560sec Leaky fuel pumps - Mercedes-Benz Forum
Reply
 
LinkBack Thread Tools Display Modes
post #1 of 13 (permalink) Old 06-15-2019, 09:25 AM Thread Starter
BenzWorld Junior Member
 
Flawlessrider's Avatar
 
Date registered: Feb 2019
Vehicle: 1986 560 SEC
Location: Vancouver Canada
Posts: 13
Mentioned: 0 Post(s)
Quoted: 3 Post(s)
(Thread Starter)
560sec Leaky fuel pumps

To whoever knows what could cause this. I’ve replaced both fuel pumps and accumulator less than 1000kms ago because the fuel pumps started leaking. I replaced most everything else in the fuel system just after. I’ve ran 2 tanks of fuel through the whole system with the fuel system gas tank additive. The lower fuel pump is now leaking again. Has anyone heard what could cause repeated fuel pump leakages. This is the second set that has now leaked on me. The only thing left to replace in the whole system is injectors (on order) and fuel lines (should be no issues).
Flawlessrider is offline  
Sponsored Links
Advertisement
 
post #2 of 13 (permalink) Old 06-15-2019, 09:38 AM
BenzWorld Senior Member
 
Date registered: Nov 2018
Vehicle: 1991 560SEL
Location: Richmond Virginia, USA
Posts: 474
Mentioned: 4 Post(s)
Quoted: 116 Post(s)
Where is it leaking from, eactly? Fuel line leading to the pump? If so, are you 100% certain you are using new and proper size crush washers, and that you have carefully, slowly torqued the bolts/nuts to the proper torque value?
lesguy is offline  
post #3 of 13 (permalink) Old 06-15-2019, 10:00 AM Thread Starter
BenzWorld Junior Member
 
Flawlessrider's Avatar
 
Date registered: Feb 2019
Vehicle: 1986 560 SEC
Location: Vancouver Canada
Posts: 13
Mentioned: 0 Post(s)
Quoted: 3 Post(s)
(Thread Starter)
Quote:
Originally Posted by lesguy View Post
Where is it leaking from, eactly? Fuel line leading to the pump? If so, are you 100% certain you are using new and proper size crush washers, and that you have carefully, slowly torqued the bolts/nuts to the proper torque value?
I didn’t install the fuel pumps the first time. I assumed that all was replaced correctly. I got under an it appeared that the fuel was leaking from one location but since the vehicle is lowered I don’t even have room to turn my head under the car. I’ll have time to put in up on jacks in the next few days.

I guess I was just wondering if anyone knew if blowing fuel pumps is a common issue starting from a different common problem. Ie. This is the second set of fuel pumps leaking recently; therefore, this is a symptom of a different issue. Is that issue common?

I’ll have a better idea where exactly it’s leaking from once I can get a better look.
Flawlessrider is offline  
Sponsored Links
Advertisement
 
post #4 of 13 (permalink) Old 06-15-2019, 10:40 AM
BenzWorld Senior Member
 
Date registered: Nov 2018
Vehicle: 1991 560SEL
Location: Richmond Virginia, USA
Posts: 474
Mentioned: 4 Post(s)
Quoted: 116 Post(s)
not aware of fuel pumps blowing being a common issue. Im suspecting its not the fuel pumps themselves, but connections on either the fuel pumps, the fuel pressure accumulator, or the fuel filter.
lesguy is offline  
post #5 of 13 (permalink) Old 06-15-2019, 10:45 AM
Moderator
 
ianrandom's Avatar
 
Date registered: Jul 2008
Vehicle: 1986/1990 W126
Location: Berkshire & Devon, UK
Posts: 12,944
Mentioned: 28 Post(s)
Quoted: 1176 Post(s)
Lifetime Premium Member
I would suspect your crush washers were reused if you got someone to do the job for you and you can't verify.
MBL87560SEC likes this.

'86 420SE
'90 420SEC


Daily transport 9spd Giant DH Comp downhill bike
ianrandom is offline  
post #6 of 13 (permalink) Old 06-15-2019, 10:51 AM Thread Starter
BenzWorld Junior Member
 
Flawlessrider's Avatar
 
Date registered: Feb 2019
Vehicle: 1986 560 SEC
Location: Vancouver Canada
Posts: 13
Mentioned: 0 Post(s)
Quoted: 3 Post(s)
(Thread Starter)
Ok cool, I’ll check all connections and crush washers and get back. Thanks for your help!
Flawlessrider is offline  
post #7 of 13 (permalink) Old 06-15-2019, 04:55 PM
Outstanding Contributor
 
luckymike's Avatar
 
Date registered: Mar 2010
Vehicle: 1989 560SEC, 1989 560SEL, 1995 E420
Location: NorCal
Posts: 3,858
Mentioned: 9 Post(s)
Quoted: 575 Post(s)
I doubt very much it's the fuel pumps.

The banjo connections to the pumps can be very finicky. I fought a weep (not a leak) for several hours just this morning. Had the car up on a rack and noticed some wetness at the rear pump. No problem, I thought, I have spare copper seals, I'll just throw some in there and be done. NO.

Fresh copper seals didn't fix it. Further cranking on the banjo bolt didn't fix it. I didn't want to take it all apart again so I cranked further until the 19mm hex for the fuel filter was threatening to round out. Still no luck.

Installed another set of seals. They say you should use new ones every time so for once I did, since I had them on hand. Still no luck.

I finally removed the little S-bend pipe that connects the rear pump to the filter to the accumulator. I inspected the sealing surfaces of the pipe under magnification and discovered a tiny scratch where fuel was clearly getting past.

Thankfully I had a used extra part and installed it. I still had to make the connections tighter than I would expect to finally have a leak-free seal.

So if you take this apart, treat all sealing surfaces with care so you don't scratch them. And keep everything clean, too. Not as easy on your back in the driveway but do your best. FYI, I don't think that s-bend pipe is available anymore so be extra careful.
AxelWulff likes this.
luckymike is offline  
post #8 of 13 (permalink) Old 06-15-2019, 05:56 PM Thread Starter
BenzWorld Junior Member
 
Flawlessrider's Avatar
 
Date registered: Feb 2019
Vehicle: 1986 560 SEC
Location: Vancouver Canada
Posts: 13
Mentioned: 0 Post(s)
Quoted: 3 Post(s)
(Thread Starter)
Quote:
Originally Posted by luckymike View Post
I doubt very much it's the fuel pumps.

The banjo connections to the pumps can be very finicky. I fought a weep (not a leak) for several hours just this morning. Had the car up on a rack and noticed some wetness at the rear pump. No problem, I thought, I have spare copper seals, I'll just throw some in there and be done. NO.

Fresh copper seals didn't fix it. Further cranking on the banjo bolt didn't fix it. I didn't want to take it all apart again so I cranked further until the 19mm hex for the fuel filter was threatening to round out. Still no luck.

Installed another set of seals. They say you should use new ones every time so for once I did, since I had them on hand. Still no luck.

I finally removed the little S-bend pipe that connects the rear pump to the filter to the accumulator. I inspected the sealing surfaces of the pipe under magnification and discovered a tiny scratch where fuel was clearly getting past.

Thankfully I had a used extra part and installed it. I still had to make the connections tighter than I would expect to finally have a leak-free seal.

So if you take this apart, treat all sealing surfaces with care so you don't scratch them. And keep everything clean, too. Not as easy on your back in the driveway but do your best. FYI, I don't think that s-bend pipe is available anymore so be extra careful.
Thanks mike! That’s super helpful. There’s always some subtle nuances in these types of jobs. That will be good to know before I get started. Hopefully save some frustrations! I appreciate all the input!

This is a new car for me so I’m still only learning about the systems she uses. Super cool!
Flawlessrider is offline  
post #9 of 13 (permalink) Old 06-15-2019, 08:35 PM
Outstanding Contributor
 
luckymike's Avatar
 
Date registered: Mar 2010
Vehicle: 1989 560SEC, 1989 560SEL, 1995 E420
Location: NorCal
Posts: 3,858
Mentioned: 9 Post(s)
Quoted: 575 Post(s)
Quote:
Originally Posted by Flawlessrider View Post
Thanks mike! That’s super helpful. There’s always some subtle nuances in these types of jobs. That will be good to know before I get started. Hopefully save some frustrations! I appreciate all the input!

This is a new car for me so I’m still only learning about the systems she uses. Super cool!
You're welcome. I think you're really going to enjoy working on these cars.

Some more tips which might help:

Have a fire extinguisher at the ready. I'm not good at this but it is good practice.

Remove the gas cap to relieve pressure in the system.

I clamp the big, thick hose coming from the gas tank to the fuel pumps with a needle-nosed ViceGrips. Slip a piece of hose on each jaw to protect the car's hose. This helps prevent you taking a bath in gas.

You'll lose some fuel when you crack the first connection. Not a lot but be ready for it. A big rag helps.

After you're done and ready to start the car, remove the fuel pump relay and bridge contacts 7 and 8 in the connector for 15 or 20 seconds. I just use a bent coat hanger. This will run the pumps and purge air from the system, making it easier to start the car. Check for leaks after fully priming and before starting the car. Man, I had a HUGE puddle this morning because I didn't check first.

Don't forget to replace the gas cap. Another mistake I made this morning. Got home and wondered why I smelled gas. It was overflowing the filler tube and going into the drain behind the filler door. Stupid and unnecessary mistake.

Hopefully that does it and you're leak-free and ready to drive.

Last edited by luckymike; 06-15-2019 at 08:38 PM.
luckymike is offline  
post #10 of 13 (permalink) Old 06-18-2019, 08:17 AM
BenzWorld Elite
 
wooky_chew_bacca's Avatar
 
Date registered: Oct 2009
Vehicle: '91 560SEC, '91 300SE (sold), '98 Yota, '02 S-10 Hauler
Location: Covington Ga
Posts: 8,889
Mentioned: 13 Post(s)
Quoted: 1282 Post(s)
Garage
Quote:
Originally Posted by luckymike View Post

I clamp the big, thick hose coming from the gas tank to the fuel pumps with a needle-nosed ViceGrips. Slip a piece of hose on each jaw to protect the car's hose. This helps prevent you taking a bath in gas.

You'll lose some fuel when you crack the first connection. Not a lot but be ready for it. A big rag helps.

Hopefully that does it and you're leak-free and ready to drive.
Let me add this since I took a partial gas bath recently, if your tank is pretty much empty you could pump out the remainder using pin sockets 7 and 8 of the FPR, pump until it starts sucking air. Next if you raise the R/R wheel and set it on a block of some sort the residual gas left in the tank will be pooled on the left side away from the outlet pipe with the strainer (I have 6X9 blocks I made just for working under the car). I tried clamping the main feed from the tank, no joy and got the bath

And yes the copper crushers need to be new ones and any rubber needs to be a snug fit (correct size) before doing the clamps

Some days it's just not worth chewing through the restraints
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
My Stable:
'91 560SEC "Ursula"
'91 300SE (sold) "Sadie"
'11 Suzuki SX4 Sport Sedan
'02 S-10 Truck
'72 SeaBird boat, "Riff Raft", overhaul restarted

Dif-tor heh smusma
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
I'm surprised that NOBODY has asked me what this is / means
To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
LOL

Last edited by wooky_chew_bacca; 06-18-2019 at 08:19 AM.
wooky_chew_bacca is offline  
Sponsored Links
Advertisement
 
Reply

  Mercedes-Benz Forum > Mercedes-Benz Sedan Forums > W126 S,SE,SEC,SEL,SD,SDL Class

Quick Reply
Message:
Options

Register Now



In order to be able to post messages on the Mercedes-Benz Forum forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:
OR

Log-in











Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page
Display Modes
Linear Mode Linear Mode



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

 

Title goes here

close
video goes here
description goes here. Read Full Story
For the best viewing experience please update your browser to Google Chrome