LBZ: Help me please, crank no start!!!

[jnieberlein]

Ok so this truck has been in some sort of disrepair since June started knocking injectors out of speck, discovered bad fuel, fpr was stuck open, so it was replaced, 5 injectors have been rebuilt, one has been replaced. The truck has required fuel pressure according to what efi live says the truck is requesting. I put my computer in another truck and it runs fine, ive took ohm readings on the ecm harness and found no shorts on the fuel injector circuts, ive back probed the injectors while cranking and they are not getting fuel (very little voltage) less than one volt. Engine fires on silicone spray, glowplugs and intake heater
Are unpluged. I cant figure this out I am misssing something please help me! Thank you

 

[GMC04DURAMAX]

Pull your crank shaft position sensor out and make sure your reluctor ring is still tight if its loose the sensor won't read a signal to send to the ficm hope this helps ran into similar problem and found that all the bolts had backed off so the ring wasnt even attached to the crank shaft

 

[jnieberlein]

Thanx. Does this apply to an LBZ, I dont have a FICM, only an Ecm

 

[GMC04DURAMAX]

Ya it will apply to all of them lbz included

 

[Bustedknuckles]

What does the rpm show on the scan tool while cranking? how many psi of rp does it build? any codes? Is your lift pump working?

 

[jnieberlein]

Rpm is between 200 and 300, desired fuel pressure is 6745 I have a spike of about 9600, then falls to right to desired of 6700ish, fuel pump is working if you depress the schrader valve on the front of the engine you'll get fuel in your eye. Lost coms with glow plug controller cuase i unhooked it while i was spraying silicone in The intake

 

[Bustedknuckles]

That is very odd. Sounds like you have most of your bases covered. Are the injectors getting proper voltage? Cam signal good?

 

[jnieberlein]

Near as I can tell the injectors are NOT firing I back probed them while cranking and saw very little voltage like less then 1volt, have not checked anything with the cam, it just dosent make any sense why they are not getting voltage, I havent found any shorts

 

[05_LLY]

Large bail conectors pluged in the whole way snd correctly on drivers side valve cover?

 

[Bustedknuckles]

Get it running?

 

[chevyburnout1]

Just FYI LBZ needs the glow plug module plugged in to run. You unplug it and it opens up the GM high speed data communication circuit.

 

[Hole Shot]

I had an LB7 do about the same thing had 6000 psi of fuel good compression no codes and it ended up being the injectors. I never did check voltage just took a shot

 

[jnieberlein]

Just an update cause I hate reading threads with no ending. Checked crank shaft and all was OK, I had all injectors sent off and tested and out of the 8 only 2 fired 1 of which was new, and 6 did not, turns out the initial water incident really wrecked a bunch of stuff, all injectors that could be refurbished were and we had to replace one more that while was in spec was still over fueling slightly. Shes back on the road :thumb: