Utah

2012 c250 sport 1.8L turbo

Car died while driving, checked fuel pump ignition fuses which checked good. Heard No noise from fuel pumps, so after towing home, I replaced both low pressure fuel pumps. Tried to start but cranked with no start as before fuel pump replacement.
next checked for spark at #1 plug. And god no spark
after That, I focused on the cam and crank posistion sensors. Replaced crank sensor first with same crank no start same with new cam shaft pos sensor.
I then went back into the drivers side fuse box to check for blown fuses again and discovered #23 blown (engine electronics). So I thought “Aha!!”, but when I tried replacing #23 with a new 15 amp fuse it immediately blew again.

Any help will be greatly appreciated!!! I’m gonna try to look for a short but I’d love some help if anyone can point me to the sensors or items powered by this #23 fuse

gamma300C

You confirmed your fuel pumps were getting power ? is there a "high pressure pump" that needed checking for failure..high resistance bad pump with abn. high Amp-draw fuse blow or chaffed wiring short (doubt) per how this all started with your Benz.

Good luck

Utah

Gamma 300c: thank you for you reply!!


1 yes I was getting power to the new fuel pumps,
2 yes there is also a high pressure fuel pump on the back of the engine, but I’m not sure how to test that. I’m sure there is an electrical input somewhere on it, but sit is a mechanical pump right?

hpfp wouldn’t surprise me though b/c I was having misfire and acceleration issues leading up to this complete shutdown. ie accelerate, CEL fault into limp mode, pull car to side of road, turn car off and wait, restart and back to full power…as mentioned in another thread(s) on this forum.

gamma300C

I was guessing per the "no fuel pump" sound initially and fuse # 23. That leaves the mysterious Engine Electronics which would point towards a trip to a Dealer or good MB scanner. Does #23 blow with ignition in "ON" or when car is started. If fuel pump make noise on ON but fuse OK, sorta eliminates them, no ? Just spinning theory.

Utah

I have to say my eyes must be going🤦🏻‍♂️. I just recounted fuse numbers and looked at the fuse diagram and it is #24 NOT #23 blowing. It was ignition was in the 2nd position when I tried replacing the original. The fuse is Still engine electronics but a 15 amp instead of a 20 amp

Utah

Problem resolved.

during my trouble shooting for the original misfire issue and limp mode, I replace #3 coil. This (Amazon) coil shorted out causing 15 amp fuse #24 to blow and in turn wipe out all the coils and causing the car to die. My bad trouble shooting led me down a fuel pump replacement road. After replacing these and it not working. I checked for spark and found none. Started checking all fuses and found the #24 blown. Unhooked items I thought were associated to the fuse and bam found a bad #3 coil. Thank you Gamma 300 for your assistance.

JettaRed

iTrader: (1)

Wow! You did a lot of work and spent some money fixing a non-problem (fuel pumps). (BTW, I believe the two things that look like pumps may be one pump and one filter.)

Do you have a Mercedes scanner? If not, get one and save money in the future.

Check Amazon for:

• iCarsoft MB V3.0 (not MB II)
• Launch Creader Elite Benz
• Foxwell NT510 Elite