LB7: Ficm problems???

[guga1979]

That was helpful info, I had a P1232 (injector4) along with the P0304.
I'm guessing the only way to find out is to replace the FICM??... Or how do I know if the injector driver circuit is open?, shorted to ground or like that like it says on the text....

 

[MAXX IT OUT]

I think I have a bad ficm. I ohm all my wires and my injectors, and they all checked out good. So I will try a new ficm.

 

[MAXX IT OUT]

I got this diagram from GM, it may help someone.

 

[bigbopper]

ficm

you probly don't have enough rail pressure at cranking , possible causes sensor, cp3 , etc , mine was pluged return line, cp3 will not pump if this happens : george

 

[guga1979]

I think I have a bad ficm. I ohm all my wires and my injectors, and they all checked out good. So I will try a new ficm.

Does your truck goes back to normal too?.... This morning my inj#4 was stuck open at 15. I started few times and nothing changed. Then I pulled all the inj connectors on the drivers side back off, played with it a little. Picked the #4 again, put it back together, and there it was, normal specs again!, with exception on #8, which is slightly above but we have ordered a replacement, along with another FICM....
Mine goes from good to bad and back without me touching it.... It's just getting more frequent to the point I'm not driving it now....

 

[MAXX IT OUT]

Does your truck goes back to normal too?.... This morning my inj#4 was stuck open at 15. I started few times and nothing changed. Then I pulled all the inj connectors on the drivers side back off, played with it a little. Picked the #4 again, put it back together, and there it was, normal specs again!, with exception on #8, which is slightly above but we have ordered a replacement, along with another FICM....
Mine goes from good to bad and back without me touching it.... It's just getting more frequent to the point I'm not driving it now....

Mine is trying to run on the number 1,5,6,and 7 cylinders only. The ECM has shut the other injectors off, so when the truck starts, it run for about two seconds and dies. When was the last time you replaced your injectors? It could be that time again.

 

[quinton]

Does your truck goes back to normal too?.... This morning my inj#4 was stuck open at 15. I started few times and nothing changed. Then I pulled all the inj connectors on the drivers side back off, played with it a little. Picked the #4 again, put it back together, and there it was, normal specs again!, with exception on #8, which is slightly above but we have ordered a replacement, along with another FICM....
Mine goes from good to bad and back without me touching it.... It's just getting more frequent to the point I'm not driving it now....

This is what's going on with our truck. Sometimes runs just fine then sometimes acts up.

 

[jkholder09]

I have found allot of rodent issues in and under the engine power distribution block.

 

[guga1979]

Very hard to pinpoint.
Last week I couldn't drive the truck because my #4 injector was stuck open everyday. So, Saturday I started the truck in the am, it was rough on idle, so I didn't even drive it. I pulled the harness off, I did the ice pick on my #4 injector, I couldn't tell if any of the wires were in bad shape, so I put all back together. Without any major changes, I've being driving the truck this week with no problems at all! Towing and everything. It's back to normal. I was ready to replace my FICM, we got one on order, but I wish someone could tell me. If the truck keeps acting up like this, most likely, what's the problem with?
Thank you.

 

[MAXX IT OUT]

Maybe some of the EFI live genius can help me here, but is there a potability of my tuning playing havoc with me or a bad ECM. I don't like the fact that I had a electrical short and then this happened. I just put in a different FICM into day and nothing. I will be doing a bunch more wire tracing and trying to get some Ohm and volt readings.

 

[MAXX IT OUT]

you probly don't have enough rail pressure at cranking , possible causes sensor, cp3 , etc , mine was pluged return line, cp3 will not pump if this happens : george

Have you had this problem before? Can you elaborate some more, i am open for anything, i just want to fix the dam truck.

 

[catman3126]

Sub'd

 

[MAXX IT OUT]

How is the best way to check the output voltage on from the FICM?

 

[MAXX IT OUT]

I was messing around with this today and it sound like i have a hole again in a piston. Crank it over with out the oil filler cap and it sound alright until it hits one cylinder and then a lot of crankcase pressure. I am going to do a compression check and see it time to do a LLY swap and a fully built engine. Any way after replacing the FICM and checking the wiring harness it looks like the problem is with the injectors, on the drivers side.

 

[MAXX IT OUT]

I guess I found my problem, and it didn't have anything to do with the injectors. I lost the exhaust valve bridge of of number 6, fixed everything and she runs great. I was going to put everything back together after checking all my injectors visually and accidentally bumped the rocker and notest this.

 

[guga1979]

Good for you! I've being pretty happy myself. After last time when I picked the driver's side injectors, it started running like a champ again. It's being about a month now! I've enjoyed the truck since.

 

[juddski88]

Did you set your own lash when you did the new springs?

 

[MAXX IT OUT]

Yes I did set the valve lash when I put everything back together, and check it before I put it back together again this time. I don't know if I never torqued the nut right, but it came apart. I have put about 30 miles on it today and all is :thumb:.

 

[MAXX IT OUT]

Yes I did set the valve lash when I put everything back together, and check it before I put it back together again this time. I don't know if I never torqued the nut right, but it came apart. I have put about 30 miles on it today and all is :thumb:.

Well this bit me in the ass again and I am stuck out of town. When I get the codes cleared it will run fine then trip again. This time it's P1262 and P0202. Any ideas? Hoping to be able to get it home.

 

[MAXX IT OUT]

Anyone think injectors could be the problem? The truck idles fine, I am going to put the truck under load and see if it trips after it has sat overnight. I am trying to get it in shape to make it 5 hours home.