Parts Catalog Accessories Catalog How To Articles Tech Forums
Call Pelican Parts at 888-280-7799
Shopping Cart Cart | Project List | Order Status | Help




Go Back   PeachParts Mercedes ShopForum > Technical Information and Support > Tech Help

Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 02-23-2002, 07:13 PM
domchang's Avatar
Registered User
 
Join Date: Sep 2001
Posts: 236
fuel tank overpressured? is this normal?

on my 1987 560SL, took it for a ride with the top down today and noticed for the first time a humming noise coming from rear of car. Once I got home I turned off the engine and could still hear this loud hummnig sound coming from gas tank area.

After looking around for a while, on a hunch, I took the gas cap off and as usual I could hear air under pressure come out of the gas tank...the humming noise immediately cut off at this point! There followed a very very faint buzzing sound that eventually went away as well.

my question is this....is the gas tank supposed to be in an "over pressured" condition? I think I read somewhere in this forum that this is to keep the fuel lines under pressure and not boiling over when the engine is hot.

the car starts fine with the engine either cold or hot. Getting 15.5mpg. I can live with the humming noise if this is normal behavior but would like confirmation of this from y'all.

tia

dom
__________________
D. Chang
Network Integration Engineer
MCSE, CLP, CCNA
Reply With Quote
  #2  
Old 02-23-2002, 10:04 PM
Registered User
 
Join Date: Mar 1999
Location: Suwanee, GA, USA
Posts: 4,712
It sounds like one of the vent valves may be getting clogged.
__________________
Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS
Reply With Quote
  #3  
Old 02-24-2002, 12:11 AM
domchang's Avatar
Registered User
 
Join Date: Sep 2001
Posts: 236
ok, sounds reasonable, where exactly are these vent valves and how do I get to them?

or do you mean the fuel pump check valve?

thanks
__________________
D. Chang
Network Integration Engineer
MCSE, CLP, CCNA

Last edited by domchang; 02-24-2002 at 12:26 AM.
Reply With Quote
  #4  
Old 02-24-2002, 10:20 PM
domchang's Avatar
Registered User
 
Join Date: Sep 2001
Posts: 236
after some more searching of this forum and others, was wondering if this humming noise is telling me that the fuel pump is going south on me....what are the symptoms of a failing fuel pump?

why does the noise stop when I take the gas cap off?
__________________
D. Chang
Network Integration Engineer
MCSE, CLP, CCNA
Reply With Quote
  #5  
Old 07-10-2002, 01:41 AM
domchang's Avatar
Registered User
 
Join Date: Sep 2001
Posts: 236
one more symptom

after a long time with the noise not recurring, it started up again this evening during a drive.

on a hunch, after I'd noticed that I was below half a tank of gas, I went to the local gas station (humming sound quite evident) and filled up the gas tank.

driving home, no humming noise at all!

I wonder what condition, when the tank is below half full, that causes that humming noise....it appears to be quite a piece of work to get to the check valve on the gas tank too....

so maybe I'll top her off when she's at half tank from now on.....
__________________
D. Chang
Network Integration Engineer
MCSE, CLP, CCNA
Reply With Quote
  #6  
Old 08-01-2002, 12:45 AM
domchang's Avatar
Registered User
 
Join Date: Sep 2001
Posts: 236
so much for previous posting, the humming noise appeared again today after a really hot day's drive home...and the fuel tank was at the 3/4 mark.

again, the noise went away soon as I opened up the gas cap after stopping the car. weird.
__________________
D. Chang
Network Integration Engineer
MCSE, CLP, CCNA
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not 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 On
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Fuel Mileage & Gas Tank Vent bisric Diesel Discussion 6 04-27-2014 09:41 PM
E300TD '98 runs out of fuel at Qtr Tank dallasdonnie Diesel Discussion 12 02-14-2005 08:50 PM
Fuel tank 1/3 full, car kills WJJ Diesel Discussion 7 07-28-2004 11:33 AM
124: 90L Fuel Tank Question jcyuhn Tech Help 4 11-13-2003 04:15 PM
Fuel Tank Capacity... David C Klasse Tech Help 8 04-25-2001 06:59 PM



All times are GMT -4. The time now is 01:01 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0
Copyright 2011 Pelican Parts - Posts may be archived for display on the Peach Parts or Pelican Parts Website -    DMCA Registered Agent Contact Page