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Topic: 8.3 Wait to Start (Intake Air Heater) (Read 722 times) previous topic - next topic

8.3 Wait to Start (Intake Air Heater)

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.

Quote
When the "Wait to Start" light goes out the pre-heat cycle is complete. Depress the accelerator pedal all the way to the floor and crank the engine."

I have never pressed the accelerator at all when starting. Reminds me of starting a flooded carbureted engine.
jor
93 225
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Re: 8.3 Wait to Start (Intake Air Heater)

Reply #1 –
Have an 8.3 mechanical 12 valve with 233K miles,starts faster then my Toyota,as soon as I hit the starter.
96 U270 BUILD 4810
85 380SL
Drummonds TN.

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #2 –
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 and Stacey Smith
Motorcade NO: 11973
1997 U295 CSGI 40'..Build No. 5036     
920 Watts on the roof..CAT Power w/fuel Inj. Programmer
2021 GMC Sierra AT4 1500
EX..2015 Jeep Wrangler Sahara
Ex 1990 U280 RSAI 36'..Build No. 3638

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #3 –
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.

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #4 –
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............... ::) 
Justin & Cathy Byrd
1995 U280 "Old Faithful"
36' Build #4673
C8.3 Cummins
Allison MD3060R 6 speed - retarder
Powertech 10KW  4cyl Kubota

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #5 –
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
93 225
95 300
97 270
99 320

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #6 –
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.

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #7 –
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. 
Jerry Whiteaker former owner 96 U270  36' #4831 Austin,TX-Owner Mods LCD TV w/front cabinet rebuild - LCD TV bedroom - Dual Central AC, either can cool coach w 30 amp - Skylights at roof AC openings - Drop ceiling for ducting of AC - Shower skylight white gelcoat/wood/epoxy frame - Air Springs/Shocks replaced - 2014 CRV - 8K Home Solar - Chevy Volt

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #8 –
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.
Toby a 94 u280
Cummins 8.3
6 speed Allison
Exhaust brake


Adopted by Derek and Annabelle

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #9 –
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.
Dub McBride 1996 270

Re: 8.3 Wait to Start (Intake Air Heater)

Reply #10 –
Could have sworn I posted this yesterday but maybe I didn't finish. Anyhow, the intake heater also has a running function:

Quote
  Post Heat Cycle
Post heating occurs as the glow plugs continue to burn for a period of time when the engine is running. Post heating helps warm the engine up faster and eliminates white smoke. Post heating times are determined by the engine temperature upon startup.

I've probably beat this subject to death so that's it!
jor
93 225
95 300
97 270
99 320