driving home, got stuck at the Golden Gate Bridge toll booth. I had to be pushed into a parking lot by a caltrans truck. Car would not start....just cranked.
I could not hear fuel pump coming on. Then, when I did hear it, car fired up. I got to downtown SF and car died at a light. Still no fuel pump sound at attempted starts.
Triple A tow driver banged on fuel pump area and if fired up.....fuel pump...or fuel pump relay...or ???? thanks in advance (I know its been covered before....but don't know where to start first)

could be a faulty fuel punp relay.

or faulty connections at the fuel pump.

I agree -- fuel pump relay would be my bet. It's known to have a relatively high failure rate. Many owners keep a spare in the car for that reason.

On many 124s it's located under the rear seat -- not sure about yours but that's where mine is.

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Steve
'93 400E

On my 300E, it is behind the battery, behind a plastic cover.
There are a couple of relays there, but the fuel pump relay
usually has "6350 RPM" or similar written on it. (This means
it cuts power to the fuel pump at that RPM.)

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VR
1967 250SL

Likely the fuel pump itself.

Bad relay unlikely to be helped by whacking on the pump cover.

Seen the same failure mode twice now on 2 different 300Es.
Whack on the pump, and it starts. Goes a while, sometimes a long while, sometimes not, randomly stops, whack it again....
gets you home eventually...

Suggest an OEM Bosch pump. I made the mistake of buying a slightly cheaper (and available on a Sunday) pump from AutoZone.
Works ok, but fits poorly, and it's much louder.

Best of luck.

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1986 300E 5-Speed 240k mi.

The first time I was in San Fran my girlfriends brother picked us up from the airport in his 1978(?) toyota. Just after crossing the bridge his car died. We spent a good 2 hours sitting on the highway waiting for a truck to come by and push us off the road. To be honest....it wans't that bad. Had a great veiw!

CSNOW was right.....turned out to be the fuel pump itself. After removing the cover and tapping on it, it would fire up...only to die on me 5 minutes later. Had to do the Sunday night Special and order from autozone. Not too bad of a fitment problem. Actually, $149 vs. $220....if fits pretty good! Will keep a spare relay in my trunk "just in case."

That is good news.

Say, is your Autozone pump loud, or is it just mine?

As for fit, the pump was much smaller, and they provided a thick 'hunk of rubber' so that it would fit in the mounting bracket.
I used a piece of sliced radiator hose instead (wrapped all the way around), which seemed to work better than the rubber rectangle provided. This made it quieter, but it's still loud.

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1986 300E 5-Speed 240k mi.

Try to run diesel in a "reverse flow" to remove the junk from the inside of the fuel pump. You may get lucky and "revive" the fuel pump. DO NOT USE GASOLINE!

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J.H.
'86 300E

csnow,

Yes the new fuel pump is pretty loud....it is a Master from Autozone, and yes was smaller in size than original and came with the rubber chunk which I cut into pieces to help fit the pump into the clamps. Might install sound dampening material inside the front plastic housing cover....or get aftermarket exhaust to add to the fuel pump sound. Can't decide to go quiet, or sporty.

Well, at some level it is comforting to hear it working...
There will be no question what is wrong if it fails!
I suppose you could also get a bigger amp to drown it out.

Would go with the Bosch if I could do it over again.

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1986 300E 5-Speed 240k mi.