CMP Fuel System Information Page

June 29 2010

Special note this page is being written with a speech recognition program as right now I have limited use of my left hand, result of a stupid shop accident, and typing one handed is a little bit slow, hopefully things will be back to normal soon, and I can get back to working in the shop. For now mind as well work on the web site. I only mention this because sometimes the speech recognition program says some very strange things so bear with me until I can get these pages fully edited and corrected.

This page will discuss various aspects of the fuel system to be found on CMP's it will include information related to restoration as well original construction. I am starting this page in direct response to a question about the layout of fuel lines running to and from the fuel selector valve on pattern eleven CMP's .

As with almost anything about CMP's what we find 60 to 65 years after construction may or may not be original. It maybe from a running modification made while the vehicle was in service or by some user of these vehicles in the last 60 years. Bart Vanderveen the noted automotive historian In CMP authority at a CMP conference in 1984 explained in response to one of the participants insistence that something was not "stock" or "original" concerning someone else's restoration of CMP. Bart's point was we're talking about a vehicle whose construction and modification was changing at a very rapid pace with improvements in response to field problems being made both at the manufacturing level the service bulletin level and at the field expedient level. These changes were coming and being made to vehicles in virtually every theater of operation from the arctic to the desert. From operating in dusty conditions were grit entered and destroyed engines and transmissions gear trains to hot and damp conditions where rust mold condensation also destroyed or damaged equipment. So so if how you find your CMP restoration project doesn't match what's in the manual don't automatically assume that it is not how used by Commonwealth Forces during and after the Second World War.

One big point I would make do not use repeat do not use any rubber NOS parts. The ethanol in most modern gases found in the U.S. will simply eat the rubber lines or rubber parts up. I have experienced personally or seen problems with the following your system parts fuel pump diaphragms fuel lines carburetor gaskets carburetor accelerator pumps fuel pump gaskets fuel filter gaskets the list goes on. If if the fuel tank was ever sealed with one of the earlier gas tank sealants to prevent leaks or trap rust particles you may find suddenly that as the percentage of alcohol used in the gasoline at the pumps increases that suddenly it dissolves the gas tank sale and plugging the fuel filter and causing the tank the leak.

The question"I tried to research as best I can and have come up short. I can’t figure out where the fuel line crosses over to the 3-way fuel valve. The best I can figure is that it goes from the tank back to the frame, 90 degree bend to the front, along the close to the frame, turn 90 beg towards the middle, goes between the frame & cab floor and through to the 3-way valve." In the images below that will try to illustrate both from my own 1941 Pattern 11 C60L and from other sources such as the various shop manuals and the Chevrolet service information bulletins issued during the war.


Above it has in MBC - 1 Below as in MBC-2

Link to MBC-1 and MBC-2 Fuel and Exhaust Manual Pages One of the first thing you'll notice is that the earlier manual has fifteen pages and the later manual has nineteen there also several changes that make the fuel and exhaust system pages more relevant to CMP's as compared with standard commercial trucks.

To the question of fuel line routing there are significant differences see the two photographs and at left it to say that they went from a generic to a specific vehicle layout.

The same basic layout is used on both Pattern 11, 12 and 13 what I've found it be different on the twelve and thirteen from what is shown in the manual and the service bulletins is which have solid steel tubing and which have flexible lengths hose. Both of my trucks had solid steel tubing all the way from the tank to the two way valve the Pattern 13 had a flexible connection could have lost the n to the fuel filter while the Patter 12 had solid steel tubing connecting the selector valve to the fuel filter mounted under the driver .

The following photos with notes show the routing of the steel tubing from the fuel tanks two the selector valve.





Note in the two pictures below picture below you'll note evidence of some leakage, the discoloration around the fuel level sender unit this is the result of the ethanol in today's gas dissolving the rubber in the cork composite gaskets I still have not found a reliable replacement.

This is the left and tank on the Pattern 13 with forward on the vehicle being to the left, steel tubing fuel line comes out of fitting on the tank goes directly over to the frame then parallel to the frame tour it's the from the truck to turn and pass through the hole in the frame. Note the rubber grommet to keep the fuel line from chafing on the frame.

This is the right tank or driver's side of the pattern thirteen with Ford on the vehicle being to the right in the picture again you can see the fuel line comes straight out of the tank with right angle to the frame and forward along the frame to the drama did hole the frame. On my pattern thirteen both of these fuel lines extended from the tank all the way to the fuel selector valve as a single piece of tubing. When I tried to reproduce the fuel line I discovered that it was not possible to feed the line through with the engine and transmission installed in the chassis and the cab in place I'm sure during normal construction the fuel lines were inserted on the production line when there were no obstructions.

Again left ankle of a pattern thirteen fuel line goes through the hole in the frame and makes right angle turn to run across the floor of the cab. As there is a service bulletin concerning installing a flexible connection at this point I suspect that fatigue failures occurred at this location. In the picture below shows left side of frame front of truck to the bottom fuel line making its right angle bend up then to the rear. The rearward bend is to bring it in line with the fuel selector valve. [The white spin on oil filter is a remote will filter for the 261 cubic inch engine in the Pattern 13]

pattern thirteen driver's side


In this picture you can see the Pattern 13 1942 C60S at the beginning the restoration process with the cab having just been removed and you can see the layout of the fuel lines.

This picture is looking up at the valve seen in the picture at left.

In the photo above you see the pattern twelve cab style on the left side just behind the running board bracket front of where the fuel tank support bracket would be located. In this case the 1 in. hole for the fuel line to pass through is yet to be cut [I had to replace the inner frame real with new material ]

On the pattern twelve with the cab mounted almost directly to the frame the turn up in the fuel line once it passes through the frame real is much smaller than on the pattern thirteen. But again the fuel lines pass through the frame at the grommets holes and turn to run and lineup with the fuel valve.

In this photo is the driver's side of the pattern twelve same hole location