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Injectors not being pulsed...
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Howard_Woodard
Novice
Oct 20, 2006, 3:05 PM
Post #1 of 5
(1428 views)
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Injectors not being pulsed...
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My son has a 1993 Silverado pickup with a 5.7 L engine. It quit cranking and the injectors are not pulsing. If he sprays starter fluid in it, it fires and runs until the fluid is gone. He replaced the fuel pump -- but the old one tested fine -- and even replaced the computer, but nothing has changed.
Using a VOM, even though everything appears to be ok, the computer, even after changing it out, won't pulse the injectors. I have 12vdc on the low side of the injectors but it does not get a ground pulse from the computer. All of the sensors have the correct voltage (12 vdc from battery or ignition or 5 vdc from the computer). All of the sensors vary the voltage back to the computer based on whatever they are sensing -- pressure, temperature, movement, etc. The computer, I suppose obviously given the above, has 12 vdc from the battery as well as from the ignition. The [brand new] fuel pump is pumping fuel right to the injectors. The spark plugs have a healthy spark when removed from a cylinder and grounded on the exhaust manifold.
Are there things besides the sensors that might act as an interlock to keep the fuel effectively shut off? I'm out of ideas or things to check.
Thanks and regards,
Howard
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steve01832
Veteran
Oct 21, 2006, 3:38 AM
Post #2 of 5
(1420 views)
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Re: Injectors not being pulsed...
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Hi Howard, if you have correct fuel pressure, spark at plugs, but no injector pulse, try unplugging the connector at the Throttle Position Sensor and cranking the engine. If it fires up and idles replace the TP Sensor. If the sensor gets stuck in wide open position it sends around 4 volts back to the computer. If the computer sees this voltage when the engine is cranking it thinks you are trying to clear a flooded condition and shuts the injectors down.
Keep us posted on what happens.
Steve
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steve43837
Novice
Jan 30, 2007, 5:32 PM
Post #3 of 5
(1363 views)
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Re: Injectors not being pulsed...
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steve,
will this cause the vehicle not to idle also. i have a 92 asrto w/ tbi and same no pulse at cranking. prime it and it starts. i can keep it on at high rpm, but as soon as it goes back to idle it dies.
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steve01832
Veteran
Jan 31, 2007, 4:36 AM
Post #4 of 5
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Re: Injectors not being pulsed...
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It would give you a rough idle and a possible MIL.
Steve
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steve43837
Novice
Jan 31, 2007, 9:33 AM
Post #5 of 5
(1353 views)
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Re: Injectors not being pulsed...
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hey steve, howard.
i tested the tps last night and it kept on doing the same thing. on another posting dan suggested that it could be the ignition module. i will try that today and i will keep you posted. than'x
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