Chrysler Front Wheel Drive Cars 4-CYL 1981-1995 Repair Information

Mechanical Fuel Pump

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OPERATION



The fuel pump used with carburetor-equipped engines is located on the left-hand side of the engine. It is a mechanical type with an integral vapor separator for better performance during hot weather. The pump is driven by an eccentric cam lobe that is cast onto the accessory driveshaft.

REMOVAL & INSTALLATION



See Figure 1

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Fig. Fig. 1: Identification of the mechanical fuel pump inlet and outlet tubes

  1. Make sure the negative battery cable is disconnected. Have a metal cup handy to collect any fuel that may spill.
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  3. Place a drain pan under the oil filter, then remove the filter with a strap wrench or equivalent.
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  5. Disconnect the fuel and vapor lines, catching fuel that spills. Dispose of any spilled fuel safely.
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  7. Plug the fuel lines to prevent leaks.
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  9. Remove the attaching bolts and remove the fuel pump.
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The fuel pump is not repairable. It must be replaced as a complete unit. Always use a new gasket when installing the pump and make certain that the gasket surfaces are clean.

To install:
  1. Clean the fuel pump and engine block gasket surfaces of all old gasket material or dirt.
  2.  
  3. Position a new fuel pump gasket against the engine block, then situate the pump in position over the gasket with bolt holes lined up squarely. Install the retaining bolts and tighten them to 21 ft. lbs. (28 Nm).
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  5. Connect the fuel lines to the pump (always start fuel line connections by hand-before using a wrench to tighten) and tighten the fittings to 175 inch lbs. (20 Nm).
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  7. Clean the block surface, check the gasket, then install the oil filter, tightening it by hand only. If the gasket is damaged, replace the filter. Refer to Routine Maintenance for the proper service procedures regarding oil filters.
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  9. Start the engine and check for leaks. Check the crankcase oil level and refill as necessary.
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TESTING



The fuel pump may be tested three different ways-for volume, vacuum and pressure. While it is best to test in all three ways, a pressure test will most often reveal a defective pump. Only if pressure meets specifications and there are still fuel supply problems is it necessary to complete all three tests.

To perform these tests, a pressure gauge capable of reading 1-10 psi (6.89-68.90 kPa), a vacuum gauge that will read 025 in. Hg (4.22 kPa), a metal container of just over 1 qt. (0.046L), several plugs the right diameter for the engine's fuel lines, a watch, and a supply of new fuel hose clamps.

Pressure Test
  1. Using a metal cup to collect spilled fuel, disconnect the fuel pump outlet hose at the bottom of the filter and plug it. Connect a pressure gauge into the line.
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  3. Disconnect the coil-to-distributor high tension wire so that the engine will not start. Have a helper crank the engine as you watch the pressure gauge.
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  5. Read the gauge and compare the pressure to the range shown in the Tune-Up Specifications chart in Routine Maintenance . If the pressure is either too high or too low, replace the pump. If the pump passes this test and you still have doubts about its performance, proceed with the tests that follow.
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  7. Remove the pressure gauge from the fuel pump discharge. Disconnect the fuel pump suction line and plug it, collect any spilled fuel, and then connect a vacuum gauge to the suction side of the fuel pump.
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  9. Again have a helper crank the engine while you watch the pressure
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gauge. The fuel pump should produce a minimum of 11 in. Hg (37 kPa)-readings may go as high as 22 in. Hg (74 kPa).

  1. If the pump passes these tests, but there is still some question about its ability to produce adequate flow (poor high rpm full throttle performance in spite of a clean filter), proceed with the volume test.
  2.  

Volume Test

CAUTION
This test must be performed very carefully! It is necessary to run the engine while checking the volume of flow. The potential for spilling and igniting gasoline is very great. Proceed very carefully or, if you are not sure you can perform the test safely, have it performed professionally.

A watch will be necessary for this test.

  1. Make sure both fuel filters are clean.
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  3. Start the engine and allow it to idle a few seconds to stabilize the fuel supply to the carburetor. Make sure the engine is warmed up and off the choke (at normal idle speed). Stop the engine.
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  5. Disconnect the fuel line at the inlet of the filter-reservoir on the carburetor.
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  7. Collect any fuel that drains out of the fuel supply line in a metal container and dispose of it safely.
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  9. Tightly seal or plug the fuel supply line.
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  11. Position the carburetor end of the fuel supply line over a large metal container (at least 1 qt./0.946L capacity) so that when the fuel line plug is removed, it will drain into the container.
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  13. With the supply line plugged, start the engine and allow it to idle for a few seconds to stabilize the fuel supply to the carburetor. Make sure the engine is warmed up and at normal idle speed. Have a watch available so you can time the test.
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  15. If not already performed, position the 1 qt. (0.946L) container under the fuel line.
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  17. Unplug the fuel supply line and allow the fuel to spray into the metal container as the engine continues to idle. Run the engine for about 15 seconds, and then stop the engine (before the carburetor begins to run out of fuel).
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  19. Connect the line to the fuel filter, start the engine, and run it for 15-20 seconds to restore full fuel level to the carburetor.
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  21. Stop the engine, and repeat Steps 3 through 10. There should be a total of four 15second cycles in which you idle the engine on the fuel in the carburetor and drain the fuel pump output into the container.
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  23. After four cycles, if the pump has moved 1 qt. (0.946L) or more into the container, it is working within specifications and is functioning normally. Otherwise, replace it, even if pressure and vacuum are satisfactory.
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