In the past week or two up here in New England it has finally cooled off. I have never had any problems starting in any temperature, plugged in or not. Last friday, starting the truck after work it was about 55 degrees and when starting, it took about 3 seconds of cranking before I had to give about 1/4 throttle and it chugg-chugg-chugged to life, with a noticeable amount of smoke until it was running smoothly. After that it ran perfectly fine, no smoke or hesitation.
This morning I went to start in 35 degrees, and it would not start. I turned it over for 2 sessions of about 30 seconds, and it seemed close with the throttle to the floor, but just alot of smoke. I then tried priming the fuel filter housing via the bleeder screw and manual primer on the lift pump and I saw alot of bubbles coming out of the bleeder screw. Once it became almost a steady flow of fuel I tried starting again, and it started within 3 seconds with a little throttle and lots of smoke.
The truck is mostly stock, 150k mi, and I've never had any problems starting in the cold, down to 0 deg. with no heaters. I was thinking fuel lines or lift pump maybe? I don't have a full set of gauges so I can't monitor fuel line pressure, but I do know that once it is running it doesn't seem to defuel untill 27-2800 rpm.

Any help would be GREATLY appreciated. I dont want to wake up 20 min earlier next week to bleed the fuel filter in the cold again.

 

ur lines may possibly be dry rotted on the lift pump itself.... Ive never actually had to deal with anything like this so im not totally sure. From what you descirbe it sounds as though you are losing prime, try checking the feed lined from the fuel separator to the pump itself, i do know mine rotted through and i had lost prime and it was a pita to start. But once running it was ok.... dont know if this will help but good luck

 

I really dont have a good answer as to why, but In my experience, cold starts ( really not that cold 35 and less ) once I was over about 130k, just seemed to be a little rougher. alot of rattling, white smoke.
Plugging in helps but still likes to make a scene when firing up.

 

It really should not be hard to start your truck in those temperatures. It definitely sounds like air in your lines to me. The two most likely culprits are the fuel lines and the fuel heater. If you haven't replaced the lines at this point, you should do it with marine rated diesel hose. The send line is 3/8"ID and the return is 5/16"ID. I would completely bypass the steel lines on the frame and make it all rubber right to the fuel heater.

The other problem area is the fuel heater. I was able to stuff the electrical plug in mine full of thick grease and the problem went away for a little while so I knew that it was the problem. Some people have taken the heater off and put it in a bucket of water and watched for bubbles. If it is your problem, many people remove the heating element and retain the housing with prefilter screen.

I have found that the lift pumps don't tend to go bad but that is not out of the question. Another possibility is that the sending unit on the fuel tank has rotted out.

One word of caution on trying to repair this. If you replace fuel system components and lose your prime but don't fix the air leak, you will have a really hard time priming the fuel system. The best way is usually to pressurize the fuel tank with an air compressor.

 

Yup - sounds like an air leak.

These trucks will start down to -35, -40 solid with no heaters. Although they sure kick up a storm at those temperatures, and I've only done it with syn. in the sump.

 

yea my truck will fire right up no problem untill around 10-15 degrees then you have to use your foot a little to keep it running for a few secconds then its fine. pluggin it in makes it alot easier from my experience warm up time is alot quicker

 

Been there done that,just finally got the hard start fixed this summer.You should replace all your fuel lines from tank to motor as previuosly posted,remove the fuel heater,check the pick up tube in the tank, replace the overflow valve and if it is still starting hard the lift pump. It was the lift pump causing the majority of my problem.
As a side note we actually have four filters in our fuel system,the main filter, the prescreen in the heater,in the tank there is a screen on the bottom of the pick up assembly, inside the pick up assembly there is another screen.
Found that one this summer when i pulled mine apart to check out the draw straw in the assembly.You have to seperate the bottom part from the top part to get to it but it is worht your time as a few guys have found theirs to be quite clogged up since they started checking them.

 

Thanks for the replies. Fortunatley this week it has been very mild so I haven't had any problems starting in the morning. I have never had problems starting in cold weather without plugging it in (coldest was just a hair above 0 degrees F), but I want to make sure I have no problems this winter because I moved to an appartment complex where I can not plug it in if I wanted to, even though I'm quite sure the block heater would not fix this problem. If I can get some time off this weekend I"ll start with new lines, then check overflow valve and fuel heater. I hope it isn't the lift pump, looks like a pain to swap out. Thanks for the help!

 

My vote is lift pump. Actually not that bad to replace. Just did mine last winter.

 

I was just thinking, and I'm curious...what in the lift pump could let fuel out/air into the lines only when its cold out? It only does this when it is below 40 degrees, almost to the nose, and once it is primed again I have NO problems starting, even if I shut it off immediatly and let it sit for an hour or so. This is what makes me think its the lines and/or fuel heater, contract to a point at a certain temperature where any dry cracks open up a little bit to let air in. I couldn't really see their condition today, as it looks like sleeved lines and I didn't have a flashlight on me. Would the overflow valve have any seals that could act the same?

 

I would absolutely say air in the lines. With all the chugging and white smoke when cranking, thats telling me your getting fuel, but there is air in the fuel. When your truck sits overnight, if you have any kind of air leak most all the fuel in the lines will bleed off pressure, when your pump starts pumping it again in, its pumping air in with fuel. Its running fine warm because you have worked all the air out of the lines and have a constant flow now so you are able to maintain a constant supply...even the smallest air leak will cause this.

 

This is exactly why I say its your lines...when the rubber gets cold its going to contract and open up any cracks you may have in your lines.

 

Thicker fuel is harder to pump.
I had very similar conditions until I changed my lift pump.

 

I just changed the lift pump and the pre heater and filter on my 97 12v there is a sight that gives a good picture of how to do it and it really was not a bad time doing it. your 98 12v will be a little different if you have the non skid brake system but should be a easy fix. Buy your parts at the Cummins dealer as the price is a lot cheaper then dodge. I live in Canada and the dodge price was 455.$ and was able to get the same pump from Cummins for 148$ so shop around. http://cumminsdatabase.com/read.php?id=118 Try this site it has good info and hope you have good luck fixing it. Sorry one thing I found that will help with putting the new pump back in is use the one of the intake bolts to on one side of the pump to get it in place the you don't have to fight the pump spring and it will go in alot easer the if you try to use the actual pump bolts one it is started then use your normal pump bolt that is left and titen it back down. you can pm me if you like.