glow plug cycles?

[strykerAKAmack]

On my 98 tahoe
The glow plug "wait to start " light
cycles on and off 10 seconds for 8 times
before light stays off .
minute 20 seconds before light stays off.
truck then fires up .
If colder than 40 degrees out I get a puff of
white smoke.
Question ... Normal for the cycle times ?
Any problems with the white smoke just on
startup?
Thanks

[trbankii]

So the light cycles on and off before you start?

Mine did that when I first bought the truck (used) - sort of "chattered" back and forth. Replaced the glow controller. Now the light stays lit for awhile, when it goes off I start the truck, then depending on temperature it will cycle on and off between zero (mid-summer) and three or four times (winter) while it warms up. Puff of white smoke on startup - I know I should get a set of new injectors into it.

I'd say the cycling before you start isn't right and is likely a faulty glow controller. Wouldn't be too worried about the puff of smoke.

[DennisG01]

It sounds like you're waiting to start the engine until the light goes out "for good"?

If so, you don't need to do that to start your engine. Start your engine as soon as the light goes out the first time. It will then cycle a few times, after it starts, until the ECM thinks everything is OK.

A short puff of white smoke around 40* is fine. As the temps get colder, you may even get the smoke for a bit longer as the engine tries to smooth out.

Plugging the block heater in for about 3 hours before you start it will have a huge impact on how easy it starts in freezing temps.

If you can't plug it in (and it's very cold out), do a couple of glow cycles, first.

Better glow plug management can be written into a new ECM program, from places like Kennedy Diesel (and others).

[trbankii]

Reading again, I think that Dennis has it. First time I read it I thought you meant it cycled back and forth fairly quickly.

[strykerAKAmack]

Yep I wait till it completely stops going on and off.
Ive tried to start it after the light goes off the first time and truck
wont start right off . It will usually start if I wait till the 4th time after the
light goes out , So Ive just gotten used till it goes thru its whole routine
Thanks

[rameye]

Mine used to do that...intermittant contact inside the glow plug controller....if somebody replaced the controller and /or overtightens the glowplug leads...it will twist the internals in such a way that poor or intermittant contact is made.

Looks like controller is flashing on and off....kinda random.

Fix...take apart controller and untwist...moderate to high skill level..

Easy...buy new controller.

[DmaxMaverick]

If you have 60G (or other slow-glow) plugs installed, assuming they are all good, the cycle time is too short. If this is the case, either lengthen the cycle time, or install quick heat plugs. You could also have a few failed plugs. The early no-start and puff of smoke is an indicator there is too little heat in enough cylinders for initial combustion.

[strykerAKAmack]

Thanks All
will look into things after thanksgiving
This is why I just renewed to the site for another couple years
Fast helpful answers to questions :)
Also finally figured why I could only read and not post .......
changed browser from IE to Opera

As for plugs dont know what is installed
glow relay I guess is a stock unit also
Guess will pick up both and install all around .

Happy Thanksgiving All

[DmaxMaverick]

If the glow cycle "eventually" gets them hot enough to fire, the problem isn't the relay, and the cycle is working properly (sounds normal, according to your description). Too cold, or too few working plugs is the problem.

[DennisG01]

I agree with DMax. From your description, it sounds like your glow cycle is perfectly normal. It sounds like you just have some dead plugs.

A cheap and dirty way to test plugs is to remove the spade connector, connect the lead from a tester light (About $5) to Battery (+), touch the probe end of the tester to the plug's spade.

Another way is to use a sensitive multimeter - looking for .8 to 1.4 ohms between the plug's spade and ground (connector disconnected, of course!)

You can find some more reading material, if you want, by searching for terms such as "test, glow, plug, no start, starting hard, etc."

[Robyn]

Every GM 6.5 I have owned, the glow light comes on when the key is turned on and stays on for about 8-10 seconds in cooler weather.
Once the light goes off the engine should start right off without much smoke, the glow light should/could go on and off a few more times ove the next 30 seconds to a minute (Post heat)

The gkiw light should not be cycling on and off fast. One long cycle followed by short on/off post heat cycles to keep the plugs warm until the cylinders get a little heat in them.

I have used 60G plugs in these engines with the standard timers and had zero issues even in cold weather.

The 60G plugs may not work as well if the injectors are not up to par.

Slobbery worn injectors make it a lot tougher to get the fire lit.

I would be looking at the glow controller.

Now the 98 being OBD2, the timing on the glow cycle may be in the ECM, but the cycles need to be about the same to get things working right.

Good luck

Missy

[DmaxMaverick]

Every GM 6.5 I have owned, the glow light comes on when the key is turned on and stays on for about 8-10 seconds in cooler weather.
Once the light goes off the engine should start right off without much smoke, the glow light should/could go on and off a few more times ove the next 30 seconds to a minute (Post heat)

The gkiw light should not be cycling on and off fast. One long cycle followed by short on/off post heat cycles to keep the plugs warm until the cylinders get a little heat in them.

I have used 60G plugs in these engines with the standard timers and had zero issues even in cold weather.

The 60G plugs may not work as well if the injectors are not up to par.

Slobbery worn injectors make it a lot tougher to get the fire lit.

I would be looking at the glow controller.

Now the 98 being OBD2, the timing on the glow cycle may be in the ECM, but the cycles need to be about the same to get things working right.

Good luck

Missy

The 98 doesn't have one. If the glow light comes on, the relay is working (power to the plugs). The PCM controls the relay, and the WTS lamp is fed by they GP harness.

His glow cycle sounds dead on correct for the conditions.

If you haven't had "issues" with 60G plugs, OBD II, and unmolested GP timing (PCM), you haven't been "cold".

[phantom309]

try unplugging the temp sensor,. it'll revert to -40 start glow times and full advance,. see how it starts then and /or/if your glow plug cycle time is longer,.
i have my temp wires interrrupted with a switch,. and i use it all the time to get it to fire off clean, also with someone working the key, check for 12v power on all 8 wires for the gp's,. especially under the turbo where the extra plugs are,.
New injectors and bosch duratems are the best combo for quick clean starts,.
INMHO of course,..i can fire off the truck in zero deg F temps with no plug in,. and minus F-F-F-F----cold with 1 hr plug in,.

Nick

[Robyn]

My experience with the 60G has been on the OBD1 systems and they are fine there.

Also used them in the old 6.2 engines, no worries.

I wondered about the OBD2 controls not being quite the same as far as glow cycle.

Our 94 Burb would pop right off at near 0F with the 60G plugs and stock glow system.

Sounded like a wounded Powerstroke though :eek:


Missy

[strykerAKAmack]

Ive never had problems with the truck starting in winter
Its sits weeks at a time with temps in the 20s and
lower here all winter .No block heater I just wait for it stop cycling and it
fires right up . Figure I can get another 300k out of her before the
chassis falls apart .