All of a sudden my fuel pressure drops to 5-6psi cruising and WOT 0......so i put another new LP just to find out the same problem...New Filter= Helped alittle....installed a Pusher pump and now when bump the key and it reads about 19 PSI instead of 12psi.....Cranking pressure is 5psi......WOT 5psi....idle is 14psi....but if you bump the throttle the pressure drops 1-2 psi......I have the Code P1689 "No Comm between ECM & Inj Pump Mod"........did have the dead pedal with P0237 "Turbocharger Boost Sensor A Circuit Low" but i cleared the ecm and it quit.....Started it this morning with the CEL on and it went into limp mode and would only do 40mph so it went back home (0.5 mile) and hasnt moved since....New LP, Inj Pump and injectors are about a yr old.....I did replace the LP about 2 months ago after i bought the truck...VP44 dieing? Fuel mileage dropped 6-7 mpg and fuel pressure drops like a rock....other than that it runs like normal and starts right up although it did have a light haze of black smoke when at WOT and bone stock<---never done that before.....please help....

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Update:

Cleared the code and it stayed away so far.....went down the road....8psi cruising and get on it and about 3,000rpm i have 0psi....with the new LP and pusher pump

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Well I've called diesel shops in the area and nobody has heard of such an occurence with such rapid psi loss and horrible fuel mileage.....Searched high and low to no avail......checked lines from sending unit to ip....even hooked a pump straight to the ip with a hose in a gas can full of fuel.....still sucks the pressure down when the rpms rise....goes from 12-13 at idle to 6-7 at 2000rpm and under 5psi at 2500rpm or above.....so that would eliminate the fuel line obstruction or obstruction in filter.....any ideas?

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Possible ECM going out? I've been told to check the voltage at the lift pump and while the pump is running.........What's the voltage supposed to be? Anything below 12v bad? Voltage go up as RPM Increases?

 

All voltages are good.....even hooked the pump up to straight 12v and had it running all the time to make sure....New overflow valve......Anybody? I guess I'll sell it to someone that has the money to fix it

 

I've got "P0230 Transfer Pump (Lift Pump) Circ Out Of Range" And if I wire the LP up direct to the battery it acts the same way and wont keep pressure.....does that rule out an ecm problem? Id like to make sure before i get the airdog system and it not work either

 

Edit edit edit, brain fart....