I am changing the distributor cap on a 1991 GMC 5 litre engine which is the number 1 cylinder on the engine and where is the #1 on the cap?

The firing order is 1, 6, 5, 4, 3, 2. Stand with the engine belts and pulleys nearest to you and the transmission furthest away.
The cylinders on the Left side are the Even numbers, Number 2 is nearest to you, number 4 in the middle and number 6 furthest away from you.
The cylinders on the Right side are the Odd numbers. Number 1 is nearest to you, number 3 in the middle and number 5 furthest away from you.
Take a close look at your distributor cap. Some are actually marked with the numbers 1 to 6 showing which where each spark plug wire should go.

4.3l v6 firing order is 1-6-5-4-3-2 number 1 is on the drivers side front. They are numbered from front to back as follows..drivers side 1-3-5 passenger side 2-4-6. Older model engines with distributor caps have number 1 on the center front post and the rotation is clockwise.

Remove spark plug cylinder #1 place cylinder end of compression time. Crankshaft pulley timing mark at 0 degree
remove distributor cap then find on the cap where is the number 1 cylinder
while placing distributor in place place rotor to face cylinder 1 wire
replace cap and wires
start engine and move dist. to the best rpm then with timing light adjust timing
hope it help

1-6-5-4-3-2 , 2-4-6 pass. side of eng. , 1-3-5 driver side eng. , #1 on the cap is at the very front w/clockwise rotation. If it is the newer flat cap style, numbers are on the cap, front to back pass. side 2-4-6, 3-1-5 drivers side.

Firing order 1-3-7-2-6-5-4-8 --------- front ' 1 2 3 4 ' of ' 'distributorless ignition vehicle ' 5 6 7 8

STANDING IN FRONT OF CAR FACING ENGINE.NUMBER 1 FIRING POSITION ON DISRIBUTOR CAP WOULD BE AT 8 OCLOCK POSITION.THEN AFTER 1 ON DISTRIBUTOR CAP 8 4 3 6 5 7 2 THATS SPARK PLUG WIRES LOCATION ON DISTRIBUTOR CAP AND FIRING ORDER WHICH IS 1 8 4 3 6 5 7 2 CYLINDERS FACING YOU ON PASSENGER SIDE IS 2 4 6 8 AND CYLINDERS ON DRIVER SIDE FACING YOU 1 3 5 7 THE TIMING MARK ON CRANKSHAFT BALANCER TO TIMING COVER SCALE SHOULD BE ON ZERO.

OKAY STANDING IN FRONT OF ENGINE ON LEFT SIDE CYLINDERS FACING YOU IS 1 3 5 ON RIGHT SIDE DRIVER SIDE CYLINDERS FACING YOU IS 2 4 6 LOOKING AT DISTRIBUTOR CAP NUMBER 1 SPARK PLUG ON CAP IN THE 9 OCLOCK POSITION YOUR NUMBER 5 SPARK PLUG ON DISTRIBUTOR CAP IN 6 OCLOCK POSITION .STARTING AT NUMBER 1 SPARK PLUG ON CAP COUNTING CLOCKWISE COUNTING 1 2 3 4 5 6 THATS YOUR SPARK PLUGS WIRES ON CAP TO ENGINE PLUGS. 6 PLUG WIRE ON CAP IS AT 7 OCLOCK POSITION.

For the 2003 Dodge Caravan (and Grand Caravan) ALL 3.3L V6 Engines (including the Flex Fuel): Also for 3.8L V6 Engines:

Firing Order:
1-2-3-4-5-6

Cylinders:
........(back).......
|...1....3....5...|
______________
|...2....4....6...|

Ignition Coil:
.......(back)
electrical connection
...........|
..........V
5........1........3
2........4........6
.......(front)

Let me know if this helped, or if you have additional information or questions. Feel Free to contact me at FixYa.com!

You didn't post your engine size so please use the appropriate diagram:




GM (Cadillac) 250 (4.1L) V8 .GM (Cadillac) 273 (4.5L) V8 .GM (Oldsmobile) 307 (5.0L) V8 .GM (Oldsmobile) 350 (5.7L) V8 w/EFI.Engine firing order: 1-8-4-3-6-5-7-2 .Distributor rotation: counterclockwise





GM (Buick) 252 (4.1L) V6 .Engine firing order: 1-6-5-4-3-2.Distributor rotation: clockwise





GM (Cadillac) 368, 425, 472, 500 V8.Engine firing order: 1-5-6-3-4-2-7-8.Distributor rotation: clockwise





GM (Cadillac) 429 V8.Engine firing order: 1-8-7-2-6-5-4-3.Distributor rotation: clockwise

the firing order is
1-6-5-4-3-2