| Author |
Message |
Roy Strickland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 4:08 am: | |
I have a '78 GMC RTS II with Detroit 8v71. WITHOUT ANY assistance (heating etc.), at what temperature should cranking become difficult? (When I first bought the bus in Aug 05, you COULD NOT hit the start switch fast enough for it not to start... I've never seen anything start that fast.) Lately with this colder weather, I have been having to hit the switch 3 or 4 times. (Short bursts, no longer than say 2 or 3 sec. each) I am just trying to figure out just how worn out my clunker is... It always starts for me in the 30's. Hasn't gotten much colder than that yet. I'd like to catch it in the teens and see how she does. What temps does everyone else have trouble starting at with no block heater or anything?? Thanks
RS |
FAST FRED
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 5:57 am: | |
Depending on the age and condition of the engine any time the temp is below 35-40F , the possibility of needing a "preheat crank ) or two exists.
6 -71 seem to be ably to go a bit lower than the 8V but that may be because the same 8D are cranking 2 less cylinders.
Down in the 20's just about everything needs a technique, or better, a block heater.
FAST FRED |
Bill K
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 10:38 am: | |
I think one of the big thing is having good batteries, if she spins over fast it will start better. I also find if I crank for about 15 to 20 seconds and then wait for about that long before trying again it usually will start. I think the fuel is vaporizing in the cylinders. |
Phil Smith
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 10:51 am: | |
Besides the above, Cold weather starting is affected by the size,condition and number of starting batteries.
I used to have 4 - group 81's and my 8v would start in cold wx into the 40's or so. Now that I changed to 2 - grp 81's, it has to be a bit warmer to start quickly.
My engine is under 10k on a fresh kit.
Has a lot to do with how fast it turns over. The quicker you can spin it, the hotter the fuel gets in the cyl and the quicker it will start.
My 2 cents
Phil in Az. - 80' RTS - |
Bob Vandawalker (Rav221)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 12:11 pm: | |
Our 6V92 if NOT plugged in takes many tries before those cylinders warm enough to sustain firing, this is in 10-30 degree weather. Will also smoke like a banshee while cranking (unburnt fuel). All pretty normal for these older engines. When the block heater is plugged in, she fires immediately without a sign of smoke.
I highly recommend a block heater, our is large and draws a bit of AC power. But, you can put your hand on the block and feel the warmth. Also the batteries are on constant charge through the inverter.
Bob V. |
Marc Bourget
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 12:30 pm: | |
Taking Phil's post a step farther . . .
These diesels are compression ignition engines.
The fuel burn occurs because the cylinder temperature, on compression, is sufficient to get the air in the cylinder hot enough to ignite the fuel when the injector squirts.
Since this is a dynamic activity (a "rate" thing - things in motion, more or less) the temperature rise follows "Boyle's Law" which is influenced by initial temperature and the rate "heat" is added to the system by the cranking speed.
[Diesel fuel's partial pressure of vaporization is ignored for this discussion, but the fuel itself is harder to vaporize, stays in bigger droplets and thus becomes harder to achieve a "rate of" burn sufficient to sustain combustion [get it "running"] the colder it gets. ]
If the engine (subject to ring sealing performance) was a variable compression (some swash-plate engines) and to some extent an increase the speed of cranking, you could achieve sufficient cylinder temps to ignite the fuel and the engine would fire off almost as well (quick) as at normal temps
(Cooooldd cylinder walls absorb the heat of compression and "fight" fuel ignition)
Onward and Upward |
Roy Strickland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 1:19 pm: | |
Thanks guys, just from what I can gather from the posts, it doesn't sound like my engine is too worn out cause it is fairly cooperative in the cold weather.
Unfortunately, my smoke under acceleration is blue, not black. Nothing I can do will make it smoke black, but it seems all but too happy to smoke blue.
But like I say, its funny... it doesn't do it all the time, but it has been mostly lately in the cold. |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 1:34 pm: | |
Roy, what oil are you using?
Richard |
John MC9
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 7:09 pm: | |
(Roy's using Walmart 15W40, Richard)
(See the thread regarding the door light) |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, January 08, 2006 - 8:45 pm: | |
Then he must change to the proper oil before he does anything else.
Richard |
Leslie Robinson (Lesrmc9)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 09, 2006 - 12:30 am: | |
A MUST READ FOR INFO ABOUT CF-2 OILS hope these work
http://eolcs.api.org/FindBrandByServiceCategory.asp?ServiceCategory=CF-2
you will have to "play" with these to find you local
distributors
thanks to the following for the above website
DetroitDiesel@yahoogroups.com
TejasCoach Works
also some excellant reading on why to 40 wt cf2 rating
oil as opposed to multigrade oil
http://tejascoach.com/ddcoil.html |
Roy Strickland
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 10, 2006 - 1:34 pm: | |
Well, it's actually got Wal-Mart st. 30 wt. oil for CF-2, but I do have a NEW 2 gallon jug of Wal-Mart 10-40 that I am gonna take back in light of what everyone has said. (It said CF-2 on it too, but I'll still get rid of it.) I wish they sold st. 40 wt. But I actually haven't put it in yet. (Lucky for me)
Thanks guys,
RS |