If you drive one of the older GT cars and enjoy doing some of the maintenance yourself, you may have shied away from the fuel system because of its complexity. It’s true that setting up the fuel injection or multiple Weber carburetors is better left to someone with experience. Checking to make sure that the engine is getting an ample supply of clean, cool air by inspecting the air filter housing, filter element and ducting for proper sealing and cleanliness is important and within the capabilities of most owners.
Make sure that the fuel cap fits snugly and that the rubber gasket isn’t cracked. If, after driving the car, a hissing sound can be heard while loosening the fuel cap, you have a venting problem. Cars from the early seventies and earlier should have vented caps which allow air into the fuel tank as the fuel level drops. Later cars have special venting systems which serve the same purpose but also capture fumes coming back out of the tank. In either event, air must be allowed in or fuel will not be allowed out.
Be sure the fuel tank is securely mounted and properly isolated with some sort of cushioning material between tank(s) and whatever is holding the tank in place to prevent holes from wearing through. Fuel tanks should be grounded to the car body or chassis to prevent electric arcing and to help the fuel gauge do its job.
Check tank and all hoses and pipes for wet spots or cracks. Check hoses for swelling or loss of flexibility. Be sure all fuel hoses and lines are kept away from sharp metal edges and away from the exhaust system. Check all hose clamps and fittings for tightness. Replace corroded clamps and any suspect hose or metal fuel lines.
A note about safety: if you must replace a fuel hose or pipe, be sure to clamp off the system between the tank and the repair using the proper tool. If clamping is not possible and the repair is not above the fuel level in the tank, the tank will have to be drained. Before starting, be sure you have enough empty gas cans, a good sized funnel, and a clean drain pan. If you can, pump as much fuel out as possible before removing the drain plug. Keep all sources of heat, spark or flame far away. That includes smokers and droplights! Have a fire extinguisher handy and preferably, do it outside. You won’t have to worry about fumes being ignited by the furnace, water heater, etc.
Draining the tanks is also a good way to purge debris and water. If debris such as rusty scale is a problem, this may be a good time to have the tank professionally cleaned and epoxy coated inside and out. If that is not an attractive option, an over-size in-line fuel filter installed between the fuel tank and the fuel pump will sometimes do the trick. If the gas you removed is old and full of debris, place a paper paint filter in a funnel to strain out the debris and mix the dirty old gas with the other fuel in your daily driver a few gallons at a time.
A few other fuel tank notes: When storing your car, keep the fuel tank full. It prevents condensation and collection of water. Over the winter add a fuel stabilizer.
Most older Maseratis use Bendix electric fuel pumps which come close to looking like beer cans. These pumps are reliable and have a cleanable pre-filter element which can be accessed by unscrewing the bottom. (The same cautions mentioned above apply to servicing the fuel pump.) Exact replacements are still available from your local N.A.P.A. store. Ask for part #6101016. Make sure it has a round red label on top for the correct pressure range. Before replacing your old pump, check to see if it’s getting a supply of fuel, that the pre-filter is clean, that it is receiving battery voltage, and that all connections including the ground wire on the pump are clean and secure. The pump should be rubber mounted (N.A.P.A. #35-144).
After fuel leaves the pump it is pressurized and flows to the engine via the “filter valve” unit, which on most Maseratis consists of an old fashioned glass sediment bowl with a paper cartridge fuel filter inside, mounted under a diaphragm-type fuel pressure regulator. On most cars it sits next to the engine, high up on an inner fender. The Weber carburetors like the fuel pressure to be 2 to 2.5 lbs., no more, no less. Checking fuel pressure with a gauge connected to the out port on the “filter valve” is a good idea. Very ofter the “filter valve”, even after cleaning out the glass bowl and replacing the filter element, will no longer regulate the pressure. New, non-original units are available but usually the easiest solution is to place an adjustable fuel pressure regulator (NAPA #730-2367) into the fuel line, somewhere not too noticeable, between the pump and the “filter valve” You also want to have enough fuel flow to the carburetors, about an ounce per second is good. If you remove the supply hose at the carburetors you should be able to fill a 20 oz. pineapple can in about 20 seconds or so. Just dump the fuel back in the tank.
This article really ends at the carburetors but you should make sure all the brass bolts holding the banjo fittings are snug and that none of the fiber washers are broken, distorted, or leaking. Check the nuts holding the carburetors to the manifolds and the screws securing the covers. Never over-tighten anything on a carburetor, and use the correct size and type screw driver or wrench.
One last note about the carburetors. The Ghibli, Indy, Bora, Khamsin, Merak, Quattroporte, and Bi-turbo all used the DCNF style of Weber carburetors. While it’s a fine fuel metering device, it has an Achilles heel – it uses an externally mounted accelerator pump with a diaphragm in it which, when it gets old, can rupture and spew fuel all over your hot engine. Consider it good insurance to change the accelerator pump diaphragm on each carburetor every few years. If you are unsure how old they are, change them.
Each DCNF carburetor has a little square cover with a screw in each rounded corner. Emanating from the center of this cover is a lever that is activated by a cam on the throttle shaft. With the engine cold, remove the four screws holding the cover(s) and replace the diaphragm(s) making sure not to tear or wrinkle them and that you don’t put them in backwards.
Following these recommendations should make your Maserati much safer, more reliable and fun.
by Wil de Groot
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