Author Topic: Fuel Pump Assembly  (Read 305 times)

joel45077

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Fuel Pump Assembly
« on: 13 September 2020, 06:41 PM »
Hello everyone,

so i finally decided to start doing work to my benz, i have a 1977 Mercedes 450SEL (Base Model) with the standard M117 4.5L V8. I went ahead and pulled the fuel pump assembly from under the tank, upon inspection, i had a few questions about the fuel damper and fuel storage reservoir/accumulator. in my Mercedes service manual, i noticed that the fuel storage reservoir/accumulator has 2 threaded holes on one side, but the one in my car only has 1. I was wondering if this is OEM, and should i buy a new single threaded fuel storage reservoir/accumulator or the double threaded one?

also, after removing the fuel damper, there was a bunch of charcoal like material in there, that when crunched smelled a bit like fuel. Has anyone else had this issue?  I was just thinking of buying a new one, just wanted to see if anyone else has seen this before.

I would like to upload images but it says they are too large.
The car has sat since the early 2000's.

joel45077

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Re: Fuel Pump Assembly
« Reply #1 on: 13 September 2020, 06:42 PM »
here is a picture of the fuel accumulator / fuel storage reservoir

joel45077

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Re: Fuel Pump Assembly
« Reply #2 on: 13 September 2020, 06:44 PM »
fuel damper, it is very dirty; this is the piece with the charcoal like material in it

joel45077

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Re: Fuel Pump Assembly
« Reply #3 on: 13 September 2020, 07:00 PM »
a few more pics of the assembly

joel45077

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Re: Fuel Pump Assembly
« Reply #4 on: 13 September 2020, 07:13 PM »
a second question i have is about how my fuel pump assembly is set up. Again, in the book, the fuel pump assembly is connected by a series of hoses, whereas mine has a metal tube that connects the fuel pump, fuel filter, and fuel accumulator/storage reservoir. I was wondering if i should keep this set up (with the metal tube) or should i replace it to replicate the fuel pump assembly in the book? i already have all the hoses to convert the system, all i would need is the fuel accumulator/storage reservoir with the 2 threaded ports, whereas i have the accumulator/storage reservoir with 1 threaded port.  again my car is a 1977 Mercedes 450SEL with the M117 4.5L V8 engine, this car is a US spec.

Any

joel45077

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Re: Fuel Pump Assembly
« Reply #5 on: 13 September 2020, 11:16 PM »
Not the best pic, but all of this crap was inside of the damper, unless there is a way to restore them, i am probably going to buy a new one

daantjie

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Re: Fuel Pump Assembly
« Reply #6 on: 13 September 2020, 11:38 PM »
Yes I would replace that part for sure as well as  converting to the hose setup you mentioned earlier.  The accumulator is a known culprit for hard starting.  Also that fuel damper looks to be a 126 part number.   The 116 has a different style damper as far as I know.
Daniel
1977 450 SEL 6.9 - Astralsilber

TJ 450

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Re: Fuel Pump Assembly
« Reply #7 on: 14 September 2020, 12:35 AM »
All the Aussie cars I’ve seen have had that hard line setup, including my 6.9. No doubt the hose setup works just as well.

I seem to remember later cars having the 126 style damper, again using this wouldn’t be an issue.

Tim
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John Moore Sr

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Re: Fuel Pump Assembly
« Reply #8 on: 14 September 2020, 03:00 AM »
Hi Joel. There were 3 versions of the fuel pump assembly. The one in your picture from the service manual is a early version. If your manual is the same as mine, there is a section titled " Survey Fuel Pump" that illustrates all three. The early 2 line accumulator utilizes inlet AND outlet connections whereas the later design with one connection, simply put, is inlet AND outlet combined.  It's basically a little pressurized fuel storage tank. Both designs contain a spring loaded diaphragm that provides a variable chamber that provides storage of extra fuel to meet the demands of the engine during full throttle acceleration. The smaller connection at the opposite end is a leak off line back to the damper at the pump. It serves as a relief or return if the accumulator diaphragm ruptures for fuel to flow back to the intake of the pump. It also provides a means of testing the accumulator to verify a ruptured diaphragm. A somewhat simple way to do this test, Is to clamp off the hose from fuel tank to damper, remove the small hose from accumulator to damper, cap off the small hose connection on the damper, place the end of  small hose from accumulator into a suitable container, then unclamp the fuel line from the tank and run the pump. If fuel flows steady from accumulator line the diaphragm is compromised. Keep in mind that when you first disconnect the small line from accumulator, there WILL BE fuel drainage until the line empties. If all is well with the accumulator it will drain out, and again, when you run the pump you will have no fuel flow with pump running.  Benz continuously "improved" the fuel pump package over the years and simplified it with less connections and different geometry as the Service Manual illustrates. As far as the 126 part number on the damper goes, it was increased in size when the 126 chassis cars came along, and replaced the previous 116 version as a service part. It's function is to eliminate hydraulic noise from the pulses of the rollers inside the fuel pump. It is a completely hollow little chamber containing nothing internally.  The black charcoal substance you show in the damper pic is from the supply hose from tank. The lining of the hose breaks down over time and will be accelerated by use of fuel containing ethanol. It also causes Sudden Death Syndrome for the fuel pump, and can cause blockage of that cute little steel line that connects the pump to filter and accumulator in the later version of the pump package. Just clean out the damper it will be fine.  I apologise for such a long semi-rambling post, and hope this helps you.   JM Sr.
« Last Edit: 14 September 2020, 03:07 AM by John Moore Sr »
1972 350SLC Euro Parts car, 1974 350SL Euro 3.5 V8 4 speed, 1978 450SLC Euro. 1979 6.9 #4630 1979 6.9 #7003 Parts Car, 1980 450SLC Parts car, 1985 380SL...and once had 1975 6.9 #142 until JuNIOR commandeered it.

ptashek

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Re: Fuel Pump Assembly
« Reply #9 on: 14 September 2020, 03:59 AM »
Not the best pic, but all of this crap was inside of the damper, unless there is a way to restore them, i am probably going to buy a new one

It's an empty can inside, so unless it leaks, I'd just soak it in carb cleaner for a few days and blast the gunk out with compressed air.
If you have access to an ultrasonic cleaner, that might be even better.
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joel45077

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Re: Fuel Pump Assembly
« Reply #10 on: 14 September 2020, 06:30 PM »
Hi Joel. There were 3 versions of the fuel pump assembly. The one in your picture from the service manual is a early version. If your manual is the same as mine, there is a section titled " Survey Fuel Pump" that illustrates all three. The early 2 line accumulator utilizes inlet AND outlet connections whereas the later design with one connection, simply put, is inlet AND outlet combined.  It's basically a little pressurized fuel storage tank. Both designs contain a spring loaded diaphragm that provides a variable chamber that provides storage of extra fuel to meet the demands of the engine during full throttle acceleration. The smaller connection at the opposite end is a leak off line back to the damper at the pump. It serves as a relief or return if the accumulator diaphragm ruptures for fuel to flow back to the intake of the pump. It also provides a means of testing the accumulator to verify a ruptured diaphragm. A somewhat simple way to do this test, Is to clamp off the hose from fuel tank to damper, remove the small hose from accumulator to damper, cap off the small hose connection on the damper, place the end of  small hose from accumulator into a suitable container, then unclamp the fuel line from the tank and run the pump. If fuel flows steady from accumulator line the diaphragm is compromised. Keep in mind that when you first disconnect the small line from accumulator, there WILL BE fuel drainage until the line empties. If all is well with the accumulator it will drain out, and again, when you run the pump you will have no fuel flow with pump running.  Benz continuously "improved" the fuel pump package over the years and simplified it with less connections and different geometry as the Service Manual illustrates. As far as the 126 part number on the damper goes, it was increased in size when the 126 chassis cars came along, and replaced the previous 116 version as a service part. It's function is to eliminate hydraulic noise from the pulses of the rollers inside the fuel pump. It is a completely hollow little chamber containing nothing internally.  The black charcoal substance you show in the damper pic is from the supply hose from tank. The lining of the hose breaks down over time and will be accelerated by use of fuel containing ethanol. It also causes Sudden Death Syndrome for the fuel pump, and can cause blockage of that cute little steel line that connects the pump to filter and accumulator in the later version of the pump package. Just clean out the damper it will be fine.  I apologise for such a long semi-rambling post, and hope this helps you.   JM Sr.


Hello, i appreciate your input very much. Do you think i should switch out the accumulator to the one with a separate inlet/outlet holes, or just buy a new version of the one i have? Do i want the diaphragm to be compromised or ruptured? (To be honest, i am not quite sure what that means... ) will this test determine whether i will need a new accumulator? i am going to attempt to do the test you mentioned above, and i will let you know the results...
..
i was given this car about 3 years ago, but it has sat since the early 2000's. We got it to start once, but that was before we knew all of this gunk was in the damper.  For now, I am going to clean out the damper, replace the hoses that i can, and try to see if the car has an easier time starting. I am going to try to drain the fuel from the gas tank since it has some from the last time i tried to start it a couple years ago, although when removing the fuel pump assembly, the gas did not smell or look too bad........

I got my service manual on eBay, it is not specifically for the 450SEL, but it's a Service Manual for Engines M116-117 (V8) it does briefly mention the three versions of the fuel pumps; and to be honest, i thought mine had the wrong set up because a long time ago, some shop stole parts from this car..... That's part of the reason why i am on this forum, in hopes that other W116 enthusiasts could help me identify whether my parts are correct......

Again, thanks everyone and i will be sure to keep everyone updated.

joel45077

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Re: Fuel Pump Assembly
« Reply #11 on: 14 September 2020, 06:36 PM »
Yes I would replace that part for sure as well as  converting to the hose setup you mentioned earlier.  The accumulator is a known culprit for hard starting.  Also that fuel damper looks to be a 126 part number.   The 116 has a different style damper as far as I know.


In order to convert the hose setup, i would have to purchase a new accumulator with the 2 threaded ports ( the one i have only has 1). Did you suggest to replace the damper or the accumulator? (Sorry for the confusion). Does the accumulator with 2 threaded ports perform better than the one that I have?

As far as the damper, I am not sure whether that part belongs there, but for now, i am going to clean it and try to see if the car will have an easier time starting. In the service manual, they appear to be almost the same, except the one in the book is black and is more round... In a previous post, someone mentioned it was an upgrade in the service, but again, i am not sure.... Thank you for your input

joel45077

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Re: Fuel Pump Assembly
« Reply #12 on: 14 September 2020, 06:39 PM »
Not the best pic, but all of this crap was inside of the damper, unless there is a way to restore them, i am probably going to buy a new one

It's an empty can inside, so unless it leaks, I'd just soak it in carb cleaner for a few days and blast the gunk out with compressed air.
If you have access to an ultrasonic cleaner, that might be even better.




thanks for the suggestion. i am going to clean it with carb cleaner and compressed air and depending on the finished result, maybe i will or won't have to buy a new one. I really appreciate your suggestion

daantjie

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Re: Fuel Pump Assembly
« Reply #13 on: 14 September 2020, 06:44 PM »
Yes I would replace that part for sure as well as  converting to the hose setup you mentioned earlier.  The accumulator is a known culprit for hard starting.  Also that fuel damper looks to be a 126 part number.   The 116 has a different style damper as far as I know.


In order to convert the hose setup, i would have to purchase a new accumulator with the 2 threaded ports ( the one i have only has 1). Did you suggest to replace the damper or the accumulator? (Sorry for the confusion). Does the accumulator with 2 threaded ports perform better than the one that I have?

As far as the damper, I am not sure whether that part belongs there, but for now, i am going to clean it and try to see if the car will have an easier time starting. In the service manual, they appear to be almost the same, except the one in the book is black and is more round... In a previous post, someone mentioned it was an upgrade in the service, but again, i am not sure.... Thank you for your input

Not sure about performance between one style of accumulator vs another but yes I meant for you to replace the accumulator.   Also absolutely drain all the old fuel out (think safety here, keep fire extinguisher handy and make sure you use respirator) so you can start with fresh fuel.
Daniel
1977 450 SEL 6.9 - Astralsilber

joel45077

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Re: Fuel Pump Assembly
« Reply #14 on: 14 September 2020, 09:55 PM »
Yes I would replace that part for sure as well as  converting to the hose setup you mentioned earlier.  The accumulator is a known culprit for hard starting.  Also that fuel damper looks to be a 126 part number.   The 116 has a different style damper as far as I know.


In order to convert the hose setup, i would have to purchase a new accumulator with the 2 threaded ports ( the one i have only has 1). Did you suggest to replace the damper or the accumulator? (Sorry for the confusion). Does the accumulator with 2 threaded ports perform better than the one that I have?

As far as the damper, I am not sure whether that part belongs there, but for now, i am going to clean it and try to see if the car will have an easier time starting. In the service manual, they appear to be almost the same, except the one in the book is black and is more round... In a previous post, someone mentioned it was an upgrade in the service, but again, i am not sure.... Thank you for your input

Not sure about performance between one style of accumulator vs another but yes I meant for you to replace the accumulator.   Also absolutely drain all the old fuel out (think safety here, keep fire extinguisher handy and make sure you use respirator) so you can start with fresh fuel.


ahh ok, thank you for the suggestion/clarification. i will definitely flush out the old fuel, and will post pictures of the tank once i take it out. thank you