HMMWV Fuel Tank Overflow?

[Predator42]

I went out to start the truck this morning and saw a small puddle on the drive way. after further evaluation I see that the underside of the fuel tank is coated with diesel. I heard that overfilling the tank could cause this. I have been filling up to the point I hear the first burp and stop. Is it possible I am overfilling or is there a serious issue I should be looking at replacing a fuel tank? feel free to refer me to another article if one already exists. I couldn't see anything.

I will post some pictures shortly.

 

[Retiredwarhorses]

It's almost Normal for these to leak if over full and parked on a sloped driveway, the tank is fine, it's the seal between the metal plate on top of the tank that is leaky when they get old. The original were cork, the later style is rubber.
i use RTV as well when putting in a new seal, evenly torque the nuts on the nut plate, replace the fuel tank vent and grommet wile I have the tank out...now, that all assuming it's leaking from there, the more common spot IMO is the rubber piece between the filler tube and tank....there are 2 hose clamps holding it on. that rubber gets real soft and the clamps loosen up.

 

[Predator42]

Thanks RWHR that is awesome advice. I rolled under there and sure enough that hose clamp was pretty loose where it meets the filler tube. I will see if that was it. Plus it is a full tank and its parked facing towards the road on the sloped driveway.

 

[KansasBobcat]

Mine had leaking hose at filler neck and hose clamp was impossible to access! Ended up dropping tank and doing what RWHR said. Tank was pretty clean except had end of an old drain plug in it. Do not tighten these plugs very much! There is an access panel MWO which allows access to top of tank that I have not done but seems a good idea.

 

[TedG]

The hose clamp on the tank side of the filler hose is accessed from underneath next to the frame rail. Unless someone installed it wrong, you can reach it with a small ratchet and 3xtensions.

 

[KansasBobcat]

The hose clamp on the tank side of the filler hose is accessed from underneath next to the frame rail. Unless someone installed it wrong, you can reach it with a small ratchet and 3xtensions.

Thank you, Ted. Figured it out when reinstalling tank. My friend,mechanic insisted on dropping tank. Kind of a PITA, for first time! I was not on this site at the time and did not get expert advice. Lesson learned!

 

[Predator42]

I just went out after letting the puddle somewhat evaporate for a few hours this morning after having tightened the hose clamp, I started it up and I still see several lines of fuel finding there way down the side of the tank and accumulating at the lowest point and then dripping off onto the driveway. What is the right way to drain the tank, and remove it for service? ...I see the plug on the bottom of the tank...seems like I should remove some fuel some other way first? Maybe not...

 

[DatGuyC]

if you remove that plug be ready for it all to come out fast, mine did and I got diesel everywhere haha

 

[KansasBobcat]

Mine had leaking hose at filler neck and hose clamp was impossible to access! Ended up dropping tank and doing what RWHR said. Tank was pretty clean except had end of an old drain plug in it. Do not tighten these plugs very much! There is an access panel MWO which allows access to top of tank that I have not done but seems a good idea.

The NSN on the fuel tank access cover kit: 2510-01-454-7077. I have seen these for sale in the past. Will not work on M996 or M997.

 

[KansasBobcat]

I just went out after letting the puddle somewhat evaporate for a few hours this morning after having tightened the hose clamp, I started it up and I still see several lines of fuel finding there way down the side of the tank and accumulating at the lowest point and then dripping off onto the driveway. What is the right way to drain the tank, and remove it for service? ...I see the plug on the bottom of the tank...seems like I should remove some fuel some other way first? Maybe not...

If you can siphon some off it will be less messy. I followed the TM when pulling the tank: TM 9-2320-280-20-2, starting on page 3-36. These are available on this site although I have the old paper ones. The drawings in the TM are quite helpful. This a 2 person task! You need a "soldier B" If you are tempted to order a new tank be sure that the part number tank will work with your parking brake. I know... Good luck

 

[Predator42]

Thanks for the TM data KansasBobcat. I have them but I haven't figured out the best way to search them for the right information. the specific pages are helpful. and thanks for the tip on the two man requirement. I tend to get into these things and find myself alone under the truck and my cell phone has conveniently fallen out of my pocket somewhere during the task.

 

[Retiredwarhorses]

The NSN on the fuel tank access cover kit: 2510-01-454-7077. I have seen these for sale in the past. Will not work on M996 or M997.

you should drop the tank to install the access plate...I imstall this on all my trucks and any customer truck I build.
but this only allows the fuel sender or tank vent to be changed...not remove the plate itself to chane the seal.

 

[Retiredwarhorses]

The hose clamp on the tank side of the filler hose is accessed from underneath next to the frame rail. Unless someone installed it wrong, you can reach it with a small ratchet and 3xtensions.

Super long screw driver works well too...I have a 2 footer.

 

[Predator42]

Planned on siphoning the tank today. Has anyone actually been able to feed a hose all the way to the fuel from the filler? I keep hitting a wall about 2 feet in. I removed the strainer and the rubber sleeve already. If not what is the best/safest way to drain the tank?

 

[Retiredwarhorses]

You have to drain it...pull the tank plug. Plus This will allow the tank to drain any setiment in the tank.
just use clean 5 gal buckets till its al out....or drive it till its low.

 

[Predator42]

Thanks that is what I figured but needed confirmation. I'm letting it run right now just to charge up the batteries and let everything wake up. Really appreciate the quick response.

 

[Predator42]

Well it is all fixed for now. the leak was coming from the most inward hose clamp. after RetiredWarHorses made the suggestion of a long screwdriver (thank you) I headed out and found one at harbor freight. Home Depot didn't have anything longer than 8" and what i found came in a set of 2 (flat and philips) about 2 feet long for about $5. With the help of my small handed daughter, she guided it from above while I was under the truck. Once she got it into the right location I gave it about 5 good twists and it is nice and snug now with no dripping/leaks. Thanks everyone.

 

[dangood]

Nice work. Way to get the little lady involved. Those little critters with the small paws that eat all our food and cry for no reason come in handy once in a while.

 

[Bobthebuilder]

Hey guys, I'm a newbie to SS and my first HMMWV so this may not be the best place to ask this particular question but it was the closest and most recent. I just got my Hmmwv and I'm in the process of draining and replacing fluids. Just finished the oil and now I'm on to fuel so any suggestions are more than welcome. My question is...where the heck is the manual fuel pump?? Driver side, passenger side, under, above? Any help would be appreciated.

 

[Dock Rocker]

I am not sure about a manual fuel pump but the mechanical pump that supplies the motor is located in the side of the block.

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