Built motor Lmm help please

02bigstrokin

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Sep 9, 2008
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Ok so I've got a 2010 Lmm im working on and can not figure out what the problem is. The customer bought the truck with a cracked piston. Pulled the motor out, bought fingers pistons for it, has the bottom end rebuilt by machine shop. I assembled everything from the short block up. Carillos, girdle, fingers, main studs, head studs, 66 over s480 billet twins, 60% over exergys, Ats twin cp3 etc etc. I made a fuel system with two fuel manifolds just like I used to have on my built 03. Got the truck put back together and running and it fuel smoked some at idle, a lot while driving but the tune was for a vgt high pressure turbo so I figured tuning was a big part. Had tony retune the truck and it ran great (still smoked more then I thought it should with 60's ) but ran strong and pretty smooth. Now after probably less then 100 miles the customer says he was half throttle and something made a noise kind of like going into allison limp mode. And now the truck will start and idle fine(fuel smokes) but it will not rev over 2200 rpms. It starts missing and shuddering almost like a studder box per say. So far I've removed the pickup assembly in tank checked for cracks/ sucking air. I've redone all the Airdog lines because they were previously routed all over the place. I've checked fuel pressure at the fuel blocks and have 10psi constant. I've taken the injectors and had them all tested. Two of them supposedly had something going on internal letting fuel bypass. I figured that was the issue. Nope. Put it all back together tonight and absolutely zero change. If I make it spit and sputter long enough it will throw misfire codes on multiple cylinders but it has no electrical fault codes. Checked wiring. Sorry for the long winded thread. Any help is greatly appreciated I'm at a loss here.
 

Frankin_truck

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Nov 22, 2013
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I wonder if the reluctor wheel on the front of the crank got damaged or even just bumped. That causing funny timing readings, could have happened when you put the motor back together?
 

02bigstrokin

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Sep 9, 2008
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I wonder if the reluctor wheel on the front of the crank got damaged or even just bumped. That causing funny timing readings, could have happened when you put the motor back together?

Well just wonder why it would have run ok for a short bit and then started acting up. I took the short block to machine shop with front and rear covers on it so I never saw the reluctor wheel honestly. Not ruling it out though
 

Harbin_22

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Dec 4, 2010
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Broke crank? That's pretty much exactly what mine was doing. Ran pretty decent but not would spit and sputter. Hope its not but I would check it out before you run it much more. Mime would be throw a cylinder 1 and 2 miss fire code
 

Harbin_22

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Dec 4, 2010
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I actually had a damaged reluctor wheel on mine and it was throwing a crank sensor code. One tooth had a little tiny knick on it and it wouldn't right after the engine went back together
 

02bigstrokin

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Sep 9, 2008
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Broke crank? That's pretty much exactly what mine was doing. Ran pretty decent but not would spit and sputter. Hope its not but I would check it out before you run it much more. Mime would be throw a cylinder 1 and 2 miss fire code

I was thinking about this. I can't move the balancer by hand any. It doesn't knock or anything? Also when it's spitting and sputtering it's fuel smoking something terrible. would a broken crank make the truck smoke real bad?
 

schulte

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Jul 31, 2010
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I was thinking about this. I can't move the balancer by hand any. It doesn't knock or anything? Also when it's spitting and sputtering it's fuel smoking something terrible. would a broken crank make the truck smoke real bad?

Take the belt off when you checked the crank?
 

02bigstrokin

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Sep 9, 2008
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Take the belt off when you checked the crank?

No I did not but I could lay underneath the truck and pushing up and down on the balancer the whole truck moves up and down but the balancer does not. And why would a broke crank idle fine, and limit rev to 2200 rpms like a studder box, and way over fuel while hitting that "limit".
 

S Phinney

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Aug 15, 2008
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I believe is timing related. C@m or crank position or reluctor. It could as well have some debris run through the injectors.
 

Harbin_22

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Dec 4, 2010
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When mine broke, at first it wasn't broke all the way. The balancer looked a little wobbly looking at the backside of it. Rank wouldn't move by hand. It would spit and sputter and run like crap and throw miss fire codes. After I messed with it for a little while the crank ended up breaking the rest of the way and then I could move it around. I hope this isn't your problem