Hard to Cold Start

[Sawtooth]

I have a '97 F250 with 195K miles. It's been hard or impossible to cold start without plugging in the block heater. I live at 6,500' elevation, and it seems harder to start at higher elevation...like 9,000' plus. I've had the glow plug controller replaced. Still starts hard. Any ideas? Right now, the only time I can really rely on this truck is when I'm within 50' of an electrical outlet when it starts getting cold (below 35 degrees). Help!

[highland512]

Have the glow plugs been replaced?? I not I would look into that and make sure that everything on the wiring harness is connected.

[95PDXLT]

have you tested the glow plugs themselves to see if they are in working order. Gets cold up here and my 95 with 195K starts relatively easy at -15 C not plugged in.