Mechanical Defect? 

Incorrect Manifold Vacuum significantly affects computer controlled fuel injection system operation and overall engine performance. Vacuum formed in the intake manifold depends on several things. Engine components such as: valves, valve guides, valve springs, pistons, and piston rings can influence vacuum readings. Other engine performance factors include valve timing, manifold leaks, ignition timing, and restricted exhaust systems.

Excessive Back Pressure in the exhaust can affect the engine's fuel system and engine performance dramatically. Large easy to read dials and a full set of adapters make it easy to diagnose restricted intake/exhaust systems.

Pressure And Flow are two different measurements! An engines fuel pressure can be perfectly normal while a low rate of fuel flow exists in the system. The Fuel Zapp let's you zoom in on the unknown factor of flow. Measuring fuel system flow should be no less precise than using a torque wrench on head bolts or a micrometer on brake rotors. Besides being an obvious safety hazard, flowing gasoline from an un-pressurized fuel line into a graduated container, timed by a stopwatch, is not an accurate way to measure fuel systems flow. A worn pump may be able to provide sufficient flow until it must generate enough torque to overcome normal system operating pressure.

FSA Buying Guide
The Fuel Zapp is a top of the line unit: high quality construction, complete adapter hose sets, and an in depth user manual to guide you through a wide range of tests. Not all competitors can match up. Here are some questions to ask when deciding between a fuel system analyzer or tester:

• Does the unit test gasoline Fuel Systems?
• The Fuel Zapp does

• Does the unit test Flex Fuel Systems?
• The Fuel Zapp does

• Does the unit test Diesel Fuel Systems?
• The Fuel Zapp does

• What material is used for the Main Body?
• The Fuel Zapp uses steel, not cheap plastic

• What material is used for the Flow Tube?
• The Fuel Zapp uses a shatter-proof polycarbonate, not fragile glass

• What type of Fuel Line adapters are included?
• The Fuel Zapp provides High Quality Hose Sets, not universal adapters

• Does the unit test Fuel Pressure?
• The Fuel Zapp does

• Does the unit test Manifold Pressure?
• The Fuel Zapp does

• Does the unit test Exhaust Back Pressure?
• The Fuel Zapp does

• Does the unit calculate required fuel volume?
• The Fuel Zapp kit includes a Fuel Volume Calculator software

• How long is the Warranty?
• Fuel Zapp includes a 3 year warranty

• Is the Flow tube assembly servicable?
• The Fuel Zapp flow tubes are

• How does the unit perform a Flow Demand Test?
• The Fuel ZAPP FSA tests flow against normal system pressure.
  Some competitors use a BYPASS valve and recommend measuring peak flow by removing all restriction (and pressure) to the flow of fuel. As any good technician will confirm, a return type fuel system is always outputting peak flow even at idle and testing fuel system flow should always be performed while pumping against normal system operating pressure (A weak pump may be perfectly able to provide adequate flow until it has to overcome system pressure). Return-less type system peak flow can be tested by commanding KOEO continuous fuel pump operation with input from the tank to the flow meter and output from the meter back to the tank while regulating normal system pressure with the crimp pliers included in the Fuel Zapp kit

Link: AutoFixWorld.com review includes detailed description of returnless type fuel system testing procedures

Contents
• Fuel Zapp Pressure and Flow Meter
• Diagnostic Testing Manual
• TA Labs Fuel Volume Calculator Software
• (2) Locking Hose Crimping Pliers
• FTC-14.1 Female Thread Connector
• FTC-16.15 Female Thread Connector
• HFL-6 Adapter Hose
• HFL-75 Adapter Hose
• HFL-95 Adapter Hose
• Ret-less Hose Connector RTL-1
• Ret-less Hose Connector RTL-2
• BF-10 Banjo Fitting
• BF-12 Banjo Fitting
• MTC-14.15 Male Thread Connector
• GM/CHRYSLER 5/16" Snap-Lock Male Adapter
• GM/CHRYSLER 5/16" Snap-Lock Female Adapter
• GM/CHRYSLER 3/8" Snap-Lock Male Adapter
• GM/CHRYSLER 3/8" Snap-Lock Female Adapter
• FORD 1/2 " Snap-Lock Male Adapter
• FORD 1/2" Snap-Lock Female Adapter
• FORD 3/8" Snap-Lock Male Adapter
• FORD 3/8" Snap-Lock Female Adapter
• QC-8A Quick Connector
• QC-8B Quick Connector
• QC-95B Quick Connector
• Adapt-BF Universal Banjo Adapter Fitting
• Adapt-EXH Threaded Exhaust Pressure Adapter
• H-4 Hose
• Blow molded case