Ok I am frustrated.

my truck sat for a while when lift kit was being installed

It was slow to start. i drove half a tank down refilled, the next day very hard to start in 70 degree fahrenheit . got it home had 17, 18, 35 codes. I decided now is a good time to replace that optical sensor that I knew i needed to for some time. same problem cranks hits a few times but will not stay running. lift pump is working, glow plugs good. initial injector timing is 25 degrees as read on snap-on mt2500g. I thought it was bad fuel but fuel is clear no water. any ideas

Did you replace the OS yourself? are the 17 and 18 codes gone? Any other codes now? The F/Sol fuse OK? You get WTS/GP light and SES light with IGN ON Eng off?

You timing is way too advanced if its 70*F outside.

no codes but still hard to start
gonna blow line back to tank to see if sock is plugged next

yes on the optical did it myself

i will check the fuse. glow plug light on ck engine light on at key on engine off

F/Sol fuse good 11.7 volts both sides of fuse. fuel line clear from lift pump to tank.

So you removed the IP and resintalled it yourself? Its advanced too far, should only be about 8-9 degrees at idle and thats advanced a bit.

Try retarding the timing by turning IP towards passenger side a little.

Make sure there is 12V to the Fuel shutoff solenoid, and you can pull it out and verify the plunger works when you turn IGN to ON.

No I did not remove pump did the optical sensor per gm manual removed top cover and removed and replaced optical sensor in same position as old one the advance is the readout on the scanner.

the plunger retracts with key on

crank RPM is 130 Starter?

You have 2 good batteries? Charge them up for a while and try then.

When you said 130 did you see it with a scanner, or did you really mean 630RPM on the guage that starts at 500?

130 0n the scanner. batteries on charger. will not get to it till tuesday morning now I work 24 hour shifts.

Ok an update. I put 2 new batteries and a rebuilt starter. it spins faster but still would not start. i unplugged the optical sensor. it will start now, takes a while. going to go through dtc17 checklist tomorrow. was suspecting the filter harness to be the problem but as soon as i plug the wiring into optical sensor not start, with or without filter harness. and will check fuel lines. gonna install airdog 150 fuel pump too.

From my experience,snap-on mt2500 scanners are inacurate on 6.5 diesels. It will not do a time set or a tdc offset learn. Timing will not read negative. I'd check all wires and connecters going to the ecm. Bent pins,pushed out pins ect.