Cranks for 2 seconds and quits

[94f450sd]

Hopefully I'm in the right spot here.

I've got an 05 c5500.had a motor put in it about 4 years ago.never ran since.we bought it.i got it running.didnt sound healthy at all.smoked like a bus and would randomly die.figured it would be quicker and easier to swap a known good motor into it.and well here I am.

Ok so what happened is after I got done swapping all the parts I had to swap and stuffed it in.wouldnt run.i finally again got it running.but it would only idle.fuel knocks like crazy.smoke so thick you couldn't see ten feet around it.found out I swapped in an lbs.

I pulled motor back out.swapped to lly injectors and crank reluctor as I've read they were different and would make the lbz work in it.im using everything but block and heads from the lly.

It cranks for 2 seconds and quits,2 seconds,quit,2 seconds quit with the key.ive read this is a bad crank sensor or loose reluctor.reluctor is not loose as I just swapped it.

I have 4 crank sensors,one is brand new.same thing with all 4.but if I plug a cam sensor into the crank sensor plug it will crank it's balls off as long as you wanna hold the key but will not start.it did fire for a split second twice using a cam sensor as a crank sensor.

I've checked harnesses.ive got continuity from the signal wire all the way to the ecm.ive 12 volts to the crank sensor,it's got a good and working ground.while cranking and probing the signal wire the voltages change,what I should be getting for voltages,I don't know.

It's not reading rpm on the dash or the scanner.

Any ideas before I burn this thing??

 

[Burn Down]

Your using lly cam and crank sensors? Positive?

 

[Burn Down]

Lly with a ficm?

 

[1FastBrick]

If you have an LBZ engine, the CP3 unit runs at a higher fuel pressure. I don't know if the controller will step it down to the lower pressure that the LLY needs.

It's probably over fueling. Hence the black smoke and fuel knock

 

[94f450sd]

Your using lly cam and crank sensors? Positive?

Yes.i ordered another ckp sensor today to be damn sure.

Lly with a ficm?

Yes

If you have an LBZ engine, the CP3 unit runs at a higher fuel pressure. I don't know if the controller will step it down to the lower pressure that the LLY needs.

It's probably over fueling. Hence the black smoke and fuel knock

I kinda figured that was due to the lbz reluctor with the extra tooth,(lly-57 lbz-58) I can't even get to atleast do that again.the 2 times it did fire for a split second using a cam sensor as a crank sensor it sounded like it was gonna purr if it stayed running.

 

[94f450sd]

Just so you know.ive been a mechanic for 30 years.but never played with the duramax.i was 7.3 stroke guy.

If you got some technical things you need to ask or have me do,please make simple for me to understand and I can do it.i have a snap on modis scanner,test light,good multimeter.

I need to get this truck running.its our new ramptruck,and we neeeeeed it!car trailers suck.

 

[94f450sd]

This is what it was doing before I found out I was dealing with an lbz. Even then before I got it to do that it was having the crank for 2 seconds thing.suddenly it quit once I got it to fire on it's own(I'm not a diesel noob,no need to go into the ether rants please.).

Now I can't even get it to at least do this again.


https://youtu.be/NZQjGpFHFUs

 

[TheBac]

Do you have the VATS (security) turned off?

So you're dealing with an LBZ, not an LLY? Running all LBZ electronics?

 

[94f450sd]

Do you have the VATS (security) turned off?

So you're dealing with an LBZ, not an LLY? Running all LBZ electronics?

I do not believe this truck has the vats.i could be wrong.i could try the relearn in the morning.


I'm dealing with an lbz running lly injectors,reluctor wheel and eletronics.

 

[94f450sd]

But if it's a vats issue,why would it crank it's nuts off If i put a cam sensor in place of the crank sensor?

 

[TheBac]

Im not sure. This is a very confusing problem.

 

[gmduramax]

Compression test? Injector stuck open? I know you probably have another issue but it wouldn’t hurt to check.

 

[gmac32]

Block off the egr. I had a truck a couple months ago that woyld crank and try to fire but wouldnt take off. Didnt set any codes or anything. Once i blocked the egr it fired right up

 

[94f450sd]

Compression test? Injector stuck open? I know you probably have another issue but it wouldn’t hurt to check.

Motor only has 86,000 miles.ran beautiful before this.

 

[94f450sd]

Block off the egr. I had a truck a couple months ago that woyld crank and try to fire but wouldnt take off. Didnt set any codes or anything. Once i blocked the egr it fired right up

It won't crank long enough to do anything but laugh at me

 

[Burn Down]

Is lly ecm original to the truck?

 

[94f450sd]

Is lly ecm original to the truck?

As far as I know,yes.i had original lly engine running.

 

[94f450sd]

Do you have the VATS (security) turned off?

So you're dealing with an LBZ, not an LLY? Running all LBZ electronics?

Has no security light but I'm out here trying the relearn anyways

 

[94f450sd]

Ok vats relearn done nothing.another new crank sensor did nothing.put a cam sensor in place of crank sensor and it'll crank with the key till the cows come home.

 

[TheBac]

Did you accidentally swap the cam and crank sensor connectors, plugged them into the wrong sensor? That has happened to people before...

This is confusing to say the least.