Firing order?

On a '87 4.0 is it 153624 with the plug on the front being #1? then the 2nd one being #5 and so on?

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

The cylinder at the front of the engine is #1. The next one back is #2, and so on. The cylinder at the back of the engine (closest to the firewall) is #6.

The easiest way to remember is to look on the intake manifold. Almost all engines will have the firing order cast into the metal

The Society of Automotive Engineers has a standard for numbering cylinders on in-line engines, and it starts with #1 ALWAYS being at the front of the engine, and counts progressively back from there.

And ALL in-line six cylinder engines (no matter what brand) have the same firing order of 1-5-3-6-2-4. It's the only way the engine can be harmonically balanced correctly.

Reason I ask is my cousin and I had a brain fart when changing the plugs on his jeep today. Somethin I have done so many times and we got things mixed up just because the new distributor cap was molded a little different where the screw holes were. The new cap wouldnt sit on the distributor like the old one so we had to rotate it 180* for it to fit properly.. Well we had already marked on the cap which wire went to which cylinder. Little did we know that the cap wouldnt fit on the distributor like the old one so we had to take it off and completely change the location of the plug wires thus losing all track of what went where. My grandpaw came to the rescue and told us the firing order so I went over to my jeep with a peice of paper and a pen to draw up a picture of the cap and which cylinders were #1 and # 2 and so on so that we would know which wires went to which cylinder.

We finally got everything straightend out and running. If we had thought of making sure the cap fitted before we marked it and put the wires on, we wouldnt have made a 10min job a 1hr job.

If the cap won't fit on the original location, it's the wrong cap.