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Base Zero TDC

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by xdelirious45x, May 25, 2004.

  1. xdelirious45x

    xdelirious45x Registered Member

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    When taking out my distributor I lost my mark for the #1 spark plug but i know by memory where it is. However, I had friends over and they were twisting the worm gear at the bottom of the distributor.

    I was told to find TDC and drop the distributor, it wouldn't really matter if the gear was played with as long as I disconnect an electrical plug that plugs into the ECM. Does anyone know what plug this is??

    I know the #1 spark plug wire on the distributor cap is on the top left of the distributor cap when looking towards the front of the truck.

    Would this work? Would a timing light find the correct gear to drop the distributor in?
     
  2. Blue85

    Blue85 Troll Premium Member

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    Sorry, I can't answer your question exactly, but I can tell you that a timing light won't help until you get the distributor close. As long as your damper timing mark is good, you can turn the crank until it shows TDC and then the rotor of the distributor should point towards plug wire #1. However, you can easily get the distributor off by 180 degrees by doing this.

    Someone else will be able to tell you the rest.
     
  3. xdelirious45x

    xdelirious45x Registered Member

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    Ok,
    My friend said there is a plug i should detach before trying to start because it will try to self-adjust my timing. Do you know where this plug is? What color wire is it?
     
  4. fortcollinsram

    fortcollinsram 1/2 ton status

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    It doesn't matter which way the rotor is pointing when #1 is a TDC, AS LONG AS IT IS POINT TO THE #1 PLUG WIRE TERMINAL ON THE CAP!!! So put #1 at TDC, then drop the dist. in with the rotor pointing in the general direction that you where you want the #1 plug terminal to be. Then put the carp on the dist. and align the #1 termianl with the rotor. Then run your plugs to the respective cylinder paying attention to firing order. Once the wires are run to the correct cylinders and the dist. cap is bolted on WITH THE ROTOR POINTING TO THE #1 PLUG TERMINAL you are read to set the base timing...

    ON a GM TBI truck, the ECM "bypass" wire that needs to be unplugged in on the firewall, under the break booster. It is a single wire that protrudes from the wiring loom. With the ignition OFF, unplug that wire (I believe it is brown or has a brown stripe) and start the motor. Set the base timing (0* for an SBC and 4*BTDC for a BBC). Once the base timing is set, turn off the motor, tighten the dist. clamp down, and plug the ECM "bypass" wire back in and you are good to go...

    Chris
     
  5. fortcollinsram

    fortcollinsram 1/2 ton status

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    another thing MAKE SURE you DID find TDC, and not the top of the exhaust stroke... /forums/images/graemlins/shame.gif other wise you are focked from the get-go /forums/images/graemlins/yikes.gif
     
  6. xdelirious45x

    xdelirious45x Registered Member

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    Yes, I found TDC by putting a screwdriver in the #1 cylinder spark plug hole. Ok I set the distributor in at TDC and it idle's at 300rpm and it sounds like it's gonna stall should i try turning the distributor to adjust it and then when it's adjusted to the right rpm, should I plug the bypass plug back in? Or will the bypass plug adjust my idle?
     
  7. miniwally

    miniwally 1/2 ton status Premium Member

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    Put a finger over the spark plug hole and have some one turn the engine over by hand to verify that you have the correct TDC. You will be able to feel the motor making compression this way.
    If you don't feel the compression building you probably are 180 off.
    If this is all good set the timing like Fortcollinsram said.
     
  8. fortcollinsram

    fortcollinsram 1/2 ton status

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    [ QUOTE ]
    Yes, I found TDC by putting a screwdriver in the #1 cylinder spark plug hole. Ok I set the distributor in at TDC and it idle's at 300rpm and it sounds like it's gonna stall should i try turning the distributor to adjust it and then when it's adjusted to the right rpm, should I plug the bypass plug back in? Or will the bypass plug adjust my idle?

    [/ QUOTE ]


    Hook a timing light up to it!!!! Put the timing light on the #1 plug wire and point it at the balancer and turn the dist. a bit slot in the balancer lines up with 0* on the timing mark on the timing cover. All the bypass plug does is keep the ECM from messing with the timing when you are setting the base timing. Who ever told you the ECM will set the timing when you have the bypass wire unplugged is full of hooey /forums/images/graemlins/deal.gif Yo ustill have to use a timing light to set the initial base timing at 0*.


    Chris
     
  9. xdelirious45x

    xdelirious45x Registered Member

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    /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif /forums/images/graemlins/doah.gif

    The distributor cap screws stripped the brand new distributor that I put in the truck. Therefore, the cap was never completely on the distributor. Luckily I bought the distributor like 4 days ago so I can trade it in for a new one. So the timing was off because of that. I probably had it at TDC about 8 times and the cap was never on! /forums/images/graemlins/doah.gif

    Anyways, Thanks for the help.
     

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