Iv had this 99 f250 7.3 for about a year and it runs out of fuel at the half tank marking on the fuel gauge. The guy who owened it before me said he replaced the fuel pump in the tank. After doing so the gauge would run out at half mark.
Any ideas how to fix this?

Thanks for the help: Goose

 

The fuel pump isn't inside the fuel tank on the 7.3, but mounted on the left frame rail under the driver area. If the previous owner dropped the tank to clean the internal fuel module filters (common for high miles/fuel tank debris) or to replace the module then he may have bent/damaged the float lever if the guage was working correctly prior to dropping the tank.. If he replaced the module to try and correct the fuel gauge error and wasn't successful, then it may not be a problem in the sender/module.. The fuel senders resistance is around 160 ohms with the tank 'full', and about 15 ohms with the tank 'empty'.. As a first step, you could take an ohm reading off the fuel module connector (tank side/disconnected) with the tank empty or close to and should see the low value. If the tanks emtpy and you see a ohm value of 70-75 or so than the sender is supplying the gauge with a half tank value.. If the value on the tank side connector reads low when the tank is empty, but climbs when plugged back in then the problem most likely isn't in the sender/module..

Question though,,,

When your truck wasn't starting before,, you had a scan tool and ran a injector buzz test and it passed (?) on all 8 from what you said.. But the cause for the no start was finally pinned to harness/UVC connection problems and a few GP's/relay.. Correct? I've seen UVC/Harness's burned, UVC retainer clips bow down or break off and cause the connectors to move off or away but shouldn't have passed the test, as well as change form running great to a no start overnight? Understand how GP's and relay might make for a harder start cold, or a lost relay, but usually harness's issues aren't instant unless a connection problem, which leads back to how it passed the test early on..

Just scratch' my head

 

thanks for the gauge reading info, i will try that and see what readings i get.

i dont understand why we could hear all 8 buzz either, but as soon as we took the cover off we seen the the plug was unpluged? the glow plugs and relay i dont think were a factor since the temp was about 55 deg. when it broke down, but still needed fixed. i have drove it to work a few times now, with no problems [knock on wood].

THANKS HAYAPOWER: GOOSE

 

Pretty common problem for the UVC harness connector retainer/release tab under the valve cover to 'relax' from age and heat and allow the connector to move off.. But it should have showed up in the buzz test, and/or should have set IDM trouble codes.. Either way, it's up and running!