My dad has an '89 F-250 and I have a '91 F-350 - both with non-turbo 7.3 engines. I've searched, but can't find a thread on this issue - I'm almost sure it's been addressed before 'cause we can't be the only two owners with the same problem.

After sitting overnight, our trucks start then runs out of fuel within 10 seconds. It seems to be losing "prime" overnight through a leakdown somewhere. To solve the problem, I added an electric fuel pump to mine - Y-ed into the fuel line before the mechanical pump, then Y-ed back into the line after the mechanical pump. It's on a switch, and I use it every time I start the truck after sitting for more than a day. I told dad last weekend that i could also do his this way.

I've changed the injector O-rings, caps, and lines on both trucks, and the fuel filter on both are changed regularly. After installing the new lines, O-rings, and caps, the problem went away on both trucks for 6 months or so, then returned. There are NO visible leaks from any of these parts.

What am I missing? . . . . . & thanx.

 

Pre-Power Stroke Diesel (7.3L IDI & 6.9L) - Ford Truck Enthusiasts Forums Here is a link to the page for your engine, maybe post your problem there.
Also if you do a search of that page for "air intrusion" you will get a ton of info.
Good luck.

 

oh your far from being alone.
it's our most common issue with this engine.
lazy k got ya covered with what to search for.