Manual glow plugs. Opinions and ideas.

[maverick350]

Some background.

I put together something of a frankenstein last year, and have had pretty good luck with it so far. Engine is a 94 NA IDI with somewhere around 250k. zf5, 4.11's. cab is a 96 f150 with 20ga steel mig welded in to replace the rust, covered with brushed rustoleum. Maiden voyage was to Maine to Virginia and back on a weekend.

Deleted the original glow plug delay system and went to a push button.

Been fighting an air leak in the return lines somewhere for a while, but the work around till I find it has been an electric override with a toggle on the dash. Yeah, the alternator is on a toggle as well.

After the truck has sat any length of time, turn on the pump, check for air at the schrader valve, and never have a problem as long as I bleed. (Another return line kit on order, as well as a check valve) probably will end up ordering the compression gaskets off mcmaster. Just seems the gaskets should be more available than they are.

Couple days ago with the temp around 5f, curious to see if the old girl would start, I plugged it in for about an hour, held the glow plugs in for 20 seconds, and tried to start it.

Typically when I hit the glow plugs the electric fuel pump will change its tone due to amp draw.... and after a few tries, it no longer changed tone. I tried flashing the solenoid with a wrench, and there was no load. checked voltage at two of the glow plugs, getting plenty. checked two plugs for resistance, measured open. pulled a plug out to inspect it,..it didn't look distorted at all.

I suspect I've been running on less than a full set of plugs for some time now as I've never checked or replaced them. I've tried to keep usage to a minimum, usually in warm weather 12-15 seconds is enough to start the truck.. but due to the cold I increased duration to 20-22 seconds.

Now with new zd9's on order, I'm curious if 22 seconds is what fried my last plugs or if it was just an exceedance of the normal life expectancy..

I'm tempted to build a bracket on the front dash and mount a 9th glow plug, just to be able to see exactly how hot they're getting in realtime.

Any experience on manual application of glow plug duration? life expectancy?

Thanks for reading

 

[cpdenton]

I think common thinking says to burn them for 8 to 10 seconds. That's what I do to mine, starts first time every time even down to about 10 degrees. Never gets much colder than that here.

 

[ironworker40]

quote: I'm tempted to build a bracket on the front dash and mount a 9th glow plug, just to be able to see exactly how hot they're getting in realtime.

Now thats some funny stuff.

 

[Black dawg]

An initial 20 second glow wont burn out a zd9, but if you dont let them cool long enough and then do it again, it is only a matter of time till they start dying.

There are better plugs out there for manual control, that wont burn out from over use.

I have seen a truck with a ninth glow plug mounted under the dash, real close to the pushbutton. You could see how hot the plugs were getting, and the glow plug close to the button would keep people who didnt know any better from holding them on to long. It gets real hot being less than an inch from your finger.

 

[maverick350]

Sounds like chances are I cooked them then.... or what was left of them. I'll check my results with the new ones and see how it goes. I haven't heard any reports on how long a glow plug will last with continuous power applied, but I'm going to guess around 22 seconds at this point.

 

[maverick350]

Sweet, someone else has thought of the 9th plug already. Validation of a rational thought process.

The only thing I've picked up on plugs so far from the forums is not to use autolites. I did not realize people were using another style for manual systems. What kind can you reccommend?

 

[Hans13]

An initial 20 second glow wont burn out a zd9, but if you dont let them cool long enough and then do it again, it is only a matter of time till they start dying.

There are better plugs out there for manual control, that wont burn out from over use.

I have seen a truck with a ninth glow plug mounted under the dash, real close to the pushbutton. You could see how hot the plugs were getting, and the glow plug close to the button would keep people who didnt know any better from holding them on to long. It gets real hot being less than an inch from your finger.

 

[mccall52]

I once drove a 1975 Mercedes-Benz 240D that had a fifth glow plug behind a perforated metal cover below the instrument cluster as factory. More or less predates the pre-glow warning lamp.

 

[franklin2]

I have the manual system and I love it. I would never hold them on for 20 seconds. Why do that? I will tell you what I have tried lately, I got the idea from my tractor. I always glow mine for 5 to 7 seconds, no more. I crank a little bit, and then glow them again for that short time. I haven't been cranking and cranking either. Just turn it over about 4 or 5 times and then glow again.

We have had a couple of really bad cold spells this year, we are in the middle of another one right now. What I have been doing lately is glowing and cranking for about two rounds, and then what I will do is hold the button in and after a couple of seconds I will crank it WHILE STILL HOLDING THE BUTTON. It seems to work well, you can hear the starter slow a little bit while doing this but there seems to be no harm in doing it so far, and I figure the fuel and air going through the cylinder may help the glowplugs live a little longer. It's just something I have been experimenting with. It seems to work really well with my kubota tractor.

 

[wh1056]

Would something like this help?

Kubota glow plug indicator

Older (1990's) Toro & Jacobsen turf equipment had them too.

Not sure I'd install them in a plastic dash though.

 

[maverick350]

I think the reason I went to 20 is that's about what it takes for my dad's old kubota tractor. Of course it's old and tired, but I figured the idi would be as well.

In any event,.. I'll be interested to see if she starts better with a new set.

And as for the indicator light, I think that's a great idea to let you know if power is in fact getting to the plugs.

But my rationale for wanting the 9th plug on my dash is to be able to see exactly how hot they're getting. Partly out of curiosity, and partly to avoid using the things any longer than I have to at 75 bucks a set.

Something I've wondered about as well, my 1986 6.9 still has the old self regulating setup, and the plugs continue to cycle even after the engine has started. I wonder if this was an oversight, or if it aids in combustion for that first minute or so.

 

[Hans13]

I've always heard that it aids in the combustion process like what you said. It makes a lot of sense if you think about it. I suppose the movement of air keeps them from burning up in the meantime?

 

[Agnem]

Always pains me to see people pull out a 7.3 controller and go to a push button. The 7.3 controller is smart and will let your glow plugs last a long time. Button pushers will find they always replace glow plugs more often than the automated system will. The main problem with the 7.3 controller, is that people don't understand how they work, and consequently get frustrated with them.

 

[Black dawg]

I agree, the whole set up is way trouble free, and dont have to worry if someone borrows the truck.

 

[franklin2]

I agree, the whole set up is way trouble free, and dont have to worry if someone borrows the truck.

I don't agree. If your wiring is like brand new and you have the proper glowplugs, then yes it can work. One corroded or loose connection is all it takes for it to go haywire. We never get those on a 20+ year old truck do we?