JUST BOUGHT A 85 F250 6.9L AND IT WON'T START! IT'S ABOUT 15 DEGREES OUTSIDE. WOULD IT BE OKAY TO UNPLUG THE BLOCK HEATER AND LEAVE IT SIT UNTIL IT WARMS UP OUTSIDE? OR SHOULD I KEEP IT PLUGGED IN FOR HOURS AND HOPE IT STARTS LATER?

i wouldnt unplug it, the fuel could jell up on ya then itd be a mess, it might just be too cold out side, i have a 99 7.3 and its about 10 here and mine wouldnt start, u might check your batts thats the reason mine wouldnt start.

99stackedpowerstroke's Sig:

1999 7.3 powerstroke 4 door 4x4 auto 6 inch guage 10 stainless steel stack, cold air intake, flashpaq programer, brush guard, new hpop opr and icp.

how long been pluged in. takes a lot of battery to get it to turn over also.

cumminsdad08's Sig:

04.5 2500 quad cab Cummins Turbo Diesel HO 6spd-4in fabtec, 35-12.5x17 on american racing, cold air, high ram, edge juice with attitude, and a set of bass fish decals (they help with the HP)

what cca battery is in it i had 750 cca bats and truck didnt like to start. jumped up to 1000 cca and fires up nicely now.

also make sure the glowplug system is working correctly.

have u read the backside of the sunvisor that says cold weather starting procedure?

DieselCrawler's Sig:

TOW RIG/DAILY DRIVER
2002 gmc 2500 hd 4x4 mprb exhaust, superchips programmer, custom intake
WORK TRUCK
2000 ford f550 7.3, 6 speed man, custom lube body. weights in at 15000 lbs.
PLAY RIG
1986 ford F250 6.9 diesel, np435, bw1345, hp60 front, welded up sterling rear sittin on 36x12.5 goodyears
i'de rather be 6.9'n than cummin' or strokin' Built by Hicktown Motorsports

YEAH I READ THE PROCEDURE AND FOLLOWED IT CORRECTLY BUT IT STILL WOULDN'T START.

let her plugged in for a couple hours, it wont hurt anything. sometimes you gotta cycle the plugs a couple of times, and i would concider some new batts, being you just bought it and don't know how old they are. being pluged in will only hurt your wallet a bit, but it shouldn't be too bad. mine stays plugged in most all the time and i don't really notice it in the bill much.

test and make sure block heater is working also. take a multimeter and test restance at the plug. if no restance block heater is shot. being an 85, u should not have the bad blocks. early 6.9 blocks were prone to cracking around the blockheater.