Sherman fuel tank overflowing

[Jon Bradshaw]

Malcolm

I have a similar issue when operating my ferret. After sitting for a winter the ferret loses prime in the fuel system so rather than sit and crank the batteries I fitted a small auxiliary tank above the engine bay to get it started. Once it gets going the fuel from the mechanical pump takes over and keeps the ferret running. The fuel tank is above the engine bay hanging on the back of the turret and will quickly overflow with fuel back flowing from the carb under the pressure of the mechanical pump.
My thought is that one of your fuel pumps is too strong and actually pulling from one tank and pushing the back flow into the other rather than through the engine. The cross leveling tube is likely too small to handle the amount of fuel being pushed up.
The trouble shooting tests I would do are-
With the left tank very close to empty, clamp the cross tube off, fill the right tank and start the engines, look into the left fuel tank and see if fuel is bubbling in from the lower (pickup) line.
You could also switch the fuel tank feed lines to the opposite pumps and see if the opposite tank fills up.....

Either way you are driving a working Sherman so good times!

Jon

[Perry Kitson]

Hello Malcolm,
It sounds like you have two problems. First, you are drawing from two fuel tanks but only returning to one. And the "balance" tube is not doing what it is supposed to do.
The fuel pump on the 2 stroke Detroit's will move 2-3 times as much fuel as the engine will use, the excess fuel used to cool the injectors, and return to tank. There is a restictor fitting on the end of the fuel rail that keeps pressure between 60-75psi, after that fitting the fuel is supposed to return to the tank it is drawn off. For some reason, both engines are returning to the same side of the fuel system. This has to be a plumbing issue, unless you folks in Oshawa have discovered a way to have a Detroit manufacture fuel!
Personally, I would only use the upper sponson fuel tanks to feed the engines. This keeps the fuel feed line above the fuel pumps. Also, typically there is a primary fuel filter between the tank and fuel pump, and a secondary filter between the pump and injectors.
On a lighter side, I once worked with an old timer who kept calling the Detroit diesels "converters". I asked him why, and he told me because "they convert fuel to noise".

[45jim]

The original fuel supply only draws from a single tank and the feed comes from the lower tank on the side selected, using the manual selector on the crew side of the firewall. The fuel selector allows left or right or off. So you must feed from one side to both engines and manually switch to the other tank when the gauge shows "E" (meaning the upper tank is empty) so as to maintain a reserve supply in the lower tank. The fuel not used by the engine is returned to the tank that is supplying the engine NOT to the other tank! The fuel supply rate is 40 gal/hr and at 25 psi.

Now, that's the stock set up.

With your modified set up it appears that unused pressurized fuel from both engines is being returned to the same upper tank and the balance pipe is of too small a size to flow enough fuel to balance the system. If you are going to feed each engine individually then you must send the fuel return to the same supply tank or increase the size of the balance pipe. As your system is still feeding fuel from the respective lower tanks the upper tanks already have a fuel return line fitting it should be a simple task of running a new line from each fuel return fitting on the cylinder head back to its respective upper tank. The existing balance pipe may function (you didn't mention its size) once you are returning fuel to both upper tanks, I suspect it is too small. The lower tank fuel feed is above the level of the pumps so no issue using the lower tanks, gravity is on your side.

Look on page 238 of TM 9-731B and the complete M4A2 fuel system is explained.

The manual can be found here.

http://www.theshermantank.com/downlo...-like-manuals/

[rob love]

I have had experience where although the size of the balance pipe wasn't bad, it was the conglomeration of the fittings on one side of it that caused a restriction, especially considering that the return lines are pumping, and the balance line is simply equalizing gravity.

[kevin powles]

Hi, I dont know anything about Sherman fueling systems but any fuel tank needs a vent to draw in air as the fuel is drawn out through a fuel pump, would it be your system balance between the two fuel tanks if off because you have a blocked vent, of course your leaking fuel cap will act as a vent on one side.

it would suffice you have a blocked vent on the non overflowing fuel tank perhaps.

just a thought.

[Colin Alford]

Malcolm,

Have you compared the fuel systems between the M4A2s at the museum?

The description and diagram of the fuel system in the Canadian 1950 M4A2E8 Drivers Handbook is significantly different to the description in the US 1943 TM9-731B.

Unfortunately the Canadian diagram is very simple and doesn’t show how the “system of valves” works to return the spill from the side that it is withdrawn.

Is the balance tube that you describe actually the “fuel bypass line”?

Recently I have been attempting to understand the differences between early and late M4A2 systems and it appears that there were many changes during the war. The early manuals are relatively easy to obtain, but I have not yet seen a late manual which thoroughly describes the altered systems.

In 1994, Don Smith’s Sherman was driven approx 30km to Borden for the EME (now RCEME again) 50th parade. During that drive, it ran out of fuel. The left tanks had been partially filled to a level that was considered sufficient for the trip, and only the left fuel valve was on. Upon investigation, it was realized that the excess fuel had been dumping into the right tanks. This may have been due to a similar issue that you are trying to diagnose.

We’re both fuel valves on? Given the 1994 issue, I suspect that your left valve may have been off and that there might be something peculiar about the late fuel system.

All,

Does anyone have access to a late M4A2 manual which thoroughly describes the fuel system?

Colin

[Colin Alford]

Sorry for the rotation of the images. This was my first attempt to post using an iPad. It seems I have encountered the same issue as others.

Colin