Lb7 wont start

[josh70mhs]

After doing injector work i cant get truck to fire. I replaced 4 injector selinoids on pasenger side. Iv done this before and isnt my first time.
Things iv tried and checked:

Replaced fuel primer seals
Pressurized the tank (plenty of fuel at fcim)
Using block off tool i blocked off each injector on fuel rail
Checked all pins on elec components
Primed until my arm fell off

Truck will only fire on wd40 but will not continue to run, im almost possitive its getting zero fuel. This truck drive into the shop with one injector bank down.It now has zero codes on dash and wont start. Ill be borrowing a tech 2 this weekend to check rail pressures. Any ideas in the mean time?

 

[Dukchunter]

Are you sure you did not knock any of the insulators off that are between the terminal post on top of the injector? It's a small plastic piece that can easily be knocked off. Of 2 are missin it could be shutting both banks down. Not sure it would throw any codes without starting tho

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[josh70mhs]

Yes im sure, im very meticulous about those connections having broke off a stud in the past. If i have low rail pressure will it throw a code?

 

[Dukchunter]

Not sure it would throw any codes without starting. I'm no expert on this just know what has happened to me. Did you check the harness near the ficm for chaffing? Known issue on these and you had that side apart. Could have tweaked it that it is grounding out.
I've learned the hard way that if it ran before I took it apart and it doesnt after then most likely I did something wrong. I know it isnt fun on these lb7s but the only way to be sure is to check it... I'm sure someone could give you a way to check rail pressure while cranking by disconnecting a high pressure line and hooking up a gauge of some sort but idk. I would say if your getting full to the injector then the injectors ar the issue somehow. Bit unfortunately it's not that easy on these trucks

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[DAVe3283]

It is all guesswork without a scan tool. You'll waste a ton of time trying various things that may or may not fix the problem. If it was me, I would wait for the scan tool, then you can see what is happening.

If you have nothing better going on, I would recommend checking the FICM connectors and bale connectors for bent pins. I flattened a couple pins out on my FICM once, and it wouldn't fire. Had to bend them back with tweezers very carefully, but then all was well.

 

[josh70mhs]

ok update, i hooked up a tech 2 , Im not getting rail pressure , it reads 130's while sitting and 150's while cranking. I have no DTC codes . Any ideas? this truck drove in the shop so i know the cp3 is good. Do i have an injector stuck open?

 

[DAVe3283]

If an injector was stuck open, you'd have smoke out the exhaust from that cylinder, and it would probably make a knocking sound while cranking as that cylinder tried to run.

You might have a plumbing problem. I'd take the fuel feed line loose off the CP3, then pump the primer and verify it is moving fuel to the CP3. Once you have good fuel to the CP3 (no more air), try and start it again, and see what rail pressure does.

 

[josh70mhs]

How much air can be in the line after the fcim? Will the cp3 bleed the remaining air out when cranking the truck?

 

[2004LB7]

If you pump the primer bulb then yes it should. You may need to pump till firm the crank for a few seconds, pump again and repeat. It helps to have a seo guy pump while you crank the engine

 

[josh70mhs]

Ok, iv pumped, and pumped and pumped some more, fuel tank is pressurized, i have fuel to the fcim with pressure . still only 250psi @rail when cranking.what should i be looking at next?

 

[Dukchunter]

So you confirmed your getting fuel to the cp3? Have you checked the pins on the plug to the fuel pressure regulator? If your getting fuel to the cp3 but not out, seems like you found where to look

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[josh70mhs]

OK , rechecked all pins and connections today. I do have fuel to the cp3. While cranking pressure only increases 30-40psi (160 psi) , with wd40 the truck will fire and pressure increases to approximately 500psi. I drove this truck into the shop with one bank throwing a dtc. I replaced a injector solenoid that ohm'd high. I now have no codes and low rail pressure. Do i assume im looking at a bad injector or two at this point or dose the cp3 seam more like the culprit? Cp3 has 230k on it, injectors have about 80k

 

[2004LB7]

Check the return on each bank. That may let you know if it is one or more injectors returning too much fuel causing it not able to build pressure. Happened to me twice

 

[josh70mhs]

How did you isolate each bank? Are you using the bottle test method?