View Full Version : What is the reason for leaving a Diesel truck on during the day?

10-30-2003, 09:56 AM
I have always thought this was something I should know, so I never asked.

Is it to prolong the life of the starting system and engine?

If it's just the starter, screw it, I'm shutting it off. If it's the engine? Hmmmmm .

If it is the engine, can you add a pre-oiler to get the oil going in the motor before you start it?

10-30-2003, 10:54 AM
I don't leave mine running because of theft, but when I do, I don't worry about it overheating,using lots of fuel, etc. I guess I leave it running on short visits because of the starter issue.

Gravel Rat
10-30-2003, 02:51 PM
In the long run is cheaper to replace starters than it is leaving a diesel engine idle longer than 5 mins. If you have to idle a diesel engine bump the rpms up to a 1000 it keeps the engine from slobbering. Otherwise shut the engine down it doesn't need to be idling if you are sitting in one spot for a long time.

Randy J
10-30-2003, 07:31 PM
If I was only going to be inside for a few minutes, I would leave mine running all the time. If I was going grocery shopping or something, I would shut it off. By far the majority of engine wear occurs on startup, so I just chose not shut mine down unless I was going to be a while. Also, with a turbo it's a good idea to get int he habit of letting the engine idle for a few minutes before shut down. It's really not necessary if you driving easy, city speeds. But if the turbo is nice and hot, and you shut it down without letting it cool down, you can coke the oil around the turbo bearings, which will shorten the life of your oil and your turbo.
You can add a pre-lubber, but I've heard horrer stories of those breaking and leaking oil out, I wouldn't trust one.
I found it easier to just leave a key in the ignition and lock the truck up.
Gravelrat has a good point, if it's cold out, or the engine is cold, you want to make sure the diesel engine is idling up around 1000 - 1200 rpm. Otherwise, there will be incomplete combustion and unburnt diesel fuel will make its way past the pistons into the oil. If the engine is warm and it's not too cold out however, it'll idle for a good 20 minutes or so without any problems.


10-30-2003, 10:08 PM
Weak battery :D

10-30-2003, 11:25 PM
Thanks guys,

Now you got me thinking :rolleyes:

1) I gota install a tach.
2) I gota install an oil temp meter.
3) I gota figure out how to gage the temp on the turbo.

OK I don't know how the heck I'm gona do the tach. I'll tap into the idiot oil lite/meter circuit to do the oil temp gage.

Would it be safe to assume that if I add a temp gage at the oil output of the turbo I can get a good idea of the turbo temp? is there a more direct way? would the water output of the turbo give me a better reading?

10-30-2003, 11:40 PM
i love the smell:D

10-31-2003, 12:35 AM
Yeah, you could just leave it running., and keep the keyless entry key with you and lock-unlock that way. Thats what i do.

Gravel Rat
10-31-2003, 12:38 AM
The most important gauges you need are a Mechanical oil pressure gauge, Temp gauge (cooling), Pyro, Boost Gauge. If you have a turboed engine you need a Pyro if you don't have one get one you might melt your engine if your not careful.

10-31-2003, 11:11 AM
Cheryl, you can go to the turbo diesel register and find out more information on extended idling times or do a search here in lawnsite. If I plan on idling my cummins past about 3-5 minutes then I turn on my Idle up feature that bumps the rpm's up to 1200 to keep the cylinders from "washing". Washing is caused by unburned fuel and the additives scarring the cylinders causing premature wear and is not good. Also , it is a good idea after pulling a load and its hot out to let the truck turbo idle down for a couple of minutes to cool. You can go to ford-diesel.com or turbo diesel register for tons of info on this issue. I made a homemade idle up from and old carb actuator plunger that works very well.