Possible Fuel Pump problem?
Thread Starter
Newbie
Joined: Aug 2012
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R350
Possible Fuel Pump problem?
Hope someone can help. I have a 2009 R350 4matic, with 54,000 miles (just out of warranty). About a week ago my wife was driving and the car lost power and the 'airmatic' error icon appeared on the dash. She pulled over and shut off the car. In a few minutes she restarted it and drove home. I drove it over the weekend but couldn't detect anything wrong. Four days later it happend to me-'Airmatic' icon appeared, car lost power and then stalled. I got off the road. When I tried to restart the car it would turn over but not start. Few minutes later car started fine and drove home.
I took it in to the dealer. They said the error code in the computer suggested a problem with the fuel pumps. The service adviser said one of the mechanics had seen this before and replacing both fuel pumps fixed the problem. They were not able to reproduce the problem, but want to charge me $1600 for replacing two fuel pumps. I am going to pick up the car and find a shop closer to my house for cheaper.
Questions: Has anyone seen this? Are there really two fuel pumps, I can find anything about that online? Am I crazy or is that a LOT of money for the job? I am pretty handy and have changed out radiators and timing belts, etc on other cars, but don't really want to mess with draining the gas tank. Could it be a relay? They said these tested fine.
Any help is appreciated. Sorry for the long post.
I took it in to the dealer. They said the error code in the computer suggested a problem with the fuel pumps. The service adviser said one of the mechanics had seen this before and replacing both fuel pumps fixed the problem. They were not able to reproduce the problem, but want to charge me $1600 for replacing two fuel pumps. I am going to pick up the car and find a shop closer to my house for cheaper.
Questions: Has anyone seen this? Are there really two fuel pumps, I can find anything about that online? Am I crazy or is that a LOT of money for the job? I am pretty handy and have changed out radiators and timing belts, etc on other cars, but don't really want to mess with draining the gas tank. Could it be a relay? They said these tested fine.
Any help is appreciated. Sorry for the long post.
Senior Member
Joined: Sep 2008
Posts: 331
Likes: 9
From: Bangkok, Thailand
W124, W203, W204, W251
There is only one fuel pump, but it's a pain to get to...the good thing is you don't have to drain the tank to replace it. You have to take the 2nd row seat and rear portion of the carpet out, then you'll see two covers that let you gain access to fuel pump (passenger side) and fuel filter (driver side). Getting those covers off is a pain because it's glued to body, it took me about 4 hours to get them off by heating and prying. Then, you'll need a special tool to turn fuel pump locking ring. I did it without the tool, but again a f**king pain! You'll need 2 people if you don't have the tool. All in all, you'll need at least 7 hours to replace the fuel pump + 3 more hours if you want to replace the filter as well. The parts are not too expensive (about $240 for pump and $150 for filter), it's the labor that drives the price up.
From the symptoms you described, it could be a bad fuel pump. It's one of those parts that always give you intermittent problem. One day works fine, the next day it gives up. The only way to know for sure is to hook up a pressure gauge to the test port on the fuel rail then drive it until it acts up and look for pressure drop. If the engine stalls and you see pressure drop, then it's bad fuel pump. If it stalls but you don't see pressure drop, then it could be something else.
BTW, airmatic has nothing to do with the fuel pump, so you'll have to get that diagnosed separately. Plus, I would avoid the dealer since they're so bull sh*t by telling you that this car has 2 fuel pumps.
From the symptoms you described, it could be a bad fuel pump. It's one of those parts that always give you intermittent problem. One day works fine, the next day it gives up. The only way to know for sure is to hook up a pressure gauge to the test port on the fuel rail then drive it until it acts up and look for pressure drop. If the engine stalls and you see pressure drop, then it's bad fuel pump. If it stalls but you don't see pressure drop, then it could be something else.
BTW, airmatic has nothing to do with the fuel pump, so you'll have to get that diagnosed separately. Plus, I would avoid the dealer since they're so bull sh*t by telling you that this car has 2 fuel pumps.
Thread Starter
Newbie
Joined: Aug 2012
Posts: 7
Likes: 2
R350
thanks...
Thanks for the advice. It sounds a bit out of my league, but I am sure I can get it done for less than the dealer. I don't think there is an issue with the airmatic system-I don't have an airmatic option and don't feel any difference in the ride level. Do 4matic cars have airmatic? When the icon appears the message says 'malfunction' so I quess it is almost like a check engine light.
Thanks for the advice.
Thanks for the advice.
Senior Member
Joined: Sep 2008
Posts: 331
Likes: 9
From: Bangkok, Thailand
W124, W203, W204, W251
All US cars have self-leveled rear suspension which is pretty much half airmatic, it doesn't matter if it's 4matic or not. If you get mulfunction message, then there is something wrong with the system.
Thread Starter
Newbie
Joined: Aug 2012
Posts: 7
Likes: 2
R350
Thanks again
I got the car back from the dealer. The advisor corrected herself that it is the pump and the filter, not two pumps. I also got the print out of the error codes, but it doesn't mean much. They don't think there is a problem with the airmatic, just the fuel pump.
one more question-could it be just the relay for the fuel pump? Doesn't it make sense to try that for $40 before going all the way? Unfortunately it really is intermittent and hasn't happened again, but I am sure it will at the worst possible time.
one more question-could it be just the relay for the fuel pump? Doesn't it make sense to try that for $40 before going all the way? Unfortunately it really is intermittent and hasn't happened again, but I am sure it will at the worst possible time.
