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1986 mercedes benz amg 420
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62 Posts
Discussion Starter · #1 ·
has a faulty fuel pump or filter as reported on shop invoice is this worth it to fix about how much will it run me car is in otherwise great shape with many xtras will sorta start but then die
 

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Premium Member
1990 SEC
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4,277 Posts
I wouldn't assume that the diagnose is correct. :(

What are the symptoms? Does the car run? How does it idle?

If you just got the car, you may want to consider having all fluids changed:
- Engine oil and filter.
- Engine coolant (drain, degrease with dishwasher detergent, rinse, run with citric acid for at least 30 minutes, rinse until the suds are gone, fill up with MB or Zerex G-05 coolant).
- Power steering fluid and filter.
- Transmission oil and filter.
- Differential oil.
- Brake fluid.

Put a bottle of Techron fuel injector cleaner in your next tank of gas to see if it helps with your issues.

Good luck with your car.
 

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1986 mercedes benz amg 420
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62 Posts
Discussion Starter · #3 ·
I wouldn't assume that the diagnose is correct. :(

What are the symptoms? Does the car run? How does it idle?

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the car will sort of start but die then wont start sounds like there no gas but has half tank
 

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Premium Member
1990 SEC
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4,277 Posts
the car will sort of start but die then wont start sounds like there no gas but has half tank
That may be caused by leaky fuel injectors.

How many miles on the car?
 

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'73 450SL, '83 300CD, '01 E320 4matic
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2,449 Posts
I wouldnt necessarily trust the fuel guage. Are you sure there is a half tank of fuel? More common on diesels, but when these sit, the fuel guage sending units have a tendency to get stuck, and it may not have any fuel in it.

I'd check that if you are not sure. Could be that simple.

If the car is actually in excellent shape, for $900, you've gotten a good deal. How many miles on it?

If you can iron this problem out, and then you don't have any other problems (doubtful) you've gotten a really good deal.

To answer your question as to whether or not it's worth fixing...There is no such thing as a cheap Mercedes- That gets said on here to the newbies constantly. I agree and disagree.... My 300SE is costing plenty to get right, only because I'm extremely anal. My 123 300CD however, cost me $1100, and I've not really had to do anything but maintain it. So good deals can be had. If you like the car, and it's not rusty, ANYTHING you have to do would be worth it for what you paid, in my opinion. Sometimes these cars can be found for a good deal. I got a good deal on my 126, despite the repairs it needs. I figure if I have to sink a total (including what I paid) of $5000 into the car, I've gotten an excellent vehicle for $5000. Go buy a new Hyundai for $12000, and see if you like that better (yeah, right). An old Benz is a great value.


-Aaron
 

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1986 mercedes benz amg 420
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62 Posts
Discussion Starter · #6 ·
the car has 131,000 and i made sure to put 10 gallons in when i purchased it gauge moved i purchased it with this problem and the invoice came with it from the shop ?
 

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Greek God of the R129
SL500-500SEL-190E
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8,559 Posts
the car has 131,000 and i made sure to put 10 gallons in when i purchased it gauge moved i purchased it with this problem and the invoice came with it from the shop ?
So get under the car replace the filter for $30 if it's bad and see what is next.
Or get the pump to from authauseaz for about $176
Can you hear the pump noise when you have key on for a few seconds?
Or take some start fuel spray and spray it in the throttle air intake and see if it will start easier.
Regards.
aam.
 

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1986 mercedes benz amg 420
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Discussion Starter · #8 ·
So get under the car replace the filter for $30 if it's bad and see what is next.
Or get the pump to from authauseaz for about $176
Can you hear the pump noise when you have key on for a few seconds?
Or take some start fuel spray and spray it in the throttle air intake and see if it will start easier.
Regards.
aam.
at first i couldnt locate the filter and pump as far as manuals and q and a (didnt really look ) but now i see it can be reached easily will it be required to empty the tank to change the filter
 

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Greek God of the R129
SL500-500SEL-190E
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8,559 Posts
at first i couldnt locate the filter and pump as far as manuals and q and a (didnt really look ) but now i see it can be reached easily will it be required to empty the tank to change the filter

No you just have to squeeze the hose coming from the tank.
Be gentle don't cut the hose autozone and others have special
tools to squeeze the hose you can use a long nose vice grip carefully though.
There are many threads on how to replace filter/fuel pump.
Simple tools needed.
Regards.
aam.
Ps.
I don't know if you have one or two pumps there are on sale for $128
filter is $18
 

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'82 Euro 500SEL, '85 Euro 500SEC AMG WB Cabriolet,'86 Euro 500SEC RUF
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You also want to remove the gas filler cap to equalize the tank pressure.
 

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'84 500 SEC Euro 040 black Lorinser 2005 sl500
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I wouldn't count on the problem being just a simple filter change or the fuel pumps going out, but it sure would not hurt as a good starting point to cure your ails. Check out this link for the filter change out paying attention to the pdf file for reference. I also used the Kragen $9.00 hose clamps to stop the flow of fuel while doing the work.
If you need the file for the pump change out and you can't find it doing a search just yell and one of us can find it.

http://www.benzworld.org/forums/w12...lacement.html?highlight=fuel+pump+replacement

As Talbir had noted it is not needed to run the fuel low in the tank, but I found I did need to clamp the lines.
 

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1986 mercedes benz amg 420
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Discussion Starter · #12 ·
thanks all very helpful tips i cant wait to get this car running again hope its a simple fix
 

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2000 ML320 / 1988 300SE / 1985 380SE / 1969 280SE
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180 Posts
Have you checked fuel pump relay?
Before putting a new filter or pump, take the FPR out and have a look at its inside.
It could be a just simple fix such as re-soldering.
I have been there too.
 
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