Hi Guys, first time owner of a Dodge, it's a used 2003- 3500 Dodge Diesel! It has about 210,000 kms and I live in northern British Columbia! Here's the problem. For some reason when it goes down to anywhere close to 0 it just wont start, turns over fine, but no signs of it getting fuel or wanting to fire. Plug it in for an hour and it starts every time. Have had it into several shops and on computer but no one has solved what is wrong. Changed the cam sensor, tightened the injection liners, replaced the pre-heat relays, all things I was told it could be with no success. Anyone ever heard of the problem or have some suggestions, not sure what to try next, would like to try and fix myself now as repair bills are killing me. Thanks

 

Have you made sure the grid heater is actually working?

 

According to the Dodge dealership I took it to, the grid heater does work when hooked to the computer, but the question is whether it is working when I go to start it! To me it almost seems like a broken wire or sensor that is telling it not to work, what do you think, ever heard of this problem! And what is your thoughts of wiring a switch direct into the truck and running the pre-heat grid manually?

 

The only thing the computer sees is voltage to the grid heater relay (the solenoid looking thing that is attached to your passenger side battery box.

After that, the ECM has no idea if the grid heater is actually working.

As long as it "sees" the grid heater relay, it thinks the system is good.

I'll give ya my truck as an example. My grid heater is gutted, there's nothing in it. There is no wires going to it either. The only thing I have hooked up is the relay so the ECM doesn't toss a code and light the MIL. But, it thinks the system is intact.

I would HIGHLY advise NOT trying to power the grid heater directly. That thing draws an enormous current. That is THE only reason you have 2 batteries in these trucks. it's the reason that your light dim and the motor bogs down a bit when it's cold.

That's a lot current to be messing with.

 

This is helping me track this problem down big time Coal Train. So now I have to ask you if the pre-heat it's working how do I test the unit to see if it is the unit, a broke wire or possibly some kind of sensor that is not letting the unit turn on? Not sure how the wiring works from the relays so if you could help me out tracing the problem from the relays I would much appreciate it. Thanks again!

 

Okay, you have the relay. This has two small wires that go to the ECM. These do not have the huge current going through them. All they are for is for the ECM to turn switch the solenoid on and off. This is the only thing the ECM sees....it's just looking for the resistance across the solenoid.

Now, there is a fused, heavy gauge wire coming off the passenger battery to one post on the solenoid. Then the other heavy wire runs around the front of the head and goes over to the grid heater. The current runs through the plates in the grid heater just like a hair dryer element. It then grounds on the front side of the heater...that's that short ground wire that goes to the plenum cover.