Engine/Transmission (1994 - 1998) Fuel Leak FIXED and a Fuel Heater Question

[Extreme1]

After a couple years of parts checking, parts changing, and minor improvements that always became temporary, the truck no longer loses prime when sitting with 1/4 tank of fuel and is back to starting after turning over about 1/4 rev! Oo.



Yup, it was the connection pin(s) in the fuel heater. It never leaked and was dry when I unplugged it. I thought it might be because of the oxidation between the sediment bowl and the o-ring but after I cleaned that up and disassembled the heater to check it, I could hear the leak when it was under vacuum after I got it all back together.



The heater is now holding down the box of spare parts on a shelf. My question is directed to those who have removed this high dollar techincal marvel (POS) and ran through a winter without it. Can I run without it and not have problems? Bear in mind my location, the fact that it gets -20 here sometimes and I might be up north sledding and can't always plug the truck in.



I replaced it a few years ago because the harness was burned up (could buy ***'y only, no parts available then) and the truck was running bad in the winter. A few weeks later I replaced the fuel solenoid so it could have been a weak pull-on coil that caused the power problem.



One more note: the part number listed in several posts for the heater o-ring (3834185-S) didn't come up as a current number at the local Cummins shop. Anyone have an update?

 

[Joe G.]

The fuel heater does NOT help you start in cold weather. There is no way it can help you start. It will warm fuel after it has been running a while, but not at the start. Better to add an anti gelling fuel treatment to your tank and throw the fuel heater away. Think about it. There is about a quart of cold fuel between the fuel heater and the injectors. It takes a lot of lift pumping to get that much fuel through the system before warm fuel can get to the business end of the injection system. There is no way it can heat all that fuel to help you start before the starter or the batteries die.

 

[DonTX]

So what exactly IS the function of that part? I have had lots of diesels, but never had no stinkin fuel heater on any of them before. .

 

[Extreme1]

The fuel heater does NOT help you start in cold weather.

Thanks Joe, I understand that part. The problem I had a few years ago was that while rolling down the road at -20, power was way off and the milage was BAD. Funny how milage isn't too big a concern when fuel was $1 a gallon.



I do use a fuel additive to keep the P7100 alive. The Bosch pump guy at Sheid's Extravaganza recommended that last year due to the LSD, ULSD makes the pump lifespan even shorter.



I'm looking for someone to say "I tossed that stupid fuel heater a few years ago and haven't had ANY problems, even without fuel additive!" If no one can make that claim, I'll whip out the JB Weld and "heal" the heater element leak for free, no big deal.



Can anyone step up to the plate?

 

[Joe G.]

I can make that claim. My fuel heater has been collecting dust in my collection of bad parts for quite a while now. I never use fuel additive.



It's really easy to remove it. Don't need to mess around with JB Weld. Just remove the pre-filter with a 17mm socket. Remove the adapter screw that holds the fuel heater in with a 8mm allen wrench. Put the screw, heater, harness, and one ring gasket aside. Put the pre-filter back up there. The only hard part is removeing the heat sensor wires from the top of the asssembly. You can do all of this with the assembly in place on the engine.



As long as you have good pressure at the P7100 pump your fuel mileage will not be affected by anything in the fuel system prior to the pump.

 

[HEMI®Dart]

Extreme,



I just went through this decision a couple of weeks ago. My connector (not the connector at the heater itself) See pics in the link, was burned. Joe says to run without a fuel heater (Joe knows his stuff). Evan Beck says Dodge is the only B-Series to use one. He leaves them out too. I was going to leave it out.



But most times I run B20. It sometimes gets cold here too. Not as cold as where you are.



New Fuel heater from Cummins p/n 3907766-S $27. 46. This is the nice new revised one. See my pics in the link.



New Harness & T-Stat Cummins p/n 3843722-S $40. 83



Pre-Filter screen & Gasket 3845400-S $5. 82



Total:$74. 11 Before tax



I figured what the heck, replace it. I won't have to worry when it gets super cold. I am happy I did ( I guess) :-laf



Pic is what I did when I connected the new harness to the OEM factory harness plug. The OEM plug was all burned w/ the terminals loose and melted wires 1" back. I cut if off to where the wire looked OK. Attached Spades to the wires, and loaded the connection w/ die-electric grease. The orange sealing gasket is salvaged from the engine connector. I will keep an eye on it.





Not sure about p/n 3834185-S. I am typing the p/n off of a bag of 3 upper quad O-rings I have. If you need one PM me and I will mail you one N/C.



Tough call on wether to leave it out or replace it.



Link w/ pics from Joe,CumminsPower98 & Me and lots of good info:



https://www.turbodieselregister.com/forums/showthread.php?t=26504&page=1&pp=15&highlight=fuel+heater

 

[Extreme1]

When I replaced the whole assembly (something on here makes *****'y a bad word) around 1999, the heater was shorted (tested the old one yesterday) and it fried the sensor which is part of the harness. So, since the truck was running bad and the part numbers of the heater components weren't available, I replaced the whole assembly. Now since I've diagnosed the heater to be leaking air and losing prime, it's on the shelf. The connection from the heater harness to the main harness seems OK but I'm in no mad rush to reinstall the heater because someone at Dodge thinks it a good idea.



Decision made: I'm going to "repair" the air leak in the replacement heater and keep it on the shelf in case the truck acts up this winter.