ive got a 1992 w250 and i had the gas tank strap rust thru and the back half of the tank sag, i had to replace the sending unit cuz it broke the nipple off the top. got it all reassembled and now it wont stay running after we prime it manually, it just dies, i bled the air like my chiltons said to do but i cant figure it out any help at all would be great!!!!!!

 

Prime it, run it, and after it dies pull the filter and see if it has any fuel. I'm guessing it won't, so you're sucking in air somewhere between the tank pickup and the LP. Either that or your pickup tube is either broken or plugged. If the tank 'dropped' when the strap broke, you might have giggled things around in there. 20 some-odd years of nastiness building up in there could well plug the pickup tube.

 

I know you replaced the sending unit but what about the o ring in the quick connect?


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I tore my hair out with much the same problem. My fuel line was rusted through and sucking air.
I used compressed air and a rag to blow into the fuel filler hole. Keep an eye on the tank because you could pop it like a balloon. You only want like 5 or 8 pounds of pressure to build up in there. Just a little distortion is all you'll need. Fuel will bleed out of your leak.
The movement of taking the tank down may have been the final straw for an old rusty line.