Is it normal for the fuel tank filler cap to be held VERY tightly by suction or negative pressure in the tank?
Every time I go to fill up, I have to seriously pull on that cap to crack the seal and it then takes a long hard drag of fresh air

Does anyone recognize this symptom?

Am I in trouble or something clogged?


I know you may may want to blame my WVO fuel use, but what is actually happening inside my tank?

Thanks!

__________________
1990 300D 2.5Turbo, two tank WVO, daily driver 300,911
1992 E300 gaser, 150k. Parts only, For Sale

[B]1984 300TD Euro 4speed Sold
1977 300D Elsbett SVO single tank Sold
1981 300TD "Silver bullet" 285k ran B100 Sold
1981-5 300D x 5 cars stripped and reused, parts for sale

Other toys:
1995 Dodge 2500 Cummins 12V P7100 Bosch mechanical pump with 2 tank veggieconversion kit, only 120k!
1959 Cadillac Dad's legacy, needs finishing

Look for a pair of lines coming out of your fuel tank, lower front side, under the car. One of the lines will have a bell-shaped vent valve on the end of the line. That valve is either clogged or has failed. Cleaning the valve will solve the venting issue most of the time.

I wondered about that vent.
It is bell-shaped and old looking. any details on how to clean and later test effectiveness

Thanks for fast response

I saw a thread while back with a collapsed tank!

__________________
1990 300D 2.5Turbo, two tank WVO, daily driver 300,911
1992 E300 gaser, 150k. Parts only, For Sale

[B]1984 300TD Euro 4speed Sold
1977 300D Elsbett SVO single tank Sold
1981 300TD "Silver bullet" 285k ran B100 Sold
1981-5 300D x 5 cars stripped and reused, parts for sale

Other toys:
1995 Dodge 2500 Cummins 12V P7100 Bosch mechanical pump with 2 tank veggieconversion kit, only 120k!
1959 Cadillac Dad's legacy, needs finishing

Sometimes it's just a matter of cleaning out some dried mud or an insect nest. The valve should pass air both ways under slight pressure.

Are you sure it is suction and not pressurized due to heating of WVO/air inside the tank?

__________________
Not MBZ nor A/C trained professional but a die-hard DIY and green engineer. Use the info at your own peril. Picked up 2 Infractions because of disagreements. NOW reversed.

W124 Keyless remote, PM for details. http://www.peachparts.com/shopforum/mercedes-used-parts-sale-wanted/334620-fs-w124-chasis-keyless-remote-%2450-shipped.html

1 X 2006 CDI
1 x 87 300SDL
1 x 87 300D
1 x 87 300TDT wagon
1 x 83 300D
1 x 84 190D ( 5 sp ) - All R134 converted + keyless entry.

Just a quick explaination: this is on the Elsbett single tank WVO system.
Electric-heated fuel filter near IP.
No other extra heat in the system or tank, if that helps narrow it down.

Car is running normal temps and weather is cooling down (at last

Complete fuel system was replaced and cleaned recently, except the vent
I will check the vent in the morning

__________________
1990 300D 2.5Turbo, two tank WVO, daily driver 300,911
1992 E300 gaser, 150k. Parts only, For Sale

[B]1984 300TD Euro 4speed Sold
1977 300D Elsbett SVO single tank Sold
1981 300TD "Silver bullet" 285k ran B100 Sold
1981-5 300D x 5 cars stripped and reused, parts for sale

Other toys:
1995 Dodge 2500 Cummins 12V P7100 Bosch mechanical pump with 2 tank veggieconversion kit, only 120k!
1959 Cadillac Dad's legacy, needs finishing

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

Good picture of a collapsed tank. either pessuresed or a vacuum, the vent is probably the culpert. remove the fuel cap, and shoot some air in the vent line after removing the bell and the plastic check valve.

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

That is the thread I had seen before and it scares me!

I checked the end of my vent's hard line.
There is only a hollow rubber bell-shaped tip; no check valve or anything to prevent mud etc from getting up into the line.
Am I missing something on this 1977 300D?

Appears clean and open on the outside; is there anything more I can test?
I don't have air compressor available, but the mighty vac would hold pressure pull on it

I know this is a simple part, but I am not sure what I am missing or need to test further to fix the suction on my fuel cap?

The system has done this ever since I cleaned the tank and replaced all the flexible lines/filters.

__________________
1990 300D 2.5Turbo, two tank WVO, daily driver 300,911
1992 E300 gaser, 150k. Parts only, For Sale

[B]1984 300TD Euro 4speed Sold
1977 300D Elsbett SVO single tank Sold
1981 300TD "Silver bullet" 285k ran B100 Sold
1981-5 300D x 5 cars stripped and reused, parts for sale

Other toys:
1995 Dodge 2500 Cummins 12V P7100 Bosch mechanical pump with 2 tank veggieconversion kit, only 120k!
1959 Cadillac Dad's legacy, needs finishing

There is a blockage some where or maybe a kinked hose?

Charlie

__________________
there were three HP ratings on the OM616...

1) Not much power
2) Even less power
3) Not nearly enough power!! 240D w/auto

Anyone that thinks a 240D is slow drives too fast.

80 240D Naturally Exasperated, 4-Spd 388k DD 150mph spedo 3:58 Diff

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics. Funny how that works

If you can't get the problem fixed in a timely manner, you can buy yourself time by creating your own "vented cap" by just drilling a very small hole in the fuel cap to eliminate any pressure differential. Obviously better to do it right, but a vented cap would prevent the need to replace your tank should the worst happen.

__________________
Current Stable

• 380SL (diesel)
• Corvette C5
• Manx
• Baja Bug
• F350 Powerstroke
• Auburn Boattail Speedster replica

I start looking underneath for kinked hoses.
Any chance this would be related to me hooking up fuel lines backwards (is that possible)?

Open to any other ideas or experience to narrow this down?

Also, do I need a check valve added to the vent line?

__________________
1990 300D 2.5Turbo, two tank WVO, daily driver 300,911
1992 E300 gaser, 150k. Parts only, For Sale

[B]1984 300TD Euro 4speed Sold
1977 300D Elsbett SVO single tank Sold
1981 300TD "Silver bullet" 285k ran B100 Sold
1981-5 300D x 5 cars stripped and reused, parts for sale

Other toys:
1995 Dodge 2500 Cummins 12V P7100 Bosch mechanical pump with 2 tank veggieconversion kit, only 120k!
1959 Cadillac Dad's legacy, needs finishing

Either the valve is obstructed, the line is obstructed, or some combination thereof. It's not a complicated arrangement.

You might remove the valve and determine if air will pass through the line.

you can bring the car over to my house, and I'll look it over with you. it should be no problem finding the issue.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

or, let me know if you are in the Gaston area, and I can meet you sometime.

__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

The 1/4 o.d.steel vent line makes multiple bends inside and outside the tank which makes it impossible to clean with a snake. In your case since you 're running svo it is most likely plugged inside the tank.


Remove the vent bell and check valve unit ( on the ones I've seen the bell is black rubber and the check valve is grey plastic) and see if compressed air will clear the line. Also alternate blowing from the filler neck.

The check valve is not a real check valve, it flows in both directions. It allows more air to flow into the tank ( vacuum) then out of the tank (pressure).

__________________
85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked