I started to reply to Sous's quotes below, and after realizing that I just recently wrote a similar reply to EXPACamper's thread, it seemed like this topic should have a thread of it's own, so that the issue can be known, and resolved.



This may not necessarily be something to be thankful for.

From Ford's language in the service manual regarding alternator, voltage, and glow plug operation... as well as Beru's language in the description of the only glow plugs they made available for our engines (Beru manufactures the Motorcraft OEM glow plugs)... measuring 14.3 volts in the cab immediately after starting within 31.5 seconds of turning the key (based on your reported 30 second wait, plus 1.5 second crank) can curtail the expected life of the glow plugs, depending on the amount of time remaining on at that voltage in that start cycle.

The voltage measured in cab is generally two tenths of a volt lower then voltage measured at battery and at the glow plug relay. This is due to a diode placed in the wiring to protect the PCM. The diode is upstream from the PCM and underhood power distribution block, and downstream from the fender mounted starter relay, which delivers all electrical power to the rest of the truck via a fused link circuit... except power to the starter and glow plugs/IAH, which are circuited separately.

Most folks pick up their voltage readings from their data link connected device, or from a cig lighter device. I have tested and verified the under reporting of system voltage at these two places. I have not specifically tested voltage through the trailer brake power supply circuit, so I will not go so far as to confirm the difference that I still suspect exists, based on my vague and fading memory of the wiring diagrams of the trailer brake circuit, last looked at over 17 years ago, when I installed my Tekonsha Sentinal... which looks like a hand brake compared to the P3 of today.

Here are a few of my photos showing voltage measured with multiple meters at different locations at the same time:













So, the foregoing photo essay is simply to say that if you are seeing 14.3 on the P3, your glow plugs could very well be seeing more than 14.4 volts immediately after engine start with your fancy new alternator. And this could be a problem for our glow plugs... that are rated at 11 volts.

I'm not a glow plug engineer, but just guessing, I imagine that glow plugs are expected to effectively heat the cylinders within a reasonable (relatively quick) amount of time under battery power alone. Even a pair of fully charged batteries, measuring 12.75 volts or above, will quickly drop to 10.5 volts when anywhere from an 80 amp up to a 130 amp load is applied, such as 8 glow plugs that are rated at 16.5 amps each, can potentially present.

So the heating resistors inside the glow plug are expected to be time efficiently effective at this lower, more realistic, battery alone while under demand voltage of something a couple volts less than a fully charged battery at rest. Hence the 11 volt rating of the glow plug. If the heating resistors weren't time efficiently effective unless the voltage was 12.7 volts or higher, then they wouldn't do the main job they were originally designed for, which was to help start the engine.

But then glow plugs became victims of mission creep. It was figured out that if the glow plugs remained on for a little while longer after the engine started, then some reduction in cold start emissions could be realized. Getting Nox low enough to meet government mandates meant glow plugs were called to the line of duty AFTER the engine started. Now, these 11 volt glow plugs were exposed to alternator generated voltage, at 13.5 volts and above.

There is a further complication... not only is the higher voltage delivering more heat to the glow plug when the engine is running... the combustion events in the cylinder itself are adding violent amounts of heat... so the glow plug is cooking from the inside and the outside.

There must have been a limit to the physical properties of resistor materials, where a resistor that is effective enough to heat quickly enough when only 10 volts of battery alone power is available in a cold non running engine... would quickly cook itself to death when exposed to 33% to 44% higher voltage. Conversely, it may be that a resistor that could survive indefinitely at 14.4 volts, would not be as time efficiently effective at heating the cylinder when fed only 10 volts.

Beru soon afterwards designed a three stage glow plug that specifically contemplated glow plug survivability during the post start, engine running, combustion cooking, alternator generating phase of glow plug cycle time for emissions reduction, but sadly, our 7.3L engines do not have THAT glow plug. We have the earlier design.

Specifically, our glow plugs are of the GV series. (Beru # GV-819, same as Motorcraft ZD-11, which is Ford part number F4TZ-12A342-A, with a Ford engineering release date code of 1994... long before Beru's newer glow plug resistor design) These are not Beru's state of the art glow plug. They were not even state of the art when our '99 up Super Duty trucks were brand new. These glow plugs are a hold over from the previous generation Powerstroke. Ford forced these older glow plugs into 3 stage emission reducing duty without ponying up for the fancier three stage GN series plug until the 6.0L engine was introduced.

Ford made up for it by calling the anemic 110 amp alternator for the Mercury Cougar into duty for the 7.3L. This alternator, at idle, can at best on a breezy day with the wind at it's back produce only 40-50 amps at idle, with 40 being more likely. And this is all the current available to restock the batteries which were just depleted from having to produce up to 2,000 pulse cranking amps to start the engine, as well as depleted from having to run the glow plugs for however long the key was on prior to start. So there just isn't enough power to go around to bring the system voltage up to 13 volts, much less 14.3 volts, within the first couple of minutes of engine operation. Hence, the old style glow plugs were protected from over voltage.

Ford realized that the car alternator wasn't enough for many applications and customers who chose a 7.3L diesel for their ambulances, work trucks, etc. So Ford offered a SECOND alternator in the diesel, INSTEAD of an upgraded single alternator, as Ford otherwise offered in gasoline engines that didn't have these glow plugs. And Ford took three more steps with this second alternator, to maintain the anemic performance of the first alternator during the first two minutes...

1. Ford made sure that the second alternator was commanded off whenever the glow plug relay was commanded on.

2. Ford changed the pulley ratio of the second alternator.

3. Ford specifically told ambulance upfitters NOT to change the primary alternator in the diesel engine to a higher amperage alternator.

That was then. Things changed since then. But those changes only apply to newer engines, not ours.

In 2003, when Ford introduced the 6.0L engine, Ford also upgraded to Beru's GN series glow plug. (Beru # GN 049, Motorcraft ZD-12, and a year later, Motorcraft ZD-13, which is Ford part number 4C3Z-12A342-AA, with a 2004 engineering release date code).

With the 6.0L, there was an increase in single alternator rating... to 130 amps, and later, 140 amps. A second alternator continued to be available, but the key thing to notice is the increase in current rating of the primary alternator. Furthermore, the 10 amp increase in the optional 140 amp single alternator is even greater at idle... close to a 20 amp increase.

By the time the 6.4L was introduced, Ford upped the ante more with Denso designed segmented conductor alternators of even higher energy producing density per cubic inch of alternator (which enabled aftermarket alternator companies to promote "hairpin" alternators to Ford T mount applications... since Ford was the original customer who called for the alternator frames to be cast). These alternators were now PCM controlled, so Ford had complete control over the protection of glow plugs, which by this time were already designed to be self protecting by Beru.

Ford offered upfitters instructions on how to convert from dual alternators back to single alternators, or vice versa, with no cautionary statements about leaving the original smaller alternator in place, as Ford had previously cautioned on the 7.3L. Since I'm not aware of any upgraded design glow plug being made available to fit the 7.3L, I have to assume that the glow plugs remain just as vulnerable to over voltage today as they did back when Ford did issue the memo to leave the small 110a alternator as is.

The following two informational slides are from Beru. My comments are superimposed in red and green letters. Must be the Season...










Glow plug tips, once burned, can break off inside the cylinder, turning the engine into an expensive pinball machine. The following photos are not necessarily of the 7.3L... they were just convenient findings from the web.













If you've upgraded your single or upper alternator on your 99-03 7.3L, I'm in the same boat as you are. What I currently (ha ha) do is turn on the headlights and the blower fan all the way to high as soon as my engine starts, and turn them off when the glow plugs turn off, a moment which I can now hear because I have become attuned to it.

Eventually, I would like to put a tunable (or pre designated) independent voltage limiter ahead of the power post on the glow plug relay, dialed to about 12.5 volts, so that regardless of how effective my larger alternator is at producing 100 amps at idle, that easily sends the system voltage right up to the limit of the alternator's internal 14.4 volt regulator... the voltage seen by the glow plugs themselves will be limited to 12.5. I have not done this yet, because as with anything, there could always be a side effect or a downside that I haven't contemplated yet.

And that is one reason for this post... to solicit feedback on the independent voltage limiting idea, and how the 2 rejected volts are either dissipated through a heat sink or utilized creatively (indicator lamp?). I've reached out to members of the forum with electrical backgrounds (like Sparky Al, for example) for feedback, and am continuing to mull over the matter.

But the main reason for this post is to share the principal concern with those who may not have given much consideration to the longevity of glow plugs with an alternator upgrade. I've talked about it here and there in the past, usually in response to another person's thread. But perhaps the topic deserves a platform of it's own, so that a solution to this specific issue can be focused on.

As I said in my other recent post... the most "active" reporters of information on forums are generally the newest users, who more recently acquired their trucks as used vehicles, and therefore have no idea what glow plugs might have been installed. And when they do report a glow plug failure, the universal chorus of advice is always an admonition against Autolite glow plugs, and an assumption that aftermarket glow plugs must have been installed. And by the time the valve covers are pulled, who cares what glow plugs were in there? Once in that deep, they're all coming out anyway, with new Motorcaft (Beru) candles put in place.

So I'm not sure that the risk of a potentially curtailed life of glow plugs as a result of a high amp single alternator installation can ever be confirmed... but based on Ford's service bulletins and factory service manual, and based on Ford fitting a passenger car alternator to the 7.3L diesel, while engineering and casting an entirely new front bracket for a second alternator, and based on Ford specifically keeping that second alternator TURNED OFF during the glow plug cycle, and ONLY during the glow plug cycle, and based on Beru's information and description of their various generations of glow plug design, I am inclined to believe that the risk exists, regardless of whether or not any owner is able to confirm it.

Let's mitigate this risk together, shall we?

Your turn to post ideas...

 

The title of this thread made me laugh. That novel there far exceeds the limits of my ADHD but I get the gist of it. I have a 200 amp alternator on mine that came with that short bus that I bought at auction. Having that voltage meter in the cigarette port is very nice and it's a shame that these trucks don't have one built into the dash. Mine does not come up over 12V for a while after startup so whatever Ford put in there to retard the higher voltage is still working here.

 

I may have some information for you later as well. Give me about 2 hours.

 

ive took a look at the voltage thing in my truck and after start usually waits about 30 - 60 seconds until it goes from 12V to 14.X volts....at least on my truck.

 

Ideas... Well crap...

You are usually way over my head when it comes to dissecting an issue, but I will try to play ball here.

I see your point, and agree that there may be a problem in the long term use of glow plugs with a higher output alternator than the OEM 110 Amps. That ship has sailed, and I have a new and expensive alternator that is rated at 160 Amps.

Maybe the glow plugs turned off just as I was turning the key from on to start in order to jump up from 11.2 volts to 14.3 right away. It was only ~35 degrees yesterday morning, so I cannot say for sure how long the glow plugs were on.

Would the glow plug relay light mod mitigate the stress on the glow plugs as long as I waited to actually start the truck until the glow plugs were off? Is this the best, cheapest and simplest way to stop catastrophic damage from possibly occurring to the engine?

Maybe instead of posting theories and ideas about the failure of the glow plug, we should post ideas and theories about how to extend the life of the glow plugs for those with upgraded alternators. I cannot count how many times I have read people putting in a different than stock alternator.

Thoughts?

 

Perhaps my glow plugs were not even lighting and the batteries happened to be sitting at 11.2 volts. It had been about a month since I had turned the key on the truck.

I would think that if your truck regulated the voltage, mine would too as they are similar in years.

 

There are areas of the tuning that shut off the glow plug relay when the PCM sees more than 14 volts. I have never played with the SuperDuty trucks in this regard but I can watch my 1995 turn on and off if I rev the engine while the glow plugs are commanded to be on.

I know that doesn't resolve the question of glow plug life cycle depending on voltage, but the engineers put some corrections in the tuning.

As for lifespan, I usually always shorten the duration of the glow plug cycle to no more than 30 seconds regardless of temperature since if it's running, that's all that matters (on my own junk anyway).

 

the way I am looking at this is "why would Ford design a truck to take different types of alternators (amps) if the system (glow plugs, relays, ect) would not be able to handle the higher amps?"

I mean if I ordered the same truck from Ford I will get options like tow package or snow plow package which both come with different equipment (and IIRC even give the option of different alt AMPs for a reg truck VS a city plow truck VS a Fleet truck (think trucks loaded with equipment, lights and other high amp needs). Just a thought in relation to the topic.

 

Cody, does that tuning apply to the trucks that have the gpcm instead of the gpr as well?

 

Thoughts? Cool Hand Luke.

That was the first thought that came to my head.

Remember the movie? Late '60's? Paul Newman before he turned grey?

"What we've got here is a failure to communicate!" is the famous tag line from that movie, and was the first thought that entered my mind.

The very purpose of posting this thread was not to "post theories and ideas about the failure of glow plugs". On the contrary, the tag line of the original post said "Let's mitigate this risk together, shall we?"

"Let's mitigate the risk together" means the same thing as let's "post ideas and theories about how to extend the life of the glow plugs for those with upgraded alternators". I already established that the risk is real. It isn't an idea. It isn't a theory. It's a credible probability, established by evidence, in writing, by the entities of expertise in the best position to know.

I've already established that I too, "am in the same boat" with an upgraded alternator. I have brainstormed an idea (glow plug power circuit specific peak voltage limiter) and shared it in the original post. And opened an invitation for anyone reading to also share ideas, on how to mitigate the problem... in other words... "how to extend the life of the glow plugs for those with upgraded alternators" that expose the glow plugs to more voltage when the engine is running while the glow plugs are still on than originally intended by Ford and Beru.

So what we have here is a failure to communicate. I'll take responsibility for it. I must not have been clear. I will endeavor to be more clear now.

I've been talking about this issue for well over a year, but more subtly and suggestively, rather than declaratively, as I have done today. But in no case is this thread intended to be a rummage of theories about glow plug failure. That potential problem was already spelled out in black and white back in 1999. See Ford Qualified Vehicle Modifier bulletin Q-67 below. Red underline emphasis added:





The goal of this thread is, was, and will be... what are those of us with high amp alternators going to do about protecting our glow plugs?

Yes. THOSE ideas. Bring em on!

 

The premise in the first paragraph has not been established. There is no available evidence to suggest that Ford designed the 1999-2003 7.3L equipped F-Series Super Duty 250 through 550, E-Series, and Excursion to "take different types of alternators". On the contrary, multiple sources of written evidence produced by Ford establish the opposite: That Ford intended only one type of alternator to be used for this specific era and engine.

The second paragraph is true, in that Ford offered a couple of optional choices in alternators. But both choices, for the 7.3L engine, involved alternators limited to 110 amps. You either select single, or dual. If you pick dual, then it will still be a single 110a system for the duration that the glow plugs are on while the engine is running. There was no other alternator choice available for the 7.3L, regardless of option package selected, for the 1999 through 2003.25 model years equipped with ZD-11 glow plugs and the emissions strategy certified and filed with the EPA.

 

Unless the Engine Oil Temperature is 131 degrees F or higher, the glow plugs WILL turn on when the key is turned on, and will remain on for up to 120 seconds, depending on the PCM's evaluation of a combination of three inputs: Battery Voltage, Engine Oil Temperature, and Barometric Pressure.

For those with a Glow Plug Control Module (also developed by Beru) instead of just a simple relay, there is a back up fail safe time out timer set to 180 seconds, should the PCM fail to kill the glow plugs after 120 seconds, which is the normal maximum run time in our application.

The "Wait to Start" indicator light will always illuminate as a bulb check during an ignition key cycle, regardless of what the engine oil temperature is, even if over 131 degrees F. It's just that in that case, the glow plug relay or the GPCM will not be commanded on, because the PCM assumes that the engine is warm enough if the EOT is greater than 131F.

So 35 degrees isn't warm enough to for the glow plugs to have not turned on. The extinguishing of the WTS light is wholly independent of, and not at all linked to, the actual glow plugs on/off time. As to when the glow plugs turned off, whether it was after 30 seconds, or just before you started the truck, etc... is up to the PCM's read of the three factors mentioned... BARO, EOT, and VPWR (voltage).

Cody can better speak to any PCM look up table modifications or glow plug command on/off strategies that might curtail or shorten the glow plug run time apart from the originally established enabling conditions. We are very fortunate that Cody digs deep inside PCM strategies. Thanks Cody!

Sous, it doesn't at all surprise me that your vehicle power quickly ramped up to 14.3 volts immediately following engine start. You reported recently installing new batteries and a new alternator. This makes perfect sense. Healthy new batteries have fewer cycle life depletions under their belt, and a vigorous high amp alternator, with double the amount of diodes in a separate enclosure to dissipate heat, is better equipped to deliver more electrical energy at lower alternator rpms... and is further aided by not having to thermally throttle because much of normal heat produced by the rectifier is being dissipated far away from the regulator in a separate enclosure. So all systems go, without the current load of trying to resurrect half dead batteries. Little wonder you saw 14.3 right away. That doesn't mean your glow plugs weren't working. It just means your charging system is producing energy really well, which is why you did the mods in the first place.

But Ford established the risks inherent in upgrading the alternator. One risk is that the existing battery cables might not be capable of handling the additional current. I don't remember if you ugraded your cables or not, but I'm sure you know to do this, and if you haven't already done so, it is likely already on you to do list.

Upgrading battery cables was part of my mitigation strategy to protect the glow plugs. If I could reduce all possible resistance between the high amp alternator and the batteries... then the alternator could keep the batteries supplied with all the recharging current they possibly could demand after their depletion from starting the engine and powering the glow plugs on their own. So rather than rely on the Ford charging system wiring, I added new fused cables directly from the alternator to each battery individually. This was in addition to the original Ford wiring, not in place of it. If electricity favors the path of least resistance, there is definitely less resistance between the high amp alternator and my batteries then there is from the alternator to any other part of the electrical system, including and especially the glow plugs.

The second component of my glow plug saving mitigation measures was NOT changing the batteries when I upgraded to my higher amp alternator. Instead of starting everything electrical all new and fresh, I purposely left my then 7+ year OLD batteries in place. I figured let that new high amp alternator earn its keep by staying preoccupied injecting more life into these older batteries. The distraction of having to provide more recharging current to hungrier, crankier, older batteries effectively hamster wheels my high amp alternator's current production capacity to meet the more demanding needs of recharging old batteries that have been deeply depleted a few times in their sordid past, rather than overwhelming the glow plugs with higher system voltage due to there being no other high current demands keeping the alternator busy. By the way, these same batteries are now over 9 years old, and still going strong. The new alternator helps them, I think.

The third component of my current mitigation strategy to protect the glow plugs... is to increase the vehicle's current demand during the first couple minutes following engine start. This is easily done by turning on the heater and switching the blower fan all the way high, and at the same time turning the lights on. I can see the system voltage on the screen of my APCM. When I did it after a cold start today, I saw the voltage drop to 12.5v, right where I want it capped during glow plug operation. With my 230 amp alternator, I would otherwise see the same 14.2 to 14.4 volts that you observed in your truck after you installed your 160 amp alternator.

So with the combination of those three mitigation measures, it is possible that the risk to my glow plugs from installing a high amp alternator may have been reduced. But what I am looking for is a more automated and failsafe way to protect the glow plugs, without my active participation.

 

I do remember Cool Hand Luke, it was a great flick.

I apologize for not receiving the intended message. We had participated in a two county foster child Christmas party just before reading your post, so my mind was a bit chaotic at the very least.

Let me ask this, once the glow plugs have turned off (be it 120 seconds, or 30 seconds) are they off for good until the next complete off-on cycle of the key? Let me be a bit more clear. Say I jump in the truck and turn the key to on which lights the glow plugs for X amount of time. After X has come and gone the glow plugs turn off. Will they turn back on at any point of the start-run cycle after turning off?

If not, then there is the simple answer. We install a glow plug relay light to let us know when the glow plugs have finisned with their task and then start the truck.

In addition, Y2KW57 what gauge wire did you use to go from the alternator to each battery and do you have a link for the fuses you used on said cables?

 

If you'd get that Hydra put in.......

I could send you some short-time/voltage sense stuff along with making the wait to start indicator much more realistic.

 

I can only ASSume so. Digging through some stuff this morning (because there aren't many "50-state" vehicles locally YET and I've not really dug too deeply into it), it appears to me that the same results are attained in the same way as the non-communist vehicles.