LML Rebuild - Crank No Start

[StephenZ]

2016 LML duramax, cp3 swapped (before rebuild all tuning is for cp3 swap), fass 165, installed Mahle performance pistons and rings, I’ve bled all the air you can possibly think. Maybe there’s more left.

I’m between 430-450psi in all cylinders as well, did a manual compression test after completing the rebuild.

I’ve got fuel at every injector, cracked all lines multiple times to make sure I had fuel and wasn’t just imagining I did. I’ve never had to bleed a LML this much,

It will hit occasionally but nothing more. (Haven’t and won’t be using starting fluid.)

The FPR exceeds my DPFR, EFIlive says around 26k at maximum while cranking, starts at 0, and gradually goes up to desired and then continues to climb to around 25-26kpsi, primed my oil pump prior to putting fuel to the system, with my mechanical gauge I’m pushing around 42psi while cranking. After I got a good pressure, I put the block sensor back in, and reconnected the electronic connector. On my EFIlive I’m reading between 37-48psi on oil pressure. It is fully deleted, as stated all tuning is the same tuning as before the engine blew up, just took it out, bought a new block and stock rebuild kit.

Question: Will not having my radiator, core support, intercooler hooked up allow for the truck to crank but no start?

All ground wires are hooked up, the two on the bottom front side of the block, and the one on the back driver side head.

Any suggestions?

Thanks.

 

[2004LB7]

Cam crank sensor or reluctor issues

 

[StephenZ]

Cam crank sensor or reluctor issues

Crank has Dot, according the Haynes Manual, correct. I guess it would be possible that when I removed them to clean the front cover they could have been damaged.

 

[2004LB7]

With your scanner can you see missed cam counts?

 

[StephenZ]

With your scanner can you see missed cam counts?

I haven’t tried or looked at missed cam counts. I’ll dive back into it tomorrow. Done everything according to my Haynes manual. Dot to dot on came and crank, CP3 didn’t require timing so just stuck it back in.

Is it possible that after sitting for 4-5 weeks, that the return line mechanism is acting up? I was reading that we need 43-44psi to close the returns or the injectors will not fire.

I’ve got white smoke out of the tail pipe recently so I’m stumped as of right now…

 

[2004LB7]

The LML does require back pressure on the injectors for them to operate. Maybe do a bottle test on the return

 

[StephenZ]

The LML does require back pressure on the injectors for them to operate. Maybe do a bottle test on the return

You know an easier way of getting the rubber return portion off of the hard portion at the back of the drivers head? I can’t get it off. Been looking for a guide, can’t see anything, Haynes doesn’t mention it, only thing Haynes mentions is to utilize a set of Pilar’s to lift the tabs of the return lines, im trying to get the soft rubber line off the hard stainless line to apply a back pressure with shop air, however I’ve been beating my head against the wall all day trying to figure it out, without breaking anything.

Thought about cutting the line and buying a hose barb to reconnect them (lol).

 

[2004LB7]

Are you talking about this one?

Source: https://youtu.be/7ueqiIEC-g4

Or these?

 

[StephenZ]

Are you talking about this one?

Source: https://youtu.be/7ueqiIEC-g4

Or these?

The bottom picture, the return one, has your rubber return line that feeds back into it right before the disconnect.

 

[2004LB7]

You need a fuel line disconnect tool like this one

https://www.napaonline.com/en/p/BK_7769081?cid=paidsearch_shopping_dcoe_google&campaign=GSC-Catch-All&campaign_id=6478877959&adgroup_id=79272987338&adtype=pla_with_promotion&gclid=Cj0KCQjw1rqkBhCTARIsAAHz7K3vQhWJUvM7s2bcRSoB9_7QqRvOnGCima-EokR8FyjINcDSS0z3mSkaAhV_EALw_wcB&gclsrc=aw.ds&

Or these

Source: https://youtu.be/DvngvwOy2ns

 

[StephenZ]

Yeah I got those, it’s not the quick connect.

It’s where the circled end goes into the hard return line portion, just before the quick connect. They sell the return line just as pictured, except I have no clue how to remove the rubber portion from the hard line. I’ve pulled on it from all different angles.

 

[Ron Nielson]

The FPR exceeds my DPFR, EFIlive says around 26k at maximum while cranking, starts at 0, and gradually goes up to desired and then continues to climb to around 25-26kpsi,

Cranking fuel pressure shouldn't be 25-26kpsi. It should be 5-6K at cranking speed. That sounds to me like the FPR is not plugged into the harness.

More information here https://oregonfuelinjection.com/ser...gnostics-repair/chevy-gmc-diesel-diagnostics/

 

[2004LB7]

Cranking fuel pressure shouldn't be 25-26kpsi. It should be 5-6K at cranking speed. That sounds to me like the FPR is not plugged into the harness.

More information here https://oregonfuelinjection.com/ser...gnostics-repair/chevy-gmc-diesel-diagnostics/

But that shouldn't prevent it from starting, right?

 

[2004LB7]

Yeah I got those, it’s not the quick connect.

It’s where the circled end goes into the hard return line portion, just before the quick connect. They sell the return line just as pictured, except I have no clue how to remove the rubber portion from the hard line. I’ve pulled on it from all different angles.

I think those ones are glued on

 

[Ron Nielson]

But that shouldn't prevent it from starting, right?

If the engine had actually been running, probably. The OP did say 'It will hit occasionally but nothing more. ' As much as anything I just wanted to point it out as something out of line with what I would expect from a newly rebuilt engine. I didn't think a cranking engine could make that much pressure, but if you crank enough, why not.

 

[ikeG]

That hose is extremely tight fitment but its just a barb. You can slice it to remove it. Even if you reuse that line, there's more than enough line to get it to reconnect.

Sent from my SM-G960U1 using Tapatalk

 

[StephenZ]

That hose is extremely tight fitment but its just a barb. You can slice it to remove it. Even if you reuse that line, there's more than enough line to get it to reconnect.

Sent from my SM-G960U1 using Tapatalk

thanks, I’ll give it a try when I get in from work today.

 

[StephenZ]

I ordered a new return line shortly after starting my rebuild. GM had said it was ok back order though - don’t see how it’s on back order but whatever.

Checked status today with the dealership, and they said it would be here Wednesday morning. So worst case scenario, if I screw up the current one, I have a replacement line arriving Wednesday.

 

[StephenZ]

If the engine had actually been running, probably. The OP did say 'It will hit occasionally but nothing more. ' As much as anything I just wanted to point it out as something out of line with what I would expect from a newly rebuilt engine. I didn't think a cranking engine could make that much pressure, but if you crank enough, why not.

Correct, if cranking long enough - you can continue to go till you max out around 25-26.5k psi. Once it goes over 7k I don’t crank anymore, plus I’m past the point of priming the fuel. I’m leaning towards the back pressure not being correct since they are piezo (May have butchered the spelling) injectors. System sat dry for nearly a month, with the ends masking taped off so dirt divers couldn’t build nests in them. All lines were put in ziploc baggies as well.

Ideally nothing has changed except for the engine rebuild - with Mahle Delipped stock pistons, rings, all new bearings, timing marks lined up according to Haynes manual, tuning stayed the same, considering I kept my CP3 conversion. So theoretically it should have been a matter of priming the oil pump, bleeding air, and starting. On my LB7 I had an instance where I had to prime for what seemed like an hour, and eventually it started. I’ve replaced the injectors in this LML before it blew a hole through the #7 piston and had to do very little priming.

Hopefully the back pressure on the injectors will do the trick.

 

[2004LB7]

While someone cranks over the engine, can you take a pair of pliers and gently squeeze the return line and see if it fires?