Hi all. It's been a while.

1991 F150, 4X4, 5.0, E4OD

I put a new MLPS switch in about a year ago which fixed my harsh shifting.

I put a new ignition switch in a couple of years ago because the old one fell apart.

This past winter a few times my truck would not start, but after moving the shifter out of Park and back it would start. I figures the ignition switch was off a little and planned to adjust it. Then it wouldn't start at all so I put a new ignition switch in and it seemed OK for a couple of days, but now it won't start again. I can jump the little post on the solenoid to the + terminal to make it start, so I think the solenoid is OK.

Could the MLPS be out of adjustment? I have noticed my backup lights don't always come on in reverse but will come on if I move the shifter a little.

Just need to know where to focus my attention.

Thanks

 

Yes, the MLPS can be slightly out of adjustment, but I also suggest you check the shifter attachment bolts at the base of the steering column. They frequently come loose and exhibit your symptom.

For reference:


courtesy of Subford

 

Just to confirm that is just through the firewall under the hood? Mine doesn't look exactly like that, but the shift arm doesn't seem to be loose. It has just a little up and down play in it when I try to move it by hand.

FWIW. It worked yesterday morning but then quit again. I tested voltage at the little terminal of the solenoid when in the Start position and it read .2 (2 tenths) of a volt. Not sure what that was telling me.
I tried loosening up the MLPS switch, but I could not make the backup lights come on no matter what position it was in, so there went that theory. It was properly lined up in the first place anyways.
I took the ignition switch out again last night and put it all back together and the starter worked for a while. I ran some errands this morning and started it probably 5 or 6 times and then when I came out of a store it wouldn't start again. I used my trusty 12 gauge jumper loop and when I got home and shut it off it wouldn't start. I pulled the shifter quickly down to about Neutral and back to Park and it started up several times. I unhooked all of the wires from the solenoid just for the heck of it and cleaned everything and put dielectric grease on all of the connectors and right now it is working as far as I know. I don't suspect the solenoid because I think I would hear a "click" when I try to start it and there is no sound.

 

No, under the dash.....inside the cab.

 

On mine it is outside the firewall and under the hood. Right in that spot that you can't reach from above or from below.
I have been looking at some wiring diagrams and it looks like there are a lot of areas that could be suspect. The ignition switch was 2 years old and now is a new one. The MLPS switch is less than a year old, but I suppose could be bad.
I guess I'll have to get my volt meter out the next time it is acting up and try to rule some things out.

 

The above image was for a 1992 and newer OBS truck. It sounds like the 1991 an older trucks are different but can not confirm.

You may also want to look close at the Ignition switch harness plug also as they have been known to melt and cause problems.



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Lol....no mistaking the origin of certain pics that have subfords name plastered all over them.