Author Topic: The Gila Box trip: Part I  (Read 2565 times)

Greenbare Woods

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Re: The Gila Box trip: Part I
« Reply #15 on: July 28, 2017, 05:40:33 PM »
I think the change to electric fuel pumps really took off woth electronic fuel injection and the common rail diesel engine, both of which require constant fuel pressure which is not delivered by the old mechanical pumps.
They then started fitting the pump in the tank to reduce the number of components needing to be fitted on the production line.


The engineers solved some problems with the electric pumps while creating others.

The new computerized fuel injection systems need a much higher pressure than the old carburetors.  A carburetor system only needs enough pressure to transport the fuel to its bowl.  An injector needs more than 30 PSI.  One car manufacturer says 37 PSI is its standard. 

Mounting a high pressure pump at the tank eliminates vapor lock problems that plagued low pressure systems for many decades.  A fuel pump mounted at the engine sucks (lower pressure) fuel between the tank and the engine.  On a hot day that can evaporate gasoline and leave the pump sucking a gas, not a liquid.  I have been stuck on the side of the road waiting for it all to cool down and condense back to liquid.  Once while on a vacation in Colorado I cooled it down by soaking a towel in the water in my ice chest and holding a cold towel on the fuel pump and fuel line while my family including little children waited beside a long empty road in Colorado.

Computerized fuel injectors result in better combustion and more efficient fuel use than carburetors so I can see why the engineers did it.  However, fuel pumps are cheaply made, fail too often, and when they fail it is sudden, expensive to replace, and leaves you stranded somewhere.

My son had a GMC van.  The fuel pump died at a car park behind a pizza place late one night.  We discovered that parts stores wanted $600 for just the fuel pump.  YIKES!   Its only a cheap piece of plastic with a small electric motor.  He finally got a used pump on e-bay for $300.  My fords have cost $250 or so for fuel pumps plus towing and labor.  One died on a holiday weekend so we spent 2 days in a hotel waiting for the shop to open Tuesday.  Tow truck, hotel, rental car, repair... it adds up.   The repair shop said their environmental laws required them to have a $1,500 device for emptying fuel tanks before removing them to replace the fuel pumps.  That raises their cost that they pass to customers.

Despite the known failures, car engineers no longer provide access panels above the fuel tank for replacement of the pumps.  40 years ago most American cars had their fuel tank under the trunk (boot).   An access opening was provided in the floor of the trunk for replacement of the fuel guage sender unit.   Many of them got cheap and saved $2 by eliminating the access hole and cover about the same time they moved their high failure fuel pumps to the fuel tank. 

I guess if I bought a new car every year or two I wouldn't have these problems.  Easy repair is low on the list of priorities of car manufacturers.






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