LML LML fuel sys info:

[McRat]

Two Fuel Rail Pressure Regulators (FRPR) are used. FRPR1 is still located on the injection pump as on previous Duramax engines. FRPR2 is located on the front of the left fuel rail. This solenoid is normally open. The ECM supplies pulse width modulation to change the duty cycle of FRPR2 to control the amount of fuel returned to the fuel tank.

The new Duramax engines are equipped with Bosch piezoelectric fuel injectors. These injectors operate a high voltage, indicated by the orange color of the injector harness.

IMPORTANT: Do not make contact with the fuel injector harness, ECM or fuel injectors while the ignition is in the On or Run position. Use certified insulated gloves EL-48286. These Class 0 gloves are rated at 1000 v. Check for functionality and check the expiration date of the gloves.

The ECM supplies high voltage and provides a ground. Voltage is supplied up to 160v at 20 amps, and can peak up to 240 v. This causes the injector to open. The capacitor discharges through an injector for initial opening and holds open with 12 v.

Injectors are grouped into four pairs: 1-4, 6-7, 2-5, and 3-8. If a condition is detected in a group, that group is disabled and a DTC is set.

On the fuel system return side, the return lines are now equipped with snap-in connections. The return side is under pressure.

A pressure retention valve maintains 0.4 to 1.1 mPa of pressure within the return lines to provide proper fuel injector operation.

TIP: Improper injector return line pressure may cause a no-start or performance concern.

If the engine runs out of fuel, or if the fuel system is serviced, the system must be primed. After priming, a feed line from the low pressure side of the pump backfills the injector return lines. The feed line will also backfill if pressure falls below 0.3 mPa in the injector return lines.

From:

http://www.sandyblogs.com/techlink/2010/06/new-duramax-diesel-engines.html

 

[Chevy1925]

Interesting, so they did away with the FPRV and put a FPR in its place from what i gather? boy if only EFI was setup for LML, it could make for interesting tuning

 

[McRat]

What I find interesting is that it uses retained pressure from post-injector fuel to assist in closing the injector. Or at least if I'm reading that right. About 150 PSI doing the math in my head. The LB7-LMM don't have pressure in the return lines.

And that the high voltage, up to 240v, is a spike to get the injector to start to open, then it holds it open with 12v.

 

[Chevy1925]

What I find interesting is that it uses retained pressure from post-injector fuel to assist in closing the injector. Or at least if I'm reading that right. About 150 PSI doing the math in my head. The LB7-LMM don't have pressure in the return lines.

And that the high voltage, up to 240v, is a spike to get the injector to start to open, then it holds it open with 12v.

Yes thats also interesting, i could see that for closing but it then makes it harder to open, so i ASSume thats why they have such a high spike to open the injector. the LBZ/LMM dont spike their injectors do they? or is it a constant 24v to open them?

 

[Bryce418]

Interesting, so they did away with the FPRV and put a FPR in its place from what i gather? boy if only EFI was setup for LML, it could make for interesting tuning

Correct there is no high pressure fprv on a lml/lgh.

 

[DIESELMAFIAPER.LB7]

240v?? Wow didnt some people say high voltage was why lb7s are so bad with injectors? Cant remember but i thought some blamed voltage that they fired at...

Very interesting info though

 

[Chevy1925]

240v?? Wow didnt some people say high voltage was why lb7s are so bad with injectors? Cant remember but i thought some blamed voltage that they fired at...

Very interesting info though

yeah i was thinking the same. i think the LB7s fire off a constant 96v and dont ramp up or down like the LML. What id like to know is just how long the injector actually stays at 12v after the "up to 240v" initial shot and why it is worth that kind of effort to drop teh voltage. Or is the initial voltage gauged upon rail pressure so as pressure goes up, the initial firing voltage goes up? very interesting stuff

 

[McRat]

yeah i was thinking the same. i think the LB7s fire off a constant 96v and dont ramp up or down like the LML. What id like to know is just how long the injector actually stays at 12v after the "up to 240v" initial shot and why it is worth that kind of effort to drop teh voltage. Or is the initial voltage gauged upon rail pressure so as pressure goes up, the initial firing voltage goes up? very interesting stuff

It was a long time ago, but IIRC, when I was doing cyl pressure testing on Big Blue (LLY), the injector voltage stayed up. I just don't remember the voltage. Or much of anything else about the project.

 

[duratothemax]

actuating a piezo transducer is completely different from activating an electromagnetic solenoid. Fingers has more of the nitty-gritty technical details about this.

They arent even CLOSE (electrically), when it comes to driving them.... You really cant compare them to LB7/LLY/LBZ/LMM injectors in any way.

 

[duratothemax]

boy if only EFI was setup for LML, it could make for interesting tuning

Why do you say this?

 

[duratothemax]

What I find interesting is that it uses retained pressure from post-injector fuel to assist in closing the injector. .

They also need pressure in the return line system because thats what the 9th injector (for regen) is tied into....

 

[Fingers]

Return line pressure actually helps the injector open.

 

[whitetrash21]

Injectors are grouped into four pairs: 1-4, 6-7, 2-5, and 3-8. If a condition is detected in a group, that group is disabled and a DTC is set.

Whats the point of this??? Why not individual conditions for each injector. Doesn't that make it harder to diagnose any issues that injector specific???

 

[duratothemax]

Whats the point of this??? Why not individual conditions for each injector. Doesn't that make it harder to diagnose any issues that injector specific???

Its just the way the internal electrical architecture of the ECM is designed...

When Bosch was designing the ECM and sourcing driver "chips", maybe they could only find drivers that were grouped in pairs? Or they did it to save space on the circuit board?

Either way...its only TWO injectors...how hard is that really to diagnose?

remember LB7/LLY's had FOUR injectors per "positive supply bus/rail", and nobody really has any huge trouble diagnosing that...

 

[ripmf666]

http://www.duramaxdiesels.com/forum/showthread.php?t=29599

http://www.duramaxdiesels.com/forum/showthread.php?p=517747#post517747

 

[McRat]

Something seems odd or a misprint.

Henry's link says the injectors use 250v x 20 amps. That's 5000 watts, or about 7 hp. That over 400 amps at 12 volts. Think alternator the size of a soccer ball.

That's got to be very brief discharge, it can't be holding that current.

 

[quadracer37]

i think the cp3.X? Is pretty interesting with the dual hi pressure outlets! :woott:

 

[coker6303]

Something seems odd or a misprint.

Henry's link says the injectors use 250v x 20 amps. That's 5000 watts, or about 7 hp. That over 400 amps at 12 volts. Think alternator the size of a soccer ball.

That's got to be very brief discharge, it can't be holding that current.

Has to be a capacitor somewhere

Sent from my ADR6400L using Tapatalk

 

[ripmf666]

Has to be a capacitor somewhere

Sent from my ADR6400L using Tapatalk

Yes have to find were I save the gm info its built into the new ecm's.

 

[whitetrash21]

Its just the way the internal electrical architecture of the ECM is designed...

When Bosch was designing the ECM and sourcing driver "chips", maybe they could only find drivers that were grouped in pairs? Or they did it to save space on the circuit board?

Either way...its only TWO injectors...how hard is that really to diagnose?

remember LB7/LLY's had FOUR injectors per "positive supply bus/rail", and nobody really has any huge trouble diagnosing that...

I thought the lb7/lly were individual. Am I thinking of something different when I think of being able to control individual injector vs the ecms detecting something amiss and setting DTC's???