I need to know where is the #1 spark plug on a 1998 gmc yukon

Point it at the #1 spark plug tower (for cylinder one). If you are on TDC of the compression stroke, it will fire and start. If you are on TDC of the exhaust stroke, this is when your distributor is 180 degrees off.
Rotor must be pointing to #1 when crankshaft is at TDC of compression stroke.

Since distributor may have been moved, best is to turn engine with #1 plug out until you get to TDC compression stroke on #1, then remove dist cap to see where rotor is pointing.

The firing order for 5.7 L is 18436572, Number 1 is on the drivers side followed by 357 all on d/s even number on passenger side. Generally, the tower that is pointed at the number 1 cylinder is the number 1. The engine has to be at TDC on the ! cyl for this to be affective. To place the cyl on TDC, take the ! cyl spark plug out and using a gauge to see when pessure is achieved is best, but you can also use one of two alternatives.... Take a small screwdriver, and you will understand momentarily, place it in spark plug hole. manually crank engine clockwise until spark plug reaches highest point and that is TDC. The problem is, that you dont know if it is power or exhaust. So, first take a small towel and wrap around screwdriver and have a friend crank engine by hand using harmonic balancer bolt. You wil feel and hear the pressure build behind the plugged hole when number 1 is on pressure stroke. Then you can use previous tip with screwdriver to hone in on TDC.

Hi there:
Spark plugs that you buy, should be pre-gapped for this application... 0.60 is the factory gap



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So you know it is not getting fuel thru the injectors.
Have you checked fuel pressure at the rail, and do you know if the pump is running when you turn the key on ?

the timing is off a bit! heres how I do it. remove the number 1 plug, stick a straw or similar in plug hole. turn engine over by the crank shaft with a wrench. when piston gets to very top of bore, just before it goes down. this is tdc. remove distributor cap and remove distributor reposition the distributor rotor button facing number 1 plug wire inside cap. replace cap and try it! please let me know if this works for you. good-day ! if you can not get to number 1 plug. just turn the crank to tdc marks are on damper pully or crank. is this a 5.7,

Need to see diagram for 96 GMC Yukon spark plug wiring

depending on which engine your truck has ;
4.8L (VIN V, 8th digit) = 8 spark plugs
5.3L (VIN T or VIN Z, 8th digit) = 8 spark plugs

YOU NEED A SPARK PLUG BOOT PULLER TO REMOVE PLUGS WIRES.

Here you go: