hello to all! its about time i join a diesel forum, as i am somewhat new to diesels.
i bought a 95 gmc 6.5 with low miles, but it seems like a few people have rigged it.

im pretty sure there is a oil press sens bypass, hence a toggle switch in cab that i was told not to touch.

ive never had the glow plug light come on the dash,had 12v to main stud, but nothing on other terminal, nor did i ever hear relay click.
i live in sw florida, and it was the coldest ive had the truck this morning (48 degrees outside) and the darn truck wouldnt start. ive never had a problem starting the truck before untill this morning. it was dumping smoke out the back, but wouldnt fire. i hunted down a glow plug relay. but before swapping gp relay, i tried the truck again, as it was a bit warmer, and it fired up. so i changed the relay, hooked up batt terminals, hoping to see gp light on dash, but still nothing. still no power off other terminal on gp relay.
then i got in the engine fuse panel, noticed the "eng-i" fuse was non existant. so i put a 20a fuse in it, and bam!glow plug light came on the dash!!! yayy! so it was on for a few sec, went out, and i fired up the truck. fired right up, but idled like donkey poo. soo i pulled the fuse out, turned key on, no gp light on dash, but truck started fine and ran great.

to make a real long story short, is the oil press sensor bypass whats causing it?

only mods truck has is kn filter, straight through exhaust(stock dia, but no soot can or muffler), mechanical boost control on turbo, and a remote pmd in the bumper.

any ideas? i want the glow plugs to work, but it runs like poop with the "eng-i" fuse in place. it runs fine with no fuse

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also, cause im sure someone will ask, i have had codes scanned. a few may be null since the truck was scanned before the trans was pulled and replaced about 2 months ago.
heres all the codes i got:
99
85
86
78
57
62
63
49
54
46
35
38
23
29
18

 

now i have an update. i got an inkling to put the fuse in the eng-i spot, and went to start the truck. it blew the fuse. it didnt blow it on the cold day,but it did today.
any one have any idea?

 

i have another-another update i put a 20a fuse in the eng-1 (i think i was putting a 10a in)

and i fired up the truck and it idled like crazy! revved like nuts all on its own. im stumped? anyone please help??

 

Is it idling ruff or revving ? If your glow plugs are bad or week it will not after glow and will run really crappy till it warms up. Check the continuity on your glow harness and see if the clips on the end of the wire on the plug end are tight and not corroded if all of this checks good I would think it's your glow plugs being that you changed the glow relay.