In what order do yu arrange the plug wires on the distributor cap or a 1990 gmc 350

coil HT lead to centre contact on dist cap ,the remaining HT leads go to the spark plugs you will need the firing order to get them on the correct plug follow this link may have to research site for your year vehicle
1967 1972 Chevrolet Spark Plug Wiring Diagrams

You can google the engine size and "firing order" to get a drawing or photo of the firing order online.
Example - - 1990 GMC 350 firing order diagram

i want to know how to put wires in order

Here is the firing order diagram for the 5.0 liter (305), 5.7 liter (350) and the 7.4 liter (454) V-8 engines (note position of locking latches/screws between the 3 and 6 and the 1 and 2 terminals on the distributor cap). Let me know if you need the 4.3 liter V-6 engine diagram (hopefully not in a 2500 series truck) or if you require any further assistance.

For GMC 350 the firing order is 1-8-4-3-6-5-7-2.

The distributor rotor turns clockwise when viewed from above, so the spark plug wires would be installed in the same order as the firing order, beginning with #1.

To find which contact in side the distributor cap that the rotor is "pointing" to, use a ratchet on the center bolt of the crankshaft and turn the engine over by hand (clockwise direction only as viewed from the front of the engine looking towards the firewall) until the timing mark on the harmonic balancer aligns with the "0" mark on the timing cover (may also be indicated by a deep "V" cut into the timing mark indicator attached to the timing cover).

Normally, the rotor will either be "pointing" towards the firewall with a bit more emphasis towards the driver's side cylinder bank, or it will be pointing towards the front of the passenger side front fender. If it is pointing towards the fender, turn the engine over again until the timing marks align and the rotor should be pointing towards the firewall as described above.

Find the closest terminal in the distributor cap that matches the rotor's alignment and install the #1 wire. The distributor cap and then be installed with the remaining wires installed around it clockwise from #1 using the firing order.

Some turning of the distributor may be necessary to get the engine statred. Once it does start, use a timing light to set the timing.

Hope helps (remember rated this).

If you are talking about a 350 Chevrolet (GM) engine, the #1 plug is at the drivers side front. To find the position on the cap, turn the engine 'till the timing mark on the lower pulley points to 0 on the scale, then check rotor position in the distributor. If it's pointing towards the firewall, make one more turn. The firing order goes in the direction the rotor turns when cranking the engine over. 18436572.

350 Chevy engine in what? 1990 Corvette? Who built it, did you?

Sounds as though you have plug wires wrong.
Firing order is 1-8-4-3-6-5-7-2

Distributor Ignition System:
Distributor rotates Clockwise. (Rotor)
Find Number 1 tower on distributor cap, go Clockwise with Firing Order.

Distributorless Ignition System:
VIEWING the engine from the Front of the car.

Spark plug wire connections along the back, starting from Left side going to Right side;
2-3-7-4

Spark plug wire connection towards the Front of the engine;
6-1-5-8

(To guess I would say you have 5 and 7 wires switched)

Left side cylinder order is 1-3-5-7, going from front to back.
Drivers side is Left side.
Right side cylinder order is 2-4-6-8, going from front to back.

Recheck the order, 18436572 clockwise. number 1 should be the one closest to the coil tower.

check to see if you have your plug wires at the right location on distributor cap. If you don't have a digram they are as follows- right side 1, 3, 5 front to rear. Left side is 2,4,6 front to rear. #1 should be on the location at front of cap closest to intake manifold. firing order is 1,2,3,4,5,6. Hope this helps. KS

The firing order is 1-8-4-3-6-5-7-2.
The distributor rotates in a clockwise direction. The engine must be on the compression stroke on the #1 cylinder. Line up the timing marks. Remove the cap and the rotor should be pointing to approximately the 5 o'clock position.

Good Luck