Truck tries startingI have a 1990 Ford F150...won't start. I have fire to the top of the distributor and to the button on the bottom side of the dist, cap but when i put it all back together I get no

Mike, Check for diagnostic codes. Check fuses/relays,wires/plugs for pinched,damage or corrosion. Could be a lot of things like distributor armature, cap, rotor, stator, ICM, coil,spark plugs,wires, make sure ground is good to distributor. Use the attached forum links,instruction, guides to help diagnose ignition spark problems, Good luck
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Resolved 89 Ford F150 302 Won Start HELP

crankshaft position sensor is bad. it uses this sensor to tell the computer when to make each plug fire. no signal no fire.

153624 clockwise in cap

bet on the module,if it's tfi it's on the side of the dist.85 could be either way,may be the older fender mounted module.
If it's dist. mounted Ford recomends replacing the pick up coil also. There is a wire with a plug on the tfi's ,you remove the "cap" to set the timing,just 2 wires with a gray cap on the end.Maybe that's the wire you mentioned.

try changing the pickup coil in the bottom of the distributor

Try the "Pick Up Coil" its located inside the distributor, you will have to disassemble distributor to replace it, if you don't want to deal with the hassle just replace the distributor with a used one. I have a 1990 f-150 that was having the same problem, after replacing several parts I finally found the problem, Pick Up Coil. Good Luck.

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!

Remove the ignition module and take to your local parts store for testing. It should be located on the side of your distributor were the wire harness plugs in. This will fix it 90% of the time.

try replacing the ignition module on the side of the distributor(common problem) also take the dist. cap off and poke the pick up module inside the dist.and see if its the consistency of bubble gum,if it is replace the distributor also,hope this helps

have you tried checking the coil? or the ignition control module on the side of the distributor...the coil is cheap but you may what to check the junk yard for the others.