7v glow plugs - show 5.2v peak - is this normal?

mkc451 · **Posted:** Sun Jan 17, 2016 11:16 pm

I am sure some of this may have been covered, but I can't find it in search. I have a 2005 Liberty CRD -- ran great for 3 years I've had it, but started having cold start issues. 185K. Worked New Years eve, 18-20 dg's all night, didn't want to start in the morning. My son is a diesel mechanic, did the Sasquatch stuff on this, does more work on Fords than anything else. He pulls out big buck scanner said GP #3 was throwing codes. Not knowing for sure if had ceramic or metal GP's... we pulled #1 -- 7v Bosch, I assume ceramic(looked like it). Ok - lucky I never had a problem, always started good. So I ordered up a set of 7v Etechno Gp's and a new module. Put them in last week. Cold all week -- thing won't start at all if it's not plugged in or started every 3-4 hours. Last year I was able to leave it for a week in sub-zero cold and it started.

So we start trouble shooting, no error codes, GP module turns on fine with scanner control. Last night we put a voltmeter on the connector to the glow plug harness, turn on key after it's sitting 12 hours in sub 20dg weather. We only have 5 volts on the line?WTF? I guess that could be normal, don't know, I didn't check it before. Got the same thing when I swapped back in the old GP Module too.

Big question: Is 5.2V peak normal for a 7V system? - plugs seem to peak @ 5.2v and drop down to around 4v in 9 seconds and cut off.

Is it possible they re-flashed the ECM w/o changing the glow plugs? How come it started so good for all these years if it was the wrong voltage? I am out the 140$ or so for the Etechno's if I need 5V gp's. Looking for some feedback.

According to the tag in the engine bay, the ECM was re-flashed in 2007, tag says: P/N:56044737A5 code: 60027 -- I am thinking that is something else, because the glow plug stuff was 2011. When I bought it (same dealer who sold it new), I went back to the Service Advisor desk and had them pull the service records before I bought it. They did put in a new ECM back in 2011 or so, maybe it came programmed for 5v but they didn't change it? The service record did not have why they put in a new ECM.

Any help or point me to sources of info?

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The glow plugs are PWM controlled, so you'll never see "just" 7V or 5V measured with a volt-meter. Only way to properly see the output is with an oscilloscope.

With that said, our experience with our shop KJ with the Etechno plugs shows that their start-ability at temps below freezing is extremely poor. They have a different heat-up rate compared to what the stock 7V tune was designed for, so they'll never start well in cold weather and do little more than keep the MIL off. We removed our Etechno plugs and put ceramics back in.

Since the 7V ceramic plugs aren't available anymore, your next best option if you live in a cold climate are the 5V Metallic plugs from Mopar.

mikey1273 · **Posted:** Mon Jan 18, 2016 9:04 am

I noticed that The OP said he replaced the Glow plug module, The relay I assume. The relay from the factory system shouldn't need changed when changing to 7v metallic glow plugs, It is however required for the 5v Bosch plugs that Mopar prefers to sell. I am wondering if he put in the 5 volt relay in with 7 volt plugs and that's why he is seeing what he is seeing.

Also I have the 5v Bosch plugs. they were installed in June or July 2015. I had no issue with them until I got to a morning with 8 degree low and I had not plugged in the block heater. then it took me 5 tries to get the engine to fire and stay running, but it did start. My point is starting performance with metallic plugs is less than the ceramic was ever. I use the block heater now at home, set up with a timer 3 run 3 hours before I leave in the morning and always a good easy start like that.

flash7210 · **Posted:** Mon Jan 18, 2016 9:31 am

What is the part number for the 5v glow plug module?
I had read that the 7v module and the 5v module were the same and the only real difference was the programming in the ECM and the plugs themselves.
But I cannot confirm that.

I also think the 5v plugs can be used with 7v programming. Which should help them run a little hotter and improve cold starting but will shorten their life.

MrMopar64 · **Posted:** Mon Jan 18, 2016 10:21 am

Running the 5V glow plugs with the 7V programming will result in plugs that are too cold during start, and overheated afterwards. It's a recipe for disaster.

The glow plug module can, for all intents and purposes, be left alone during the swap. The new one has a slightly higher current capacity, but it'll function the same.

jws84_02 · **Posted:** Mon Jan 18, 2016 11:55 am

MrMopar64 wrote:

Running the 5V glow plugs with the 7V programming will result in plugs that are too cold during start, and overheated afterwards. It's a recipe for disaster.

The glow plug module can, for all intents and purposes, be left alone during the swap. The new one has a slightly higher current capacity, but it'll function the same.

Won't 5v plugs on 7volt burn hotter? But also go bad quicker

mkc451 · **Posted:** Mon Jan 18, 2016 2:22 pm

mikey1273 wrote:

I noticed that The OP said he replaced the Glow plug module, The relay I assume. The relay from the factory system shouldn't need changed when changing to 7v metallic glow plugs, It is however required for the 5v Bosch plugs that Mopar prefers to sell. I am wondering if he put in the 5 volt relay in with 7 volt plugs and that's why he is seeing what he is seeing.

The http://www.idparts.com/liberty-crd-glow-plug-module-56044671ac-p-2749.html relay works with either 5v or 7v according to IDParts.. My son always replaces the relay when he replaces the glow plugs -- it's always seemed like a good practice from a preventative point of view. Original relay had same issue anyways. My son is going to hook his O-Scope up tonight and check it as GD said .. just to see.

Anyway, the plugs we pulled were marked BOSCH 7v so the Etechno 7V's should be correct. As green diesel says, if the Etechno plugs really just don't work, I need to look at other solutions. I am in Michigan so starting in the cold is a foregone conclusion. I am already having a tough time keeping this after this winter, it's my every day driver and being a Service Eng, I need vehicle that site all night out in sub-zero and still start in the morning when I am on a job. Previously it did that, now it appears I will be asking a lot of it. If I could find a couple of the ceramic's in good shape used, I would just put them back in.

If a GD tune enhances a 5V glow plug setup to work anywhere near as well as old ceramics, I would consider that. Hell they are only about 2hrs away from me. But with 185k on this (though I've got no other real issues), don't know if that is a reasonable alternative.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The 5V metallic plugs are still capable to start the engine at -20F unassisted. It's not the most pretty start compared to newer more modern diesels, but if the battery is in good shape then it'll fire.

dirtmover · **Posted:** Tue Jan 19, 2016 10:03 am

jws84_02 wrote:

MrMopar64 wrote:

Running the 5V glow plugs with the 7V programming will result in plugs that are too cold during start, and overheated afterwards. It's a recipe for disaster.

The glow plug module can, for all intents and purposes, be left alone during the swap. The new one has a slightly higher current capacity, but it'll function the same.

Won't 5v plugs on 7volt burn hotter? But also go bad quicker

The GPs are started at a voltage much higher than their nominal to rapidly bring them to the correct operating temperature. Once up to temperature the voltage is dropped back to the nominal 7V, or 5V, depending on the programming. What MrMopar64 is alluding to is that this initial high voltage burn is much shorter for the 7V programming because the ceramics require less energy to bring them up to the correct operating temperature. This initial burn time is too short for the 5V metal sheathed plugs which require more energy to reach the required temperature. With the 7V programming once that initial boost is over the 5V plugs would continue to be driven at 7V for an extended period which is not good for them.

The shorter initial burn provided by the 7V tune is also the reason that the Etecno1 product is marginal. A custom tune for the Etecno1 would give us a viable product but I don't know if anyone is prepared to put in the effort to develop this?

Going back to the original post the glow plugs are rated at RMS voltage whereas the OP is measuring average voltage with his multimeter set to DC hence the voltage appears too low. A 'scope or true RMS meter will give a correct reading.

Yeti · **Posted:** Tue Jan 19, 2016 2:51 pm

last release software give 11,65v for two second and 2,35v for 10 second and you can put 5v or 7v with the same controller , the voltage is a % of the battery voltage , the PWM is a simple on off , example in short word , axis X = 5v and Y= time ,one second divided by 6 bit on and 6 bit off you obtain 2,5v and you can measure with a multimeter

not a mistery

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

dirtmover wrote:

jws84_02 wrote:

MrMopar64 wrote:

Running the 5V glow plugs with the 7V programming will result in plugs that are too cold during start, and overheated afterwards. It's a recipe for disaster.

The glow plug module can, for all intents and purposes, be left alone during the swap. The new one has a slightly higher current capacity, but it'll function the same.

Won't 5v plugs on 7volt burn hotter? But also go bad quicker

The GPs are started at a voltage much higher than their nominal to rapidly bring them to the correct operating temperature. Once up to temperature the voltage is dropped back to the nominal 7V, or 5V, depending on the programming. What MrMopar64 is alluding to is that this initial high voltage burn is much shorter for the 7V programming because the ceramics require less energy to bring them up to the correct operating temperature. This initial burn time is too short for the 5V metal sheathed plugs which require more energy to reach the required temperature. With the 7V programming once that initial boost is over the 5V plugs would continue to be driven at 7V for an extended period which is not good for them.

The shorter initial burn provided by the 7V tune is also the reason that the Etecno1 product is marginal. A custom tune for the Etecno1 would give us a viable product but I don't know if anyone is prepared to put in the effort to develop this?

Going back to the original post the glow plugs are rated at RMS voltage whereas the OP is measuring average voltage with his multimeter set to DC hence the voltage appears too low. A 'scope or true RMS meter will give a correct reading.

Developing the tune for the Etechno plugs is not "hard" per se, that can be done quite easily. However, to do it is mandatory to have an instrumented glow plug with a thermocouple inside. In the discussions we've had with Etechno they weren't able to make one for whatever reason.

Once the pre-glow phase is complete (reach operating temp as fast as possible), the glow plugs go to the rated voltage only during crank then go back to a variably controlled voltage during the running phase to maintain temperature based on engine load. Very rarely are the plugs actually driven at their rated voltage.

tcoilburner · **Posted:** Wed Jan 20, 2016 12:40 am

I have found with the Etechno plugs that if I wait to start depending on temp 5-10 seconds after the glow plug light goes out my engine seems to start easier. This is my first winter here in Mid. Michigan with these plugs. The first 145,000 miles with the ceramics where much easier.

dirtmover · **Posted:** Wed Jan 20, 2016 8:37 am

GreenDieselEngineering wrote:

Once the pre-glow phase is complete (reach operating temp as fast as possible), the glow plugs go to the rated voltage only during crank then go back to a variably controlled voltage during the running phase to maintain temperature based on engine load. Very rarely are the plugs actually driven at their rated voltage.

Can you elaborate a bit more on the time between pre-glow and cranking e.g. is one delays cranking for a few seconds do the plugs receive nominal voltage at that point.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

dirtmover wrote:

GreenDieselEngineering wrote:

Once the pre-glow phase is complete (reach operating temp as fast as possible), the glow plugs go to the rated voltage only during crank then go back to a variably controlled voltage during the running phase to maintain temperature based on engine load. Very rarely are the plugs actually driven at their rated voltage.

Can you elaborate a bit more on the time between pre-glow and cranking e.g. is one delays cranking for a few seconds do the plugs receive nominal voltage at that point.

Pre-glow is first during the key-on, after that you go into start-readiness glow (this is the time after post glow and before cranking). The readiness glow lasts for several seconds based on a curve in the calibration dependent on coolant temp. If you do not crank in the prescribed time limits the glow plugs turn off. If you start cranking the system shifts to the start glow maps. After the engine starts, it goes into the post-glow mode for 1-3 minutes depending on coolant temps, etc. Hope this is useful to you.

tcoilburner · **Posted:** Wed Jan 20, 2016 11:10 pm

GreenDieselEngineering wrote:

dirtmover wrote:

GreenDieselEngineering wrote:

Once the pre-glow phase is complete (reach operating temp as fast as possible), the glow plugs go to the rated voltage only during crank then go back to a variably controlled voltage during the running phase to maintain temperature based on engine load. Very rarely are the plugs actually driven at their rated voltage.

Can you elaborate a bit more on the time between pre-glow and cranking e.g. is one delays cranking for a few seconds do the plugs receive nominal voltage at that point.

Pre-glow is first during the key-on, after that you go into start-readiness glow (this is the time after post glow and before cranking). The readiness glow lasts for several seconds based on a curve in the calibration dependent on coolant temp. If you do not crank in the prescribed time limits the glow plugs turn off. If you start cranking the system shifts to the start glow maps. After the engine starts, it goes into the post-glow mode for 1-3 minutes depending on coolant temps, etc. Hope this is useful to you.

How long will the glow plugs heat in the start-readiness mode, in the Eco-tune Full torque reprogram that I have? Say at 15 degrees or less and coolant stone cold too.

funnyman06 · **Joined:** Sun Jul 06, 2014 7:46 pm **Posts:** 180

GreenDieselEngineering wrote:

The 5V metallic plugs are still capable to start the engine at -20F unassisted. It's not the most pretty start compared to newer more modern diesels, but if the battery is in good shape then it'll fire.

This winter I have been having issues starting with my 7V Etechno once it gets below 15F, it sounds like there is not much that you can do to the tune to help the 7V plugs heat up properly. So everyone should move to the 5V plugs and this should cure most cold start issues related to poor glow plug performance? This is good information to have out there because on IDParts website they explain that the 5V Bosch and 7V Etechno are equivalent to each other and that neither is really an improvement over the other. I think ill order a set of 5V plugs and get those swapped out.

JD3020 · **Posted:** Sun Jan 31, 2016 12:57 pm

I put Etecno's in my CRD a month ago, and have the same complaint. This POS will not start in cold weather unless its plugged in. My original ceramics had broken tips and were throwing codes, but still started better than these. Honestly pissed off that i wasted any money on the Etecno's.

Wish these were like my 7.3's. All the PCM does is turn a relay on, for up to 2 minutes. Glow plugs see full 12v the entire time. As long as the plugs are reasonably healthy(very rarely do they fail), and the relay works, the truck will start in any temperature. And those Bosch plugs are only $8-10 a piece.

flash7210 · **Posted:** Sun Jan 31, 2016 3:12 pm

Search eBay.
I've seen some waaay overpriced CRD glow plugs that I can only assume are original ceramics.
Also there are some 11 volt glow plugs from Europe. I don't think they would work with our ECM programming but maybe you could develop your own glow plug control circuit. Just need a timer, a relay, and a switch.

dirtmover · **Posted:** Sun Jan 31, 2016 7:32 pm

flash7210 wrote:

Search eBay.
I've seen some waaay overpriced CRD glow plugs that I can only assume are original ceramics.
Also there are some 11 volt glow plugs from Europe. I don't think they would work with our ECM programming but maybe you could develop your own glow plug control circuit. Just need a timer, a relay, and a switch.

There was a guy posted here a couple of years ago that was using 11V plugs with a controller from a Mercedes. He lives about 30 minutes from me so he's able to start it in pretty cold weather.

funnyman06 · **Joined:** Sun Jul 06, 2014 7:46 pm **Posts:** 180

I wonder what it would take to adopt the 11v plugs from Europe. I too have had better luck starting my 85 6.9L IDI in the cold with its beru glow plugs than this thing. Hopefully all of my parts get in soon and I can update you guys on my own experience.

7v glow plugs - show 5.2v peak - is this normal?

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