Glow plug troubles... again

franklin2

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Please don't add a "let's see if this doesn't blow" fuse to your glow plug system.

You can get the fusible link wire from a number of sources but this seems to be the most commonly available packaging.

https://www.oreillyauto.com/detail/...-fusible-link-universal/flc14bp/4414532?pos=3

The wire in the package is labeled 2.0 sqmm

For the GP system Ford used two 4-5" runs of the 2.0 sqmm fusible link wire that was soldered onto maybe a 4awg wire headed to the GP relay.

Your GP system shouldn't pull more than 80amps for a short duration I think? Maybe even less I can't remember off the top of my head. Fusible link protection is almost purely for short circuit protection, not "overload" protection (yes a SC is an overload but it's protected against differently). Inrush current is pretty high but that drops pretty quick for what we are discussing here. A 200 amp fuse in this kind of system is going to suport 200 amps of current for a long duration. So if you put that much fuse inline it's best to make sure you have cabling that can also continuously support that much current. If you don't, and say your relay welds it self closed, then you've got full current being drawn continuously (again maybe 80amps). That's going to get that wire pretty hot but probably not cause a wire in good condition it to melt and SC. Now we add 20 years of heat and vibration to our wire and now the relay welds it self. Now we've got a hot wire with weak insulation and chaffing that say leads to a melt through and a small current leak. With the already loaded system it won't take much of any kind of additional current bleed to ground to overload the fusible links and they melt away and the circuit is opened and safe. Maybe even the damaged section of the wire can be repaired. If you have replaced the fusible links with a 200 amp fuse, that fuse is going to allow up to 200 amps to pass through a wire that is not capable of supporting that load increase in an already loaded system. You will have significantly more damage to that wire as well as every wire that it touches as it runs through the harness. I would not recommend using a fuse for the glow plug system vs the fusible links unless you know how to select the correct style of fuse for this application. It's not just picking one capable of handling the max inrush.

I disagree with the above. Fusible link or a fuse, they both serve the same purpose. I am sure your fusible links would pass more than 200 amps for a period of time before they burnt in two. Just like a 200 amp fuse has a short time period before it blows.

I like fusible links. They are small and compact, and can be wrapped in the harness out of the weather. But their function is the same as a fuse.
 

Black dawg

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It has been a few years, so my numbers will be off a bit, I tested amp draw on one plug. Amps started out around 30 and quickly fell as plug heated. Seems like amps at 10 seconds was about 10-15 and then fell off even lower with a little more time.
 

aggiediesel01

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I disagree with the above. Fusible link or a fuse, they both serve the same purpose. I am sure your fusible links would pass more than 200 amps for a period of time before they burnt in two. Just like a 200 amp fuse has a short time period before it blows.

I like fusible links. They are small and compact, and can be wrapped in the harness out of the weather. But their function is the same as a fuse.

The period of time is extremely important. The fusible links are not mine, they are an internationally accepted and used product to provide economical, reliable, long term short circuit protection. There are many different fuse designs and types. Proper selection of a fuse is about knowing and understanding the area under the fuse curve not just knowing what the peak current draw is. I am not qualified to teach an "interrupt/overload protection" class but I have attended a number of them and what is being suggested is not what I've learned. There are fuses that perform the same function as fusible link wire but using a fuse that was designed to protect an alternator on a glowplug system and expecting the fuse to appropriately protect the circuit and wiring is not the way I would make a selection. You may have been able to guess correctly and are free to disagree and do as you please.

Here is some additional information to help others with decision making. The wire selected by Ford for this load on the '92 and newer trucks is most likely a metric size based on my measurement of ~.200" diameter. That makes it a 16mm2 wire which is in between a 4 and 6awg. (http://www.buyawg.com/pdf/metric-size-to-awg-size.pdf) For PVC type insulation common with automotive wiring and assuming that the engine is cold (to eliminate temperature de-rating curves) that wire is designed to carry between 40-60 amps continuous. I can't find a temperature related curve for short time overload intervals but it's just a math formula. If someone can find it, it's possible to see what the rated current might be for short time intervals.

In the document below I was not able to find a 200amp fuse similar to what has been described. The largest one listed in that document is 80amps. According to its fuse curve, it will flow 100amps for over 1000secs. In in this case a wire designed for 40-60 continuous. Will the GPs run for 1000 seconds? Not likely but I don't want to have circuit under my hood that is not adequately protected.

For your reading pleasure:
https://www.littelfuse.com/~/media/automotive/catalogs/littelfuse_fuseology.pdf?la=en


You must have 4 glowplugs out....

Sent from my SM-N960U using Tapatalk

Take a look, at 15sec this glow plug is drawing ~11 amps (x8 = 88amps) Competitor is at 13 which is (x8 =104amps). I use DieselRX on my '97, that's what I was remembering. I was off a little but none of my plugs are burned out.

This also is an excellent illustration of why having all of your plugs working and not repeatedly cycling what good plugs are left is so important. Knowing that plugs being burned out makes the controller short cycle the system and knowing that it's common for folks to cycle them multiple times to get a few cylinders hot enough to lite off; you can see that the amount of current being drawn for these short time periods on the remaining plugs is very detrimental to to the wiring and the plugs. The wires, connectors and plugs are not designed to spend extended amounts of time at the high current draw period of the chart.
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79jasper

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And that's a different glowplug than the idi. You will not find anyone here that intentionally runs anything except the beru.
One of our members did a lot of testing/playing with the glowplug system. I'll see if I can find the thread.

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aggiediesel01

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franklin2

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Here are the type fuses we are talking about. They are only there in case that large wire get's damaged or somehow shorted to the engine block or some other ground. It's not going to protect the controller or any of the individual little wires going to the glowplugs. Just like the Ford fusible links will not protect that stuff either. With the large fuse or the fusible links, the little wires or anything small in the controller is going to go up in smoke in short order. What we are trying to do is keep that large wire from getting against the engine block, and turning red and catching something on fire. All the while letting the glowplug system do it's job. If you figure an initial 30 amps on the plugs, that figures to be 240 amps. Of course the fuse would blow, that is why I asked the question on how big a fuse he was running and what held under real world conditions.

I have seen the aftermath of large unfused wires faulting to ground. Luckily in in the one case I saw, the lead battery terminal melted and broke the current path before something else bad happened.

https://www.amazon.com/Absolute-ANL200-2-Pack-Fuses-Plated/dp/B005EUTLYW

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aggiediesel01

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Thanks for posting the fuse, here's the trip info for it from this site:

https://www.bluesea.com/products/5129/ANL_Fuse_-_200_Amp

According to these curves, it will take a minimum of 300amps, possibly up to 500amps, for 10-15sec to trip this fuse (150%-250% of rated value). It will take 600 up to 900 amps for 1 sec to trip.

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My opinions:

That fuse definitely won't trip on in-rush. For those choosing to use this fuse, my suggestion would be to make sure you have adequate cabling both upstream all the way to the battery and downstream of this fuse in order to support this current without significant damage to your wiring harnesses and surrounding components. If the cabling on both sides is left stock and any kind of fault other than a direct short circuit of the entire cable feeding the GP relay to ground, it is very likely that there will be significant damage to the harness and surrounding wiring and components. If someone is really prefers a fuse for this application, based on the evidence provided in Oldbull's test, I might recommend finding a fuse in this fuse family that is maybe 100amps. That should give someone 150amps of usable current out to 10sec. I would prefer to go lower, maybe to 75, but to each his own and I would recommend repeating oldbulls test with a user's particular style of GPs to make sure of in-rush current and sustained current during the cycle. At least measure the current draw over the expected period of time in your particular truck.

An example of a fault that could create serious damage to the harness without blowing this 200amp fuse but would likely melt the fusible links would be; if a single glowplug connector (that had the connector crumbled off) came loose from the glowplug and made contact with the head or intake manifold. Then, there is a potential short to ground when the glowplugs are energized. That particular short would probably not allow 300amp to be drawn for >10sec. I believe this kind of fault would be cleared by fusible links or a maybe a 100 amp fuse but I feel pretty sure that this style of 200amp fuse will allow a damaging amount of current to flow from the battery to the starter relay, damaging that wire. Then the post of the starter relay could be overheated damaging it's case, and then the cabling from the starter relay through the fuse to the GP relay and the downstream wiring out to the faulted glowplug connector.

Don't forget, opinions are like a**holes, everyone has one and they all stink (except mine, mine are like roses). Everyone is entitled to make their own choices. I really have nothing against fuses or those who want to use them, I've selected many for many different applications. I just want to make sure that if there is knowledge out there to help everybody make their decisions informed, then I want to make sure they have that information. I also appreciate the effort the Ford engineers went to make the wiring reliable, safe, and economical. They were't perfect with what they did but overall I think they did a pretty good job for this application (Headlight circuit is another story). Again, knowledge is power and should be used to make informed choices. There are no wiring harness police to come make sure every thing is as per factory design so it's up to each individual to manage their own levels of risk as we are all entitled to do.
 

chillman88

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I might recommend finding a fuse in this fuse family that is maybe 100amps

Fact is, a 150amp fuse blows in this application, I know, I've done it. Pretty embarrassing when it's 60 degrees out and your truck won't start, just as everyone is leaving work coming out laughing... :frustrate

I could try a 175 and see if that holds. They're not that expensive.
 

aggiediesel01

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If anyone has access to SAE Standards, SAE J156_201901 and SAEJ 156_201210 have information related to what the SAE proscribes for calculating and approving materials for use as fusible links. I would be interested in learning more about what they say. The only information I've read so far about the designed use of fusible links comes from my experience in electrical circuit design with the IEC and ABS and it's not totally applicable.
 

chillman88

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If anyone has access to SAE Standards, SAE J156_201901 and SAEJ 156_201210 have information related to what the SAE proscribes for calculating and approving materials for use as fusible links. I would be interested in learning more about what they say. The only information I've read so far about the designed use of fusible links comes from my experience in electrical circuit design with the IEC and ABS and it's not totally applicable.

And for what it's worth, I'm not arguing with you, just stating my experiences. Don't want the wrong impression conveyed.
 

aggiediesel01

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Fact is, a 150amp fuse blows in this application, I know, I've done it. Pretty embarrassing when it's 60 degrees out and your truck won't start, just as everyone is leaving work coming out laughing... :frustrate

I could try a 175 and see if that holds. They're not that expensive.

Same class of fuse (ANL)? If so then the manufacturer must have significant quality control issues with their manufacturing process. The curves are set through calculations and testing. If a manufacturer builds a fuse to a particular class then it is supposed perform according to the curves or they should not be allowed to put approvals on their packaging. I don't know if CEA, CES, MECP, or SEMA holds manufactures to particular standards. I know UL, NEMA, ABS, and others do and if a manufacturer wants to put that approval label on their package there's a significant amount of testing and records to be done and kept.
 

chillman88

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Same class of fuse (ANL)? If so then the manufacturer must have significant quality control issues with their manufacturing process. The curves are set through calculations and testing. If a manufacturer builds a fuse to a particular class then it is supposed perform according to the curves or they should not be allowed to put approvals on their packaging. I don't know if CEA, CES, MECP, or SEMA holds manufactures to particular standards. I know UL, NEMA, ABS, and others do and if a manufacturer wants to put that approval label on their package there's a significant amount of testing and records to be done and kept.

Honestly the one that blew I don't remember. It could very well have been the original one from the early 90s S10 that I pulled the fuse block from.

I may try your way with a few new ones just to see what happens.

What does your data say the safe load for 4ga should be? Honestly don't know if it's copper or aluminum, it's whatever the parts store had on the shelf for pre-made starter cable.
 

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