I'm completely stumped
 

This all started a few weeks ago when I (like and idiot) ran out of fuel. The truck was running fine before then, but now it's having trouble starting. After I first ran out of fuel I had a fair amount of trouble getting it started (like most people do) but I eventually got it going. I drove it that day and ran a bunch of errands, and every time the truck started up just fine. I let it sit over night and it wouldnt start. I tried everything, jump starting etc... finally the only way we got it running was by using starting fluid. After it started up it again ran great all day and would start back up every time. I knew my batteries were almost dead (when I tested them one was putting out 127 and the other 250 cold amps out of 850) so I planned on replacing them to see if that helped. At the same time my alternator gave out, so I replaced the alternator and both batteries. It cranks faster now but same deal, no start without starting fluid. It will start back up if it has been started in the last 6 hours or so but if you let it sit for a long time (such as over night) it wont start without fluid. So then I was thinking there must be air leaking in the system somewhere. So we pressurized the tank with an air gun and listened for leaks. We tightened a few clamps and such but we could still hear a leak. It sounded like it was coming from the top of the front tank. I should mention I've only been using the front tank. So instead of dropping the front tank and checking the seal, we decided to test it by filling up the back tank which I did last night. Let it sit over night and same problem, wont start without starting fluid. I'm stumped, I don't really know what to check next. Any ideas, tips or advice? Thanks guys.

Some good reading in the fallowing link. It sounds like a weak relay or glow plug issue to me. I don't understand why your problems just started with running out of fuel though. Others with more knowledge will surely post more advice.

https://www.ford-trucks.com/forums/4...ke-thread.html

Also, I didn't test the back tank, so that could be leaking air too. Seems odd though that both tanks would develop leaks at the same time unless I did some sort of damage to the lines when I ran out of fuel. Also forgot to mention that I checked the fuel bowl/filter. Filter it fine, could probably be replaced but that's not what causing this issue.The O-ring to the fuel bowl was in good shape too, but we cleaned it up and sealed it just in case.

First STOP using starter fluid. I know it is tempting and you gotta do what ya gotta do but stop now.
When was the last time your cleaned the FPR screen? I don't know if that will do the symptoms you are describing or not. When you clean the screen take it out and hold it in your fingers. Don't use a Q-tip or whatever, take it out. What is the ambient temperature when you have troubles?

When I got my F250 the glow plug relay was bad, and I had to stat it with starting fluid but when I got the relay fixed and it starts easily. Probably just a bad relay or worst glow plugs.

A down and dirty way to check the GPR is: Turn the key "ON" and watch the battery/charging gauge. You will see the needle bounce up slightly when the WTS goes off in 20 seconds or so (depending on the ambient temperate). Continue to watch for another 2.5 minutes. If it does "jump" up more in 2+ minutes than the GPR is most likely toast.

I know not to use starting fluid. I'm been starting it that way as infrequently as possible. I always by pass the glow plugs when I start it, but still, I know it's bad. I've only owned the truck since September so I've never cleaned the FPR screen (actually I'm not even sure what that is). The previous owner replaced the glow plugs not long before I bought it, so hopefully it's not that. I'll test the GPR. One other thing I forgot to mention. when my key is in the ignition, my battery light comes on and my volt gauge reads very low (below the "N" on normal) and then once it starts the battery light shuts off and the volt gauge jumps back to normal. I know the volt gauge is always lower while the glow plugs are heating up, but I don't think the volt gauge was this low before and I know the battery light was never on. Also Cope, the temp has ranged from about 25* up to 50* or so. Temperature hasn't seemed to make a difference.

If its the gpr , you can clamp a jumper cable clamp on the 2 large posts , if it starts right up cold , you need a gpr ...

I knew my relay was bad so I did till I got a relay.

Yep id say gpr. Turn the key on run out lay a screwdriver across the 2 big posts for about 30-45 seconds go back in and crank it and I bet it starts. If it was a hp oil problem or fuel I don't think using ether would matter because as soon as it burned all the starting fluid it still wouldn't run. Hopefully you didn't burn up your glow plugs with the starting fluid. Next time you have to use ether to get started make sure you pull the power terminal on the gpr so the glow plugs don't run

It wouldn't start even when I had it hooked up to jumper cables. Now that was before I replaced my batteries which were toast, I haven't tried to jump it since then, but before it wouldn't start even if I was jumping it.

Also, I'm not looking at my engine now, but if I remember correctly the gpr is mounted to the passenger side fender, correct?

I would plug it in overnight and see if it fires right up in the morning.

No, that is your starter relay...

Your GPR is to the left of your fuel bowl.

I'll try it, however I live in an apartment building and they do not allow me to plug it in over night so I want to see if there is a permanent fix. Before all of this started, it had no trouble starting in temperatures less than 20*. This morning it was 50* and it wouldnt start. I definitely want to get this solved ASAP, i've been using as little starting fluid as possible, but still, I've read too many horror stories about what ether can do to a diesel.