relay that runs for ten seconds when the key is turned on and then shuts off? A guy on the veterans board had all sorts of trouble with excessive fuel at idle with an electric.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #5  
Old 01-16-2003, 04:36 PM
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I am returning to my hard-starting problem. First, I plan to rebuild a priming-type fuel pump and install it.

Then I plan to replace the rubberized diaphragm and rubberised gasket on each carb. The car runs well at speed and at idle when finally started from cold. In addition to replacing the accelerator pump items, should I try to replace the jets and seats? M-B no longer supplies the large carb rebuild kit, but does supply a kit with figer gaskets and rings. Royze sells a kit but that too does not contain the jets and seats.

What are folks thoughts? Thanks
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1959 M-B 220S cabriolet
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  #6  
Old 01-16-2003, 10:03 PM
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Douglas:

Sounds as if you have open vents on the carb, and the gas is all evaporating! More of a problem now that it used to be, since the gas is a bit more volatile. Common problem on pre-emissions control carbs, by the way.

No need to replace the jets, the are just an orifice, and if the car runs well at speed, they are fine. I would replace the accelerator pump seals and etc, though.

Peter
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1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
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  #7  
Old 01-18-2003, 01:35 AM
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Would a leaky fuel pump diaphragm let the fuel leak back?
Or a leaky float bowl valve, more likely...
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1981 300CD (Benzina)
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1976 Jaguar XJS-saved a V-12 from the chevy curse, what a great engine!
1988 Cadillac Eldorado (better car than you might think!)
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1976 Yamaha XS 650 (sold)
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  #8  
Old 03-19-2003, 03:31 PM
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I found the main answer. I obtained an original, priming lever type of pump, rebuilt it, and installed it. Primed the system and the car fired up immediately and smoothly after sitting several weeks. I have to think the Solexes as designed necessitated this type of starting assistance.
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1959 M-B 220S cabriolet
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  #9  
Old 03-19-2003, 05:59 PM
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If there is a return fuel line you might add an electric fuel pump. Not original but workable.

Then there is a modern electronic fuel injection system. We won't get into that.
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Currently 1965 220Sb, 2002 FORD Crown Vic Police Interceptor

Had 1965 220SEb, 1967 230S, 280SE 4.5, 300SE (W126), 420SEL

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  #10  
Old 03-20-2003, 01:40 AM
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Douglas,
Where did you find the priming-lever pump? My '60 220S has the same problem. Unfortunately the P O replaced the original pump with a non-primer. In winter, I can go over a week without excessive cranking, but it's really a problem in the summer. I now keep a 1 pint squirt bottle handy, to prime the Solexes and save my starter.

A solution I used on my '57 DKW coupe, for which no priming-lever pump was availible, was to fit an electric 'ticker' type pump.
I now turn on the ignition and first, listen for the ticking to slow to a stop as the carb is filled, then it's ready to crank.

Happy Motoring, Mark
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  #11  
Old 03-20-2003, 12:42 PM
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See the indicated fuel pump article on the "ponton page." It indicates sources and part numbers.

http://www.mbzponton.org/valueadded/maintenance/fuelpump/fuelpump.htm

A revision to its footnote 19 is in the works to take into account the fact that the same priming-type fuel pumps were also originally fitted to some or all of the 1960s fintails that came with the Solex carburetors originally; for example, the 220b to 1963 and the 220Sb to 1965.

Does this provide what you need? Contact me if I can be of further help.
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  #12  
Old 03-20-2003, 02:57 PM
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Douglas,
A superb fuel pump article!

I rebuilt my (late) 180b priming-lever pump sometime in the mid '70s but wound up replacing it with the newer type pump in the late '80s. I think I was told that kits were no longer availible.
I may still have the origial pump carcass around somewhere but I'm unsure if it's still rebuildable. For now I can still prime (with gas, not starting fliud!) so I'll hold off on an electric pump.

One problem I had with rebuilding my old DKW fuel pump may apply to old Mercedes pumps. I discovered that the new, flat valve discs supplied with the DKW pump kit didn't seal well in the worn, rounded valve seats in the old pump body. I went from weak, intermittent pumping, to NO pumping, hence the elecric pump.

To anyone seeking an electric pump for a 6 volt car, J C Whitney still sells a Walbro 6 volt fuel pump. As that pump operates at somewhat higher pressure than some original import fuel pumps, Purolator makes an in-line adjustable pressure regulator. It's no longer availible from J C Whitney but can be found in some autoparts and racing supply stores.

Happy Motoring, Mark

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