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Discussion Starter #1
Hello all...
First... I would like to apologize to any of you that may have readof my plight in the generalmb forum...

2000 ML320,178k miles.....

Last week the truck was fine all day, during a heavy rain storm... After getting home, halfan hour later I needed to go to the store.. the truck decided it wasnt goiing...It was bogging down badly.... I left it run for about 1/2 hour and nothing better... Just to check Iscanned it and got p0400,EGR...
After doing some research here i decided to remove and clean out the tube, which was packed.. Put it all back together and nothing changed,so I figured it has 178k miles, maybe EGR valve is bad... Got a newone from dealer and replaced next night... Although it did run better,it wasstill bogging down here and there.... Left it run for a bit, checked codes and got p0170 and p0173, leading to the MAF...Now,I did replace this In june of last year, along with new fuel filter...I got the MAF on ebay, I know, forgive me father for I have sinned, so I ordered another one from autohausaz and got it the next day... Installed it and same problem.... Thought maybe it was bad... Swapped it from my98 E 320,same MAF, and it was still not working..... After searching more on here, I thought vacuum leak.... Checked all connections and although they were good, I removed and replaced all.... That did make it better but didnt solve it... Now at about 3500rpm, it boggs down... Read some more, thought maybe fuel pressure... got a gauge and at k/o, e/o has 30... k/o e/r, was at 50, but the more I revved it the lowerit went... Eventually got down to 10psi..... Some have suggested fuel pump... Maybe fuel filter? someone even said o2 sensors, but they should throw their own code... Maybe cat convertor? What do you think?
 

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2000 ML55
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I might be wrong, but I believe 12 psi is the bare bones minimum fuel pressure you should be running at speed. I believe your fuel pump guess might not be far off.

It is, however, a guess...

Also, how old is your fuel filter?
 

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Discussion Starter #3
last time I changed the filter was in June of last year, but I drive alot, so that was about 25k miles ago...
 

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2002 ML55 AMG, 2005 Chrysler Crossfire Coupe Limited, 1999 C280
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With no technical knowledge whatsover, if I had to take a guess from what you describe, I would say check your fuel pump first then move on to the catalytic converters.

Good luck!
 

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02 ML320 06 ML500
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Did you replace the fuel filter yourself or was it replaced by a mechanic or dealer? And if so, are you absolutely sure you got a new filter?
 

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Dang, man...quit throwing money at the problem! I know from recent experience that getting advice from a forum is helpful but to keep throwing money at the car is insane. You could have it diagnosed at an Independent shop for far less money and then you can fix the problem yourself.

Having said that, I will offer no magic bullet recommendation as that would be wrong.

Do yourself a favor and stop spending money without a proper diagnosis. It will save you money!!! DAMHIK...

Good luck,
 

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I agree .. throwing money at it seems counter productive. .. But .. LOL .. since u cleaned out your egr anyways, maybe you should remove your throttle body and clean it as well .. since it is right there anyway. My throttle caused a small amount of bogging so I removed it and stuck it in throttle cleaner (it had gunk in it) and its been perfect ever since. Its easy and free and at the very worst, you eliminate it from your list :).
 

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Discussion Starter #8
Yes, I am sure its the new filter... changed the fuel lines at the \same time, that were needed for the new style of filter....
I would have a shop do it but I work.... from 7am to 7 pm, my own business, so its not like I c an wander over there... but I understand the need for it...
 

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1999 ML320
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273 Posts
Did you try reseting/unhooking battery cables and driving it a bit between reading codes and replacing parts?
 

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Discussion Starter #10
ok.... Heres what happened last night.... Got in it after getting home, started it up and it took longer than normal.. After it started, I attempted to drive it and it bogged down immediately.. I leftit running for about half an hour, and when it was operating temp, it was much better, but then at around 3k rpm, it started bogging down again... Took it hope and just to see, I scanned it and no codes pending... Hmmmm.... Any thoughts?
 

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Discussion Starter #11
I'm on my phone now and haven't been able to look at that yet... I won't have a chance til I get home....
 

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Discussion Starter #12
I was able to look at the 44 page document on my phone and I will admit, it made no sense. By reading that I am only more confused.. My phone wouldn't pull up the other 3 pdf files... The one I was interested in was fuel pressure, so I could compare it to what I got during my check the other day..
I also understand that all the electrical components won't change fuel pressure... I am simply explaining what's going on... Since I am no longer getting codes, I thought pump or filter..
 

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1999 ml430
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check the fuel pressure regulator first before doing the pump, if you start at 50 it should stay there if the regulator is working no matter the rpm
 

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Discussion Starter #14
the saga continues.....
finally took it to an indy joint.. Funny thing, there was one about 1 mile from my house.. I was able to limp on over there and he checked into it.. As I mentioned before, he thought that since the fuel pressure is so low, it could be the regulator, or pump.. I limped home and installed the new filter.. Started it and drove for about 1/2 mile and it was perfect... Jumped on the freeway and it died.. I started this test drive at 145am... Got home at 237am and went a total of maybe 1 1/2 miles. The next morning I threw my fuel pressure tester on and at first start it was about 40psi, after maybe 2 minutes it was around 5 and eventually died again.. Hmmph.... Fuel pump?
 

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1999 ml430
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when doing a pressure check if you start the car right back up does it still go up to 50psi and then back down? You should take it to a shop that can
!safely! do a flow check to determine if the pump is actually failing or the relay is bad and shutting off minutes in. Starting at 50 indicates the pump can work and if bad it should be louder than normal. Don't be fooled by the loss of pressure, if the regulator is good ( vac line unplugged changes pressure value) on the flow check the pressure loss could be a relay or for that matter any number of bad connections at the pump,fuse,relay etc. and of course a bad fuel pump. I hope some of this helps your endeavor
everyone have a nice evening
 

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...your problem could be number of things.

However, if I recall correctly the fuel pressure must stay at certain level (do not have access to manual right now) 30min or so after you turn off your engine.

I had similar problem with my C-class, but (in my case) it turned out to be bad purge valve

K
 

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Discussion Starter #17
Finally...
Got my pump yesterday,but didnt have a chance to change it til today...
Got it installed, started it up and let it run for about 1/2 an hour... While it was running I could already tell a difference, just at idle... Put the pressure tester on it and while running, the pressure was at a steady 60psi... Turned it off and in about 1/2 hour it went from 60 to 52.. an hour later it was at 30...
Took it for a quick jaunt up and down the freeway and all is well.....
Thanks for reading and all the suggestions..
 

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Thank u my 2000 ml320 is doing the exact same thing I thought fuel pump but was worried I might be wrong you telling me all this really helped so thanks again
 
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