I was just looking at some Cummins documentation and came across something of which I was unaware. The engine is an 8.3 mechanical manufactured in 1996. The Cummins Engineering Bulletin describes the Intake Air Heater system and the proper starting procedure.
I have never pressed the accelerator at all when starting. Reminds me of starting a flooded carbureted engine.
jor
Have an 8.3 mechanical 12 valve with 233K miles,starts faster then my Toyota,as soon as I hit the starter.
My CAT fires right up in warm weather.... If it gets down in the 40's needs the engine heater to make her happy.
John
John, news to us, we wait to start, often several cycles (key off, key back on) if cold, but don't go full throttle.
We can start on first crank but did add a normally-closed relay with a dash momentary switch to keep fuel off, so we can optionally run starter a few moments to circulate some oil before firing. Relay disrupts small wire from Aux Start solenoid connected to fuel solenoid pull-up coil.
The intake manifold pre-heat/fuel injector on ours doesn't work. It hasn't worked since I have owned it, put over 30,000 miles on it and it is now at 118,000. The coldest temps that I have tried to start it was the mid 20's, without using the engine block heater (which I try to use if possible). It has always fired up immediately so I really don't see the need to get the system working. maybe one day when I have nothing more important to do............... ::)
I think it's interesting that Cummins recommends that the accelerator be floored. Not sure what the intended effect is though. In addition, the intake air heater has a "when running" purpose as well. Here's the three page document for your reading pleasure.
jor
John, your diagrams help understand our wait-to-start intake heater. I copied them and was looking for a folder to store them, and low and behold found this 20-page Intake Air Heater attachment in my computer.
You may already have it, but it may be a help to diagnose a failed heater.
Throwing in my 2 cents. I'm not a diesel engine expert at all, just having gained a little knowledge from owing one. The part about depressing the accelerator all the way to the floor (from the bulletin) applies when the temperature is below 45 F. The injector pump to the best of my knowledge (please correct me if I am wrong) will not allow a really large amount of fuel to be injected at a low rpm. Opening the accelerator may allow a little bit of extra fuel to be injected that could help during cold starts. Like others I have started my 8.3 at freezing temps, no block heat, without opening the throttle. No problem as long as the chassis batteries are good. No experience with temps well below freezing.
Not sure if this information is in the engine manual or just in the bulletin. Maybe someone will check.
Occasionally when my engine is hot and the outside air hot, I have had trouble getting it to start. Opening the throttle has helped in getting it started. Most of the time though it fires in about one second.
On most diesel engines the throttle doesn't actually put more fuel in per rpm so much as It does advance the timing of the injection.
If you do press the throttle to the floor be sure to get your foot off the pedal the second it fires. Jor knows this but a newbe to diesels reading this thread probably doesn't.
Could have sworn I posted this yesterday but maybe I didn't finish. Anyhow, the intake heater also has a running function:
I've probably beat this subject to death so that's it!
jor