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1987 420 SEL
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2,090 Posts
Discussion Starter #1
Hello all. I want to inspect my fuel pump assembly components for loose or corroded connections. I know I need to drive around until the low fuel yellow light comes on to decrease the amount of fuel in the tank.

But I also wanted to know if the special Mercedes (fuel line hose clamp) is really necessary to stop the flow of remaining fuel when you disconnect the fuel suction and delivery hoses? Or, can you just drain the remaining fuel in a plastic container once you have the fuel assembly removed from the car? How much fuel remains in the fuel pumps and accumulator?

Any advice is greatly appreciated. Thanks.
 

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Registered
1991 560 SEL
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260 Posts
I seem to remember pinching off the hose with a vise-grip, and soaking up the rest of the gas with my arm, shirt, and hair. I got messy, but I changed the pumps without any fancy tool.
 

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1987 420 SEL
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2,090 Posts
Discussion Starter #3
That's what I figured so I have 2 big plastic containers, plastic drop sheets, old rags and a bag of kitty litter that will catch the remainder of the excess fuel.

It sounds very messy so I also have some face masks and goggles. Will get started early in the morning before the temperature gets warmer. Definitely going to take my time doing this job.
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,281 Posts
Hi Prochambers,

You might consider releasing the pressure in the fuel tank too - before you undo anything. You know - that 'whoosh' sound you get when removing the gas cap sometimes.[:)]
My wife had the 560 for a several hundred mile drive last Spring. She told me the gas cap made that sound (which she wasn't used to with our Valvos), & not scared her - but darn close..

MBL

P.S. Do you have any 'Bulb Grease' (dielectric) to put onto the plug connectors while you've got 'em apart?
 

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1987 420 SEL
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2,090 Posts
Discussion Starter #6
P.S. Do you have any 'Bulb Grease' (dielectric) to put onto the plug connectors while you've got 'em apart?

Edited by MBL87560SEC 4/11/2005 7:11 PM


Hey MBL. What is the purpose of using the 'Bulb Grease' on the plug connectors?

Also, I know about releasing the pressure out of the tank prior to unhooking everything. I just didn't mention it, but thanks for bringing it up.
 

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1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,281 Posts
Hi Prochambers,

Dielectric 'Bulb Grease' keeps moisture away (= corrosion), & ensures long-term conductivity within plug/socket or bulb/socket connection. It is a staple in a Valvo Service department (at least was). You can/should be able to get it at an autoparts or hardware store.

I thought it might be a good idea, considering where the connectors are located (& their [?] age)....

Here's my tube & I'm stickin' to it!

Cheers, MBL

[8] You can see how much of it I've used on my own car since Nov, 2003. What is it about those 'cobbler's children'......?
 

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Registered
1987 420 SEL
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2,090 Posts
Discussion Starter #8
Hey MBL. Come to think about it, I already have some bulb grease from when I had to change my turn signal bulbs. Good looking out though.
 

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Registered
Two '87 570SECs, one '87 560SEL
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4,448 Posts
Don't know how much it costs for the 1.25 oz tube of grease, but I bought a 2 oz jar of "pure silicone grease" for $7.95 from a local scuba diving store. They use it to grease up fittings, I use it on pretty much all my rubber parts and o-ring fittings during installation. Used it on the dog-bone bushings last week and the installation went (pun intended) smoothly. I like the idea of using it on electrical connections and it looks like I'll start using it on light bulbs now too.
 

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1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,281 Posts
Hi Prochambers,

The B/grease is just a belt & suspenders approach to electrical feed considering the location environment of the pump..

I've probably missed something along the line,,,, I'm wondering why the discussion regarding fuel spillage etal, if you are planing to just check the electrics? I imagine your next post will include 'fuel filter' or leaking 'fill-in-the-blank', so I apologize ahead of time if something flew way over my nest here.[:)]

MBL
 

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Registered
1987 420 SEL
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2,090 Posts
Discussion Starter #11
Hey MBL. I've been noticing a fuel smell coming from the outside back of the car where the fuel pumps are located. So, I want to get under there this weekend (early Saturday morning) and disconnect everything and put them on a bench and inspect all components to play it safe. Then i'll know how to proceed after the inspection. It could be something as simple as a split hose or corroded connector. And since the pumps are probably the originals, I want to know first hand what their condition is.

I'm picking up the face mask and googles tonight. Pee uuuuuuuuuuuuu!!!!
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,281 Posts
Hi Prochambers,

I meant to get back to you yesterday........

Any way, I do hope you find the leak without too much hassle,

I was thinking along the lines of possible fuel sender or filler issues, while you are under there.....

About the pumps themselves, (If you know this already I mean no offense.) please refrain from any attempt to 'bench test' them off the vehicle. The pump motor commutator & brushes run in[/] the gasoline flowing through the pump. A pump removed from a car & subsequently powered up on the bench can become a bomb in that there may be oxygen present in that cavity - brushes ark - POW!

You have no idea how much the importance of this factor was impressed upon us (I hate to think about how long ago... ) young techs during Fuel Injection classes at Volvo Service School.

If you've not seen it, here is a good page on the Bosch K Jetronic which we love so well. [;)]

http://www.auto-solve.com/mech_inj.htm#MFI03

Hope things go well. MBL
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
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4,281 Posts
Hi Prochambers,

Glad it is a simple fix & with warmer weather too. [:)]

My car is going to the MB hospital Thursday as it has a really annoying vibration at highway speeds. Just had 4 new tires installed Friday, did it with the old ones too. I cannot 'drive through' the vibration either. Vibrates on accel from 60 right up to 90, (ran out of clear space on the road). Seems better if I decel, then put the car in N & coast. Comes back while maintaining speed & if accelerated even lightly. I've just ordered the Frt. flex disc & will get the tires balanced again.

I leave for Georgia (pos. Florida too) Friday AM.... early. A good 560 cruise.

Cheers, MBL
 

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Registered
1987 420 SEL
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2,090 Posts
Discussion Starter #16
Hey MBL,

What brand of tires did you put on? Hopefully it's something very simple like a balancing issue. Come to think of it, I need to have my flex disc checked as well just as a pre-ventive maintenance thing though.

If I don't speak with you before then have a safe trip to and from. Let me know how you make out the vibration issue.
 

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Moderator
1991 500SEC sub 50K mi. 1987 560SEC Now 150K mi. 2018
Joined
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4,281 Posts
Hi Prochambers,

I got some V rated 205/65/15 TOYOs, not very exciting looking but much better traction Dry/Wet & higher rating for tread wear (than the Michelins) as well. One is really limited in choices available, if you stay with the stock 15" rims. 16 opens a whole world up.

It has to be at least the flex disc.. shook pretty good on brisk accel. 60+ till 90 & cruising when just accel a bit to maintain speed.

Thanks for the safe round trip wishes. I'm traveling from Boston to Carrabelle on the Gulf Coast with a couple of stops in Atlanta.

I'll start packing tonight.

Cheers, MBL
 

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Registered
1991 300 SE
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18,534 Posts
The accumulator holds fuel system pressure when the engine is hot and the fuel pump is off. The heated fuel in the fuel lines in the engine bay will attempt to evaporate, the accumulator keeps this from happening allowing a smooth start when the engine is hot. The accumulator will hold pressure for about 20 minutes, after which time the fuel lines will be cool enough for easy starts.

When the pump is running the accumulator ensures a smooth flow of fuel as the pump creates a pulsing effect as it moves the fuel.

A hard hot start is a classic indicator that the accumulator has failed and should be replaced.
 
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