Glow Plug Question

[turbopower6]

Hi all,
I just replaced all of the glow plugs using Bosch Duraterms (with anti seize) and put in new injectors from Bill Heath while I was in there.

Last winter It was difficult to start unless it was plugged in for a few hours. Without plugging in it would not start. New batteries did not make the difference. When it was running and warmed up it would fire right over as it should. Let it get cold.....well let's say it was always a pucker moment if it would get you home.

The Question: the AC Delco glows I removed were not swollen (thankfully) came out like spark plugs (easy) and looked to have intact tips at the business end. Sooo---oo how would I know upon a visual inspection if these were the problem? Seem to look fine from my view.

Some more insights: the wait to start light cycles as it should, I can hear the relay clicking does this mean the system itself is really working as designed?

I am finishing up the "adventure" now and will not have a really cold night to test it out so I am hoping next winter we are GTG!

I added the glow harness and 2-0 Battery cables from PT Wiring while I was up to my elbows in the beast and looking forward to not being back inside anytime soon!!

Thoughts?
Thank you!
Ted

 

[Burning oil]

Test old one by hooking a jumper cable to terminal and grounding the body.
Some engines won't start on a 100* day w/o GPs.
WTS light and relay can cycle but don't mean GPs are working.

 

[Will L.]

Test all 8 wires are getting power.
What rpm is the engine turning over at when cold?

 

[JMJNet]

What model year?

 

[Husker6.5]

There is no visual test for glowplugs. Test them for continuity to ground. If open, it's bad. The relay can operate, but that doesn't mean that voltage is going to the glowplugs. Check for battery voltage at the hot side terminal on the GP relay. Check the fuse for the glow plugs (not the relay fuse, the power fuse) if there's no voltage present at the hot side terminal.

Also, NEVER cycle the glowplugs if you are boosting off of a battery charger. The 15-16+ volts from the battery charger will fry out the glowplugs, which are designed to operate off of 12.4-13.8 volts of a battery.

 

[turbopower6]

What model year?

1996

 

[turbopower6]

There is no visual test for glowplugs. Test them for continuity to ground. If open, it's bad. The relay can operate, but that doesn't mean that voltage is going to the glowplugs. Check for battery voltage at the hot side terminal on the GP relay. Check the fuse for the glow plugs (not the relay fuse, the power fuse) if there's no voltage present at the hot side terminal.

Also, NEVER cycle the glowplugs if you are boosting off of a battery charger. The 15-16+ volts from the battery charger will fry out the glowplugs, which are designed to operate off of 12.4-13.8 volts of a battery.

Thank you..that is great insight. I should use an ohm meter now that they are out of the engine and bench test them to see if there is continuity. I will check the GP relay as well when we get set to fire the engine next week.

 

[turbopower6]

Thank you..that is great insight. I should use an ohm meter now that they are out of the engine and bench test them to see if there is continuity. I will check the GP relay as well when we get set to fire the engine next week.

I just need to know what the shape they were in for my own peace of mind. This engine runs flawless wne it is running it , like many diesels, does not like cold weather....like its owner...;-)

 

[WarWagon]

There is no visual test for glowplugs.

UM... Yes there is. They are called GLOW plugs for a reason. If you doubt the controller, remove an injector, cycle the glow system and look in the precup to see if the glow plug is glowing. Specifically the old Non-ECM controllers will start to short cycle and not get the plugs hot enough. (Not 100% applicable to the OP's newer ECM controlled plugs.)

Duraterms take longer to heat up and may require a 'tune' on the 1996 for longer glow times. An override switche in the cab for self limiting plugs will also work.

Cranking RPM and air free fuel aka no air leaks from sitting overnight and draining the fuel system are other things to check.

 

[Husker6.5]

War Wagon, I was saying that you just can't "look" at a glow plug and tell if it is good or bad (unless it has overheated and swelled). Of course you can remove one, mount it to a bench vise and put a battery to it to see if it glows.

The nice thing about using a multimeter to check them is that 1) You don't have to remove the glowplug, just disconnect the wiring harness plug and check for an open between the spade terminal on the glowplug and the engine. 2) You don't have to deal with bench testing and dealing with a (possibly) red-hot glowplug. 3) It's a lot quicker to just unplug one at a time and check them with a multimeter than it is to pull and bench test each one.

Yes, you can run a manual override switch for the glow plugs, but I never ran one on my 94 6.5 and with the 60g GP's in it, it never had a starting problem with it unplugged in the winter here. Many was the time it would sit all day on a job site unplugged in below 0°F weather and 8-10 hours later I would fire it up, load up, and head out. My "trick" (that I learned and we used to use with our 6.2 equipped CUCV's and Hummers in the Army) was to cycle the WTS three times before starting. I even accidentally left it unplugged overnight when the temperature dropped to -8 and it started unassisted the next morning - albeit a little smoky and rough for a couple of minutes until it started warming up, but it did start.

 

[Dmaxxd]

Hi all,
I just replaced all of the glow plugs using Bosch Duraterms (with anti seize) and put in new injectors from Bill Heath while I was in there.

Last winter It was difficult to start unless it was plugged in for a few hours. Without plugging in it would not start. New batteries did not make the difference. When it was running and warmed up it would fire right over as it should. Let it get cold.....well let's say it was always a pucker moment if it would get you home.

The Question: the AC Delco glows I removed were not swollen (thankfully) came out like spark plugs (easy) and looked to have intact tips at the business end. Sooo---oo how would I know upon a visual inspection if these were the problem? Seem to look fine from my view.

Some more insights: the wait to start light cycles as it should, I can hear the relay clicking does this mean the system itself is really working as designed?

I am finishing up the "adventure" now and will not have a really cold night to test it out so I am hoping next winter we are GTG!

I added the glow harness and 2-0 Battery cables from PT Wiring while I was up to my elbows in the beast and looking forward to not being back inside anytime soon!!

Thoughts?
Thank you!
Ted

Just a thought, next time your working on an electrical related problem (glow plugs), and are going to use an anti seize compound, go to your nearest electrical supply and see if you can buy Coppershield, this is an anti-seize compound that is primarily all copper, and will only enhance any and all connections as well as make super easy to remove!! Really good stuff!!

 

[turbopower6]

Just a quick update on our 1996 Suburban "adventure" ...
We finally got it fired up!
I was anticipating a long cranking process to get it to fire since we had all of the injection lines off while I replaced the injectors. Much to my surprise...this was not the case!
Thankfully I installed the updated Lift pump control harness from John Kennedy earlier which allows for priming the fuel minder without cranking the engine. Since I replaced the filter during this recent work on the truck I was able to prime the fuel minder before I tried to start the truck.

After I did that I cranked her over after the glows (new) cycled and .....wait for it.....SHE FIRED UP INMEDIATELY after having sat on the drive way through the winter since last October. It was like it was running yesterday. It ran for a minute smoothly then stumbled for a moment or so until the air worked out of the lines and we were good to go. No cracking and bleeding fuel lines necessary. Amazing!


The new battery cables from PT Wiring (Bruce) allowed the starter to spin over so fast I could not believe it! This was a huge improvement for the truck

Now she is running (and starting) better than ever at 192,000 go figure!

Thanks to all for the input and insights as I expect to stick with the "adventure" for a long time.

Once I figure out how to upload some pictures of the work I will post them.

 

[JMJNet]

Just to recap, what do you think was the issue that caused the hard start?

 

[turbopower6]

Just to recap, what do you think was the issue that caused the hard start?

The hard start in cold weather without being plugged in I believe was a combination of items all of which I addressed at this service interval: new injectors ( old ones had >150,000 miles as far as I know);new Bosch thermatru (sic) glows with the better/improved PT Wiring Solutions harness; and the new PT Wiring battery cables which make this puppy spin over way faster than ever. I am betting when it gets colder the better cables,new injectors and glows will have solved the cold start issue. Based on what I see on the forum, cranking speed,solid injectors and fully functional glows will go a long way towards good starting behavior in cold weather and warm weather.