Hey there,

I have the 2004.5 Ram Cummins, and any time the temp is below 60, I have power loss. The truck will start fine, and run fine for a few minutes, then start to slow down. If the temp is below 30, I'm lucky to be able to maintain 45mph. When it is having these issues, the fuel pressure in the rail can drop as low as 2500 (yup, hundred, not thousand). I still have 12-14 psi from the lift pump. The rail pressure will just start to drop slowly until it bottoms out. The colder it is, the worse the problem is. I changed the lift pump (before I bought gauges), then replaced the injector pump. I am told that injectors would either be bad (leaking) or good (not leaking), and would not slowly lose pressure. Also, If I can keep the truck running long enough (stay out of the throttle, but keep moving), it will eventually (20-30 mins) free up and start running with power again, and the rail pressure will slowly rise back to normal.

Sorry for the long lead in, but I am wondering, since the problem is specifically cold related, if perhaps my problem is the fuel heater. The relay is good, and even when the problem is occurring, it still clicks when you remove it (making me think the computer still wants the heater), but the heater is only drawing power for the first few minutes. After that there is no draw on the lines feeding the heater.

my question is, should the fuel heater be on all the time when the temp is cold, or is it only at startup? And, would the fuel heater cause the problems I am having? It really does feel like fuel gelling, I use anti gel, just not sure it is enough without the heater?

 

Are you talking about the fuel heater inside the fuel filter bowl assembly???

http://www.dodge.com/bodybuilder/200...tionsystem.pdf

According to the wiring diagram on page 34 of 46, the fuel heater is always ON when key RUN.

 

I would try to replace the fuel heater relay if the heater came on for a while and then went off.
The relay coil took too much current and the 7.5A PTC increased its resistance (and hence the relay dropped out) to protect the other electric circuit.

 

I would replace the rail relief valve because you have a rail pressure problem. You could also have some loose crossover tubes going to your injectors. When they are cold, clearances will open up. When the engine get's heat in it they the clearances will tighten up.