Big Mac

My early '03 has 143,000 mi on it. At temps below 15 F, my truck does not want to start at all. It turns over, but does not fire. At temps from 25 F down to 20 F, it will start, but barely, then it runs fine. There is never any smoke at start up. If plugged in for 4 or 5 hours, it always starts, right down to below zero. I have no problems starting with temps down to freezing. The lift pump was replaced with a FASS 95 2 years ago. The grid heater has been replaced last year. The Intake Manifold Air Temperature Sensor and MAP Sensor where bad and have been replaced. Currently there are no codes.
My mechanic does not want to start throwing parts at it until there is a problem part identified or a code leading to a problem shows up. Chrysler just says pull, test and replace any bad injectors. Period. My wallet says no. And my mechanic does not see symptoms of bad injectors.
If anyone has suggestions on what the problem might be, they would be most welcome. I just want my truck to start reliably for me when its really cold out and I can't always plug it in, but it seems that this may be too much to ask.

Scotty

I was just dealing with this with an 03 my friend owns. We put an air dog on it and it still likes to crank if its sat for awhile...even plugged in. I am leaning towards injectors leaking down on his truck. He too said he does not want to remove or do anything with the injectors due to the $ involved.
I understand that completely. However, if an injector decides to quit completely or stick open...etc It could be a lot worse and a lot more $.
When we put the air dog on, it did help but theres still an underlying problem of which I think will be resolved with new injectors...later in the spring when his budget allows...hopefully before something gets worse with what he has now.

Scotty

FMB

If you are on original batteries, its time to change. If not, clean termanals and grounds.

BigDave12768

Have you tried? My truck starts easier when I run it http://www.fppf.com/polarpower.asp

Spooler

Get a rail pressure gauge and check it at this temp. You should have at least 5,000 psi to start. If you don't, you have a bad injector or three. Take them out and send them to F1 diesel to have them rebuilt. Hole lot cheaper and you have the tips upgraded as well while he is at it.

ian515

x2. F1 is amazing.

Big Mac

Thanks all for the suggestions. By the way FMB, I replaced both batteries 3 years ago and have been load tested are still good. This morning it was -2 F and I had lots of cranking power. Truck was plugged in and it started right away. I'm positive it wouldn't started without being plugged in though.

Spooler, I'll discuss the rail pressure potenial problem with my mechanic and have him check it to see if it is at or below spec. I'm no mechanic myself so don't understand what is happening if there is low rail pressure. Could you explain how low rail pressure (as influenced by leaking injectors) affects starting when it is really cold out? And why there is no effect when ambient temps are higher? Are there any other outward symptoms that might indicate bad injector(s) too?

As for additives, I use an Amsoil product for water dispersal etc. Also, I buy fuel at brandname outlets which sell winter-grade fuel. I've never had the Water-in-fuel light on nor have I ever seen contanimated fuel drained out of the water-fuel separator. If there is a better product, esp. for use with ULS fuel, I remain open to trying it though.

FMB

The reason I mentioned batteries is I was told awhile back that when they start going bad, there is plenty of juice to crank over the starter, but not enough to run the computer. The starter would run even as low as 6-8 volts, on both batteries, but not the computer which requires higher voltage to start. If the computer doesn't start, it can't tell your injectors to open.

So why in cold weather and not warm? Batteries can give you more power when warm vs. cold. Does heating your block also keep the engine compartment warm enough to keep your batteries warm? I dunno. I guess to test the battery theory, you could NOT plug in the truck overnight and when you go to start in the morning, have someone crank it over as you check voltage "at the battery post" with a good volt meter. Note the voltage if it doesn't start and compare it to the voltage when you check it again after pluggin it in for 4 hours. (Cheap test if you own a meter, and yes, like a load test, but in the cold of morning)

AK RAM

Hmmmm. That just proved it will crank fine with a little heat on it. Sounds to me like you may have a heater issue still; either fuel heater, grid heater, or both. One or both may be working, but not working that well due to age. Couple that with a high mileage engine that doesn't have the best compression any more and you get exactly what you are dealing with when the temps drop. The fix? Plug it in or get an Espar or Webasto heater.

If you had low rail pressure or a bad injector or two, I'm pretty sure you would have more of the regular "bad injector" or "low rail pressure" symptoms, which it doesn't sound like you have. It would be hard to crank whether plugged in or not, which you don't have. You would have lots of white smoke at start-up, which you don't have. Finally, it would do it all the time, not just when the temps drop below 20, which it does not. I would focus my efforts elsewhere. To test the theory, leave the truck in a heated garage or barn or warehouse over night. Probably just ask your mechanic to leave it inside one night assuming his shop is heated. Don't plug the truck in or anything. Crank it the next morning and see how it acts. It should fire right off with no long crank times, no loping, no white smoke, no rough idle, nothing. It should run smooth. If it does run smooth you have a simple "heat" issue.

FMB

Another item to spend money on ($25) is an IR thermometer. To use this in your case, open the hood, turn the key on to warm up your grid heaters, take the temp of the grid heater as it warms up and see how it is doing.

Although this is just another idea, it is a good excuse to buy another tool. I use mine occasionally to check exhaust manifold temps of each cylinder at idle and to check tire temps while on a trip where a hot tire usually means a leaker (low pressure builds more heat) and I try to catch it before it blows apart on the Fox.

longbed

You do not have battery problems. You do not have heater grid problems. What you have are injectors that do not work properly. I also own a 2003 so engine truck and I was plugging it in to start when cold. I replaced the lift pump,fuel filter ,crank sensor , both batteries ,Rail pressure relief valve all in attemps to repair no start under 35 degrees. At 145000 miles even if it was at the time 80 outside it would not start. I purchased 6 rebuilt injectors and installed them. It starts like new. It is 18 out now not plugged in and it will fire right up. Also as a side note my number 6 injector connector tube had a shine on the tip like it my have been leaking. Maybe maybe not but i did put a new one in. Good luck. My no start without being plugged in started at 99000 miles.

Guardrail

The easiest way to check the grid heater is to cycle the key to run with your headlights on. See if the lights dim. That will at least tell you if the grid heaters are cycling on and off. I find it hard to believe that injectors would cause the problem if it starts fine when it is plugged in.

CRToney

IR thermometer can be used to temp exhaust from each cylinder. Higher or lower than normal would indicate a problem. I have one and haven't really check my truck much. They do differ but I don't know how much is too much. Someone else will chime in I'm sure.