Cold weather fuel delivery issue.

[MBuechle]

When temps are below 20F, after about 5 miles of expressway driving I see my CP3 inlet pressure slowly drop. When it gets between 1 & 2 psi the fuel rail pressure will start to drop from 19 Ksi to about 13 Ksi at which point the CEL comes on with a fuel delivery code. The engine continues to run normally. If I slow down the pressures will recover. If the fuel tank is 3/8 or less, the CP3 inlet pressure will recover to about 5 psi in a couple of miles. If the tank is full it won't. My questions are:

Is the CP3 supposed to be able to supply full rail pressure with <2psi at its inlet? Is there a way to check it's health?

Does the lift pump get week with age? Is it a centrifugal or gearotor type pump? Is it a brushed or brushless motor?

Could microbial growth be obstructing the lift pump inlet screen?

Additional info; I have a Baldwin BF1212 and Donaldson P551313 on the frame. Both have 100 watt heater pads and Neoprene insulation blankets on them. Have a Baldwin PF7977 in the stock filter housing, verified it's heater is working.
The CP3 has 255000 miles on it. Lift pump is factory of unknown age, from looks could be original.

 

[AH64ID]

I would add a anti-gel and see if the issue goes away. If it goes away the fuel heaters are not able to keep up, if it doesn't go away I would suspect the lift pump is getting weak.

The OEM fuel heaters are 300W, so 100W on an exposed filter may not be enough.

 

[MBuechle]

I would add a anti-gel and see if the issue goes away. If it goes away the fuel heaters are not able to keep up, if it doesn't go away I would suspect the lift pump is getting weak.

The OEM fuel heaters are 300W, so 100W on an exposed filter may not be enough.

Tried PowerService anti-gel, no improvement. Filters are insulated:

but, yes, one suspicion is that 100W is not enough to keep up with highway fuel flow rate. The theory being that the fuel warms some during the 3 mi low speed drive to the freeway and then the heaters become overwhelmed by higher fuel flow a few mile down the freeway. I can get 200w pads. 300w is 20 amps, through what looks to be a 16 or 18 ga. wire? I ran 12 ga. down to my heaters, thermostat controlled relay straight from the battery.
Will add, in warm weather if I hammer it, say merging onto freeway, fuel press will fall to 1psi.

 

[AH64ID]

Where is the temperature sensor located? On the heater, or remote?

The CP3 is designed to operate on neg 5 to pos 15 psi, but if your rail pressure is dropping you are hindering flow.

 

[MBuechle]

Where is the temperature sensor located? On the heater, or remote?

The CP3 is designed to operate on neg 5 to pos 15 psi, but if your rail pressure is dropping you are hindering flow.

Temp sensor is on radiator support, above the factory OAT sensor.

 

[MBuechle]

I suppose a thermocouple on the filter discharge line would answer a few questions.

 

[AH64ID]

You could also bypass the thermostat and see if there is a difference.

But I’d suspect the pump might just be getting weaker and has a hard time with cold fuel even if it’s not gelling.

 

[MBuechle]

Actually, it currently is bypassed due to failure. Replacement still sitting on my workbench. I know they are working, I’ve climbed under and verified.