“Partial” Glow Plug Controller Bypass

Thank you!!

Yeah, thats what I originally did, but found my truck wasn’t starting as well as it did with the controller and it was taking A LOT longer, so I decided I wanted something different. Totally personal preference.

And I mean, technically my controller is still bypassed completely. It no longer controls the gp’s in anyway ever, I do that myself with a toggle switch in my cab, just like you. All that I added was a new circuit from the controller to lights in the dash to relay that lost information to me. More information = better decisions and better, safer starting. Now all I have to do is cycle my glow plugs 1 time for about 20-30 seconds; whenever my “after-glow cycle” light goes out, and she fires. Waiting 20 seconds in between short burn cycles wastes time and cylinder heat in my estimation, when the glow plugs are designed to safely operate for a longer duration with the regulation of the controller, without cycling. But, again, there are many different ways to skin a cat.

Yeah I saw a picture of your switch setup! I really dig it! I’ll eventually cut out that whole space and put something similar. But for now i really like the switch being under my stick and arm rest.


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Thanks!
Yeah,I can definetly see benefits with that setup, although I think 20-30 seconds a pop is really pushing the GPs IMHO. I am curious though, what's the benefit of that vs the factory setup? Either way you are utilizing the controller. I agree that by waiting in between cycles wastes heat, but I personally feel a lot safer doing that.





Rock

 

The benefit is all the same benefits you get from any fully manual system; all my glow plugs won’t go down due to a confused controller flipping out when one or more of my glow plugs go out, I’m not needlessly running the gp’s when the truck is warm like the controller wants to do every time you turn the key, and I’m in full control, not a computer.

Again, my controller is COMPLETELY bypassed, I’m manually turning the plugs on or off myself ALWAYS. All the controller is doing now is relaying its useful information to me via lights in the dash, rather than to the gp solenoid.

I’ll have to time it tomorrow morning, but I’m pretty sure the controller will signal to run the glow plugs for a full 20-25 seconds during a cold cold start here where I’m at. I’ll update here when I know for sure, but when my system was stock with new plugs on cold mornings the wts light alone would stay on for about 15 seconds AND THEN the glow plugs would go on to run for another 15ish seconds afterward, with no cycling. So, if the stock system is doing that, i can only assume the manufacturer designed it that way and that the glow plugs can safely manage that under the circumstances. Again, the controllers actions are totally dependent on temperature, so its judgment dramatically changes with the outside temperature and with how heat soaked the engine and plugs are.

I guess only time can really tell, but I haven’t seen a single convincing piece of evidence for the statement that it’s unsafe to cycle the plugs for any longer than 15 second increments under the right circumstances, especially when stock 7.3 idi systems want to run the plugs continuously for much longer than this when its cold. So, to me it just seems to be a case of monkey see, monkey do, and as a general rule, sure, its pretty safe and gets the job done for most guys, but I’m not most guys. Whether thats a good thing or a bad thing idk yet, but I’ve done pretty good so far.

Jake

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I realize that what works for me, might not work for someone else, and the other way around. The important thing is that it works good and you are happy with it, and it does gives folks more options in the future. I personally like the simplicity of having just the solenoid and switch and leaving the controller out of it all together, but that is because I like things as simple as possible.




Rock

 

My cold start this morning:
17*F
WTS light on for 19 seconds.
Then controller signaled to turn the glow plugs off after an additional 21 seconds....

The controller requested a grand total burn time of 40 seconds!!!

I typically start cranking at 20-30 seconds and it fires right up (anything less and I begin to have a hard time), then I let the plugs remain on for a few more seconds to clear up any rough idling.

And yes my controller works just fine. When the temperature outside gets warmer this burn time will be dramatically shorter, proving the controller is doing its job. For example, when its 32*F the wts light usually goes off after 12 seconds and will run the plugs for an additional ~13 seconds.

In my mind this is telling me that perhaps the plugs are designed to run longer than people think when the temperatures are cold. Again, my controller didn’t want to turn the wts light off until after nearly 19 seconds! Thats a considerable amount of time compared to what people say the max on these plugs are, and thats just the the pre-glow cycle and how long its takin for the glow plugs just to heat up to starting temperature...

Another thing to note is that the 6.9 idi system is very different and will light up much quicker than the 7.3’s and it is much more prone to burning out plugs than the 7.3 idi system for this reason.

Just to put it out there too, this doesn’t mean I’m recommending people go out and start running their plugs for this long, quite the contrary. I’m just trying to breakdown contradictions in the evidence of some preexisting convictions and statements about the glow plug system and what its limits are, because the math just never seemed to quite add up in my mind. If you’re running the stock system you’re likely running your glow plugs for longer than the 15 second rule when its cold, and thats totally fine.


In fact, my original reason for deciding to bypass my controller was out of concern that my glow plugs were darkening prematurely after using the stock systems judgments all winter (although they test and work fine still). So, I wanted to take that judgment into my own hands, but determined also that the controller communicated useful information that I still wanted, and also that it sets a good benchmark for what the absolute limit of the gp’s is for those “worst-case-scenario” kinda cold starts where its sub-zero, blizzarding and I’m somewhere remote. With this system I get essentially the best of both worlds and actual visible data and comparisons and therefore can understand what works best and most efficiently for my truck in different circumstances.

So, in closing, sure I strongly disagree with the statement that these gp’s can’t run any longer than 15 seconds without burning out. They can and will glow continuously for 40 seconds, repeatedly without burning out. I’ve done it all winter, and most with the controller do this whether they know it or not. Do I think you should? Definitely not if you don’t absolutely need to, but on occasion if you need to, sure.

I believe the 8-15 second rule is a good, safe standard for most trucks and circumstances, but not a limit, if you need more then run them for longer, just know that longer glow times will always eat away at their lifespan significantly, theres just no way around that. But I mean, you’re essentially doing the same exact thing as running them continuously for 30 seconds when you cycle them again and again and again. They don’t cool off as fast as you’d think, a 15 second cycle time x2 with a brief cool off in between is literally exactly the same as 27 seconds of continued burn when its all said and done. 5-8 seconds pulsing seems to be a better, more efficient strategy in my mind if you’re truly worried about the lifespan of your glow plugs, but that only works if your truck will start that way. Mine rarely will because it’s pretty darn worn out in the compression department, therefore I have to compensate with my glow plugs, until I get it rebuilt.

The main thing I’d say is if its cold try to crank the engine over with the plugs still glowing and keep them running briefly as the truck idles. A quick shot of glow, turning then off, and then cranking it over or waiting around to start it will rarely ever work. The engine either starts from fuel being directly ignited from the hot tip of the glow plug + compression, or from enough chamber heat to facilitate a full compression ignition. If the tip isn’t glowing then you’re solely relying on cylinder heat that you’ve collected, and you don’t build up chamber heat in a frozen 85 pound iron cylinder head without a longer gp cycle.

Thats my 2 cents, hopefully some find this thread informative to them. Information on the glow plugs and controllers in these trucks seem to be super confusing and contradicting and sort of all over the place IMO. A whole lot of assumptions and personal preferences and experiences and not a whole lot of cold, hard evidence and proof. This thread is still far from being actual proof or evidence of anything, but is as close as I can get, for now.

In the future I plan to do a more in-depth thread showing exactly what the solid state controller does with the glow plugs out of the truck and show how it reacts to different inputs and scenarios, then compare zd9 glow plug life spans using different starting strategies and mechanisms. So stay tuned for that.

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Very interesting on burning them for 40 seconds non stop.

These controllers vary somewhat, but the most I have seen for total on time (not counting after glow) is about 25 seconds. My truck will run them very close to that 25 seconds at anything 15 degrees or less.

The beru zd9 plugs havent been holding up that well for the last couple years.....interesting to see how long yours will last at 40 seconds.

 

Yeah about the same for me. Anything below 15 degrees and my wts light is on almost for 25 seconds. And its crazy because thats just part of the glow plug cycle, the plugs don’t turn off at this point which I find strange, like why do they run for close to 20 seconds longer? Especially if “they’re not supposed to”, right?

The real kicker to me is that even with fresh plugs, on our first few colder days the thing wanted a solid 25-35 seconds of glow just to fire up, anything less and it just had a very hard time, but my truck has pretty low compression nowadays and I could definitely use an upgrade to the starter so fixing both of those things could certainly fix that for me.

Yeah im interested to see as well, although I’ve kinda already written them off for next winter after looking at them... Just not worth it to try and put them through another winter imo.


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no......what I said was I have not seen a controller hold the relay on for more than about 25 seconds.

I have always wired my wts lights so that it is on when there is power to the plugs.

 

Oh I see... interesting...
Yeah idk why my controller wants to keep the gp’s on for so long. Partially the reason I bypassed it. Im just shocked they took the abuse so well for so long. I mean the plugs still glow great and have no swelling or irregularities, but they do have a little bit of carbon deposit.


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Great thread.

What are your thoughts on these GP's?

These are 7k old Motorcraft Beru's. I installed new plugs when I installed my new engine. The first 3 burned out at 7k miles and the other 2 at 8k. I purchased them from Amazon and they arrived in the Motorcraft bag and look genuine.

Did I get a bad batch of plugs? I did not have this issue with my previous engine, maybe lost 1 or 3 over 100k miles.

As the new plugs burn out I've been replacing them with my used plugs. I'm hopeful that if anymore plugs burn out that it is the new plugs and not cylinders that have already been replaced.

 

There are a ton of fake motorcraft parts out there, especially on ebay and Amazon. You have to be careful, not only for price gouging, but they are just repackaged junk.



Rock

 

I have heard the guys on here talking before about the timing being advanced on the engine is hard on the glowplugs. Part of your problem?

 

That is the worst looking set of zd9 plugs I have seen. What is your timing set at? What injectors?

 

8* and Moose mates.

 

Yikes those look horrible. Could be knockoffs, or your plugs are over cycling (bad controller or sticking solenoid) or gp harness is bad and its sending too many amps to only those three plugs or your timing or injection is bad and your motor is just eating them. Idk, could be many things, but i wouldn’t ignore it whatever it is. I wouldn’t be surprised if your pistons have been chewing on the broken tips of those gp’s at one point or another. Hopefully not!

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