So, you want a custom external gasoline fuel pump ?  

Let's try a little bit if engineering?
This page is for a stock loop systems, only.  See drawing below:
I will show you, why external pumps fail .
Some folks want to add an external pump and keep the dead internal pump, inside the tank, how is that going to work? Sucking fuel in a stalled Gerotor Stock pump.?
It is not going to work.
If keen on doing that, replace the dead pump with a short pipe, inside the tank rack. Keep the filter sock !
There are may kinds of pumps:  Gerotor, Vane, roller and Turbo pumps.

Most pumps, not Gerotor, have a pulsing output that EFI , just hates. (causes the ECU/PCM to go nuts trying to correct that mess, endlessly)
The many early European "FI" had 2 pumps like a BMW 318i, the tank lift pump and a roller high pressure push pump mounted to the side of the gas tank. In fact, this car uses anti pulse device, just in front of the pump.
Safety?, the external pump is best  mounted on the side of the tank, so that in a collision, the tank doesn't hit the pump , puncturing the tank or snapping lines. (use flexible lines to the pump, for best safety)

Common DIY practice and failures on old 1987 Suzuki Samurai 4wd.  They want to run the wrong tank (CARB tank), is the reason for the external pump, or don't understand the internal tank pump benefits?.
Suzuki Spec.'s
  • The stock pump runs at 12 to 15vdc under most conditions, (charged battery)
  • Gerotor smooth output.
  • 60 LPH (liters per hour flow)   If you use a 255+ LPH pump, it may overload the stock regulator, causing huge engine flooding and misfiring. Why do that?    The 80 HP engine only needs 30 LPH max.flow at max engine load.(lowest possible)
  • 60 PSI shunt spec, (runs at 35 psi with regulator) PSI = Pounds per square inch.
LPH means liters of fuel per hour , about 1 quart/hr to us Gringo's.
(candidates?, not tested by me....)

Finding small external pumps that can suck air and prime is near an impossble task. (YMMV, or your luck might vary, etc)

External PITFALLS 101 and facts:
  • We forget, the pump has a lift spec. Most pusher pumps (Gerotor) have very poor lift spec. ( 1 or 2 inches) unlike Lift pumps.  (2 words there,  LIFT and Pusher)
  • The best external setup is a gravity feed external pump. (self auto feed)
  • Most external pumps will not work unless mounted in the location of the lowest EXPECTED fuel level , that is  usually at the bottom horizontal line of the tank.
  • The External pump does not like to pump air,  it only likes to pump fuel, and needs fuel to cool it and to lubricate it. (yes, running it dry ,does in fact burn it up)
  • One way to get the external pump to self prime, is to mount it, so the tank can siphon to the pump (the siphon only works, with the pump below the tank)
  • Make sure that siphon tube is not more that 2 inches high or it may not prime.  The rise of the tube , must be short as possible, only as high as the diameter of the pump is  good goal.
  • If the siphon is primed day 1, and set up right (mounting spot, etc) it will stay primed and the pump will stay primed,.
  • The EFI system will starve at below 28 PSI on most cars. Even for a short time.  (there is no float bowl like CARB.'s have, to hide this condition)
  • The Cheap external pumps must be mounted down low, so when your are 4WD wheeling, and now it's all (parts and pipe) going to get hit....against ROCKS...  that internal pump, sounds better all the time huh?
  • Do not run the pump off of the direct ignition feed, but do use the stock Fuel pump relay output or the car will be unsafe at any speed.
  • Buying a huge overpowered fuel pump then finding out you overloaded the stock fuel pressure regulator (reads too, high all the time) oops. The engine demand is 8 GPH at full throttle. Save your cash and grief.
CONSIDERATIONS:  Tired of Stalls, and lost primes, and being stranded?
Engine Stall Ways?:
  • Losing prime in fast turns?, then stalls and won't start?  (my  1999 Jeep  does that Day 1 stock, in fast turns (crappy tank baffles), but recovers fast, due to internal tank pump, works best)
  • Got low fuel and it stalls (sucks air , lost its prime , now dead?)
  • Parking for a week, at the air port and the engine will not start.?
  • Getting random  pump cavitation? Stalls?  
  • Lost prime at high angles, like when Crawling offroad or parking on very steep hills? (ever park in San Francisco? or like terrain?)
  • Will your poorly designed pump setup, fail in cold weather, or hot ? (fuel density varies by temperature and so does the poor pump , trying to prime with air)
  • On race cars, they use an  internal tank LIFT pump  or 2 pumps, one for lift inside, then one for the push outside  (external) for the high pressure, and with a Catch tank. All this , prevents STALLS.
Most pusher pumps are gerotor pumps. (or turbo pumps with the  same issues)
This type pump does not pulsate (something EFI hates)
This pump will not suck air or pump air at all or only 1 or 2 inches, up hill and with the weight of the fuel blocking, that air pocket, in line down lower, making that physical sucking air act, much harder.
This pump does not want to run dry, or in to a shunted head (clogged filter ) or it DIES FAST.
This pump hates, filth being inducted, that can jam the rotor easy, or gall it to hell. {Run a 100micron (min) input SOCK.(pre filter) ( like the stock car had , by design)}
The internal tank pump, runs the most quiet.
The internal tank pump is more safe in a crash (lots of proof there,etc...endless DOT proof.....).
The rear mounted pumps will not vapor lock and for sure mounted inside the tank where it runs cooler.
The pump lasts longer (cooler) inside the tank., and primes instantly, no matter what.
All pumps, have limits, please read the data sheets.

Gravity fed pumps are best, then siphon fed. (external)
Many Cheap pumps flat out will not suck air. period, not even 1" from fuel.

Never (external pump) mount a filter rigidly to any pump with metal nipples. (use flex lines) The natural vibrations, will crack it and with disastrous effects.

Never put a fuel pump inside, the trunk or passenger cab of any vehicle, or the lines. Use the body shell of the car to protect you, from liquid fuel splashing , in an accident or a simple leak. Fuel at 60PSI can squirt a long way.
Same goes, for using low pressure CARB type, fuel fittings on 60 + PSI EFI system parts.  That includes not using EFI rated fuel hose clamps, on the high side.

Great Links:
Some kids, just do this over and over. Watch them.
http://www.youtube.com/watch?v=rtMCDr-n6wU

http://forums.off-road.com/jeep-short-wheelbase/48940-external-efi-fuel-pumps-need-prime.html#post261572

Below is a pump, that does lift good and pushes good, but you may not like the price.$300 +  and is too big.

http://www.weldonracing.com/product/8-6/A2007-A_High_Pressure_%28-8_inlet___outlet%29.html

Also too big.
http://fuelpumpsupply.com/a600a.htm

NASCAR
Facts on race cars, help understand what can go wrong.
http://racing-forums.com/threads/nascars-fuel-system-discussion.40275/#post-480547


Many pumps are flow rated at no load "open", 0 PSI, this is useless. EG: 255 GPH pump is really 50.
Do read the loaded 40 PSI spec to match our pump.
Lower pressure pumps. (once to check out...???)
Airtex has no product matrix tables on their home page,  making pump selection very hard.  I must find time by accident the read the data sheet.
Examples:
The E2111 AIRTEX is the stock inside pump for Suzuki Sidekicks, (after market brand)  flow 40-50GPH (151 LPH)   and max PSI (shunt) 80-90 PSI. This pump is  2.5 times spec. flow.
Airtex #E8307 (50 GPH / 120psi) roller vanes.
Airtex #E2182  (50 GPH / 90 psi)
Airtex #E8228 (univ) 38 GPH at 100psi (open GPH)
The E2000 30 GPH @ 70 PSI (114 LPH free flow)   ( I'd try this pump) external.
(bigger is not always better, not with Pumps, (FP reg, overloaded) not only that, but the larger pump can overload the EFI 12vdc power bus. , our stock pump current is 4 amps, not 14)
Any will work so long as, it dont overload the FP reg, or not go to 60 PSI shunted (output blocked) If fact, I'd not want to much over that 60 PSI limit.

MSD? pump?

JEGS basic:(nice graph !)

50 GPH at 40PSI rated.$70 (in tank pump) TRE-342

The MPI damper on the end if the rail and may work ok with pulsing vane pumps.(theory and the FPR does the slow surge damping controls)


The stock MPI loop system. Multipoint Injection.
This system (ECU tables) relies on the fact that the FPR runs a constant pressure across the injector (key word , ACROSS)

MPI Suzuki, FPR = Fuel pressure reg.


SPEC means the engineering full specifications. ( a large page of facts)  or to a tech, the full data sheet on the pump.  Nothing less. Read it and learn what the pump can do and what it can NOT DO.
Returnless systems: How was this done (on modern cars)
 (the pressure regulator was moved into the tank.. and is not vacuum modulated like the above)
This system runs a constant fuel pressure at all times (a new dumb TANK FPR). (and is monitored by the PCM)
The returnless system , the PCM monitors injector rail pressure  and induction vacuum (plenun manifold presssure) (and knows altitude at all times)
The new  PCM computes injection rates, knowing the pressure on both sides of the injector, the plenum and the constant fuel FPR pressure. (with  the vacuum line missing, now...)
The old system:
Example , at idle the high plenum vacuum wants to suck more fuel out of the injector, see?  So at high vacuum the loop system FPR lowers fuel pressure, at idle. (and rapid deceleration)
At wide open throttle the fuel pressure is max. with the loop FPR. (at Wide open throttle the old system would drop fuel pressure 1 for 1)
All this changes with Returnless systems.
Injectors vary rates by measured pressures (not only PWM modulation)
A Suzuki will increase rates with fuel pressure of 30 to 45 PSI from 189  to 214 cc/min, or if the return line is blocked to 247cc/min.  (steady vacuum)
The ECU on our old cars, knows the rates stay at a constant, across the injector (fuel to air side). FPR regulation.
The modern PCM returnless, knows the pressure is not constant across the injector any more, and computes injections, based off what it measures. (MAP and Rail pressure)
The old system had to compensate these conditions: FPR is 1:1 ratio device , vacuum to fuel pressure. ( plenum pressure to fuel pressure ratio)
Eg:
Wide open throttle.  plenum 0" HG or 14.7 PSI (absolute)  This is called atomospheric pressure above your head at Sealevel.
Idle.                        plenum 20" or 9.8 PSI   "
Deceleration.           plenun 29.9?   0 PSI. (near) "

The old FPR could in fact, vary fuel pressure near 14 PSI. from  45 PSI key on  and near 40 PSI at idle or near 30 PSI  fuel pressure at max Deceleratation, throttle plate closed , right foot lifted. ) At Sealevel.
The old FPR automatcially compensated for altitude. at 10,000 feet the air pressure is only 10.1 PSI.
The new system measures all this and does not use the FPR to do the heavy lifting. The new FPR is just a pure  mechanical pressure regulator. (and bypasses to the inside of the gas tank)

The new system has  single pipe from the fuel tank to Rail.  (less pipes to leak or break in a crash ) The sad part, is the filter was moved to the tank too. (a Royal Pain)
(EPA mandates, all,; due to no more loop,  which decreases fuel heating  and thus less evaporative losses to the atmosphere (smog))
Many folks on old cars ,add a body hatch cover (with gasket) and allows access to the fuel pump rack in the tank.


rev 2   ++++5 -07-2014