Fuel pump failure on 2012 Mercedes ML350

My wife was driving a 2012 Mercedes ML350 on a highway when the engine suddenly stopped and she was lucky to get over to the shoulder before being hit. The car was towed to the dealer who said the fuel pump died. Is it normal for a fuel pump to fail so quickly, killing the engine and resulting in such a dangerous situation?

The NHTSA safer website had two incidents of the same model and year vehicle with over 50K miles out of a dozen or so reported ML issues. How do I find out if this is a common problem?

My old 70’s VW Rabbit would do that once in a while. Stop running for no apparent reason on the freeway. It was always the fuel pump relay for me, not the pump. I’m not aware of any systematic issues with MB fuel pumps. I expect this was just a fluke. And are you certain the problem was the pump and not the electrical power to the pump? If the pump or the fuel system gets a little clogged with grit – sand usually is what the contaminant usually is – the pump has to work harder and will draw more electrical current. This can, like I say, damage the fuel pump relay, or the wiring between the relay and the pump. The electrical connection at the pump corroding is a common source of fuel pump problems.

You have to remember that MB doesn’t manufacture the fuel pumps that they install in their vehicles. They’re purchased from a supplier/vendor.

Just like the airbag recalls for many makes of vehicles, and the ignition switch recalls for many GM vehicles, these were supplied by a supplier/vendor.

So either there was a bad run of fuel pumps from the supplier/vendor to MB, or the supplier/vendor had to cut costs in the manufacturing of the fuel pumps in order to make a profit.


I don’t see anything about the fuel pump, but there are some known issues apparently with
the fuel system control module, the fuel filter, use of E10 fuel, and the fuel filler door. An MB dealership shop can explain those to you, but I doubt they have any bearing on what happened. As @Tester says, probably due to just a bit of bad luck, your car got a defective pump is all.

And yes, a fuel pump can work fine one moment and completely fail the next. And when it happens, it can be dangerous as the car will likely have no engine power.

Edit: If you think you may have gotten bad or contaminated gasoline at some point, before installing a new pump it would be a good idea to determine if the fuel supply remains contaminated or the fuel filter is clogged.

Agree with above, and sometimes if you run your tank close to empty, junk could get sucked in and damage the pump. Had friend with an Explorer that the pump failed just one week after running the tank to empty.

Was the fuel pump manufactured by Bosch, by any chance?
I ask because the Bosch fuel pump in my Volvo would burn out every 13 months or so.
I probably replaced the fuel pump on that car at least 5 times.

European cars & European parts…you gotta love them…

Mechanical parts can fail at anytime. Over the years…it’s happened to me countless times.

That’s why there’s no substitute for redundancy for high reliability.
How much more would it cost to have two smaller fuel pumps and check valves to isolate one that fails?
Not a big impact on a high-end car.
Double up on some other small parts that can cause engine stall.
Parallel relays, second crank position sensor, etc.

These failures where engines stop running happen across every make/model even newish for a variety of reasons. Two incidents reported is pretty low and not enough data to make any judgement of a problem. Report yours of course.

Warranty will take care of you and like majority of incidents nothing happened just wasted time involved.

@circuitsmith stalled cars are so rare in my everyday travels commuting I don’t see the need or reason to create the complexity and redundancy of duplicate parts.

There could also be a misdiagnosis involved. The fact the pump may not be working could possibly be due to a pump control issue rather than the pump itself.

A jumper wire to the pump circuit could answer that question.

As to Bosch pump quality I’ve never found them to be any more problematic than any other. That’s from work on SAAB, VW, Volvo, BMW, etc.
The ones I’ve seen that failed generally had high miles on them or suffered contamination.

I hate to think about the fuel pump problems I had with my Riviera. Cost me $800 plus each time. Always used OEM and had one fail same day, within a month, and one almost one year to the day. Never really figured it out after replacing all the relays, wiring to the computer back, pigtail, etc. The dang things still failed. Banging on the tank with a 5# hammer would sometimes get me home and sometimes not. Towed it 50 miles and when it got off the hook at the shop started right up again. If I ever have a fuel pump go again, I’m trading cars shortly after.

“The ones I’ve seen that failed generally had high miles on them or suffered contamination.”

I dumped that POS Volvo when it had ~76k on the odometer, and the fuel pumps started failing at (IIRC) 18k miles.

So, I have to rule out high miles, but it is entirely possible that I was dealing with dirty gas. Because it was possible to use leaded gas in that car–unlike many others on the market at the time–I did use leaded gas in order to save several cents per gallon. However, the only station in my area that still sold leaded regular gas at that point was one Amoco station. Maybe they had really dirty tanks.

Just before the pump would crap-out, it would start buzzing very loudly. If I was very quick, I could put the replacement pump in before I got stranded on the road, but that type of proactivity (is that a word?) wasn’t always possible, so I did get stranded several times with that cursed Volvo.

I think my late 70’s VW Rabbit had a Bosch electric fuel pump and it never failed in the 15 years I owned that car. The fuel pump relay failed, and the wiring to the fuel pump relay failed, which burned out the relay plate. But the pump itself never failed. On my early 90’s Corolla the fuel pump, fuel pump relay, and associated wiring continue to perform like new.

Be glad–VERY glad–that you never owned a Volvo from the '70s!

Yeah, I see what you mean about that darn 70’s Volvo of yours … lol …

I currently work in a Mercedes parts department and fuel pump failure on m.y. 2012 ML 350 is an uncommon occurrence.

A key ingredient to long fuel pump life in a submerged fuel pump is never letting the fuel in the tank get to a very low level. In simple terms , fuel pumps require fuel to “cool” them and keep them from overheating. The same principal applies to any submerged pump, whether it be in a well or in an aquarium.

Let’s hope the pump can be replaced without dropping the tank. Couple hr job if ur lucky

I’m going to be a sourpuss, in regards to that parts guy’s response

I don’t think a parts guy is going to be handing out too many fuel fuel pumps . . . for ANY brand of gasoline powered vehicle, that is only 3 years old

When I was at the Benz dealer, many years ago, almost every single fuel module that got replaced under warranty, was because the float part had failed, not the pump

The good news . . . and this is dated knowledge, again . . . is that I don’t recall dropping tanks to replace Benz fuel modules. The access was usually under the rear seat, or underneath the car, on some saddle style tanks

I use the word module, because nowadays that’s the way things are . . . a fuel module, consisting of pump, sock, sender with arm, etc. Many of them also come with a pressure regulator and fuel tank pressure sensor

db4690 is correct in calling the fuel pump a “module” , but then again most people not in the automotive service industry still refer to it as a pump, and this is pretty much in the same vein that an internal combustion engine is referred to as a “motor”. Quite often now a technician will refer to it as a fuel delivery unit. It’s your call. Never heard anybody refer to their “rat engine”!