… mechanic in understanding and diagnosing Alfa Romeo SPICA fuel supply system … caveat, keep in mind that Alfa Romeo did not necessarily change the …

More PDF Content

SPICA FUEL SUPPLY SYSTEM DIAGNOSTIC GUIDE 1 This guide is intended to aid the owner-mechanic in understanding and diagnosing Alfa Romeo SPICA fuel supply system malfunctions. It is not a substitute for the official factory repair publications. No claim to absolute accuracy or utility is expressed or implied. The reader uses this guide at his own risk. Contents System Description Good Shop Practices when Working on Fuel Systems Typical Failure Modes of the SPICA Fuel Supply System Diagnostic Guide APPENDIX 1 Replacement of Supply Pumps and Substituting Alternate Pumps APPENDIX 2 Fuel Tank APPENDIX 3 Testing a Fuel Supply Pump APPENDIX 4 Testing the Front Fuel Filter Pressure Relief Valve (PRV) (Earlier models only). APPENDIX 5 Installing an inertia kill switch and electrical relay for the fuel supply pump. APPENDIX 6 Testing the Fuel Supply Pump PRV (’75 on, if equipped with 3-port pump) APPENDIX 7 Testing an In-Tank Boost Pump (’75-’81 models only) APPENDIX 8 Schematics Ver 7, Nov 2004 SPICA FUEL SUPPLY SYSTEM DIAGNOSTIC GUIDE Comments or suggestions about this guide can be addressed to John Stewart, email: roadtrip999@hotmail.com 2 System Description As an early caveat, keep in mind that Alfa Romeo did not necessarily change the specifications and equipment design in strict accordance with model years. It is possible to have cars of the same model year with components from different manufacturers or systems that are slightly different from one another. In the following descriptions, references are made to model years, but you must look at your particular car to determine the exact system design and component installed. In addition, previous owners (PO’s) may have substituted components from other model years. Something else to consider is your own ability and knowledge. This guide assumes the reader has a basic knowledge of automotive systems, experience in mechanical repairs, and safety practices. The fuel supply of the SPICA Fuel Injection System has traditionally proven to be the most troublesome part of the system. Specifically, the most common failures are: 1) Clogging of the rear in-line fuel filter. 2) Weak or failed fuel supply pumps. 3) Rusted, leaky, and dirty fuel tanks (that clog rear fuel filters). The fuel supply system for the SPICA (say “speek-a”) injection system is a medium pressure (10-20 psi) closed loop recirculating system. See Appendix 8 for schematics of the fuel system. On ’69 thru ’74 models, fuel gravity exits the fuel tank, goes through a in- line filter, then to the fuel supply pump where it is put under 10-20 (ideally 15-18) psi and pumped forward to the canister type main fuel filter on the right side of the engine compartment. The canister has several functions. It filters the fuel again, has an inline pressure-sending unit that detects pressure below 7 psi, and may have a pressure relief valve ( 69- 74). The pressure regulator is inside the big cap screw that secures the brass fitting that the fuel return line passes through. If the pressure is above 17 psi, the relief valve opens and vents fuel back into the fuel return line to the tank. If below 7 psi, the top left red light on the center instrument panel illuminates. After the front fuel filter canister, the fuel enters the SPICA Injection Pump through the rear fuel inlet fitting where it is used for engine and cooling/lubrication purposes. Unused fuel exits the pump through the front fuel outlet fitting. This fitting has a restrictor orifice (3/32 ) that allows the supply pump to maintain adequate pressure in the injection pump fuel galleries. If, for some reason, you remove both fuel fittings and inadvertently reverse them (putting the restrictor in the rear), you will have “apparent” good pressure (fuel low pressure warning light OUT), but have very little pressure in the injection pump fuel galleries and the engine will probably not run well, if at all. After passing through the restrictor, the fuel passes though the segregated top section of the main fuel filter (containing the PRV) and then back to the fuel tank. A healthy pump will emit a medium frequency audible  hum into the passenger compartment and produce about 10 psi under battery-only power, and about 15 psi with the alternator running and a charging voltage of 13-14V. As you can see, the fuel supply pump is very sensitive to voltage and current. Lower than 12V seriously degrades the pump speed and pressure. Wiring with high resistance, a weak battery, or a failing alternator will have a direct affect on the efficiency of the supply pump. In 1975, the fuel supply pump was replaced by a 3-port model incorporating an integral pressure relief valve in place of the one that was in top of the front (main) fuel filter. However, some post ’75 cars did retain the PRV in the front fuel filter. Also, due to emissions regulations, the fuel vent system in the trunk was connected to the Oil Separator (right front of the engine compartment). See Appendix 8. In later models, Alfa fitted a small in-tank boost pump attached to the bottom of the fuel gauge sending unit assembly. Cars with boost pumps will  69- 74 2-port Pump Installation (right axle area). Fig 1  75- 78 3-Port Pump Installation (right axle area) Fig 2 3 have connections for two components on the top of the tank (one for the fuel level and one of the boost pump). Within the tank, the pump is connected to the top flange fittings by a rubber hose. It supplies fuel under positive pressure (3.5 psi) to the main supply pump. Alfa’s thinking was to reduce the chances for vapor lock cavitation and to prevent loss of supply to the main supply pump during hard cornering with low fuel levels. As noted above, the system has two fuel filters. The rear fuel filter is a simple high-flow in-line replaceable unit. The front filter can be one of several different types depending upon the year. Up until 74, the front filters were canister type. Starting in 75, it turned into a screw on type. The tops of the fuel filters look similar but are very different.  74 and earlier had a pressure relief valve (set at 17 psi) incorporated. These filters will have four hose connections. Later filter assemblies did not have PRVs, but rather, had a PRV built into the pump (3- port model) and have only two connections (fuel feed input & output). The SPICA injection pump must have very clean fuel to operate properly and prolong the life of the injection pump. The injection pump plungers are manufactured with VERY close tolerances (50 millionths of an inch) and therefore need clean, non-abrasive fuel to prevent wear. The injectors operate at approxi

Download SPICA FUEL SUPPLY SYSTEM DIAGNOSTIC GUIDE pdf from www.wesingram.com, 14 pages, 1079.68KB.
Related Books

Leave a Reply