I have a 99 F350 with a 29 gallon tank. I filled it up yesterday and the total gallons was a little over 24. The low fuel light was on and the gauge only goes up to almost 3/4. I recently bought this truck. I've searched for a thread on here possibly addressing this but have been unable to find one. I've been going through possible issues in my head....anyone else ever had this issue or know what the problem is? Any help is greatly appreciated.

 

Welcome to guzzle's In-tank Harpoon Mod Web Page

Welcome to guzzle's In-tank Hutch Mod Web Page

You can usually squeeze (painfully slowly) another 5+/- gallons in. I have put upwards of 8 gallons in (filling to the neck) this way, but without doing the Harpoon mod it takes FOREVER.

One of the best mods I have done was the Hutch/Harpoon mods, and I did it with Strictly Diesel's kit. Top notch kit. Makes filling up ALL the way much quicker/easier.

 

Mine has a 39 gallon tank and when my low fuel light comes on I have never been able to put more than 32 gallons in it. The low fuel light does not mean your tank is empty, just that you need to start looking for fuel soon so you don't run out. So, if you fill up when your light comes on you won't actually be putting in what your tank capacity is.

I have a 69 ltd that the gauge won't go above 1/2 a tank, but it works perfectly from 1/2 a tank to empty. I just fill it up until I know it is full and then don't worry what the gauge says until it gets below 1/2. Does your gauge start going down immediately(tank not really full) or does it hang out at 3/4 until you drive it a while(tank full, gauge not reading correctly)?

 

In contrast, I have put 33 gallons in my 30 gallon tank after doing the hutch/harpoon mods. Stays on/above the "F" line until I get ~120+/- miles.

 

I can only put 32 in a 39 if I fill up when the light comes on(I usually fill up at 1/4 tank and don't let it get low enough for the light to come on), but I wanted to see how far I could go once the light came on and ran it another 90-100 miles. I was able to put the full capacity in then, so I probably only had half a gallon in the tank and filled the neck up with half a gallon or so. My wife likes to run our bronco almost bone dry a lot and I have put 30 gallons in its 29 gallon tank many times lol.

Nothing wrong with those mods, just too much work for too little return for me. I'm just wondering if the OP is actually only 3/4 full or if the gauge is just reading wrong.

 

Well, one of the thing about doing the hutch is removing the mixing screens, they are a joke, and it would allow him to inspect the pickup and the float/sending unit. He may have broken the float on the sending unit.

And again....MUCH more fuel capacity alone made it worth it for me.

 

The vent is plugged.

 

My fuel guage does start dropping immediately. The first time I tried to fill it up I put a little more effort into trying to get more fuel in it until it started coming out and it went a little higher than where the guage went this time. Once it stopped this time, I only tried a couple more times and said F it.

I will definitely be doing the Harpoon Mod at a minimum. I can see the issue now having seen the pics of how far the fill and vent tubes go into the tank.

I failed to mention that I have the V10 in my truck and from what I've briefley read about the Hutch Mod, it seems as if it applies to diesels only, am I incorrect about this? If I'm going to drop the tank, I might as well do it all at once.

However I was curious if all fuel pumps you could buy if you ever needed to replace one, would they still have this issue and need to be modded, or does it apply to the factory pump only?

Thank for all the help everyone, I really appreciate it!

 

My bad for assuming diesel, I don't come out of the 7.3L closet too much, lol

 

I may be missing something here, but I am not seeing where the extra capacity comes from. When I put 32 gallons in my 39 gallon tank it isn't because there is 7 gallons of air space in the tank but because there is still 7 gallons in the tank when I stop to fill up (I know, because the neck is full and gauge is on full). I have never had to spend 20 minutes filling up, much less that long just to top it off like the link says. I have no problem filling it all the way to the top of the neck, or doing so quickly, so I'm not seeing the advantage to the mod.

 

Well first, I was talking diesel, as we just clarified. And if you look at this pic, you can see how much space there is in between the bottom of the fill tube, and the top of the tank.



And I know especially with diesel here, it foams pretty bad. Like I said in my earlier post, I would have to fill up VERY slowly, but could fill upwards of 8 gallons in past where the nozzle "clicks" off. That's a lot of space/fuel. 120 more miles on the road between fill-ups.

I'm not overly familiar with the gasser setups, as I have only worked on 150s, not the super duties.

 

I was typing my reply before I saw you clarify the diesel part, so I didn't see that . Gas doesn't foam like diesel does, so that really isn't a problem on gasser trucks. I drive a diesel for work(international prostat) and even with the saddle tanks I can squeeze in 5-8 gallons extra per tank if I don't let it foam up.

 

My truck has a 29 gallon tank, I have had it for 6 years and have driven it with the low gas light on for awhile. I have not put more then 25 gallons in. The light is just a warning you will still have 6-7 gallons left when it is on. Ok once I did put in a hair over 26 gallons, but I was in North Dakota and I missed the last exit and my GPS said it was like 50 miles to the next station. Made me a bit nervous.


I would suspect a faulty sending unit. Could have a cracked float also.

 

there's a Technical Bulliten or Service Bulliten about clogged vent canisters that results in the fuel pump shut off from kicking in.

you can hold the fill nozzle back a little once it kicks off to see if it resumes fueling. if it does...your canister is clogged.

 

Thanks for all the help everyone. I will look to see if I can find this TSB and once I get the fuel level back down, I'm gonna see about dropping the tank and having a look see at everything. I did notice today when I parked in my driveway, which is slightly uphill, when I started my truck, the fuel gauge was up above the 3/4 line. Of course it dropped once I was back on level ground.