CarTalk.com Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

Fuel problem

my pickup is giving me trouble replaced fuel pump, filter flashed computer cam sensor seems to be fine…truck will run one day then will not start on another…1500.GMC year 2000…5.3 litre motor auto trans 4x4… .thinking on replacing computer as a last ditch effort…when we hook the computer analyzer it shows no problems…anyone experienced this

Are you sure you’re getting spark?

Are there any DTC codes displayed or pending? If the engine doesn’t start one day, but works ok others, it is usually one of these:

  • No gas (check fuel pressure at rail, verify injectors are firing)
  • No spark (use an inexpensive spark test gadget at each spark plug wire)
  • Timing problem (use timing light to verify that #1 plug is firing at correct point on crank pulley gauge, if it isn’t, most likely to consider is a faulty crank sensor if your truck uses one.)

AFter that, it could be a variety of problems including the ECM. Before replacing the ECM though, do a compression test. Best of luck.

You might want to check for a faulty crankshaft position sensor.

When the ignition switch is turned to run position the fuel pump will run for a second or two and then shut off. Then when you go to start the engine, and if the crank sensor is malfunctioning the computer won’t see a reason to run the fuel pump/injectors or the ignition system.

Tester