How do the wires go on the distributor cap of a 1991 Pontiac Firebird?

Answer 1

A large number of problems seem to arise when shade-tree mechanics remove ALL of the plug wires, and then attempt to re-install them from scratch on a motor with the crankshaft and/or valve-train in an unknown position. This is often the case, for example, after a rebuild. First, you need to know for sure which cylinder is used to TIME the motor. Don't presume that you know. Most Pontiac engines use cylinder #1, for example. Also be sure that you know which cylinder is which. Typically cylinders are numbered from front to back, in the order in which the connecting rods are sequenced on the crankshaft. In the case of V6, or V8 engines, this typically puts all of the odd-numbered cylinders on one side of the block, and all even-numbered cylinders on the other. 1) Remove the spark plug from the cylinder used to time the motor. (Reminder: Pontiac = #1 2) Have a friend slowly rotate the engine by hand using a ratchet or a breaker bar and a socket on the front end of the crankshaft. Be sure to rotate the engine in its normal direction of operation. Now is a good time to observe the distributor rotor to see which direction it is rotating (clockwise or counter-clockwise) as the engine is being turned. Here comes the most important step -- the step where most errors occur. 3) Place your thumb over the now-empty spark plug hole as you observe the timing mark on the balancer. AS THE MARK APPROACHES TOP DEAD CENTER (TDC), you may or may not observe pressure building under your thumb. If you do observe pressure, the cylinder is on the compression stroke, and you should stop the engine with the timing mark at about 5 degrees BEFORE TDC. If you do not observe pressure under your thumb, it's because the cylinder is on the exhaust stroke, and the exhaust valve is open. Rotate the crankshaft one entire additional turn, until the timing mark again approaches TDC. You should feel pressure now. Many shade-tree mechanics simply forget that the crankshaft goes around TWICE for every combustion cycle in a given cylinder. They assume that the spark-plug should fire every time the timing mark is at TDC -- when in fact this is only true HALF of the time. 4) Now that you've verified that the timing cylinder is on its compression stroke, and you've set the crankshaft to 5 degrees BTDC, identify the distributor cap TERMINAL at which the distributor ROTOR is currently pointing. Rotate the distributor slightly (as if you were adjusting timing) if necessary to get the rotor pointing DIRECTLY at any given terminal. 5) Attach the timing cylinder's spark plug wire to the terminal identified in Step 4. (Reminder again: Pontiac = #1 Continue attaching plug wires in the direction around the distributor cap that you identified in Step #2 above. Follow the firing order that is found in your service manual, and which is sometimes cast or stamped into either the intake manifold or a valve cover. Most Pontiac V8s use 1-8-4-3-6-5-7-2 The first wire (after the engine was properly positioned in Step #3) goes from the #1 cylinder to the distributor cap terminal at which the rotor is currently pointing. The next cap terminal CLOCKWISE from there gets wired to the #8 cylinder. The next one to the #4 cylinder, etc. 6) The engine should now be close enough so as to be able to be started, and the timing adjusted using conventional methods. fireing orders as follows-2.5L Engine 1-3-4-2 / 2.8L Engine 1-2-3-4-5-6 3.1L Engine 1-2-3-4-5-6 Both the 2.8L& 3.1L engines front left facing the engine -lft side 1-3-5 Rhtsid 2-4-6 on the plugs.