I'm looking at an 04 Mercedes SL500.  

Parked for a long time, battery ran down, tried putting in a new starter/front battery.

Cranks but no start.  

No fuel in the fuel rail and can't hear the fuel pump working is all I know so far.

Tried changing out the crank position sensor, still no start.

I checked on-line and seen the location of the fuel pump related fuses and fuel pump (k27) relay.  Fuse check I know to do, how do I check the relay?

I cant find a pin out diagram test for the fuel pump relay socket, is it possible to test this with a volt meter without breaking anything?

Is it possible to check injector pulse and spark with basic tools/volt meter on these engines (M113 V8)?

Any other suggestions on troubleshooting are welcome!

Try some ether and see if the engine will fire. If it does, then you need to fix you fuel problem.

The relay should click when you put 12v to it.

Hmm, I guess having someone turn the key while my hand is on the relay, I should feel it click if there is signal and the relay is working.

Not sure I can get ether around here though.

Diesel starting fluid is normally ether.


example  Starting fluid



mm

Gotcha, will check that out!

So I took another look at the car.  Key in "on", fuel pump relay clicks.

Pulled a plug wire, put a screw driver in, and grounded it against valve cover.  Had someone turn the key to "start"r.  Very strong spark.

Pulled an injector plug.  At key "off", no voltage.  At key "on", around 8v.  At key "start", cranking, no indication of pulse.

Pushed in the fuel rail shrader valve while cranking, a bit of fuel comes out  but does not spray out with force.

Harbor Freight has a fuel pressure tester for $19.99 that should fit.  At least, it fit to the schrader valve on my 99 slk.  USE TEFLON TAPE on the threaded connections at the valve and at the gage end as well.  Best way to check if the fuel pump is working.  

Be sure to charge the battery fully, then disconnect it for a few minutes and reconnect it.  None of my Mercs ECMs deal well with a charging cycle while connected.  

The ECM will have to relearn all it's adaptations, but it should start.

You are going to need some sort of good code reader that will read the CAN bus.  I have Mercedes SDS, but it's pretty costly and you still need DX skills.  I have basic to intermediate skills and there are some things I've come across that had me stumped.  I just posted one of them lol.

Did you plug the crankshaft pos. sensor back in?

If you ohm it out the spec is 1k (1,000) ohms.


Its really one of the only things that causes these cars not to start, I know its kind of a PITA to get to it but I'd verify wiring connections at the sensor and that the new sensor itself is actually good before chasing through a bunch of other things that may not be the problem.


Adam

Crank sensor is a common problem on those cars. Known for intermittent no start.

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The 04 SL500 also has two batteries....better check both.

Also MANY Mercedes have issues when jump started.  My dads SL500 blew out an ECU when his battery went dead.  My CLS AMG Benz just had the battery die; the dealership jumped it and it blew out the steering wheel ECU.  Yes, there is a steering wheel ECU and now my horn and steering wheel buttons don't work.  I looked online and they replaced the ECU with one with better "ESD protection".  Of course I'm on the $500+ hook for it.

Update:  Got it running!  Thanks all for the help!

It was the fuel pump.

A new crankshaft position sensor was the very first thing I put on.    After installing it I checked for spark by pulling a plug  wire and grounding it to the valve cover.

I got a brand new front starter battery for this project, expensive sucker that was, MB seems to be the only one that has these available.

Cranked just fine but wouldnt start.  

After confirming power to the pump and confirming it wasnt turning on, I put a new one in and it started right up.