Cutting out..300SL

Hi to you all...not sure if I'm using this forum correctly!!.
I have a 1986 Mercedes 300SL with a genuine 45K on the clock...I was driving it from London to my home in west Wales....all was fine for 100
miles or so then she cut out on me....I pulled over on the hard shoulder and she started after about 5 min....She was fine for another 50 miles or so and the same happened....I got her started but after another 50 miles it happened again....I called the AA and they kindly transported me home....I asked them to drop the car off with our local MBZ dealer.....They have failed to find the fault!!......Any ideas from anyone out there....I was wondering if I could have a faulty fuel pump relay...not sure where it is though......
Any ideas would be great...
Mike
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Fuel pump relay is the first and probably best idea.
Second idea, given the 50 mile intervals to failure, is that the fuel tank's vent is closed so a vacuum is created as the fuel is consumed. After 50 miles about two gallons has been removed from the tank - about 10% of its cubic volume - which the fuel pump cannot match. The next event is your chance to prove or disprove this theory - just open the gas cap - a vacuum confirms, no vacuum - forget it!
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Thank you very much for responding....
If I remove the cap I do get a vacume noise....Is this good or bad?
I drove the car today for 15 miles...parked it on the drive...went to start it and no luck...will turn over but will not fire....?
Regards..
Mike T.G. Lambach wrote:

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I definitely think it is the fuel pump relay. It is probably original... even though you don't have the mileage to wear that relay out, the age gets to it.
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Hi...thank you for responding..
are you able to tell me where the fuel relay is situated on the 300SL.
Kind regards.
Mike Tiger wrote:

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No idea where it is located... usually in fuse box or behind the cover behind the battery. A slightly bigger than cigarette box with the worn "kickdown" on it.
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