i own 99 f 350 with 170,000 miles,7.3l.this truck is very hard to start when below 50 degrees.tried plugging in for the night,but to my surprise ,it acted the same exact way.crank,crank,crank,and then somemore.she will start,but i mean after about 20 cycles of the key.then runs great ,and even starts great for the rest of the day.ok,heres the other part.in the morning, when its 50 degrees outside or higher,she will start within a second or two,with just one cycle of the key.im stummped.this truck runs great,has no rough idle when started no matter what the temp.blows out very little smoke when started and clears up within seconds.has no loss of power ,have 8000 lb tt and has no problem anywhere.i have replaced the starter,because it was dead one morn.but that fixed that.since then replaced gpr with no change.bought new motorcraft gps ,but have not yet installed them,dont know ,maybe one or two are bad and causing this?will ck wire harnesses when i install them and replace them probably,i know a major prob area.but this starting fine above 50 has me baffled.maybe i need to move to aruba,cause im not getting rid of this truck.please,can someone help.

 

The glow plug system has a controller that gets a signal from a temp sensor,

Look into that ,

Also a easy way to check the glow plugs is just hook a test light to the positive side of the battery,

If your test light finds ground thru the glow plug and lights up, good, if not bad,

 

i know the older diesels have a controller under the gpr.my gpr is mounted on a metal bracket.is it possible this system is operated through the pcm ,not sure but i dont think this year has a seperate controller,but by any means i am not a diesel mech,production date is 3 of 98,but is 99.well,anyway,gonna replace glow plugs.cant wait to see what i find when i get them v covers off.tested glow plugs but weird.2 on left bank show really slow resistance climb but ?.im assuming these 2 are bad.been running great,but its been above 50.

 

Harness connectors were a problem, and usually you'll see a bulge in the outer UVC connector and/or on the inside connector/s at the UVC connector from heat.. The right/passenger valve cover lower rear bolts are easier to get at from the wheel well area.. The 7.3 needs 500lbs of HPOP oil to start and should be checked with a scan tool or manually to rule out any pressure problems during a cold crank.. Being it cranks long and hard, it doesn't sound like a cranking 'speed' problem.. A glow plug test with a scan tool would help to diagnose system function as well. Is the glow system active if checked at the UVC harness connector on a cold crank?

 

i was told to ck two outer uvc pins for resistance.thats how i checked them.probably not the correct way.thats why i was saying a weird reading out of the one outer pin on one side.ive made an attempt at this,and i feel im getting resistance to connector at vc.really need to pull covers off to get to these plugs and test them .thank you for the input.will post what i find.

 

finally figured this thing out,the EOT sensor was the problem.without having a gp module on this year,this EOT sensor plays a big part on turning on gps when cold.it was 28 degrees out the day after i installed it,fired up after just one gp cycle.awesome.the truck thought it was warm no matter what the temp.also changed resevoir oil and it was black.change engine oil every 3000 miles ,still clear,but top oil dirty.i guess that puts that theory to rest.change that pump oil every 6000 miles.makes a huge difference,runs better,even slightly quieter.thanks for the help.