Rabu, 02 Juni 2010

My 1990 Chevy 1500 Pickup Truck 5.7L 350 Won't Start

My 1990 Chevy 1500 Pickup Truck 5.7L 350 Won't Start

The 5.7-liter V-8 is a motor that has resided in Chevy trucks in various forms since 1967. The base model produces 145 to 165 horsepower. From 1990 to 1998, the C and K 1500 models became Chevy's best-selling trucks of all time. The basic engine design is still used by Chevy today. In 1990, the engine was equipped with a throttle body injection system and a simple electronic ignition that makes diagnosis and repair of starting problems simple.



    Test voltage at the battery. Battery voltage should be between 12 and 13.5 volts. While still holding the multimeter leads to the terminals, have an assistant attempt to crank the motor. This will test the battery under starter load. The voltage should not drop below 9 volts. If it does, the battery needs to be charged or replaced. Even if the battery still turns the vehicle over, voltage below this value will not activate the electronic control module or the fuel injectors.


    Remove the starter and have it tested by a local auto parts store if the battery has a full charge -- and the starter simply clicks and the engine does not turn over. The store personnel will be able to tell you if the starter is bad or not, and needs to be replaced.


    Check for fuel. Ensure that the fuel gauge is functioning, and there is fuel in the tank. Test fuel pressure. With the key and the AC both in the off position, attach the fuel pressure gauge to the fitting on the fuel line. Attempt to start the truck, and take the reading from the gauge. It should be between 9 and 13 pounds per square inch. If it is not, check the fuel filter and ensure that it is not clogged. Also check power to the fuel pump, and ensure that the fuel pump relay is working. If these steps do not work, the fuel pump will need to be replaced, or the fuel pump regulator is bad.


    Check for spark. Remove the No. 1 spark plug wire and install an inline spark tester between the plug wire and the plug. Have an assistant attempt to crank the motor, or use a remote starter button, and watch for spark. There should be a hot white spark in the window of the spark tester. The most common cause for no spark on a 1990 Chevy 5.7-liter engine is a bad control module. Remove the control module, and have it tested by your local auto parts store. If the module tests well, remove the coil from the top of the distributor cap, and have it tested as well. Check all distributor and coil grounds, as a bad ground can also cause no spark.


    Check the timing. While the distributor cap is removed, have an assistant crank the motor, and ensure that the distributor rotor is turning. If it is not, the distributor shaft or gear is damaged, and the distributor will need to be replaced. Install the distributor cap, and with an inductive timing light, test the timing. With the inductive clamp around the No. 1 spark plug wire, aim the timing light at the timing tab just above the harmonic balancer. The timing light should illuminate the timing marks when it flashes. If it does not, see your service manual or the emissions sticker under the hood of your truck to determine timing specifications and adjustment. Timing differs on those trucks designed to meet California emission standards.


    Check for compression. If your 5.7-liter motor will still not start, use a spark plug wrench to pull the No. 1 spark plug and install the compression tester adapter. Crank the engine for approximately five seconds and then check the reading on the gauge. It should be between 90 and 110 psi. Using the same procedure, check all the other cylinders as well, reinstalling each plug before testing the next cylinder. Write all of the results down. The cylinder readings should all fall within specifications, and should not vary by more than 5 percent. If they do, there are internal engine problems. Consult a professional for proper diagnosis and repair options.

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