cold weather and timing

[phantom309]

cold weather starts,. timing etc,.

Well here in edmonton its getting cooler in the mornings,.
seems the truck is having a tough time getting started,.
I have noticed it will really rattle like its supposed to, only after if starts,.
I put this IP on last winter, its the 5068 pump, but i didn't get it timed properly,.just lined the marks,
These electronic pumps, are they supposed to be able to time themselves?
or does that only happen after its running, and can bump its own timing as it needs it? The pump needs adavanced physically for better cold starts?
From what i read physical location isn't that critical? or is it just critical for cold starts?
I,m a little confused here,.

Nick
duraterms still the best?

[phantom309]

I looked at another 6.5 truck today, its a 95, so obd1 as well,.
when it starts it lights off quick and noisy compared to mine,. guy says he bought it that way,.i wanted to borrow the ecm to see if mine would do the same thing, but the guy is uncomfortable about that,.
Mine goes noisy,. (cold advance i,m assuming) about 2-5 secs after starting,.
Do these pumps revert back to 0 degs when they shut off?

[Yukon6.2]

Hi Phantom309
Do'es it smoke white when it starts?
I belive my tow truck has a fuel leak,when it starts it runs quite,smokes white,not responsive on throttle.\for a few seconds depending on how long it's sat. Then the exhust clears,rattle returns,and so does the throttle response.
Any help?
Thomas

[phantom309]

Hi Phantom309
Do'es it smoke white when it starts?
I belive my tow truck has a fuel leak,when it starts it runs quite,smokes white,not responsive on throttle.\for a few seconds depending on how long it's sat. Then the exhust clears,rattle returns,and so does the throttle response.
Any help?
Thomas

I hear ya on that but i put a whole new fuel system on last year with a different filter,. she,s just acting different now its cold,.
yours has a mechanical advance for cold starts i think,.

nick

[DmaxMaverick]

Air in the system will have the same affect, EFI or MFI. Retarded timing.

[phantom309]

Air in the system will have the same affect, EFI or MFI. Retarded timing.

Maybe you,re right,. maybe i,m missing the obvious on this one.
I did put the larger filter on ,. and the feed line to the pump is downhill i thought that would always keep a head of fuel at the pump,.maybe its siphoning back somewhere,.
I was going to add a check valve in the feed up to the filter,. but somebody said the pumps come with a built in check valve?
Could the IP be siphoning back thru the return line?
Being an electronic pump,.it would shut off with the key which kills the ecm which kills the motor, IF the fuel shutoff solenoid has a leak past it when its closed, would that siphon the fuel back to the tank?
i used a different lift pump,. it looks the same but has more pressure to it, but i can.t find out info on it for internal check valve etc,.
not so easy to tinker with stuff when you,re living in a motel or the bunk of a truck,.

Nick

[DmaxMaverick]

The OEM lift pump is checked. You'll have to look up the specs on an aftermarket/other pump. Most are checked.

The "siphoning back" theory may be happening. Usually, if you have no system leaks, it doesn't happen, because the supply and return lines balance pressure when not operating. If you have a leak, it will normally cause an external fuel leak if on the supply side, and air intrusion if upstream of the lift pump. A bad fuel filler cap (vent) can cause air intrusion during an overnight period (fuel/air in the tank contracts as it cools, causing a vacuum). It exploits any weak seal or coupler, that may not leak under pressure. Keep it simple.

[phantom309]

The OEM lift pump is checked. You'll have to look up the specs on an aftermarket/other pump. Most are checked.

The "siphoning back" theory may be happening. Usually, if you have no system leaks, it doesn't happen, because the supply and return lines balance pressure when not operating. If you have a leak, it will normally cause an external fuel leak if on the supply side, and air intrusion if upstream of the lift pump. A bad fuel filler cap (vent) can cause air intrusion during an overnight period (fuel/air in the tank contracts as it cools, causing a vacuum). It exploits any weak seal or coupler, that may not leak under pressure. Keep it simple.

The fuel cap i drilled,. to make sure it was not pulling a vacuum,.
I,ve no obvious fuel leaks,.and i,ve checked front to back with a very bright LED flashlight,.
I dunno yet,.
I know my glow plug connections are rotted on,.i,m thinking i might step up for a new aftermarket harness,.this old one is pretty ratty,.

[Yukon6.2]

Hi Phantom
My Tow truck is a 97/98.
When i get my house finished a switch to mechanical will be on my to do list,along with an engine switch in my crew and hopefully my turbo will find it's way in too.
I never timed the pump when i switched the engine in my tow truck,the donar was the same year and running fine.The tow truck is inside all the time.
Hope you find your cause
Thomas

[Robyn]

IF the timing is outside the parameters of what the computer wants to see, and the TDC OFFSET IS NO ATTAINABLE the thing will set a code 88

As long as this is not happening the IP is within reasonable settings, maybe not perfect, but workable.

One of the most overlooked items effects cold starts is the injectors.
Glow plugs are of course a biggy, but if the injectors are popping low and peeing a stream instead of a nice fine mist in a cone shape, the start up will be poor to worse.

A 6.5 with good injectors and plugs should snap right off even in very cold temps.

My 94 Burb with the fresh engine, would RAP right off with clean exhaust down to near zero F temps.

Cold, that thing would make a Powerstroke Cringe.

Even with good plugs, if the fuel delivery is sloppy, its not going to lite off well when its cold.

As mentioned, drain back can be an issue, but I suspect the squirts are tired.


Yank a couple, have them tested and see what the spray looks like.
2000 psi minimum pop, and if they squirt a sloppy pee stream, therein lies the trouble.

A had a second Burb that had bad injectors, and it would fire off on about 4 holes, then shudder, shake and pour forth copious amounts of nasty white smoke until the other four ponies got lit off.

Compression is always important too, with about 320 psi being bare bones for a good start.

Give this a go and see wassssup


Missy

[arveetek]

I notice the exact same symptoms with my '95. If you recall, I replaced the IP back early this spring with another used pump. She runs great, but the first morning starts are funny. Especially now that it is getting colder out.

This morning took a few seconds of extra cranking, and then she started, but had very little diesel rattle, and lots of white smoke. Then a second or two later, the diesel rattle becomes very evident, and the smoke goes away. I can tell that the timing is not advancing until AFTER the engine has started. I don't know if the stepper motor is sticking, or if the ECM is not telling the stepper motor to advance the timing prior to starting. I didn't have this issue until after I swapped pumps. And I did perform a TDC offset relearn with a Tech II scanner after replacing the pump.

I'm not sure where to go with this one, but it sounds like you and I have the same symptoms. And I believe it is directly related to swapping the injection pumps.

Casey

[phantom309]

I notice the exact same symptoms with my '95. If you recall, I replaced the IP back early this spring with another used pump. She runs great, but the first morning starts are funny. Especially now that it is getting colder out.

This morning took a few seconds of extra cranking, and then she started, but had very little diesel rattle, and lots of white smoke. Then a second or two later, the diesel rattle becomes very evident, and the smoke goes away. I can tell that the timing is not advancing until AFTER the engine has started. I don't know if the stepper motor is sticking, or if the ECM is not telling the stepper motor to advance the timing prior to starting. I didn't have this issue until after I swapped pumps. And I did perform a TDC offset relearn with a Tech II scanner after replacing the pump.

I'm not sure where to go with this one, but it sounds like you and I have the same symptoms. And I believe it is directly related to swapping the injection pumps.

Casey

I had a conversation about 94-95 obd1 stuff along time back,. and everyone that had one said the same thing, they started sorta funny and then came to life,.after only a sec or two,.

IF the timing is outside the parameters of what the computer wants to see, and the TDC OFFSET IS NO ATTAINABLE the thing will set a code 88

As long as this is not happening the IP is within reasonable settings, maybe not perfect, but workable.

One of the most overlooked items effects cold starts is the injectors.
Glow plugs are of course a biggy, but if the injectors are popping low and peeing a stream instead of a nice fine mist in a cone shape, the start up will be poor to worse.

A 6.5 with good injectors and plugs should snap right off even in very cold temps.

My 94 Burb with the fresh engine, would RAP right off with clean exhaust down to near zero F temps.

Cold, that thing would make a Powerstroke Cringe.

Even with good plugs, if the fuel delivery is sloppy, its not going to lite off well when its cold.

As mentioned, drain back can be an issue, but I suspect the squirts are tired.


Yank a couple, have them tested and see what the spray looks like.
2000 psi minimum pop, and if they squirt a sloppy pee stream, therein lies the trouble.

A had a second Burb that had bad injectors, and it would fire off on about 4 holes, then shudder, shake and pour forth copious amounts of nasty white smoke until the other four ponies got lit off.

Compression is always important too, with about 320 psi being bare bones for a good start.

Give this a go and see wassssup


Missy

I wish i could Robyn, but i,m living a gypsy lifestyle right now in different locations and motels etc,.and the truck is my only transportation,.
the injectors were new (or at least sold to me as new) 2 years ago,.i figure 50,000 miles,.
I,ve no idea where to take them here in edmonton, this is an oil patch town,.
and not too many small places with freindly folks where you can get small stuff done at a good price,.
The compression could really be down on a couple of pots too,.she is getting long in the tooth,. over 200,000 miles,.
I keep scouring the ads for another truck,. but i,ve a bunch of time and effort into this old rust bucket and its taken me across the us and canada in some filthy weather, and i,ve napped in it a few times too,Its the happiest 6.5 i,ve had with its 3:42 gears,.
It,s kinda like an old dog, its getting near time to put it down and its breaking my heart, so i keep putting it off,.
I bought the old thing 3 years ago for $1000 originally for the engine for my dually, now 70,000 miles later,.
Sorry for getting off track here,.

Nick
PS i tightened up all three nuts holding the pump on, and gave it a little more advance, made no difference,.
damn pump was loose tho,.. DOH!!

[arveetek]

I had a conversation about 94-95 obd1 stuff along time back,. and everyone that had one said the same thing, they started sorta funny and then came to life,.after only a sec or two,.

Mine used to start great before the pump swap. Funny thing is, yesterday she fired right off immediately with no smoke! Today she stumbled a bit and hesitated again, as if the ECM was trying to decide where to put the timing....

Casey

[greatwhite]

For reference, my 98 will rattle like the dickens for the first 1-2 seconds and then settle into a normal 6.X diesel clatter after that. I'll usually get about 2-3 "crak-crak-crak" noises and then back to a standard "chuckle-chuckle" 6.x noise. No white smoke either, just a very quick haze/puff of black/grey. That's from a dead cold start (IE: not plugged in) here in Newfoundland in the winter.

Keep in mind that my engine is VERY healthy though. I'm into the drivetrain for well over 10,000 grand now and it's still under about 20,000 odd KMs total.

Don't ask why, it makes me sick to think about it and I could have had a nice used DMax by now. But at least the truck runs better than the day it rolled off the GM assembly line and has confused more than one DMax driver when it simply won't drop back into the rear view mirror at the green light or passes it towing up a mountain pass...

If your TDCO value is really advanced, it will be much louder in cold weather than it was in warmer temps. Since you don't know where it currently is (need a scanner to tell), there's no way of telling if that's your problem.

On a positive note; as Robin mentioned, if you're not getting code (check engine light) you're somewhere within OEM specs. A very loud startup with an advanced TDCO setting won't destroy it, but it sure won't make you feel good about turning that key on first thing in the morning.

Can't think of why it will be quiet on a cold start and then get louder though. That's a new one on me.....but the white smoke does seem to indicate it is retarding the timing (or it is retarded) and then dialing in advance after it's running. Perhaps it's a cold start scheme in the PCM and retarded timing eases starting just as over advancing timing came make starting harder.

I'd have to get down into the programming to say for sure. I haven't dug that deep in the code for a looong time.....and I only work in OBDII these days anyways although OBDII and OBDI are very similar in these trucks.....