In Tank EFI Pump Conversion

In Tank EFI Pump 01

One of the common stumbling blocks during a typical EFI install on the Corvair is the fuel delivery side of things.    Obtaining a clean install and one without the noise and ground clearance issues with an external pump[s] is the issue at hand.  Our EFI kits are quite complete as they contain all the necessary brackets, fittings, plugs, special adapters, sensors, etc.   But no matter how many suggestions or help was given to the installer regarding the fuel delivery system, the end result was always one of less than satisfactory. 

The most common issue was the noise and vibration from the external EFI pump.  Other installs required both a high volume, low pressure, feed pump and a high pressure EFI pump.  These installs, as you may surmise were also quite noisy.  Secondary issues included ground clearance and plumbing of the high pressure EFI system as well as problems associated with using an older fuel tank which generally had an accumulation of rust, dirt and other foreign matter in the tank.  While these small debris may not cause major issues with a fuel system designed for a carburetor, these same small particles will wreak havoc on an EFI system.

After investigating the above issues, it was determined that the best way to approach this hurdle was to start from scratch and supply a new tank with a custom made in tank EFI pump system specific for a Corvair EFI install.

A new tank is used and all sheet metal and tube parts used for the conversion are stainless steel. The pump assembly sits in an semi-enclosed, full length, cylindrical sump which mounts on the top of the tank and extends to the bottom.  A filter element with a generous surface area is attached to the pump, assuring a clean supply of fuel to the pump and protecting the pump from damage.

EFI In Tank Sump View

Pump Assbly

A standard GM EFI style lock ring retainer and O-Ring is used to affix the pump assembly to the tank.  The inlet and return ports are on the top of the tank, but one could also use the stock feed line on the bottom of the tank for the return, if desired.


A custom made top mount fuel level sending unit is also available.  This is a solid state type sender which has no external float, hinge arm or wire wound wiper assembly.  This design has many advantages.  The full length axial configuration does not require a float to pivot at the end of the arm.  There are no wiper contacts in the assembly to wear out, bend or become corroded.  The full electronic assembly is housed in one compact, self contained, unit.  Nothing hangs out from the unit, so nothing is bouncing around in the tank during normal commuting, spirited driving or full competition events.  These custom fuel level sending units are available in the 90 ohm configuration for late cars and 30 ohm for the early cars.  We can also supply sending units in other resistance ranges to accommodate custom fuel level gauges.

The in tank EFI pump assemblies are available as complete conversions with new tanks or as a kit for customers who would like to weld the adapter plate in their tank.

All modern EFI cars have the fuel pump enclosed in the gas tank.  This configuration has a number of advantages: 

Quiet operation.  An in tank pump install affords a silent pump operation as the pump is not mounted on a body or frame member on the Corvair.  When mounting an external pump on the Corvair unitized body the sound of the pump is transmitted into the car.  Externally mounted EFI pumps most often have unacceptable noise related operating issues.  The constant drumming noise of the pump can taint an otherwise nice install.

Cool running, better longevity.  The pump runs cooler when mounted in tank as the volume of fuel acts as a cooling fluid and heat sink.  External pumps do not have these advantages and they are subject to the hazards of living outside and are more prone to damage and early failure.

Better Performance.  By placing the pump right in the tank the entire length of fuel line to the engine is pressurized with fuel.   There is no chance of vapor lock or starving of the engine due to pump cavitation.  These are notable issues with an externally mounted pump which typically would require another 'pusher' pump to be used.  Pusher or feed pumps, are mounted by the gas tank and push fuel to the high pressure EFI pump which is mounted by the engine.   High pressure EFI pumps are not designed to pull fuel, but to push fuel at high pressure.

Lower Cost.  Since only one pump is required, you save the costs of the required 'pusher' pump, surge tank, connecting lines and fittings.

Higher Reliability.  With one pump in the system vs. two pumps, you have doubled your reliability.  Another way to look at this is with one pump you have reduced your possible failure points in half.

You can quickly see why all modern EFI cars have an in tank pump.

The in tank EFI pump assemblies are available as complete conversions with new tanks or as a kit for customers who would like to weld the adapter plate on their tank.

Please contact us at the link below for additional information. 

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