I have a 1999 F150 XLT with V8 and a few years ago I had to replace a leaking heater core. I had to do a lot of "chiropractic" work on many parts of the dash and steering wheel to get the heater core out. I had to do this twice because the stinking replacement also sprung a leak. I think this might be why I am now having a few specific issues. The first one only showed up recently and that is my fuel gauge is reading empty with the empty light on. sometimes it comes back when driving but 95% of the time its all the way down pushing hard on empty. I have run the instrument cluster test and can see that the gauge needle will rotate cycle properly but the "fuel" portion of the test always shows me 255 all 3 or 4 times I have run the test. I cant seem to catch it when the needle is not on empty. I have heard that this could be the sending unit or the anti slosh module and I am much more keen on trying to poke the slosh module if that is truly the answer rather than dropping the fuel tank.

the other issue which has somewhat corrected itself but I want to check its adjustment is how it at one time it would only crank 50% of the time. it seems to be good now but I want to investigate the neutral safety switch or the MLPS but I have not seen a guide specific to hunting that sensor down and am looking for guidance on where to locate that thing. also and probably related, my shifter cable assembly broke sometime around the time I did the heater core replacements. A portion of plastic of that assembly was gummy on the surface and its was brittle as heck. The new cable works fine but I wonder if I bumped something out of alignment. the shift needle seems aligned properly though.

but really, the fuel gauge is my biggest problem at the moment as the truck pretty much cranks every time now. I'm just too curious for my own good and want to check that neutral safety switch while I'm in there for the fuel gauge.

things I think I need to investigate:
where is the neutral safety switch and what is the care and feeding of it to make it happy if it is out of alignment?
where could I find the sending unit wires without dropping the fuel tank so I can do resistance tests to know for sure if its the sending unit or the anti slosh module.

Thanks in advance

 

The start issue could be a bad ground. For example, when I experienced a similar issue just twisting the steering wheel to rock the truck was enough to correct the issue temporarily.

-Mark

 

Hi Mark,
What ground point were you referring to? I did change the starter solenoid a few years back on the firewall and that wasn't the issue. I did however put the new solenoid back on a super clean firewall and applied no-ox-id to the contacts to optimize the connection. Since it hasn't done the no crank thing in ages, I cant test the idea of starting it in neutral but I have seen in other threads that there is a neutral safety checking module somewhere under the cab on or near the transmission. I haven't spent time chasing it down since the truck starts 100% of the time now.

main fixing goal now is the fuel gauge resting on empty but comes back every so often. it seems to work (when I have noticed) at 3/4 tank. But when I looked again later into my last trip it was dead again. not sure if a sending unit would behave like that.. Looking for anyone's experience with the anti slosh module behind the instrument cluster since I really dont want to drop the fuel tank.
Thanks,
Peter

 

I wonder if you might also have a loosened neutral safety switch. rocking the truck back and forth and it correcting itself sounds plausible. That body motion could have temporarily realigned this module to put things back in neutral.

Here is a video I found of a mechanic under the truck replacing that neutral safety switch. I had seen a different video where the person working on the truck encountered this module with loose bolts and the timing of it had slipped.

 

Peter,

Glad the truck is starting, can't help you with the other issues though.

-Mark

 

I just spent this afternoon swapping out my on steering column shift handle since the rubber boot around it was ripped and the plastic-on-metal bushings that guide the shift action were not only loose, but were being ground up into a find powder and not doing their job anymore. Ill never understand why manufacturers make anything with plastic grinding against metal when its obvious the plastic is going to give out at some point. I used this time to pull my instrument cluster out and take a peek at the anti-slosh module. It turns out I dont have an anti slosh module, or if I do its built into the single large circuit board that is the entire instrument cluster. So, I guess the next step is dropping the fuel tank and pulling that sending unit out for a look see. Probably just going to swap it and the pump out since I'll be in there. Ill update when I get around to that task. hopefully I can get that done before the dead of winter sets in.