Betsy purchased a brand spanking new dodge 3/4 ton 4x4 to pull her 5th wheel, five years ago .

Her son has been a mechanic for Caterpillar for 16 years.

Since year one, she has waited 7 minutes after start up before putting the trans. In go.

Do most diesel drivers do this ? From a cold start.

I can't speak to the automatic transmission as my Dodge 2500 Cummins is a manual, but I will wait a bit after starting before driving.

Warm weather - a couple of minutes.

Cold weather - at least five minutes or until the winshield is thawed enough to scrape clean.

I also let it cool down before shutting off the engine. I like to see my EGT gauge come down to 400 degrees for a minute or two before shutting down but I don't know if that's even a consideration on the newer engines.

quote:

Originally posted by bendable:
Since year one, she has waited 7 minutes after start up before putting the trans. In go.

Do most diesel drivers do this ? From a cold start.

No.

If I did I'd be late for work every day. Seven minutes of warm up? Seriously?

Once the dummy light goes off, start up and away you go.

No. Oil pressure stabilizes and I go. If I was pulling my 5th wheel and it was already hooked up and cold start I would let it idle a bit longer like a couple of minutes. I'm also in the habit of letting EGTs come down before shut down but have no evidence that it's necessary. I've been with the FD for 25 years. Alarm goes off, it's fired up and off we go. Pull in and shut down. I haven't heard of any turbo coking or engine issues from what we do. My truck is treated way better than what goes on at work.

At a flat idle? No way! Never flat idle a diesel engine for extended periods of time as fuel washes the cylinders and ends up in the oil. Seven minutes to "warm" up the engine is crazy. That is just a waste of fuel and not generating much heat anyway. I'm not saying get in and put it in gear before the starter stops spinning, but seven minutes is definitely a waste of fuel.

Not needed.
My Freightliners and Internationals go key on, engine light off, start and go.
Cooler weather and I wait for the intake heater light to go off and start from there.
Only time I think about letting it run a couple minutes is in below 0° weather.

Define cold in “cold start”. Below about 50f, I’ll let my truck idle for a few minutes when I’m using conventional oil. The engine seems sluggish for the first few miles if I don’t. The transmission hit 140f after 7 miles and only 180f after the next 7 miles back.

Since you mentioned a 5th wheel, I’m going to guess we aren’t talking freezing cold since most campgrounds shut down before then. When we are camping, I don’t wait at all because it takes 5 minutes to get hitched up anyway.

Back when I had a mechanical diesel without glow plugs (CAT 3406B), it would take five minutes or so to get all the cylinders firing well. That was when it was 10° or below. Now that all trucks are computerized, it’s really no time at all. In an engine with glow plugs, it’s start and go.

It’s a pickup, not a locomotive.

I have a couple of large diesel engines that I run everyday. They do idle for about 10-15 minutes just because I'm letting the air conditioners cool the doggone things down so I don't sweat to death while driving.

On my International, I started it and when the air pressure alarm stopped, good to go. On shut down,
I allowed it to "idle cool" the turbo before shut down.

If it’s a 5 year old truck that she’s letting idle for 7 minutes every time she starts it then she’s actually doing far more harm than good. Modern diesels don’t like to idle for extended periods and doing so causes buildup in all the exhaust treatment systems, which is about the only weak link in modern diesel engines. Unless it’s super cold and I haven’t plugged my block heater in, I start my truck, let it idle for maybe 30 seconds and go. If I haven’t plugged in the block heater and it’s super cold then I’ll let it idle for maybe 90 seconds from the point that the idle smooths out, probably not more than 2 minutes from when I turn the key. Modern diesels inject diesel at such a high pressure that it’s almost combusting when it’s injected in the cylinder. Extended idling does more harm than good.

That would be quite awful if we had to let our ambulances warm up for 7 minutes before responding to a call.

Chris

quote:

Originally posted by petr:
At a flat idle? No way! Never flat idle a diesel engine for extended periods of time as fuel washes the cylinders and ends up in the oil. Seven minutes to "warm" up the engine is crazy. That is just a waste of fuel and not generating much heat anyway. I'm not saying get in and put it in gear before the starter stops spinning, but seven minutes is definitely a waste of fuel.

Agreed, I would be worried about cylinder wash. When the engine is cold some diesel is not burned up. This washes the oil from the cylinders causing wear and thinning out the oil. Some older diesels took a while to warm just idling so it exacerbated the problem. I’d take it easy for a mile or two but would not idle.

I have a 7.3 diesel and I can tell by the sound of the engine after I start it if it is ready to go or not.

The engine tends to smooth out about 30-60 seconds after starting indicating to me that the oil is circulating as it should and it is ready to go.

[QUOTE]Originally posted by petr:
At a flat idle? No way! Never flat idle a diesel engine for extended periods of time

Have you ever been in a truck stop at night? If it's hot or cold there are a 150
trucks idling their engines for ten straight hours.

quote:

Originally posted by petr:
At a flat idle? No way! Never flat idle a diesel engine for extended periods of time

Have you ever been in a truck stop at night? If it's hot or cold there are a 150
trucks idling their engines for ten straight hours.

Flat idle, not high idle.
Can you bump up the idle on diesel pickups?

Most semis do not use the trucks engine when parked for heating and cooling these days.
We install quite a few aux power units. Battery, small diesel 3 cyl and even swamp coolers.

Most fleet rigs have a 5 minute idle then they shut off, which is a pain in the ass because you have to keep blipping the throttle.
Some have a high idle override where they won't do that if they want it programmed that way.

When drivers have a gripe about fuel mileage and it's requesting regens all the time I pull up the fuel data.
Nearly every time the idle time is over 50% and it also shows how many thousands of gallons of fuel was burned to do so.
Multiply that by the current cost of fuel and wow.

I reset the fuel data, hand them the printout and tell them to stop idling the truck so much.
They usually burn more fuel idling than what an aux unit costs.

quote:

Originally posted by Schmelby:
[QUOTE]Originally posted by petr:
At a flat idle? No way! Never flat idle a diesel engine for extended periods of time

Have you ever been in a truck stop at night? If it's hot or cold there are a 150
trucks idling their engines for ten straight hours.

Those engines are already warmed up.

Lt CHEG brought up a good point about the emissions components of a modern diesel; one that I’ve learned the hard way. Unburned fuel gets catalyzed by the diesel oxidation catalyst (DOC) and the door from burning diesel fuel gets trapped by the diesel particulate filter (DPF). When the DPF gets full, the engine runs an active DPF regeneration cycle converting the soot to ash. It does this by injecting fuel in front of the DPF, the fuel burns and heats the ceramic honeycomb matrix the DPF is made out of really hot. It’s similar to running a cleaning cycle for your oven or running your grill super hot to clean the grates.

The issue is that you have to drive the truck at least 20 minutes above 35mph for the regen to complete. Otherwise, the DPF just fills back up and the engine will call for another regen. Eventually, the DPF becomes to clogged for the regen to work and then the DPF needs to be replaced. It’s over $4,000 on my truck. Unlike the big diesels where the DPF is a separate part that can be sent off to be cleaned, the one on my truck is welded in one unit along with the SCR and the DOC.

Short trips, stop and go traffic, and idling are not good for the emissions systems on these engines (the pickup trucks).

Glad I asked,
Seemed a bit excessive for a non commercial vehicle.

I know zero about diesel motors.

What does not make sense is,
The kid, her son was brilliant in school,
Went from washing trucks too top welder/ engine mechanic in five years.

I know nothing about diesel trucks. But the question I have is: Who the heck has 7 minutes to spare every time they start a vehicle?

Nope!
Maybe 7 seconds or so depending on the ambient temps. As stated above an idling diesel doesn’t generate much heat. It’s best to drive it conservatively for the first couple of minutes if you can, then go about your day.

BTW, I’ve owned over 20 diesel machines from 3.0 to 12 liters. Currently have 2.