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1982 300TD, 1995 E420, 1949 GMC 1Ton flatbed, 1973 Buick Centurion Convertible
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11 Posts
Discussion Starter #1
Ladies and Gents, I am trying to rehabilitate a 1995 E420 that has been sitting for quite some time. I've replaced the fuel pumps and filter (under the rear passenger seat but each time I turn on the ignition, the 30A fuse on the fuel pump relay blows, ANY IDEAS as to where I should start?

Thanks!
Dennis
o_O
 

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W124 Moderator
86 190E 2.3L 16V, 2 95 320TE's, 02 S500
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12,665 Posts
Could be a bad pump. Connect one pump at a time to determine which one may be the problem.

Sent from my XT1710-02 using Tapatalk
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,040 Posts
Tell us more about these pumps you put in. Are they new or used? Are they genuine Bosch or knockoff brand? Are they the exact type for your motor, etc, etc, etc?
 

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1982 300TD, 1995 E420, 1949 GMC 1Ton flatbed, 1973 Buick Centurion Convertible
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11 Posts
Discussion Starter #4
Thanks guys. The pumps are new. Purchased last week from the local Mercedes Benz dealership.
 

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1982 300TD, 1995 E420, 1949 GMC 1Ton flatbed, 1973 Buick Centurion Convertible
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11 Posts
Discussion Starter #5
Sorry...they are new BOSCH brand pumps.
 

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1982 300TD, 1995 E420, 1949 GMC 1Ton flatbed, 1973 Buick Centurion Convertible
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11 Posts
Discussion Starter #6
..and according to the parts department at the dealership, they are the correct pumps for this model. They appear to be the exact same pumps that were on the car when I bout it as well.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,040 Posts
Did you try the old pumps before removing them? IF the fuse did not blow and you verified voltage at the (old) pumps then I think you can assume the new one(s) are defective.

Although very rare, it can happen at times.

On the other hand, if the fuse blows with the old pumps then you have a electrical issue.
 

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W124
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Check your wiring of the pumps. You can also disconnect the pumps entirely and see if the fuse blows. Maybe the relay is at fault.
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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17,040 Posts
^This X 10. I suspect a short to ground problem vs. a problem with the new pumps.
 

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1982 300TD, 1995 E420, 1949 GMC 1Ton flatbed, 1973 Buick Centurion Convertible
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11 Posts
Discussion Starter #10
Well, I've determined by problem. The "short to ground" suggestions seemed a likely place to start, so I carefully inspected the connections from the relay to the pumps. It seems the problem was all a result of the guy holding the wrench! I had connected one of the positive leads on the pump motor too close to the the pump housing, causing a short at the pump. After reorienting my wiring connections, everything worked well. After 5 years of sitting, the car now runs well! The only dashboard indicator light showing is "low windshield washer fluid"!
Thanks all for the outstanding suggestions!
 

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Premium Member
'92 300TE 4matic 280,000miles, '92 300TE 4Matic 'Ice Blue Metalic' 101,000miles
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10,241 Posts
This is where not being there makes it so frustrating to diagnose 'by wire'. It's impossible for us to know what a PO or present owner has done. Sometimes pride keeps people from telling the whole truth.

I'm reminded of the pages and pages of dialogue I spent trying to figure out a forum member's 4Matic problems. Only to find out that he had tried to fix his pressure transducer himself, but neglected to tell me that fact. Replaced that and the car's 4Matic starting working again. So now I sort of approach 4Matic ownership advice as what haven't you done, replaced or inspected yet.

Kevin
 

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'95 E300 DIESEL, '91 600SEL, '92 600SEL
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^This exactly. And if there's any doubt as to a suspect part being functional (or not), based on the sheer age of the car it is best to assume that said part best days are long gone.

In other words, if in doubt throw it out.
 

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1982 300TD, 1995 E420, 1949 GMC 1Ton flatbed, 1973 Buick Centurion Convertible
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11 Posts
Discussion Starter #15
The fuel pump relay does have a fuse in it (30A).
 
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