Vehicle towed to lot. Verified cranks no start condition. Fuel level only 1/8th tank. Added 8 gallons Diesel fuel #2 grade to vehicle fuel tank. Fuel level now barely past 1/4 tank. Tried priming fuel system manager and bleeding fuel system to see if air in lines is probable cauce of crank no start condition. Primed and cranked vehicle 4 or 5 times to no avail. Proceded to follow engine cranks but does not run flow chart SI document # 1459667 ( see attatchment ). No current DTC's were stored in any Modules. Inspected engine for external diesel fuel leaks, none found. Inspected engine oil quality for signs of diesel contamination. No odor was detected, engine oil was not over full either. No diesel contamination is evident in the crankcase or engine oil. Key on pressure is 1.4 mpa ( within desired specifications ) Ignition 1 signal parameter is 12.2 volts. Mesured diesel fuel sample specific gravity to check for water, gasoline, bacteria, or other fuel contaminates. Fuel checks out OK. 35 a.p.i. is the desired specifc gravity for # 2 grade diesel fuel. Range 32 - 36 a.p.i. Install Diesel low side line Vaccum gage to Fuel system service port. Pumped fuel system manager to 8 psi pressure would however drop to below 2 psi within 2 minutes. Chart directs me to FUEL SYSTEM DIAGNOSIS HIGH PRESSURE SIDE ( see attatched SI document # 1379467 ) Tested fuel pressure relief valve return rate from bank 2 Fuel Rail. No leak from pressure relief valve was noted. Removed Driver side Injector Fuel return line harness fromm injectors. Hooked up Yellow volume test return hoses and proceded with injector return testing to see if an injector returned to great of a fuel quantity. Return rates under 4 ml specification for fuel. ( see chart below ) Ran through same return measurement procedure for passenger side bank of fuel injectors. Return rates under 4 ml specification for fuel. ( see chart below ) .

Cylinder # Diesel fuel return in Mililiters

1 1

2 1

3 2

4 1

5 1

6 1

7 2

8 1

Flow chart indicated to replace Diesel fuel injection pump. Called GM technical assistance to verify findings and diagnosis of vehicle, as well as to see if there are any preliminarys on this sittuation. Mr. _________ of GMAC Technical assistance told me there was no current bulletins or preliminarys that are aplicable. I reviewed my diagnosis with him and he agreed with my decision to replace the diesel fuel pump.

Proceded with disel fuel pump replacement procedure in accordance with SI bulletin # 1380440 ( see attatchment ). Upon fuel pump replacement, vehicle still in same condition, vehicle cranks and does not start. Upon trying to force start with silicone spray... vehicle will run and idle smoothly. The problem is definately fuel related. I contacted GM technical assistance center once again. Mr. ________ of GM Technical Assistance suggested I rework the crank no start flow chart again as the problem could be two fold as a faulty diesel pump and a leaking fuel injector. He also suggesed I Preform a vehicle compression test to verify engine compression as well as eliminate the possibility of injector leaks around the injector pintle into the cylinder and combustion chamber itself. I told Mr.______ that I had succesfully ran the vehicle on a silicone induction and therefore i was certain that compression was not an issue in this case. He suggested @ least glow plug removal to inspect for excess fuel in the cylinder with a potentialy faulty injector. I agreed.

I proceeded with all of the above testing I have listed again, as well as removing the glowplugs to look for excessive fuel vapor. The Fuel return from all eight injectors was 0 ml. No fuel vapor was shown to be coming from the cylinders with glowplugs removed. I checked and rechecked pump inlet pressure @ rubber fuel line to back of injector pump. Suficent volume and pressure were noted. 10 p.s.i. Removed High pressure line from # 7 injector and cranked vehicle over. No fuel whatsoever was emmited from the fuel rail outlet. Which means the pump is not pumping. I called GM Technical assistance again. I spoke to ______ again. I explained the vehicles current condition as well as my testing results. He suggested another new pump, as this one is not working. Ordered new Diesel fuel pump.

Install new diesel fuel injector feed pump to vehicle. Reassembled vehicle and primed fuel system manager bleeding all air from diesel fuel feed line to pump until high volume, bubble free, fuel runs free at pump inlet. Reattatched inlet hose to rear of pump and primed diesel fuel manager to 10 p.s.i. Attempted to start vehicle. Vehicle cranks no start. Tech 2 indicates only 1.4 mpa fuel pressure in high pressure fuel rail. ( 10 mpa is minnimum for starting vehicle ) Removed 2 wire plug from fuel pressure control solenoid located on rear of fuel pump assembly. Used schematic in SI 2000 to perform strategy based diagnostics on solenoid control circut. 11.96 volts provided on purple wire with white stripe, with key on. .002 ohms resistance to ground on yellow PCM controlled ground wire. All O.K. Contacted GM Kansas City Traning Instructor Mr. _____________ for diagnostic assistance. Still waiting on his call...... anyone here got any ideas or heard of anything similar??????

ANY INPUT WOULD BE GREATLY APPRECIATED

Can you pump up the system with the primer? If you put the gauge on it you should be able to see pressure when you prime it and then vacuum while cranking.

Crankshaft position sensor(reluctor)?

yes it primes to 10 p.s.i. yes it sucks down into a vaccum while cranking
problem is not in fuel system low side. Fuel system manager pumps up fine.


Reluctor behind Balancer huh????? Interestingly enough my service manager went to a meeting yesterday and when he discussed this with a GM engineer he suggested the same thing. I confrenced with a few techs in the shop and it doesn't make a lot of sense to us cauce we had it running on silicone spray. I don't see how it could be timing. My GM instructor said it could be timing and the reluctor wheel..... but he said it was a slim chance.

He thinks perhaps it is in the commandment of the fuel pressure solenoid on the back of the fuel injector high pressure pump. ( Third pump means third solenoid, hence it's not the solenoid its self ) He gave me some info on how to check circuts to solenoid.

Have you guys ever seen this or heard of this? Could I be on the right path?

a reluctor wheel or ckp sensor won't stop the high pressure pump from building pressure though. What does the pressure do if you crank it with the fuel pressure regulator unplugged?

Tried unhooking the solenoid electrical connector, it still doesn't build any pressure though. My Instructor said from the LLY book that GM had sent him, It shows that the solenoid is pulse width modulated. It has to be pulsing to allow the pump to build pressure. I guess from what he said in one position fuel isn't allowed into the pump main housing at all, in the other it diverts it to the pump return outlet to the return side of the fuel circut, and as it modulates back and forth there is a passage in the middle that allows fuel to flow towards the pistons in the pump. Like I said , I'm not sure on all of that but thats what he told me he understood from the fuel flow schematical breakdown of the pump in his book.

Tested both circuts for the FRP regulator solenoid, Neither Purple w/ white stripe (supply voltage) or Yellow ( command circut, ECM controlled ground ) showed to be shorted to Battery voltage, or Ground, when unhooked from both the ECM and the FRP solenoid. These circuts tested Fine when isolated.

Tech 2 shows 23% to 24% FRP Solenoid commandment with key on. This is within standard of 20% or more.

The diagnostic chart for DTC 0090 FRP Solenoid shows according to my findings. It needs a fuel pump !!!!!!!! Grrrrr..... some how I don't think this vehicle needs a 3rd pump!!!!!

Im not sure however that the FRP Solenoid couldn't be commanded to a purge fuel mode by the ECM. You would think it would store a DTC though....

anyways I'm gonna work my Po335 Crankshaft position sensor chart and see where it leads me. It could be a Crankshaft position sensor/ reluctor wheel problem that makes the ECM command the FRP solenoid to divert all fuel to prevent bending valves or something...... I know it's kinda a strech but I can't think of anything else at this point.

Lemme know if you guys think of anything else........

If you spray something flammable into the intake and it runs, then it sounds like a fuel delivery/timing issue. Is the fuel return rate, measured say, at the fuel cooler okay?

Removed crankshaft position sensor and checked Reluctor ring for looseness or misalignment. All seems to be in order Reluctor is tightly mounted, free of broken teeth or defects, and is properly alligned. CKP data on Tech 2 shows 120 - 180 rpm durring engine cranking. I don't believe the Reluctor wheel is the problem.

I can't find a fuel return value specification at the return cooler. I think I will remove the AC commpressor from the vehicle and see if I can weasel the fuel return line off of the fuel pump and see what kind of fuel quanity I have returning dirrectly from the pump though......

One more thought; does the voltage check out alright at the injectors?

Yeah.... I don't think it's the fuel injectors. There is no known noid light for these injectors that I know of, let alone a procedure to check them... at least not that GM's SI 2000 program has in it's service tests and procedures. I'm not sure how you would go about it on your own though... all the service training I have had for the Duramax engine shows the fuel injectors to use a 72 volt AC current signal for pulse width modulation of the injectors. Hence the FICM ( Fuel Injector Control Module ) The FICM handles all the high current AC switching as the PCM commands it to... so no high voltage stuff has to make it's way into the PCM.

I did take the return line off of the back of the fuel injector pump to see how much return flow it's putting out. It is quite a large amount, Approximately 50 milileters during a 15 second crank interval!!! I can't find a GM specification for this, but that seems excessive to me. It has to be that damn FRP solenoid. I know it's not the solenoid itself ( been replaced 3 times ) but the pumps seeing fuel, it's not putting anything to speak of out of the pressure side and it's dumping most of it out the pump return.

I believe that the solenoid is the only thing that controls pump flow... Does anyone know of anything else that can divert fuel flow??????

Or of any simmilar case's ( even on the older LB7 motor )??????

Can't be the FPR solenoid, eh? Been replaced three times? If something has killed the solenoid three times, why not four?

Did you check the pressure relief valve to make sure that you are not getting any fuel from it? TAN/TAC whatever you want to call them, on the last one I was talking to them about said you should not see a drop of fuel come from that.

If you havnt checked, I would take off the fuel fill neck, while cranking make sure that the gear is turning, also make sure you also see the nut/shaft turning.

any luck so far????

TAC suggested we try the fuel pressure relief valve, even though I had not found it to be leaking.... only becauce the individual i spoke to said he showed several cases of technicians working every aspect of the crank no start condition and finding nothing... the problem was still the relief valve in several cases though. I replaced the valve to no avail.... the vehicle still cranks no start. I also tried exchanging ECM's with another new durramax on our lot. My trucks ECM would start and run another Vehicle.... so I have ruled out the ECM.

At this point the vehicle is being bought back from the customer by GM..... this was our District Service Mangers call after a general lack of help or good ideas from TAC or our Engeniering represenative. So I guess this is case closed for this one.... I would sure like to know what is wrong with it though...... If anyone has any ideas i will be checking this thread periodicaly in the future.... I do appreciate all your guyz help though.

As the dealership that took the truck in, if GM tears it apart and figures out what was wrong will they tell you? If they do let us know.. I'd hate to have that happen on mine..

Hey, I just filed Lemon Law remedy on my 2005 Kodiak 5500 with the Duramax LLY. It has been in the shop 5 times in 30 days for fuel pressure problems and going into limp mode. Also lost cruise control indicator light on dash. Nothing makes sense. Dealership replaced injector pump, and it failed 45 miles later, back in limp mode and with rough idle. Seeking GMC by back now. Total miles driven, about 1200. Truck made 300 miles once with no apparent problem. I see a lot of post on this site about power and fuel pressure problems with confused diagnostics by mechanics. I think the mechanics are good, but they have a tough problem to figure out.

Yeah.... tell me about it... I'm not sure if we'll get any info on the solution to this problem or not... I'd really like to; it's killing me not knowing!!! The vehicle is still on the lot for now.... Tavis let me know if you hear anything about yours, I'm curious............ circumstances sound pretty similar to my case I'm dealing with.