Wats firing ordor on distributor cap 1988 ford f150

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with distributer cap off have someone crank engine and see if your rotor is turning if not repair distributer or replace.

make sure all gas lines are hooked up. and vac. line are not open.

Go to any parts store and ask them for a print out for your truck's firing order.

If you are getting fuel and spark at the cylinder then check the timing. It's not uncommon for worn timing chains to jump at shut off or start up. To check turn the engine over until the timingmarks on the crankshaft line up at 0. Trace the wire back from #1 piston, which is the front one on the passenger's side. On the cap it should be just to the right of the tab that locks the cap in the proper position on the distributor. Lift the cap and check the position of the rotor button. It should be directly under the tower for the wire or it should be 180 degrees off. If so turn the engine 1 turn until the timing marks line up at 0 again and look under the cap. If it's not lined up with the #1 wire, turn the distributor until it does. Tighten the distributor down and try the truck. If it fires you are looking at replacing the timing chain. If it jumped once it will jump again. Hope this helps.

The F100 ended in 1983, so there is some confusion on your 1987 Ford F100. The F150 started in 1983 and was available in 1987, but not the F100. You have this listed under the 1981 Ford F100 category.
The 300 CID = 4.9L In-Line (Straight) 6-Cylinder.
In order to best answer your question I have included both the 1981 F100 4.9L and 1987 F150 4.9L below. The only difference is with the Distributor Cap Configuration and Connections.

For the 1981 F100 300cid=4.9L:
Firing order:
1-5-3-6-2-4
Cylinders:
(back)
...6
...5
...4
...3
...2
...1
(front)
Distributor:
...(back)
.........4..[.]-clip
2
...................1
6
................5
[.]....3

For the 1987 F150 300cid=4.9L:
Firing Order:
1-5-3-6-2-4
Cylinders:
(back)
..6
..5
..4
..3
..2
..1
(front)
Distributor:
.......(back)
.................4
.....2
[.]
.......................1
..6
.........................[.]-clip
....................5
.......3
.........(front)

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

Hi:
Some basic instructions:

Before you remove the old distributor, rotate the engine until the #1 cylinder is up on Top dead center, the timing mark on the crankshaft damper pulley is lined up, and if you remove the distributor cap, the rotor assembly is pointing towards the #1 spark plug wire hook up. If you get the engine set up like this, then remove the hold down bolt from the base of the distributor, dinsconnect the electrical connectors, and install the replacement distributor in the same manner.

sounds like your coil needs to be replaced, or the coil wire. Try wire first its cheaper.

i need a diagram of the firing order for this please