1996 7.4 suburban will not start

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by jsweeyor1, Aug 29, 2013.

  1. jsweeyor1

    jsweeyor1 New Member

    HELP!!!!! I have a 96 Suburban 7.4. I was driving a month ago and stopped at the light. When I pushed the gas it lunged and quit. I have changed the timing chain and gears, Plugs, Wires, Cap, Rotor, Cam Sensor, Crank Sensor, Fuel Filter, Fuel Pump and have no change. It acts like it wants to start but it will not fire. I have 56 psi at the plenum with the new pump. I am not getting any codes when a plug it into a code reader. Any suggestions as I am stumped.
  2. rileyjr16

    rileyjr16 Epic Member 5+ Years 1000 Posts

    Are you getting fuel to the engine? Are you getting spark at the spark plugs?
  3. jsweeyor1

    jsweeyor1 New Member

    I have 56 psi at the plenum and I pulled the #1 plug and checked the spark and it is ok.
  4. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Next question would be since youve got spark at the cylinder and fuel at the cylinder are you getting spark and fuel at the right time.
    I see where you replaced parts, were any of these parts known bad and identifiable as contributing to the original problem or is the present no start condition a continuation of the issue?
  5. Conlan Rose

    Conlan Rose Epic Member 5+ Years 1000 Posts

    We know you replaced theses parts, but did you make sure all of them are plugged in all the way or the harnesses may be damaged. just having a crank sensor unplugged will cause the truck no to start.
  6. jsweeyor1

    jsweeyor1 New Member

    The only part I know for sure was bad is the timing chain. It had jumped a couple teeth and is now correct. The other parts have just been a quest to try and get it to start.
  7. tbplus10

    tbplus10 Epic Member Staff Member 5+ Years 5000 Posts Platinum Contributor

    Ok jumping time was the original issue.
    Did you check the valvetrain when you assembled the new parts?
    The 7.4 is an interference engine, to not get valve damage after jumping time would be lucky.
    Is it possible your 180 out?
  8. jsweeyor1

    jsweeyor1 New Member

    I did not check the valve train. I set the timing marks on the crank and cam sprockets both at 12 o'clock as indicated in the repair manual.
  9. edsmagichands

    edsmagichands Member 2 Years 100 Posts

    X2 on valve damage.how does it crank, fast, slow, normal,lopeing? given the fact the chain jumped, a compression test is in order. i'm getting the chain jumped, you replaced it & still no start, so you started throwing parts at it to no avail ? is that correct? start with compression test & let us know.
  10. jsweeyor

    jsweeyor New Member

    It cranks normal. If I spray starter fluid in the intake it will backfire out the intake. I will have to rent a compression tester and work on that tomorrow.

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