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Fuel-Pump Replacement A Ford Ranger pick-up that refuses to start gets a thorough checkup and fuel-pump replacement. From "Weekend Mechanic" episode WKM-407

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Diagnostics

Aside from the fuel-delivery system, which Bruce Bonebrake suspects to be at the root of the no-start issue, other possible sources of the problem could be the computer system, the ignition system or a broken timing belt. Some diagnostic tests will be required to narrow down the cause of the problem. Bruce runs through a series of checks and diagnostic tests in order to isolate the cause.

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Figure A

Inspect and Test the Battery

• Visually inspect the battery and cable for signs of damage or corrosion, particularly at the terminals. Ours revealed considerable corrosion (figure A).
  

• Additionally, a volt meter connected to the negative post, and with the positive terminal simply touching the battery surface and corrosion residue (figure B), registers 3 volts (figure C), indicating the presence of acid corrosion on the outside of the battery. At the very least, this battery needs a good cleaning and servicing of the terminals.

  Figure B

  
  

  	Figure D
  	Figure E

• Using a scan tool with a battery tester (figure D), hook the scan tool up to the battery.

• (If you don't have a battery tester, you can remove the battery and bring it to a service center for testing.)

• Input the cold-cranking amps for our particular battery and check the results (figure E).

Our battery test indicated that the battery was good, but that a recharge was in order. This was likely related to the corrosion we found. A good cleaning and recharge of the battery will be a good idea, but the test ruled out the battery as the sole source of the no-start problem.

Check for Spark

• To see if there is a spark from the ignition system, hook up a spark plug tester to the ignition plug wire and attach it to a ground location (figures F and G).

• Crank the engine and wait for spark. Our test indicated that we did have spark, so that factor was eliminated as the cause as well.

  Figure F

  Figure G

  
  

  Bruce checks the operation of the fuel delivery system with a fuel-pressure gauge.

• To check for fuel pressure, you'll need to connect a fuel-pressure gauge directly to the fuel pump. Disconnect the line at the fuel filter and connect the fuel tester into one line and out the other. This ensures that any pressure produced by the fuel pump will register directly to the gauge.

• Turn the ignition on and see if there is any fuel pressure.

Figure H

Test Fuel-Pump Fuse

• Test the fuel pump fuse using a computer-safe test light (figure H), which will guard against shorting out sensitive computer circuits.

• In our case, an illuminated indicator light on the test light tells us that the fuse is good.
  

  Figure I

• To check the fuel injection system, we use a noid light injector-tester (figure I). The noid light for our application plugs into the fuel injection wiring harness.

• Crank the engine to check the results. In our case, the noid-light test indicates that the fuel injection system is working fine.
  

  Figure J

  Check Fuel Cut-Off Switch

  • The final test is to check the voltage going to the fuel cut-off switch (figure J). Our vehicle is equipped with this switch as a safety feature. In our vehicle it is mounted to the firewall and its purpose is to turn off the fuel pump in the case of collision, reducing the chances of spilled fuel in a flame-hazard situation. Our switch appears to be operating and working fine.

  Weekend Mechanic Expert Tip: If you should ever happen to bump into something and then your vehicle won’t start, it could be that the fuel cut-off switch has been tripped. Typically to reset these, all you need to do is push the button back in and then you’re good to go. Information about resetting the cut-off switch can sometimes be found in the owner's manual.

  The series of checks and tests has essentially narrowed down the problem to the fuel pump. We'll need to gain access to that pump, and in this vehicle it is mounted in the fuel tank. In some cars, there is an fuel-pump access cover that you can remove, allowing you access to remove the ascending unit fuel pump assembly and replace the pump. On most vehicles you have to drop the fuel tank down and remove the assembly. The good news with this pick-up truck is that we have an easier option--removing the truck bed to access the assembly. After removing six bolts and a couple of electrical connectors, the bed can be removed to access the pump without having to drop the tank.
  
  
  

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  ALSO IN THIS EPISODE:
  	Fuel-Pump Replacement