No codes, extended crank time, worse during colder weather. FPR Duty Cycle Question

[Mudtoy]

Hello all, new here, customer's truck higher mile 2015 Ecodiesel. Truck just got back from dealership, same problem as before. Basically, they told him to spray a little ether in it to get it going sooner. Unbelievable! Originally truck cranked a little longer than is normal during summer months. This has been going on for some time and as mentioned, takes even longer in the winter. The lift pump was replaced a couple of years ago at dealership and the high-pressure pump was replaced this last month at the dealership as well. Has new DPF and filters as well. Lift pump pressure and volume were tested to verify it's good.

We are a general repair facility and do a fair amount of diesel work. We use a Snap on Zeus scanner and are familiar with common rail theory. To get right down to it, I can see that desired/target fuel pressure is about 4000 psi cranking and looking at the data while cranking, the actual pressure is only getting to about 1500 at about 38% duty cycle. Having diagnosed other common rail systems in the past, the duty cycle should increase to build more pressure until target is reached. Once Target pressure is achieved, duty cycle drops to maintain desired pressure while running.

Shouldn't the duty cycle be higher while cranking? I think the default on other trucks is about 65%... I looked for a way to command it on the scanner and couldn't find a function. On an older Ford we would full field the FPR briefly to see max pressure output of pump.

Any help is appreciated.

 

[TC Diesel]

First HPCR do not conform to logic, they conform to experience. The long cranks are likely related to return rates to high Injectors or the Electronic PRV is malfunctioning. Unplug FCA and see if it starts? -0 Volts is default WO FCA.

 

[Mudtoy]

Thanks, I was suspecting injectors as well. Just curious as to why the duty cycle doesn't ramp up. Michell has very little info on this fuel system.

 

[TC Diesel]

It likely a fail safe cycle. VM has electronic limiting operations.... which I don't care for. It just another gizmo to fail and requires another gizmo to test.

 

[Mudtoy]

Appreciate your time, gonna get a scanner on it in the morning and pull the plug on the FCA. Will report back.

 

[Mudtoy]

It likely a fail safe cycle. VM has electronic limiting operations.... which I don't care for. It just another gizmo to fail and requires another gizmo to test.

Further research suggests the high pressure pump is at max duty cycle for 30 seconds during cranking. Having done the lift pump pressure and volume test the diagnostic flow chart takes you to fuel injector return rates as the next test. This seems to require a special tool worth $2000 dollars. Have you done this test by any other method than purchasing this tool?

Thanks for your time.