2005 Silverado Duramax LLY Crank No Start, please help

shirazdrum

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Sep 9, 2020
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Hi guys,

I started my truck , a 2005 2500HD Duramax LLY to warm it up after a few days. It started right up with no hesitation. I went to get in after a few minutes and it died. I cranked but it wouldn't start. and it's been 5 days now. Here's the list of things I checked and I know:

1. Batteries are fully charged and I have a charger running constantly to make sure.
2. Filter is new (changed twice) and filter head and pump bulb are in good order and rock hard after 2 pumps. No visible fuel leak anywhere and no air in the low system.
3. FRP Fuel rail Pressure shows above 15000 PSI cranking (assuming rail pressure is good).
4. RPM shows about 130 RPM while cranking (assuming crank sensor is good)
5. FICM Fuel Injector Control Module wirings are in good order, no cuts or breaks and both big connectors receive ignition 12v and both have grounds. I opened it and no sign of burn or water damage.
6. Injectors 2 & 7 are both ice picked and connected.
7. All fuses and relays are in working order.
8. I disconnected the FPR fuel pressure regulator and still no start.
9. There was never a RPM surge before.
10. there are no codes at all. If I keep cranking it until it cuts off the power after 30 seconds, I managed to get it to throw two codes: pending P0611 that never saw again and P0090 but never both at the same time. And the P0090 was because I disconnected the FPR.
11. I've checked every wire on this truck from ECM to FCIM, no cuts, no broken wire.
12. It's not a security issue, the light never stays on.

To me it sounds electrical. We have air, fuel?, timing (I hope) and compression. It doesn't even sound like that it want to start, no fumes anywhere and the exhaust is bone dry. I broke down and sprayed wd40 down the intake and she runs for a split second, so that tells me that the injectors are not opening up. The fuel pressure is plenty so it has to be electrical.

Please help as this is a farm work truck and the animals are going hungry. I'm stuck down in South America for Covid-19 and there are no AutoZones that I can throw parts at it. I have a OBDII scanner, no TECH 2 or fancy things but do have a fully stocked shop here.
 

shirazdrum

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Sep 9, 2020
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Wires look visually good, nothing disconnect or broken but as far as testing it no.. wouldn't it throw a code?
 

2004LB7

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Dec 15, 2010
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Sounds like maybe the FCIM is dead. Have you tried disconnecting the batteries and waiting for a few minutes then reconnecting them? See if it will reset any errors
 

shirazdrum

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Sep 9, 2020
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Batteries have been disconnect several times to no avail.
I also checked every wire coming out of the ECM, FICM and nothing is broken or cut as far as I can tell. I opened up the FICM, it's clean as a whistle with nothing out of ordinary looking at it with magnifier and taking macro pictures.Took off the fuel line from the outlet of the filter housing and steady flow of fuel is coming out. I put the shop vac on the inlet of the injection pump right before the schrader valve on the hard line and nothing comes out!. There should be fuel in the cp3, all the injector lines and the rails!

Is it possible that the fuel pressure regulator is stuck open or closed and blocking the flow? still there are no codes and my scanner is reading high fuel pressure on the rails, and when i disconnect the regulator, the pressure goes up to high 20K.
 

2004LB7

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Dec 15, 2010
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If you crack an injector line open and crank the engine over do you get fuel out of the line? You said earlier that you read 15k psi while cranking? That seems unusually high. If it is true then you have no restrictions with the fuel and your cp3 is likely fine. If the pressure regulator is stuck, then it is stuck open and it should still start.
 

shirazdrum

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Sep 9, 2020
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If you crack an injector line open and crank the engine over do you get fuel out of the line? You said earlier that you read 15k psi while cranking? That seems unusually high. If it is true then you have no restrictions with the fuel and your cp3 is likely fine. If the pressure regulator is stuck, then it is stuck open and it should still start.
I'll try that now. I'm taking off the entire engine harness, removing the loom and going over every wire one by one right now. Then i'll pull all the glow plugs and check of injector mists. changing all fuel lines to transparent lines and let's see where it goes. You don't happen to know if the LB7 FICM is the same as the LLY? I know that the fuel ports are on top next to each other but i wanna know if their guts are the same. The pin-out look identical. The reason i'm asking is that there are a million LB7 FICM out there and not many LLY that i can find for a reasonable price. The fuel that passes through the FICM is only for cooling, so i can reroute the fuel lines if needed.
 

2004LB7

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Dec 15, 2010
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Isn't there a voltage difference between LB7 and LLY injectors? I think they will swap out and communicate ok but not sure about the injector voltage
 

shirazdrum

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Sep 9, 2020
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I think the LB7 was 90V and the LLY is 48V, but again I've read that LB7 injectors (higher voltage) work on LLY (lower voltage) as well. Now what i don't know is that if LLY injectors work on LB7. I really don't wanna play mad scientist and burn 8 injectors too!
 

TheBac

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Apr 19, 2008
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IIRC, LB7 was 96v, LLY 95V, LBZ 48v. Been a good long while since that thread, though You cant use LLY injectors in an LB7 anyways.....
 

shirazdrum

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Sep 9, 2020
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Thanks Tom. In that case the FICM from LB7 won't work with LLY, as the high voltage drivers are pushing more.
 

TheBac

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Apr 19, 2008
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Like I said, it's been a long while.

ON EDIT: I was wrong. LB7 96, LLY 48, LBZ 24. You guys were right. Not sure why I remembered it like I did. My apologies.
 
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shirazdrum

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Sep 9, 2020
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Here's the update, the FICM finally let the magic smoke out. I went through every wire, every fuse, every connection on ECM, TCM and changed and repaired everything that looked suspicious. After two days of wrapping and looming, finally I cranked the truck. Right away the it threw a P0652 code telling me that Voltage B was out. Checked the fuses and the EDU 25A was blown. Changed the fuse, and it repeated itself. Took off the FICM connectors and checked all the wires for short to ground and there was none. then i smelled the FICM and there it was.

I opened up the FICM just a few days ago and there was no burn mark, no smell,... and all of a sudden we have a blown capacitor. Why, I hope you can tell me. The capacitor is a 40 cent part so i'll take a shot at it and we'll see.
 

2004LB7

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Dec 15, 2010
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Capacitors generally only fail from a few ways. Too high ripple current then the cap was designed for resulting in over heating - unlikely. Reverse voltage - unlikely. Too high voltage - possible.

You may get away with replacing it but I suspect you will find the problem to persist. Capacitors don't generally fail on their own, something causes them to fail. Good luck though. It would be nice if it did work
 

shirazdrum

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Sep 9, 2020
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Capacitors generally only fail from a few ways. Too high ripple current then the cap was designed for resulting in over heating - unlikely. Reverse voltage - unlikely. Too high voltage - possible.

You may get away with replacing it but I suspect you will find the problem to persist. Capacitors don't generally fail on their own, something causes them to fail. Good luck though. It would be nice if it did work
I can't think of anything that would send high voltage to the FICM, the only possible thing is the alternator failing and sending AC voltage.
 

dndj

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Apr 13, 2019
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Those look like aluminum electrolytic capacitors. Many types of electrolytic capacitors degrade over time, have a finite lifetime even when used within specs, and will vent just like your photo shows. Just find some with equivalent or higher voltage and temperature rating, same capacitance, construction. I mail order a lot of my electrical components from Mouser. I would attempt replacing them, not very expensive so there's really not much to lose with trying.
 

shirazdrum

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Sep 9, 2020
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I took the board off and unfortunately it's not just the capacitor, there are a few resistors on the back that are blown as well. I found another FICM and it's on its way south so hopefully that will fix the problem. I'm gonna relocate it to the fender with a big aluminum heat-sink and eliminate the fuel line going through it. I can't imagine how much cooling that little bit of fuel going through the middle is doing, considering that the fuel line passes directly over the engine, under the turbo before entering the FICM and the fact that it's mounted on the valve cover.

I have one question though, are the rubber spacers for the mounts supposed to isolate the ground or are they just for vibration? They look like insulators to me as even the bolts are covered. Right after it blew, i checked with a test light and the case had ground with no plugs attached. But again the fuel line that goes through it is metal and it's touching the engine in several places and the diesel is a conductor too! I'm not sure.
 

ZeroGravity58

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Mar 23, 2008
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I moved my FICM on my lb7 and ran it dry without a heatsink for awhile with no problems. It never got hot to the touch. I unbolted the bracket off the valve cover and mounted it where the 2nd battery was. I had to extend all the wiring about 18".
 

DAVe3283

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Sep 3, 2009
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I'm not sure if the case is supposed to be isolated or not. As for running it dry, I've been running my LB7 FICM dry in the stock location since 2015, and more than 40k miles. Not using any heat sink or anything, it's just sitting there. Works great.

Sent from my ONEPLUS A6013 using Tapatalk
 

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