Hey everyone, I am a new user so I am sorry if I screw anything up.

TLDR; I think my ignition cylinder is causing strange shorting behavior in several circuits that are connected to it.

I have an '87 F150, single tank model with the 4.9L 300I6. At least 400K on the clock, but it was running great up until this happened. Regularly maintained for its entire life, etc. - I have been having a number of electrical gremlins for months now that I have been unable to narrow down until a few nights ago. The symptoms listed all came on abruptly and almost simultaneously, and have not since resolved themselves. I have done a LOT of diagnostic tests and nothing comes of it.

1. Fuel pumps begin to behave erratically. In-tank pump shutting off or not functioning at all, causing inline pump to cavitate and it becomes quite loud. Truck unable to accelerate, underivable.
2. Wiper motor no longer getting power. Replaced motor to now avail (I know, should've tested circuit first). Fuses are all OK.
3. Rear ABS light came on and has not turned off since. Replaced rear ABS sensor, no change. Took out fuse for the light, but the light stays on.
4. OEM tape deck/radio no longer able to do anything but display the time. It seems as though it is not being switched by the ignition, but is getting 12V.
5. The DLC connector pin that is supposed to be able to power the fuel pumps when it is grounded does nothing.

Some notes:

• I have replaced both fuel pumps after I confirmed the rear pump was dead by bench testing. Replaced the other as a precaution as I did not know if it had been damaged from picking up the slack. Fuel pump relays seem to be fine, getting power, click when ignition is turned, no buzzing. Getting power to the connectors. Have tested the pump circuits with a EECIV breakout box and both tested just fine with resistance and voltage on the new pumps. New inline fuel pump is still cavitating, but not as loud, and it seems to strain when I start up the truck, it takes a few priming cycles to stop making noise.I can hear the rear pump running with a stethoscope.
• I replaced the wiper motor after getting lazy and not testing the circuit. It is not getting power. At least it looks nice.
• Have not tested radio ignition wire. Probably would be a good idea to do so.

A couple nights ago, I came across an issue that seems to tie all these things together. I was screwing with the wiper switch and realized that for a brief moment when I ignite the truck (does not happen in ACC, only RUN), the wipers get power. So with the truck still running, I put slight forward turning pressure (like I was trying to ignite it, not pushing it in) on the key in the cylinder, and BOOM, wipers stay on, ABS light goes off and stays off, and I swear I think the truck even started running better! All of the issues come right back the moment I take pressure off of the ignition cylinder. I pulled out the circuit diagrams for the ICM and related circuits, and it turns out the fuel pump relays and the wiper motor are all connected to the same circuit connected to the ICM.

So now that I have written a book of mostly irrelevant info, does anyone have any suggestions? I am thinking its the lock cylinder itself, but I have heard the ICM is a known point of failure. Any help is greatly appreciated.

 

I would get to the ignition switch by removing the plastic cowling from around the steering column, 2 phillips head screws accessible from the bottom side. You may have to drop the steering column from under the dash first, simple, remove 2 or 4 small bolts accessible from the bottom.

When you get the cowling removed, make sure the actuator, the rod connecting the key cylinder to the ignition switch is intact. If all is well there, the ignition switch may just need adjusting. Loosen the screws holding the ignition switch and slide the switch closer to the steering wheel.

If it comes to where you need to replace the ignition switch, get a Motorcraft if available otherwise the best name brand.

 

Excellent, I will try this when I get home tonight. Thank you very much!