HHMWV Fuel tank leak

Before doing all that, just replace the gasket. That was my problem

Ajax MD said:

Sorry to dredge this up.

I have a leak, might be the gasket might be the fill tube. It definitely happens when the tank is more full than less full. My truck is very old, has to be 80's because it has the old mirror mounts. I have the old parking brake (disc on drive shaft).

What's the latest on replacement fuel tanks for the older trucks? Can they be had? Do the new tanks fit if you retrofit with the parking brake upgrade?

Thanks.

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Sorry did not fully understand what you are saying, if it only happens when it is full them TOBASH is probably right, I just don't fill the Detroit all the way up cuz I am lazy, I think that is supposed to be standard procedure anyway.

TOBASH said:

Before doing all that, just replace the gasket. That was my problem

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On that note, I do not have the fuel tank access mod. I have seen it posted somewhere. Is it in the TM section?
Would I be able to fit a wet towel on top of the fuel tank while I cut out the access panel with a angle grinder/cutter as an ignition safety measure?

Ajax MD said:

On that note, I do not have the fuel tank access mod. I have seen it posted somewhere. Is it in the TM section?
Would I be able to fit a wet towel on top of the fuel tank while I cut out the access panel with a angle grinder/cutter as an ignition safety measure?

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I would think the wet towel would be a nice way to buffer the possibility of a Big Boom. I always thought the welders I worked with were "partly to mostly crazy" when they would weld on a gas tank. Fill it up with gas. As close to full as possible to have a smaller space for the vapor to exist in. And pile on the wet rags or towels - AND wet them several times during the cutting process.

I would drop the tank before I cut anything. I have the access panel and there isn’t much room between wires and hard lines. I found this access panel and it looks like it has everything you need.

The access panel will not give you enough "access" to repair the leak unless by a very remote chance it is the fuel sending unit so you may as well drop the tank.

Mogman said:

The access panel will not give you enough "access" to repair the leak unless by a very remote chance it is the fuel sending unit so you may as well drop the tank.

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Oh, the access panel doesn't give enough access to replace that top panel on the tank itself? That's a bummer. I guess it's just for replacing the fuel sending unit. Well, before I cut or drop anything, I want to crawl in there and find the definitive source of the leak. I may be just over filling the tank.

The #1 leak point for fuel tanks when full is the filler neck to tank hose…either loose hose clamp or the rubber
is as soft as a wet noodle, only leaks when full or parked on a grade.

mine had an actual hole drilled in the top of the tank. No idea how it got there, because there were no holes in the truck above the tank, but it was there.

When we need more access to a diesel fuel tank for cleaning, we use a 4" hole saw and install a 6" access plate made by Seabuilt. We have installed them on both water and diesel fuel tanks. You notice I didn't saw gasoline......

Captaincarrier said:

When we need more access to a diesel fuel tank for cleaning, we use a 4" hole saw and install a 6" access plate made by Seabuilt. We have installed them on both water and diesel fuel tanks. You notice I didn't saw gasoline......

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I bet you know what a "fuel polisher" is!

TNDRIVER said:

I bet you know what a "fuel polisher" is!

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I may have 80-100k invested in such.

Ok, I have the TM and I've disconnected everything the manual calls for but this tank won't quite come out.

We're talking the old style fuel tank. I've removed the driveshaft to make life easier even though the TM didn't say to do it.
Which end typically releases first, the front or the rear?

I've removed the short rubber section that connects the fuel fill pipe to the tank. I've disconnected the breather hoses. It's very, very close but I'm not maneuvering it quite right. What's the trick?

Also, I've confirmed that my fuel leak is from chafed fuel lines that run from the top of the tank to the metal lines that run to the engine. It's an easy fix if I can just get at least one end of the tank to drop.

Advice appreciated!

Ajax MD said:

Ok, I have the TM and I've disconnected everything the manual calls for but this tank won't quite come out.

We're talking the old style fuel tank. I've removed the driveshaft to make life easier even though the TM didn't say to do it.
Which end typically releases first, the front or the rear?

I've removed the short rubber section that connects the fuel fill pipe to the tank. I've disconnected the breather hoses. It's very, very close but I'm not maneuvering it quite right. What's the trick?

Also, I've confirmed that my fuel leak is from chafed fuel lines that run from the top of the tank to the metal lines that run to the engine. It's an easy fix if I can just get at least one end of the tank to drop.

Advice appreciated!

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Well, the drive shaft has to come out to remove the fuel tank, make sure to remove all inboard straps, especially the short one bolted onto the cross beam, drop the rear of the tank down and slide it backwards, you may need to rotate the yoke on the differential.
The fuel tank vent is connected at the top of the tan, as well as the sender harness, so it’s a must to have the fuel sender access panal installed so these can be disconnected prior to removal

The drive shaft is removed. I think I'm just not wiggling this thing quite right.

Retiredwarhorses said:

Well, the drive shaft has to come out to remove the fuel tank, make sure to remove all inboard straps, especially the short one bolted onto the cross beam, drop the rear of the tank down and slide it backwards, you may need to rotate the yoke on the differential.
The fuel tank vent is connected at the top of the tan, as well as the sender harness, so it’s a must to have the fuel sender access panal installed so these can be disconnected prior to removal

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Ok, so the rear of the fuel tank should drop down. It's hung up on something or I'm just being too gentle with it. It was hung up on the short rubber hose that the fuel fill pipe connected to but I removed that and it's noticeably more free but still won't quite drop down. I know the tank will slip out if I can just get the rear end of the tank down.

In this photo I clipped from YT, the red circle indicates the leak. These two fuel lines are dripping. The fuel tank is empty and when I started moving things around, they still dribbled a fair amount of fuel. They appear to be wedged between the transfer case and the tank. I suspect that they are not properly secured and ended up chafing through or something. I won't know exactly what the problem is until I can drop the tank.

Ok, I got the fuel tank free. The fuel fill stub was just hung up on the frame. A gentle twist and it dropped down.

I was right- Somehow the metal fuel line sections got pinched between the front fuel tank strap and the transfer case. Years of jostling and chafing ate a 2-3mm hole in the metal fuel line. It is stunning that the engine ran, rarely stumbled and has only stalled on me once. The truck never stranded me.

In the photo above in my previous post, what is the plastic line attached to the white nipple, running to the front of the truck? How can I disconnect it?

Thanks.

Ajax MD said:

Ok, I got the fuel tank free. The fuel fill stub was just hung up on the frame. A gentle twist and it dropped down.

I was right- Somehow the metal fuel line sections got pinched between the front fuel tank strap and the transfer case. Years of jostling and chafing ate a 2-3mm hole in the metal fuel line. It is stunning that the engine ran, rarely stumbled and has only stalled on me once. The truck never stranded me.

In the photo above in my previous post, what is the plastic line attached to the white nipple, running to the front of the truck? How can I disconnect it?

Thanks.

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Heat

I could use some assistance interpreting this parts drawing.

Basically, I want to purchase the two metal fuel lines coming directly from the fuel tank. These connect to rubber sections a little further upstream which then possibly turn into metal sections again if I interpret the diagram correctly. The exploded diagram doesn't show the fuel tank at all, it's kind of a disembodied view.

Which numbers do I need?

Looks like 1 and 5
But not sure that is the correct drawing, what model truck?