Hey guys. I've got a weird issue with my 2008 ML320CDI:

Two times now, with my wife driving, our ML has died unexpectedly, which produces a fuel pressure code on the dash. The first time it happened, my wife pulled to the side of the road, and attempted a restart. The ML started and drove the rest of the way, no problems.

This last time it died, she couldn't get out of the road, and it only restarted when we got to the dealer, at which point it was running fine. The dealer can't reproduce the fault, and the code isn't specific to either of the fuel pumps, injectors, or anything else in the fuel system. They're "guessing" that it's the low pressure fuel pump, but they have confessed to me that they're just taking a stab in the dark. I'm not sure what else to do. Any ideas?

 

I would hope they started with the basics. Fuel filter? Connections to fuel pump? Crash sensor for fuel pump? These are just a few that come to mind. There are some TSBs on this:


Check of fuel pump in engine 642 and engine 651
Topic number LI47.20-P-054504
Version 1 Design group 47.20 Fuel pump, filter
Date 09-20-2012 Validity Models 246; 204; 207; 212; 218; 221; 251; 164; 166 with diesel engine Reason for change Return pressure and return quantity in attachment changed...

Fuel System - Runs Rough/Fuel Loss/Driveability Issues
Date: April 2, 2009
Order No.: S-B-07.16/80d
Supersedes: S-B-07.16/80c dated Jan. 14, 2009
Group: 07


Check Engine Light Illuminated / DTCs 2306-002 and 2078-002 (T-B-14.40/26, July 16, 2008)
Topic number LI14.40-P-045904 Version 1 Design group 14.40 Exhaust-gas Aftertreament Date 01-29-2009 Validity Model 164.122/822 Model 251.122 Reason for change
Complaint:
Check Engine Light Illuminated / DTCs 2306-002 and 2078-002
Cause:
If you receive customer reports in the above model vehicles of the check engine light being illuminated, this may be caused by the wiring harness for the differential pressure sensor (B28/8) in the right footwell being caught under the battery cover and possibly having been damaged. In addition, fault codes 2306-002 and 2078-002 may be stored in the CDI-4 control unit.


Those are 3 separate TSBS that the dealer should have access to.

 

Yeah, I'd like to think the dealership would have considered the TSBs but I'm not sure. It seems like they were focusing on trying to duplicate the fault, which didn't happen. At least they didn't charge me...

 

We're having the same problem. Had a low fuel pressure code and high pressure code. Died with my wife driving it, dealer can't replicate it. ML still at the dealer.

 

Tell them to check the pressure differential sensor.

I just drove our ML 2300 miles because we had to move, and when I arrived, that's what the dealership here said they found. It hasn't gone into limp mode, and it hasn't died since we replaced that sensor.

 

I have had two related problems:

One day the CEL came on, it was complaining about DPF pressure. Ran a DAS test and it said the Differential Pressure Sensor was failed. I bought one at the dealer for just under $100 and replaced in 5 mins by crawling under the truck (no need for a jack if you are thin enough. Raise the suspension all the way first). You'll need the special CLIC pliers that are used for fuel lines.. I just cut off the clamps and replaced with worm style.

About a year later, I started the truck and it ran for 10 seconds then died. It was just idling and boom.. it shut down. Tried to start again and it just cranked and cranked.

Waited 2 mins deciding what to do, then started again and it was fine. I was a 30 second drive from home, so I zipped home (sweating!) hoping that it wouldn't die on the way.

Ran a DAS test and it complained of low fuel pressure. That means either the filter or the 2 fuel pumps.

Was about to replace the filter in the next few weeks, so I had one on hand. Decided to go ahead and replace it.

Fixed the problem.

This was a DEALER SERVICED truck and I have invoices showing all the work (including filter replacements per schedule). The filter I removed looked really old, and when I looked up the date code it was late 2006 (on a 2007 truck)

The original factory fuel filter was still on my truck after approximately 200,000km (120,000miles).

So unless you have personally changed the filter or know for sure it has been done, order a filter and change it yourself. Then start troubleshooting. The cost of an hour labour is more than the cost of the filter... so replace first then start looking at fuel pumps/etc.

I was surprised and did the filter 'on a whim' because I basically assumed every filter was <10,000km old. It wasn't