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Thread: 1995 chevy 5.7 k1500 - no injector pulse, what to check ??

  1. #1
    Senior Member Douglass's Avatar
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    1995 chevy 5.7 k1500 - no injector pulse, what to check ??

    Ok here is what i have, 1995 chevy 5.7 k1500.

    I have no injector pulse. the truck ran great last week and
    just passed smog with below average readings.
    I drove the truck last Wednesday it drove fine,
    parked it tried to start it on Sunday and it would not.

    Here is what I have checked/done. Battery is just recharged(new),
    I have about 12 psi of fuel pressure at the filter, I have spark
    I sprayed some carb cleaner and it fired pretty quick.
    I put one of those special lights on both of the injector plugs
    and got nothing while cranking the engine.

    My question is what controls the injector pulse, and where does the signal come from?
    I have spark, and fuel supply, just no injector pulse.

    Oh yeah after I plugged in the battery today (had to recharge it)
    I tested the fuel pressure after I was finished I plugged the fuel line
    back into the fuel filter, and I decided to try and start it.
    I fired up and ran great for about 10 seconds
    then it just shut off like someone turned the car off.
    this is when I sprayed the carb cleaner to verify I still had spark.

    thanks for any help,
    Douglass
    Last edited by crabtruck; 05-03-2011 at 12:08 AM. Reason: title

  2. #2
    Senior Moderator chevychase's Avatar
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    I would suspect ignition module. The one in dist. on bottom. You can check for resistance take wire loose ... get a meter set to ohms.
    Should read 800 to 1500 ohms.

  3. #3
    Senior Member Douglass's Avatar
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    it is new and has about 20 miles on it. I will double check it though. Anything else that the truck uses for fuel injector pulse? I also replaced cap, rotor, fuel filter, egr, spark plugs, wires, egr cyonoid, purge control valve, coolant temp sendor & sensor, new oil change, water pump, radiator, oil cooler lines, t.state. the one part that I did no replace is the ignition coil pick up. I think I have to remove the distributor to change it.

    Douglass

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    Senior Moderator chevychase's Avatar
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    Try this clean the grounds at or around thermostat housing.... Ecu maybe not getting signal to fire injectors.
    Also try holding throttle position down 1/4 then 1/2 ect. See . You can test pickup coil same way resistance 800 to 1200 ohms.

  5. #5
    Senior Member Douglass's Avatar
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    ok checked the grounds at the t-state look good, I do have supply voltage to the injector wires. I will check the icm some time this week. I will probably pull the distributor as well and change the pick up too. Question what role does the oil pressure switch/sender play?
    Douglass

  6. #6
    Senior Moderator chevychase's Avatar
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    It will not be in the equation till vehicle is running. ecu will sense no oil pressure around 400rpms cut pump off.
    What type icm did you buy? the cheap ones at advanced hong kong type ... not worth buying.
    If you can check fuel pressure at tbi .. on supply line .

  7. #7
    Senior Member Douglass's Avatar
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    I bought one from rockauto.com, it was the airtex/wells brand. Is the ICM the only part that the computer uses to control injector pulse? I also noticed today when I was cranking the engine it took a while for the oil pressure to register. I almost thought it did not work. I am going to change that part due to age.

  8. #8
    Senior Moderator chevychase's Avatar
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    Did you replace temp sensor located beside thermostat housing? If it is reading high vehicle will not crank.

  9. #9
    Senior Member Douglass's Avatar
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    yeah i replaced both, the one next to the t-state & on the side of the block.

  10. #10
    Senior Moderator chevychase's Avatar
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    On the oil sending unit. We had a big discussion on this at another forum.
    Will one crank if not sensing oil , or bad . Well long story short they will .
    Some of us myself also cranked, and ran our trucks all day with unit unplugged.With no problems.
    It is a secondary safety switch. Have not read up on yet but will.
    So lot of people have been misinformed on this.



    All that you have checked ,and replaced you will have to see if ecu is getting power. Maybe problem.

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