Backfire through Sniper throttle body

Discussion in 'Technical' started by MountainDrre, Mar 2, 2019.

  1. MountainDrre

    MountainDrre Member

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    Car ran perfectly before changing by valve cover gaskets and disconnecting my spark plug wires to organize them. I plugged all the wires back where they should be, I tried to start the car tonight and while turning over, poof sound up and out of the Sniper throttle body. I tried to crank it a few more times, would not start, only just turn over and then poof again, but this time it fireballed. Checked all spark plug wires by disconnecting and then reconnecting. Unhooked everything from the battery let it sit then reconnected. Will not turn over, I do have fuel pressure. Might be a timing issue from what I’ve read, but not sure how the timing could be off.

    Any suggestions?
     
  2. Krazy Comet

    Krazy Comet Tom Supporting Member

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    Unless dist moved, timing is not your problem.

    Are you sure firing order is correct? a 5.0 HO is different from std 302. Also plug wire order is count counter clockwise.
     
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  3. MountainDrre

    MountainDrre Member

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    Yeah all that is correct, didn’t change anything. Didn’t disconnect wires from distributor when organizing.
     
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  4. McD1970

    McD1970 New Member

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    Is it possible you accidentally crossed a couple of wires?
     
  5. MountainDrre

    MountainDrre Member

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    It is possible. I checked for this several times over the two hours of trouble shooting. Plans today are to start with new spark plugs, in case I fouled one or more early and pull the wires and route them again. I did not mention the first couple times while trying to start the poof of air/fuel sound was accompanied by a thud.
     
  6. bmcdaniel

    bmcdaniel Senile Member

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    A "poof" through the intake is usually either a cylinder firing while an intake valve is open (wrong firing order) or lean fuel mixture (shouldn't be a problem if your injectors are working). The "thud" tells me it's probably the wrong firing order.
     
  7. MountainDrre

    MountainDrre Member

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    10-4. I will report back later today.
     
  8. MountainDrre

    MountainDrre Member

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    Unplugged the spark plug wires and reinstalled, fired right up. Only thing I can think of is that I didn’t have a good connection on one of them at the spark plug. Thanks for all the help guys. I really don’t like the long boot connector (pictured below), harder to know if it’s all the way down, flex. Much prefer the 90 degree elbow/shorter connection.
    B49568D2-2B1A-43D2-BAE4-CD5A45321046.jpeg
     
  9. 71gold

    71gold Frank Cooper Supporting Member

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    good job...:thumbs2:
     
  10. Krazy Comet

    Krazy Comet Tom Supporting Member

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    If firing order was correct it should have started with three or four wires laying in street.
     
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  11. mojo

    mojo "Everett"- Senior Citizen Supporting Member

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    Firing order was the problem;-- good, partial, no connection would not cause the problem you had!
    Glad you got it resolved.
     
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  12. MountainDrre

    MountainDrre Member

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    So I attempted to take it for a drive today after the issues. It is stuttering bad unless full throttle and noticed black smoke, smelling strong of fuel out of pipes. Could this be a timing issue?
     
  13. groberts101

    groberts101 Member

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    Could be ignition related but almost sounds more like a stuck injector. Does this efi unit have LED's for operational testing?

    Have you also confirmed sufficient and consistent fuel pressure?
     
  14. MountainDrre

    MountainDrre Member

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    I called Holley tech support. They asked me to send them a log at idle and driving around. They cited possible electrical interference when I organized the spark plug wires to hug around the valve covers.

    I don’t think the injectors have LEDs and I should probably install a fuel pressure gauge.
     

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