I have a 1995 C280

My vacuum locking pump mechanism located on the right side in the truck stopped working.I replaced that.When we put the battery back in the car, my boyfriend remembers that he had the key in the ignition. (Not sure if that matters).Once the battery was connected the car would not start.So we had to jump start it to the starter solenoid.
I purchased a push button switch that is jumped from the solenoid.I think the anti-theft device might be locked and that is the reason why I can’t start the car.I only have one basic key for the car not a remote.For the last month this is how I have been starting my car.So that one problem.

Now Two weeks ago, my car stopped working.It will crank but not start.I am trying to figure this out myself because money is very tight right now.I listened to someone and replaced the fuel pump and fuel filter which both did not need to be replaced.The car is still not working.I checked to see if it was getting fuel and it is.I believe the spark plugs are good.I will be checking that tomorrow, but I was told that they are good.My battery is losing charge and I had to replace with a new battery.

I don’t know what to do know.Oh also, the driver’s side and passenger side doors will not unlock with the key. I have to unlock and lock the car from the truck.This just started acting up also.

Don't replace things just because someone says to replace them. These things can be tested to see if they are getting electricity and/or working.

Also you can replace something with a wrong part or not correctly install it, then you have two problems.

Because your money is tight, I would recommend getting a multimeter and learning how to use it. Watch automotive videos on youtube where they show you how to use a multimeter for testing this or that. Search for the words multimeter mercedes or multimeter automotive.

Next get or borrow a 10 amp automotive battery charger. A fully charged battery is 12.75 volts DC. Learn to keep the battery charged and periodically check its charge as you work on the vehicle. I keep a charger connected if doing a lot of electrical testing/work without the engine running. NOTHING will work properly with a low battery!

Check the fuses.

(ALWAY check the battery and fuses FIRST if having an electrical problem!!! No electricity - no workie!)

Find out if the alarm is factory or an aftermarket add-on. In either case, learn if the alarm disables starting on the vehicle. And if you need the FOB to disarm it. If factory, you can get a FOB from a Mercedes dealer. (If aftermarket, then from the manufacturer of the alarm perhaps?) Or you can get a wiring diagram and disconnect the alarm and particularly the disabling function so it will start (if that turns out to be the problem by TESTING with a multimeter and schematic wiring diagrams).

This is the way I fix cars. If you don't know this stuff, then find an automotive electric shop or alarm shop. This is pretty much advanced electrical troubleshooting. Just tracking down the wiring diagrams for an aftermarket alarm can be challenging.

Mercedes wiring diagrams can be found with a google search.

A full set of bronze/copper replacement fuses from fleabay.. delivered for $10
Do not use aluminum fuses ! They have a sneaky way of failing in a manner you
cant see.

A cheepie multimeter or DMM of DVM again on fleabay .. delivered for under $10
The average village idiot can learn to use one in about 10 minutes.. very easy to do.
(Not inferring you are one BTW)

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