I found smoke coming from the electrical connection at the fuel heater and pulled it off (after allowing it to cool), found it fried with plastic melted around the metal electrical connection. What causes this and what can I do to ensure that it will not happen again once I replace the wiring harness with new connectors? Does this mean that the fuel heater needs replacement as well? What can I check? Instructions?

 

It means the the wire size is inadequate.
This is a very common occurrence, most people end up permanently disconnecting the heater.
As long as you always treat your fuel with anti-gel additive there is no need for the heater even in the Yukon.
Pull the small relay on the firewall next to the shutdown solenoid relay to cut power to the heater.
You can totally remove the heater easily, instructions are here http://www.cumminsforum.com/forum/94...m-writeup.html

 

i guess the designers and engineers for diesel engines are wrong...i wonder what else we can remove? fuel filters? air cleaners? trans coolers? the list is endless....my point is fuel heaters are needed in cold areas......do an internet search on the function of diesel fuel heaters

 

EDIT.
I have three other CTD 5.9 engines in farm equipment, none came with fuel heaters.
In fact my two Dodges are the only two diesels I own out of over 20 engines that have fuel heaters.
None have ever had filter plugging due to gelling as long as additive is used.

 

most electrical connections that burn up, are the result of poor connections, not undersized wire (speaking of factory wiring). The connections become corroded due to the oxygen in the air, or getting water in the connection and as the conductivity of the connection weakens the resistance rises, leading to HEAT, and it will eventually burn up the connector.

So, replace the connector, and if make sure that the fuses / fusible links are of the proper rating, and if you don't start blowing fuses, then your fuel heater is fine. You could also do a resistance test on the fuel heater, if you wanted to get an idea of how much power it uses. Volts = Volts/Ohms

 

Correction: Amps = Volts/Ohms

 

I have to thank all for your responses. This is a great forum and my first posting. I did some further digging and found the burnt connection was at the temperature sensor, not the heater connection. I realize it should run without the heater working, but living in Canada north of 48 it gets down to below 0 degrees F and I'd rather be ensured that the heater works. I'll review the Cummins site posting as suggested by infidel - for removal and inspection (I'd rather not do without it). As for the wiring it is all original and, plcnut, you are right on the money that it was corroded due to moisture and the like causing the short-circuiting. I will check all circuits and try to run without it in the short term. Meanwhile I will attempt to hunt down a replacement wiring harness and temp sensor locally but likely will not find one. If anyone knows of a supplier with quick service for this, let me know. I'll also let you know the end result of my fix. Would you believe that in the process of inspection, I found a fuel drip from the fuel filter assembly that appears to be coming from around the water-in-fuel drain valve. Is this repairable or does one need to replace the entire fuel filter housing?

 

just remove it, you don't need it

 

Suggest you ask your question here http://www.cumminsforum.com/forum/forumdisplay.php?f=10

You'll find a lot more northerners with years of cold weather experience.

 

And your response is totally useless. If you can't contribute without the critical remarks . . . . don't contribute.

Fuel conditioner is a crutch in this setting. The fuel heater keeps the filter from plugging with wax particles.

As others have said, if Dodge/Cummins didn't think it was needed, it wouldn't be there. Sure some can get by without it.

To each his own.

 

You can get a filter with the water drain in the bottom of it. I don't know what the number is, but that is what I did when the original valve went bad.

 

Thanks again for your help guys, I also checked with the cumminsforum as suggested and yes, there are people out there running diesels without the fuel heater. I've also checked the price on a replacement unit (one can't just buy the temperature sensor and the wiring pigtail as a separate item) at $C287 from Cummins and $C430 from Dodge dealer . With an additional couple of hours or so for installation, I can buy lots of diesel fuel conditioner for winter use. Thus I snipped off the burnt contacts of the fuel temperature sensor and reinstalled the wiring pigtail and I will now drive the truck without the fuel heater working (following the same procedure in adding fuel conditioner that I used on my former Ford 6.9 Diesel for 13 winters).

 

Really cold days we usually know about in advance, just plug in the engine heater {aftermarket} and starts easy.

 

One way to cut down on electrical connection problems is to coat the connectors with dielectric grease. This is a silicone based grease that doesn't conducte electricity in and of itself. It will promote an electrical connection though. Two pieces of metal coated with it won't have corrosion build up on the connection. Don't get carried away with it though. A little goes a long way. A small tube will run about US$4 and a bigger one will run around US$6. I nornally use Permatx that I get at AutoZone so it's available. Sometimes it's called "tune up grease".

 

The problem with the fuel heater on the 12 valves is goes on at 50f and doesn't turn off until 70°.
It is on far too long so the wires heat up and melt.
It's very poor design and far different than the newer engine's fuel heaters.

I've worked on hundreds of 12s up here in the north and almost all of the fuel heater wires show signs of over heating.
I always disconnect them and warn the owners to use antigel additive in the winter. Better than the wires melting though and causing a leak that results in hard starting or even a fire.

They wouldn't even have to use additive if they could trust that station fuel is winterized enough. Sadly trusting the stations is a crap shoot.