Rough start 94 e320
 

Hello guys im having some issues with my 94 e320.
It has around 230k miles and a new engine harness replaced around a year ago.
Everytime i start the car it just keeps cranking and whenever i hold down the gas pedel it begins to start. Usually in the morning it starts perfectly, but during the day i can bearly get it to start. Any suggestions on what could be the problem?

Also i to have an issue with MPG, it seems that i am only getting 13mpg when the tank is full to 1/4 empty. Any suggestions on what to help with mileage?

Thanks for any help you can offer

Fuel pumps or fuel line check valve or even the fuel filter as you shouldnt have your foot anywhere near the gas pedal while starting.

If its starved for fuel then check fuel pressure and go from there.

I would suspect a defective fuel pressure regulator. Given the mileage it is something you may want to look at, especially if original.

Are you getting any error codes from the computer? I have a '93 300E with the same problem as you are describing and have yet to nail it down. I noticed with mine that if you have just turned the car off after driving a ways, it can be extremely hard to get it to fire back up. Have you noticed anything else strange that might help lead to your problem? Checking the pressure on the fuel rail is a good idea, and it should be around 60 psi I believe. You may also want to see if there is someone near you that can check your ETA, and you probably want to check the wiring on it yourself. It has the same degrading wire as so much of the car had, and isn't replaced by changing out the upper or lower harnesses. Hoping you have a trouble code that helps lead you to your solution.

Check the fuel trim. If it is starting fine in the morning then it is probably not the check valve. The MAF sensor sounds like the culprit.