So let me preface this by saying I've spent the past two days searching multiple forums trying to figure out the issue with my 1995 C280 to no avail.

I started the car as usual and let it warm up for a few minutes before leaving work. When I came back outside the car had shut off by itself and the ABS and battery light were illuminated and now it refuses to start no matter what.

My first thought was the battery so I tried giving it a jump but no success. Next I tried putting in a brand new interstate battery off the shelf at my work, again no success. I'm confident the car has spark because when cranking you can hear the car firing but it won't turn over as if there is no fuel.

Tried spraying carb cleaner in the intake after the MAF and it did run for a few seconds.

My next move was to check out some forums and see if someone else had a similar issue. I've read several posts about intermittent starting but none when the car would not start at all. There we no signs that this was gonna happen ie) rough running, cold start/hot start issues. Car starts the first time every time... Until now.

Sorry for the long winded post but I wanted to make sure I was thorough. If anyone has any insight as to what it may be before I start throwing money at probable fixes it would be a big help. Gonna have the mechanic at my work help me troubleshoot tomorrow.

Thanks all, and happy fourth!

Suspect the fuel pump or its power supply.

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Prost!

Put a pressure gauge on the fuel rail and see what you get.

If nothing, put an incandescent test light across the fuel pump terminals and see if it lights.

Jumper the fuel pump relay ( should be green relay in the trunk, next to fuse block ) and see if you have light on / pump running / pressure.

Next, pull the hose from tank to pump and see if fuel comes out. The C class tends to corrode the level sending units giving improper level reading. There are two sending units on this car due to the 2 sump tank. These sending units are accessible from the bottom of the tank.

So I checked to see if I had pressure in the rail and it appears I do. I'm not sure how much because I couldn't find the proper fitting for the fuel pressure gauge.

We took the fuel pump relay out and hooked it to a power supply and tested it and it seems to be working ok. The fuel pump will prime with the ignition on but after it primes it shows 0.0 volts on both wires to the pump.

Me and the mechanic concluded the relay is the likely suspect so I have ordered one from Mercedes and it will be here Thursday. Hopefully this solves my issue. Will confirm once I put it in.

Don't randomly throw parts at this car.

Did you jumper the relay, have pump running and try to start the car? If still no start, the relay isn't the problem since it is out of the circuit.

The ECM runs the pump for a few seconds when the key is first turned on to prime the system. If it does not see a tach pulse or cranking signal it shuts off.

The injectors see battery feed through a relay or ignition switch then the ECM grounds each one to fire it, make sure you have power at the injectors.

I jumped the relay and hooked up a jump pack to the car and it started up for about 10 seconds but it wanted to stall out, had to keep the rpm at about 2000 to keep it running. I'm still confused as to why the ABS light is staying on, doesn't that indicate something's up with the overload protection relay?

I tried hooking up a 38 pin Mercedes diagnostic tool to the snap-on scanner we have here but I couldn't get it to communicate with the cars ecu.

Injectors have power when the ignition is on but I need another set of hands to check if there's power when cranking so I will be doing that tomorrow.
I

I think the 1995 was the last of the years with the self destructing wire harnesses:

Rough RUnning C280 Wiring Harness - MBWorld.org Forums

I only think of this because you have two simultaneous but seemingly unrelated problems which could both be electrical. Similarly it could involve a bad ground somewhere. I realize these are not very specific ideas but if a ground goes bad then everything goes out the window so to speak. For starters take a look at the wire harness conductors and see if any are cracking or turning to powder.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

The car has had the wiring harness replaced by the previous owner so I hope that isn't my issue.

But a bad ground is definitely something I will look into.

Check out the OVP relay also. I don't know much about it since my car doesn't have one. I am not even sure your car has one.

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1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Car has 12.5 volts going to the injectors when ignition is on and it drops to 8 volts when cranking is this normal? Gonna see if I can get the proper fitting to check the fuel pressure at the rail.

And mpolli my car does have the OVP relay which is another thing I was thinking could be the culprit but from what I have gathered from the forums the car should still be able to start intermittently. My car will not start at all and its been 4 days and I have tried everyday.

Could all my issues be something as simple as a crank sensor. It just seems odd to me that the car shut off and wont start at all with nothing to indicate there was a problem before it happened.

Eight V is pretty low, I'd do a battery load test. A fully charged lead acid battery is about 12.66 so 12.5 isn't bad for state of charge.

If the battery tests good, I'd follow the inj circuit and maybe apply a jumper to battery power then crank. MAKE SURE you are applying power to the positive side of the injector, it you apply positive power to the ground side of the injector you will burn up the engine computer.

Measuring voltage tells you battery state of charge ( how _full_ the gas tank is )

A load test tells you capacity of the battery ( how _big_ the gas tank is. )

I know its been a few weeks since I answered the post but I just wanted to make a reply of what fixed my problem to help others in the future.

After much troubleshooting and replacing the OVP and fuel pump relays I put 2 more gallons of gas in the car (was at a little over a quarter tank before) and it started right up which had me scratching my head.

I left to go home for the night in the car and it died again at the stop light just down the road and would not turn over like before.

I bought a cheapo brand fuel pump for $30 and a Bosch filter which actually cost more than the pump lol. Got the pump and filter yesterday and put it in and after a few turns of the key to prime the lines and pump and it turned right over.

Only problem is the the new pump seems to be leaking before the crush washer at the output nozzle of the pump causing the car to lose fuel pressure when sitting for a while. After a few cranks it turns over but is still frustrating. I guess you get what you pay for. Gonna replace with a genuine Bosch pump once the tank gets low because while replacing the pump and filter I found the lines from the tank to the pump are dry rotting.

Just want to thank everyone for their replies and help narrowing down what the issue was.