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Thread: Engine turns over but won't start

  1. #1
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    Engine turns over but won't start

    I have a 96 GMC Sierra with the 5.7 Vortech, back in November I replaced the engine due to a severe rod knock. For the first few days it ran like a champ then when I filled the tank I started having problems. My truck started hesitating and stumbling all over its self. I thought that it was the gas so I put some fuel treatment in it which never made a difference. I replaced several different sensors with no change. I finally took it to a shop and the problem was that it was not holding time, he would set it and it would jump 20 to 30 degrees. I opened it up to replace the timing chain and found 1/4 inch of slack in the passenger side. I made sure everything was lined up properly and I have good compression. I am getting spark, fuel, and air but no start. It came closer to starting when I pulled the #2 wire so I rechecked my timing and firing order but no luck. My plugs are burnt. I need to get this thing running again. Any ideas?

    Thanks.

  2. #2
    Senior Moderator chevychase's Avatar
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    Sure your getting spark..fuel. How do you know your getting fuel? Did you try to prime it through the throttle /air intake?
    How did he try to set timing? You have to have a scan tool that will do timing.
    When you get #1 piston to top dead center where is rotor pointing ..should be at #1 on distributor cap.
    Need to check fuel pressure has to be at least 58 psi and hold this..no drop in psi.
    You can check it with just key on ..does not have to start.
    Timing will jump all over unless you do it with a good scan tool ..have to set to timing ....hold rpm,s at 1100 set timing by turning dist.
    Will set at 2 degrees before or after top dead center. Tighten dist. recheck. But you will need to get rotor pointing close to#1 to start ..if it is timing.
    Might be fuel pump or fuel regulator hence added fuel ran bad ..oh how about fuel filter maybe bad.
    If you get it running use scan tool to check others fuel trims ect.

    Gitter done have fun. Running on empty...running blind...running behind.....
    IF I CAN GET YOU TO SMILE BEFORE I LEAVE.

  3. #3
    Senior Moderator chevychase's Avatar
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    Oh change plugs if burnt/ bad will not start.

    Gitter done have fun. Running on empty...running blind...running behind.....
    IF I CAN GET YOU TO SMILE BEFORE I LEAVE.

  4. #4
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    Put new fuel pump and filter in and is at 60 psi. I have the scan tool but cant get it started to check the time the timing marks line up and the distributor is at #1 just will not start.

  5. #5
    Senior Moderator chevychase's Avatar
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    Where are you seeing timing marks? These do not have any. Try priming it..will take a little more fuel to prime gong in throttle body.
    Cause it is air intake only. Are you sure getting spark at the plugs? Does it backfire while trying to start?
    If your getting fuel ? and spark and rotor pointing to #1 should start.
    You still did not answer on how do you know it is getting fuel?

    Gitter done have fun. Running on empty...running blind...running behind.....
    IF I CAN GET YOU TO SMILE BEFORE I LEAVE.

  6. #6
    Senior Moderator chevychase's Avatar
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    Can check pink wires at injectors with a pulse light or meter see if they are pulsing.
    Also spider injector. Here is a link with some info . If you are sure it is getting fuel and spark about only thing it can be .
    If it was a crank or cam sensor would not get spark. Part 1 -GM 4.3L, 5.0L, 5.7L Index of Articles

    Gitter done have fun. Running on empty...running blind...running behind.....
    IF I CAN GET YOU TO SMILE BEFORE I LEAVE.

  7. #7
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    I have a fuel pressure tester on it and it stays at 60 psi thank you for the advise I will let you know what I find.

  8. #8
    Senior Moderator chevychase's Avatar
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    You have 60 psi good . But you need to find out if fuel is getting to injectors.

    Gitter done have fun. Running on empty...running blind...running behind.....
    IF I CAN GET YOU TO SMILE BEFORE I LEAVE.

  9. #9
    Forum Moderator Boudin's Avatar
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    Listen to CC....he is the resident expert as well as the self described resident nut.

    Just remember, you need fuel+spark+air to make an engine run. Anytime you have a non-starting situation, it is best to check these three basic components. Air is hard to not get and even with a dirty air filter, it should have plenty to start. You mentioned fuel pressure at 60 psi....which is perfect, but like CC said....make sure you are getting it at the injectors. Lastly, spark.....which is your most likely culprit. Due to the modern computer controlling timing, advance, etc....I would look to the codes to direct you on what is causing the problem here. The computer takes in a lot of information from a lot of sources to determine the spark. One bad sensor....or disconnected sensor....etc could cause the computer to not provide the correct spark to run the engine.

  10. #10
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    The first thing I thought of was the timing chain/gears/marks were not replaced properly or in alignment. While I understand you made sure it was done correctly, there could ahve been a mistake.

    Just for laughs, I remember when I was about 17 years old, I had a 1960 ford truck & I replaced my timing chain once. I carefully put the gears & chain all on correctly. I was confident in my knowledge. The problem was, I timed it according to the marks like a V8... I had the six cylinder. It never would get in time & start. I did everything I knew to do. I was very confident I did everything corectly. So, I asked a friend & he went thru it step by step & when I described how I put the chain & gears together with the timing marks on the chain.... he just said... lets tear it back down, you timed it like a V8, not like the six. I cant remember what the difference was or where the marks were supposed to be but... anyway, thats my story

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