Imploded fuel tank - so sad! - PeachParts Mercedes-Benz Forum

cj* · #1 03-13-2012, 10:40 PM

So - this is my first post though I've been using this site for over a year for my first Mercedes 300D, and it's pretty sad. I have been having fuel starvation issues, or so I thought, ever since I got back from a road trip to Portland, OR - and finally tracked it down today - my fuel tank has collapsed - oh no! The car is actually running great and there were only a couple of little issues I had in OR - but everything was running great once I got back to CA. The posting from boneheaddoctor (link below) shows exactly what happened.

http://www.peachparts.com/shopforum/diesel-discussion/303219-what-happens-when-tank-vent-gets-clogged.html

So I have a couple of questions - 1.) can this happen from anything other than a clogged vent? My mechanic said he blew this out right before I left - but he did say there was rust in it. Could he have blown rust into the tank and then the rust could of clogged the supply line???? 2.) Can you salvage a sucked in fuel tank - or am I screwed and have to replace it - along with a fuel sending unit!!!? I've already taken it out when I first got it and cleaned it all up, replaced the tank screen, so I can replace it myself.

Any ideas out there - I appreciate your help,
Carrie*

Also - I know when it happened and realize now that the tank was sucking in air upon opening the fuel cap - I just thought it was the increase elevation. I didn't know this could happen - I am new to all of this. Wish I would have looked at the below link earlier!

http://www.peachparts.com/shopforum/diesel-discussion/189602-fuel-tank-vent-warning.html

tangofox007 · #2 03-13-2012, 11:10 PM

Quote:

Originally Posted by cj*

can this happen from anything other than a clogged vent?

The problem is due to a vent system malfunction.

Quote:

Originally Posted by cj*

Can you salvage a sucked in fuel tank

Pressure collapsed the tank; pressure will expand it.

Quote:

Originally Posted by cj*

Also - I know when it happened and realize now that the tank was sucking in air upon opening the fuel cap - I just thought it was the increase elevation. [/COLOR]

An increase in elevation (assuming that elevation was the only variable) would have the opposite effect.

EDBSO · #3 03-13-2012, 11:11 PM

I don't know that I would try it but I have read that the tank can be blown out with air pressure. I have also heard that a "good" tank can be expanded to increase capacity with air pressure. Not for me either.

StaggerLee · #4 03-13-2012, 11:24 PM

I "expanded" the fuel tank in one of my wagons by blowing compressed air in to the return line while plugging the feed line. I don't think I did anything with the vent and it didn't take very much air.

I stumbled upon this procedure while trying to blow all of the fuel out of the tank before removing it. Next thing I knew the tank was it's normal shape

ROLLGUY · #5 03-13-2012, 11:25 PM

I have had the same problem.
The tank vent is on the driver side just forward of the wheel behind the rear footwell. Remove the valve (plastic thing with a cone shaped rubber part), and blow compressed air through the steel line. Be sure to remove the fuel cap. If there is a restriction, feed a wire through the tube. If it is clear, compressed air should blow through freely.

StaggerLee · #6 03-13-2012, 11:34 PM

RollGuy is refering to clearing out the vent line.

You'll need to leave the cap on to create enough pressure to re-expand your tank.

ROLLGUY · #7 03-14-2012, 12:38 AM

Quote:

Originally Posted by StaggerLee

RollGuy is refering to clearing out the vent line.

You'll need to leave the cap on to create enough pressure to re-expand your tank.

Yes, thank you.

cho · #8 03-14-2012, 05:54 AM

Quote:

Originally Posted by ROLLGUY

I have had the same problem.
The tank vent is on the driver side just forward of the wheel behind the rear footwell. Remove the valve (plastic thing with a cone shaped rubber part), and blow compressed air through the steel line. Be sure to remove the fuel cap. If there is a restriction, feed a wire through the tube. If it is clear, compressed air should blow through freely.

well guys, you got me worried

I have also some suction sound

when opening tank cap on gas station.
does anyone knows position of vent lines on w126 coupe so I can check them...
some pic...maybe...

TX

edit : ok,got it

.

charmalu · #9 03-14-2012, 09:17 AM

Your PDF looks like a diagram for a 126 gasser. but item #51 is the vent check valve, and that is the area where the vent is located on the Diesels.

I just went through this on a 82 240D a few days ago, had pressure when releasing the fuel cap. removed the vent check valve and the Bell piece. bell open, but blowing through the Vent check was difficult. so reamed the little sucker with a screwdriver. blows good now, both ways.

CJ* sorry to hear about your tank imploding. If it wont expand with air, finding one in the PNP`s is impossible. they punch them full of holes. best is to look in CL or locally for someone parting out a 300D with a 21 Gallon tank.

Here are your links

What happens when a tank vent gets clogged.

Fuel Tank Vent Warning

Charlie

cho · #10 03-14-2012, 10:51 AM

Quote:

Originally Posted by charmalu

Your PDF looks like a diagram for a 126 gasser. but item #51 is the vent check valve, and that is the area where the vent is located on the Diesels.

I just went through this on a 82 240D a few days ago, had pressure when releasing the fuel cap. removed the vent check valve and the Bell piece. bell open, but blowing through the Vent check was difficult. so reamed the little sucker with a screwdriver. blows good now, both ways.

thanks mate, I kept mine old (gasser) tank, but some serious reaming is gonna take place

"blows good now, both ways" - should it be both ways?

.

Renntag · #11 03-14-2012, 11:28 AM

Try adding air pressure to push the tank back out. Just be gentle about it. ie: dont let loose 100+psi all at once. I would imagine that if you attach a line to the fuel lines you wouldnt need much air pressure to push the tank back to shape. Even the cheap 12V tire inflators should do the trick. You just have to figure out how to attach to the fuel lines and plug the vent line. Once pushed back out, clear the vent.

Note to all: There should almost never be a significant rush of air when removing the fuel cap.

I have not seen a plugged vent on an MBZ diesel to date, but it is good to know to look for it.

Tanksowner · #12 03-14-2012, 11:32 AM

Quote:

Originally Posted by Renntag

Note to all: There should almost never be a significant rush of air when removing the fuel cap.

I have not seen a plugged vent on an MBZ diesel to date, but it is good to know to look for it.

Define "significant rush of air". I filled my 85 diesel up this morning and when I opened up the cap, I heard a tiny bit of air come out, but it didn't really raise a whole lot of suspicion.

tangofox007 · #13 03-14-2012, 12:10 PM

Quote:

Originally Posted by Tanksowner

Define "significant rush of air". I filled my 85 diesel up this morning and when I opened up the cap, I heard a tiny bit of air come out, but it didn't really raise a whole lot of suspicion.

Define "tiny bit."

The valve in the vent system will allow a slight positive or negative pressure differential, so a slight rush of air (subjectively defined) is not abnormal.