Fuel Tank Vacuum? 88 300E

[BobDee]

Does any body know why sometimes when taking off gas cap there seems to be a vacuum in the tank and sometimes there dosn't? Car runs fine but suffers from poor initial starting. Sounds like the problem that has been aired many times on this forum. Not really serious enough to fix it yet. Could the vacuum effect be a symptom?

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BobDubery
1988 300E 128K

[jeffsr]

Tanks usually run with some degree of negative pressure, (to keep fuel fumes out of the atmosphere). Usually does not have much of an effect on starting.

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Jeff Lawrence
1987 300e
1989 300e
2000 Dodge Grand Caravan SE

Have to agree, not related to starting problem. Normal.


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Mercedes-Benz Master Guild - 2 years
Shop Foreman - 20 + years - dealer.

[BobDee]

Thanks both for comment. I thought that the vacuum somehow put the fuel pumps under a greater load and that could aggrevate the poor start condition. When I get round to it I'll replace the fuel pump valves that seem from the info on the site to be the best and lowest initial cost bet.
As an aside, you folks are really fortunate in being able to get MB parts and accessories so cheaply. I have ordered the CD rom from the shop. In the UK it is "only available to dealers". Our parts prices here are astronomic; weird really given the Common Market, no duty from Germany to the UK. Maybe all MB parts are made in the USA!
Regs

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BobDubery
1988 300E 128K