IDI Runs Erratic

[scjarena]

1990 F350 7.3 IDI I bought as project truck needing work. I replace one head due to a crack. I put everything together, replaced all leaking fuel o-rings, etc on top of engine. I don’t see any current leaks. I’ve been driving it around for about 150 miles and down the highway it feels like it surges just a little. Throttle response seems really quick, if I barely push on the gas the engine revs quick. This makes it a little difficult to drive slow like thru a neighborhood. Previous owner retrofitted a 4 speed. It somewhat feels like an old gas engine that has a slight vacuum leak where the engine feels like it runs a little erratic and the RPMs go down kinds slow. I’m not sure if the intake could be leaking air in, or maybe the injector pump timing needs to be adjusted. I’m also thinking I still need to burn out some crappy fuel left in the tank. I’ve gone thru about 3 tanks fills and I’m adding diesel fuel treatment for water. Any ideas or where to start? Thanks

 

[79jasper]

Air intrusion.

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[scjarena]

I guess I need to inspect all the lines from the tank to the pump. Is the any tricks for finding leaks in the lines under the truck? I have installed a clear hose on the filter return line.

 

[79jasper]

Just more clear line. Lol
I would suspect pre-pump though. It's sucking air while running.
There's a rubber line between the frame and pump that likes to rot.
The caps/return lines will cause a start then die situation.

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[scjarena]

Ok, so far I replaced the rubber fuel hose from the frame line to the fuel pump, and from pump to filter head. I bled the Schrader valve. I have a clear line between the filter head to the return lines and it still has air in it while truck is running. Shouldn't this line be solid fuel with no air? I'm not sure of a good way to check the lines for air leaks to the tank and to the selector valve. Thanks