w124 '88 300TE fuel delivery problem
 

I'm having what I think is a fuel delivery problem with my daughter's wagon. The tank capacity states 19+/- gals. but when it has used only about 15 gals. it will buck and stall as if it is starving for fuel. This assumption is supported by the following, if I let it run until it stalls out before I fill the tank, it will take a few tries (cranking) before, what I assume, is the air getting purged from the system and the engine finally catching and starting. It will then run fine until another 14-15 gals have been used. I am assuming (I know, a dangerous thing to do) I have used 15 gals. because that is all I can fit in at the filling station. This would theoretically leave about 4 gallons still in the tank but unavailable for some reason. My low fuel indicator light never comes on except when I crank the car to start it.

Volvos have a history of cracked hoses between the prepump and the tank outlet which can exhibit symptoms similar to what I am experiencing here. Is it a likely scenario for the Benz? I know my pre-pump is functioning but haven't checked the main pump yet. Is there a quick/easy way to do this? Where should I connect? I do have a gauge with a bypass valve for checking flow.

Should I be looking at anything else before I pull the sender/pickup unit?

Any advice is appreciated.

K

Anybody out there?

I had a similar problem with my '88 TE. It occurred mostly when going around a corner. There is a cup in the tank where the fuel pump takes suction. The purpose of the cup is to keep fuel near the pickup during cornering, etc. Fuel is drawn into the cup from the rest of the tank by an eductor nozzle. The feed for the eductor nozzle is the fuel return line from the engine. On my car a small piece of a plastic baffle had broken off and lodged in front of the eductor so it could not serve it's purpose. When the fuel level dropped to the point where the eductor was required to fill the cup (the eductor is open at the top so it has no real purpose until the level gets low) the car would stall. It would restart if you let it sit a minute or so.

I removed the third seat and the floor panels. I removed the sending unit and I could see the problem. I fished the part out and the problem was solved. There are some drawings of this system on the 124 Chassis Manual.

Thanks, I'll go exploring this weekend. :D