Fuel Flow Volume... Wait it a minute, I thought it was about pressure!

Fuel Volume is a concept hugely overlooked in today's automotive repair shops. It is a simple concept, but the availability of good fuel flow/volume gauges has made this procedure fairly difficult. Often the repair tech replaces parts unnecessarily to find out to his/her dismay that the problem is still there. See what this is all about on the previous section "lack of power" and get the reference values, found no where else here...



The following are specific guidelines for the use of the fuel flow/volume gauge. Differences can be found between systems, however, these actual specifications apply to most fuel systems. (These values were taken in actual vehicles in the field).

systems with a fuel pressure regulator:

*PFI & SFI - Between 0.3 to 0.5 gal. per minute.

* TBI & Vortex (CPI) - 0.4 to 0.8 gal. per minute.

** 85 Century ( 2.5L) Single TBI = 0.35 gal per min. at 10 lbs.

** 95 Bronco ( 5.0L ) PFI = 0.6 gal per min. at 35 lbs.

** 93 MX6/626 ( 2.5L ) SFI = 0.45 gal per min.

** 96 E-150 ( 5.8L ) SFI = 0.45 gal per min.

** 90 Corolla ( 1.6L ) PFI = 0.15-0.20 gal per min. at 33 lbs

** 97 Maxima ( 3.0L ) SFI ( Dual speed fuel pump )

( 1st speed )13 volts - 0.40 gal per min.

( 2nd speed ) 9.5 volts - .15 gal per min.

--- WOT while goosing the throttle - 0.25 mls per min.---

** 91 RAM VAM 5.9L = 0.6 gal per min.

** 94 Corolla ( 1.8 ) PFI = 0.45 gal per min at 40 lbs.

** 91 Sentra ( 1.6L ) PFI = 0.5 gal per min at 38 lbs.

** 96 Cadillac Seville 4.6L (NorthStar)=0.4 gal per min at 42 lbs.


Systems without a fuel pressure regulator ( Returnless systems ):

In order to test returnless systems, a fuel shut-off valve should be used in-line with the fuel flow gauge. Simply connect the shut-off valve at the output hose and close it. Connect a charger to the vehicle’s battery and jump the fuel pump. Record and compare the dead-end fuel pressure to the correct specs. Open the shut-off valve (let fuel into a safe container) until the fuel pressure just starts to drop bellow specs. At that time, record the fuel flow. Use the rule of thumb—Anything under 0.30 gallons per minute is probably not enough to maintain proper air/fuel ratio.

Continuous fuel injection system (CFI German cars):

** 86 Mercedes 300 = 0.7 gal. per minute at idle and while goosing the throttle. ( 85lbs of press.)


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