My truck has been doing this for probably 6 months. What it will do is sometimes it will not crank over at all, i can hear the solenoid being activated on the passenger side fender well, and when the key is in the start position there is power on both terminals. What i usually have to do in order for it to start cranking is, 1: Get my girlfriend to turn the key, dont ask why it just seems to always work when she does it, 2: Wiggle the smaller 12 Gauge wire that goes to the solenoid on the starter itself, 3: Just let the truck sit and try it later in the day.
Lately i havent been able to get her to crank over no matter what i do, i get underneath the truck with the trunk in the start position and jump the terminals on the starter solenoid with a screw driver, the starter will turn over but not engage.
This is driving me nuts, i have a feeling that it is my starter solenoid, but any input would be appreciated.
1996 Ford F350 Regular Cab 5spd with the 7.3L PSD, 4x4, 35.5x12.5x16.5 All-Terrain T/A's, 3.73s', DIY Electric Reg Return Fuel Sys, 3" Downpipe, AFE Stg 2, 17* HPOP, IDM Mod, SB Con-O, Cat and Muffler Delete, AutoMeter NV Series Boost, Fuel Press. and Pyro, Autometer 3 Pod A-Pillar, TS Performance 6 Pos Chip. HPX Mod, 355,000 Miles