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smokey start ups....

interesting info i found on a hummer site:

When cold, two things happen. Both controlled by the temp switch (which is in the back of the passenger side head and accessible easily by removing the engine cover or not so easily from under the truck). One is the fast idle solenoid which is on top of the injection pump. This solenoid just gives a little more fuel and you can do the same thing by stepping on the pedal a little. Opening the "throttle" with the pedal does NOT advance the timing, it just gives more fuel. More fuel is a good idea when cold because there is more fuel droplet area available to ignite. Gerald's stomp is a good idea. The other thing that happens is timing advance. This is low on the passenger side of the pump. Advanced timing produces the louder rattle. Advancing the timing helps combustion with a cold combustion chamber because the fuel gets more opportunity (time) to ignite. It is in the combustion chamber longer. The timing is advanced by allowing the case pressure in the pump to bleed off, this allows the rotating group to spin on the axis and the result is the injection happens a little bit earlier in the cylinder. If your engine has significant miles on it, you may not hear the increased combustion rattle since the timing chain does wear and the result is that the injection timing is retarded.
As others have mentioned, the first troubleshooting is to determine that you have 12 volts on both wires (green I think) when cold. If not, look at the wiring or replace the temp switch. The fast idle solenoid is on top, you can measure the stoke to see if it's working or listen for a click when you apply 12 volts with a jumper wire. BTW, the usual failure for the fast idle solenoid is the very little wire that connects to the spade terminal breaks off and can be soldered back on. The advance mechanism won't necessarily work if there is 12 volts. They stick inside the pump when they fail. To check the cold advance, when it's cold, start it up, then quickly and carefully remove the lower green wire on the passenger side of the injection pump and see if the engine sounds different and quieter and maybe rougher. If yes, then it's working. If not, when the engine is cold again, start the engine and use a jumper wire to apply 12 volts and see if the engine sounds different and louder. It should, and if it doesn't, either your timing chain is stretched to the point that the timing needs to be adjusted, or the advance mechanism is sticking. I think this requires pump replacement. Have the timing checked before replacing the pump. Also make sure the lift pump is functioning properly and the filter is clean before replacing the pump. Always start with the lift pump and filter function first. Many injection pumps have been replaced unnecessarily. All of this is correct for NA engines (DB2 injection pump) for sure. I don't know if the details are the same for the electronic pumps (DB4 pump) on the turbodiesels.
Some other observations:

  1. The prechamber GM 6.2/6.5 will start better than any direct injection diesel in cold weather because the compression is higher which results in more compression heat which ignites the fuel. This statement assumes all other variables are equal. The biggest variable is charge air heating. If the charge air is heated better in a direct injection engine, it can start just as good or better than a prechamber engine like our GM's. The Cummins for sure and I think the Navistar now use a heater grid in the intake plenum to preheat the air instead of glow plugs. My dad is a Dodge guy (poor him) and his Cummins starts fine down to 10 below, but my Hummers start easier and smoother.
  2. I live in Wisconsin. I have started my 93 6.2 na in 35 below zero weather without it being plugged in. It didn't like it (oil pressure was slow to come up) and neither did I, but I had no choice. It fired right up. I mention this so you all know that if everything is working right, the engine will work very well in cold weather. It is much easier on the engine to plug it in, so I do whenever I can if the temp is below 20.
  3. I use a non-alcohol fuel additive with lubricity additive all year.
  4. Normally, I get a little white smoke (unburnt fuel) when I start mine. More white smoke when cold and a little more as the Hummer gets older and the compression is dropping off. Right now, I am troubleshooting a rough start, with lots of white smoke problem. It is intermittent, doesn't happen all the time. My lift pump is on it's last legs and may be the problem. I will replace it and the fuel filter first. The other possibility is the tempswitch is going bad or the advance mechanism in the pump is sticking occasionally.
Click to expand...
 
cegusman said:
Yes you can. Only need to be on for 5 min. most. But I would just hook it up through the switch in the head. Really no reason to have it going to a toggle switch.
Click to expand...

well, i don't have that thing on the back of the head in my truck any more, so i'll need to do a switch.

cegusman said:
There will be 2 spades. I will have see if I can get a pic of mine when I get home.
Click to expand...

i think i'm screwed then, because i only have one spade... :( i'll direct link that pic so you can see it.

DSC00067.jpg
 
okay, so i went out there and figured out that the little black thing pictured below my yellow IP wire is a plastic switch that can be removed. i'm fairly certain this is specific to the high idle.

i pulled it off and found a shaft under it. with a little cross bar through it that can be rotated. i then pulled on the throttle cable and saw that it rotates this shaft and viceversa. this makes me think that the cold advance solenoid is simply that one remaining spade pictured above... i'm going to go put some power to it and fire the truck up and see how much she smokes. :D
 
actually, after reviewing that schematic you posted, i'm wondering if i just need to ground that terminal out?
 
grrr. now i'm just confused. that thing i quoted from the HUMMER website makes it appear that the plastic thing i pulled off is the timing advance....

spinning. :(
 
colbystephens said:
okay, so i went out there and figured out that the little black thing pictured below my yellow IP wire is a plastic switch that can be removed. i'm fairly certain this is specific to the high idle.

i pulled it off and found a shaft under it. with a little cross bar through it that can be rotated. i then pulled on the throttle cable and saw that it rotates this shaft and viceversa. this makes me think that the cold advance solenoid is simply that one remaining spade pictured above... i'm going to go put some power to it and fire the truck up and see how much she smokes. :D
Click to expand...

That is the throttle position/TCC unlock switch for the 700R4. A TH400 has a vacuum switch/regulator mounted in that position.

You have an SM465 right? You won't use anything in that position with a manual tranny.
 
When I get home tonight I can take some good pics that show you where everything is at you need to know. I can send you a temp switch in with the brake parts as well.
 
:woot:

i put 12 volts to the spade that is on top of my IP, right behind that yellow wire that's picture and suddenly i don't have a smokey start problem!! it still smokes, but it's SIGNIFICANTLY better!!! :D :D :D not to mention it's only 32* outside right now - so a little smoke is understandable. :D :D :D

thanks guys!!
 
colbystephens said:
:woot:

i put 12 volts to the spade that is on top of my IP, right behind that yellow wire that's picture and suddenly i don't have a smokey start problem!! it still smokes, but it's SIGNIFICANTLY better!!! :D :D :D not to mention it's only 32* outside right now - so a little smoke is understandable. :D :D :D

thanks guys!!
Click to expand...

That is the correct terminal... I didn't see it the first time I looked at the pics. The black deal right next to it is useless with a manual tranny though.
 
well, i'm glad to know that! in other news, i've been wondering why my truck seems to idle higher than it should recently. when i pulled that little black cover thing, i found that a small piece of black plastic was lodged underneath the throttle arm there and forcing it to stay idling high... :doah: glad i had to pull that sucker off! it made crawling rather too fast. :D
 
On another note, you have a rebuilt motor with the old used IP on it? If that is the case, I would budget out a rebuilt IP in the not so distant future. Then do a professional timing on the motor once that is installed.
 
that's right. and you're right - i definitely should do that. my problem is that i end up saving the money and then there's more fun stuff to spend it on... :doah: i am needing an 8274.... and some tubing... and a dana 60... and...

:D
 
I am missing the temp switch on the rear passenger head on my '83 pick-up. Total mystery as to why it's not there. Paulie never had anything done to it and said the cold advance always worked when he had it. i never removed it...

Anyways, as a temporary fix i wired up a toggle switch and used an existing hole at the bottom lip of the dash for the switch itself. I flip it on for cold starts, and leave it on until the temp guage starts to move (usually about 5 minutes) It does make a big difference.

Rene
 
i am amazed at how much of a difference this makes. don't think i want to start it in the garage on a super cold day still, but even if i had to, I'd be okay. it's about 30* right now, and this thing is starting cleaner from cold than it EVER has, even on an 80*+ day.

thank God for CK5. :D

i should mention that if i had a normal garage, i'd have no problem firing it up in there. however, my garage is 2 bays deep, one bay wide so i have to fire the truck up in the middle of the house. also, i back into the garage, so my exhaust wouldn't get out of the garage before i'd want to shut the garage door.

IMG_7075.jpg


if my ass end was toward the garage door, it would be fine... :doah:
 
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Then you'd be covering Claire's wonder Bug in soot. Soot on the wonder Bug = no nookie...;)

Rene
 
Glad to hear you're making headway on your diesel :D

Lookin' more and more like it'll be IP replacement time for me...
 
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