"Correct" amount of time for GP glow cycle?

[coletrain777]

So I know that most everyone agrees that you should only activate your GP's for 12 seconds max (manual push button) at a time, but I am wondering...

I have been watching lots of coldstart videos lately of IDI's starting in cold weather, and I have noticed on more than one video that the WTS light has stayed on for 15 seconds or more (on two video's I watched where the temp was below zero the light stayed on for around 20 sec's). These were videos where they still had the GPR controlling the cycle time. As I understand it, this light is on during the GP activation cycle, so that would mean the GP's were heating for around 20 seconds???

I have tried this a few (very few) times this winter and notice the truck starts easier with the longer cycle time. I realize that our GP's are the fast burn style, and that keeping them on too long can burn them up, but if it's really cold is this really an issue? I am not trying to start a debate or argue with those that are "in the know", just wondering...

 

[Black dawg]

which system do you have? plugs?

 

[coletrain777]

7.3 bullet style, ZD9 Beru's.

 

[franklin2]

The proper glowplugs as you well know are expensive. I believe most people including myself who have the manual button system like to be conservative, hoping it will give the plugs longer life. I personally only hold my plugs on for about 8 secs, crank the truck about 3 revolutions(I know it won't hit a lick with this short cycle) and then glow the plugs again for another 8 secs. On the second cranking try it will usually start unless it's really cold. If it won't start after about 5 or 6 rev, I will do it all over again, and that's usually worst case.

It's all personal preference and what you think your truck "needs" to start. Some people may click their heels 3 times before they try, whatever works for you.

 

[mrbrink]

Oregon fuel injection reccommended 5 seconds on my bosch's. I'm on month 2 with them and even in 15* weather it'll fire off in a couple revolutions. I'm also on a manual push button

 

[coletrain777]

Do we have evidence that 15 -20 seconds is detrimental? If so, does this mean that GP life is slightly shortened, or that there is a strong risk of burning up new GP's quickly? I am all for being conservative, and I am not looking to push the envelope, I just like to know the "why's" and "how's" of things. I just haven't seen this issue really discussed before...

 

[BigRigTech]

I usually do mine about 5-10 seconds for the current temps but in colder weather 15 seconds will be my upper limit. Look at it this way, with manual GP's you are cycling them far less than a controller would...My truck can sit for a few hours and it will start a lot of the time without GP's....IP timing makes a huge difference in starting, a smidge of advance makes a world of difference.

 

[david85]

Something that needs to be mentioned is that 1983-1986 trucks do not use a resistor on the glow plug circuit to cut the voltage down. In theory, 12V gets to them because of this but in reality, its usually closer to 10V once you factor in voltage sag.

1987 and up trucks have a resistor on the controller that drops the voltage down to about 5V (this is what I've read, I haven't been able to measure it first hand). This means that all things equal, the older trucks cannot safely be switched on for as long as the newer ones.

With the OEM beru glow plugs, 10 seconds seems to be enough to get mine running on the first revolution at temperatures at or above 32F. However it will sputter a little at temperatures below that. I'm thinking to experiment with slightly longer glow times to see how it performs.

 

[coletrain777]

That makes sense! I think I am going to up mine to 16 seconds at temps below 20f and maybe a full 20 seconds at temps around 0 or below. That maybe a little risky though???

 

[dyoung14]

Useing manual plugs on the 87+ style you have no idea of how to controll the plugs or how long to heat, the controller heats them till the get to a certain amount of resistance when that is achived they kick off, and it will never over heat them and usually plugs dont go bad for twenty years as long as all of it stays working correctly, my girlfriends truck has the origanal glow plugs in it all 8 still burn

 

[bubblegum]

and it will never over heat them

What if the control thing goes foo-foo all of sudden?

 

[Diesel JD]

Never is too strong of a word but the solid state controller is a much better design than the 83-86 system if only because failure mode is short cycling rather than the relay sticking on and burning up the whole batch of plugs. Honestly I think the ZD-9s are best left with the factory controller and if you want to do manual plugs a 12V plug might be better. I have no evidence to back up the idea that ZD-9s won't live a long life with a manual system, it just seems logical that they might not like long cycle times since they were designed for a controller that never feeds them 12V and switches the power off when they get too hot.

 

[Goofyexponent]

I had a set of them bosch plugs.....then I installed ANOTHER set of them bosch plugs....within a month. Now I have Beru plugs....and I ain't goin back!!

I think the longest I hav eseen my plugs stay on was 18 - 20 seconds.....and it was COLD out! But with that said, as soon as I hit the key...Ignition!

Timing DOES help these things start, as well as a good working timing advance.

There was a thread in here a while back about a guy who tested the GP's to death with a battery charger. I will see if I can find it and post the link to the YT account. This shows how long a GP can burn before it's had enough and gives up the ghost.

 

[Goofyexponent]

http://www.youtube.com/watch?v=e7Azfql5AEU

Here you go!

 

[BigRigTech]

I have yet to burn out a GP with my manual setup, close to a year on the system. The main thing I hated about the controllers was the fact that a burned out GP or two and that little ******* just starts short cycling and clicking...Atleast with a manual system you can get it started in peace. I check my GP's quickly during oil changes.