No crud in fuel tank strainer

[MunichTaxi]

I emptied the gas tank and removed the fuel tank strainer
(on my 1970 W108). To my suprise, it was not dirty.

I wonder if the crud just falls into some cavity, instead of contaminating the screen?

[Adenauer]

You may just have a clean tank but to be sure, you could pull the sending unit and scope out what is laying on the bottom for sure. There's a swirl pot in the tank. If I recall, I think the strainer sits in the middle of it. with a flashlight, you can look directly down into that area of the tank.

[MunichTaxi]

I'll probably do that, since the tank is empty (full of fumes, and still very dangerous).

When i removed the hex plug at the bottom, I noticed it was brass. Assumably brass, to reduce sparks.

[Adenauer]

Safety would be a good thing. An explosion-proof flashlight would be advisable. Careful with the sending unit. It's pretty delicate inside. I recommend also, to re-install it using a new gasket.

Would you mind getting back here with what you've found inside the tank. Always interested when someone says the strainer was good to go. Did you clean the strainer at least using a burst or two of carb cleaner?

[Adenauer]

On the Diesel side of the house...

http://www.peachparts.com/shopforum/attachments/diesel-discussion/48231d1191358670-fuel-tank-strainer-benz-002.jpg

[Arthur Dalton]

I did a detailed atricle on Swirl Pot function.

Starts at post # 12.

1971 280sl stalling when hot

They are used on MFI engines.

[rusty_parts2001]

I am having the same issues on my 64 SEb, with the MFI. I've done a complete tune-up, changed the fuel filter AND fuel pump, and the starving for fuel issue crops up 10-15 minutes into the drive. I have no problem in immediate starting it up after it finally stalls. I checked the fuel filter last night again, and there was a red oxide powder coating the bottom of the cannister. This filter has only been in for less than 50 miles. Before I move on to the fuel strainer in the tank, I'd be interested in the outcome of your effort to track down your problem.

[Arthur Dalton]

The easy check for swirl pot blockage is to simply put in 1/2 tank of gas ..if the fuel starve problem ceases, you know that pot inlet is plugged b/c at 1/2 tank, the pot is a non issue as the gas goes over the top of the pot b/c of it's open top design.
That is the first test to do.
The screen can be check at the same time by taking the pump inlet hose off the pump and dropping it into a pail.....if the screen is plugged , you will not have a good gravity flow......

The only function of the pot is to assure uninterrupted gas flow at low tank fuel conditions.........that is why they use the Swirl system in FI Track cars that do a lot of high speed cornering.


A pot is nothing more than a tank within a tank, but the gravity feed from the main tank into the pot is aided from the venturi force created by the pressure from the fuel return line entering the pot just next to [above or below] the entrance hole in the pot..it is this swirl action that actually sucks the gas into the pot from the main tank [ venturi action].......so a blocked entance hole OR a blocked fuel return line will result in fuel starvation to the injection system, but only when the fuel supply is LOWER than the top of the swirl pot...
Which leads right back to my first 1/2 tank test ..............

Carbs do not need a pot b/c they have a fuel bowl/float reservoir.

[MunichTaxi]

I'd be interested in the outcome of your effort to track down your problem.

I was replacing the half-rotten rubber fuel line and return line; thought I'd check the strainer, also, on my carbed W108. Never had any problems before I did this job.

RustyParts, your problem might be a lack of venting of the tank. I had that happen on a motorcycle: Engine would shut down, I'd wait 5 minutes, Engine would run, Engine would shut down, I'd wait 5 minutes etc...

I don't know how these gas tanks are vented; someone else could offer a suggestion.