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1999 ML320
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13 Posts
Discussion Starter #1
I recently replaced my 1999 ML320's fuel pump with a brand new bosch OEM one. The install went fine and I had no problems hooking up the the two fuel lines along with the four pin power plug. That fixed the problem and my car ran like a dream for about two/three months and then died one day while I was driving it. Baffled, I got it back to the house, took the seats back out, accessed the top of the fuel pump and reset the plug on the power cable. It started right up like nothing was wrong. It ran fine for the next month and then quite just like before. This time I was smart enough to leave my seats out for a while to see what would happen. Again, all I did was re-seat the the power plug on the fuel pump and BAM, it was running again. Well this has continued for about 4/5 months (I'd have to jiggle the plug about once a month) until recently when this past week it started happening about everyday. A couple of days ago the car stopped running and no amount of re-seating/jiggling of the plug would cause the car to start. One thing that I have notice is that the far right pin on the female pump side is slightly blackened and the matching connector for that pin on the male plug side is also darkened as opposed to shiny silver.

If anybody has an idea of what's going on, I'd sure appreciate your advice.
 

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Dallas, Texas
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6,991 Posts
We all know what's going on. You have bad connection. No amount of jiggling will fix it. At first sign of trouble you take connector apart and replace affected pin. Now that male pin on cover itself got charred even if you replace female pin fuel leak may appear in near future.

I thought pump on ML was made by Pierburg and level sensor by VDO. Never seen Bosch pump on ML. Did you replace entire assembly?
 

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1999 ML320
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13 Posts
Discussion Starter #3
Thanks for your reply, and you're right that the pump is a pierburg (I mistakenly said bosch).

I guess I know that there's a bad connection, but there are some questions that i still have. What do you mean by replacing the affected pin? The pins are a part of the fuel pump itself. It seem like in order to replace the pin on the male (pump) side you would have to replace the pump itself, or would you just replace the sending unit? I suppose I'll have to take the pump out to see. Why, though would there be a bad connection on the new fuel pump when it is identical to the last one? Also, should I replace the plug the goes to the fuel pump (and where could I buy one)?
 

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Dallas, Texas
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6,991 Posts
You can get plug housing 010 545 08 26, female connectors 665 545 76 28 and seals 665 545 74 80. Male pin on pump assembly lid has to cleaned or pump replaced again.
 

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1999 ML320
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13 Posts
Discussion Starter #7
Thanks man, I order those and they should be here in a few days. One more question, do you know the part number for just the fuel level sending unit (without the actual pump)? I might end up having to replace that.
 
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