I know we're talking about a 300. I've got a 190E, and I had issues with the cold start valve. It made the thing hard to start first thing in the day.

There's a check valve on the fuel pump.

How old is your OVP? If you don't know, might replace it. I did, and my computer system came back to life in a day of driving.

Check ALL vacuum lines for leaks.

Check the fuse for your gauges first. Old fuses can corrode. I replaced all fuses on my car when I got it, and have never had an issue.

I have never had to pump the pedal to start my car. You shouldn't have to either.

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My first Mercedes Benz. 4/6/07.

1984 190E (201 024) 2.3L four.