Why all the cold start issues...

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

The cold starting problems on the KJ are strongly correlated to the change from 7 volt ceramic glow plugs to either 5 volt metallics from mopar or the 7 volt metallics from etecno. The ceramic plug was designed to heat to about 1300 F, whereas the metallic glow plugs are only good for about 1050 F. This alone will have a negative effect on the start.

It is possible to change the glow plug duty cycle to have longer glow times or slight higher pulse width, however this also entails a much greater risk of a plug failure...which is already a problem since there seem to be quite a few of the metallic gp failures. This method will not be a robust solution.

There is one other major design consideration that cannot be fixed when changing from ceramic gp to metallic gp. The original ceramic glow plugs were positioned directly between the spray pattern on the injector nozzle. This means fuel sprays around the glow plug and not directly on it. THIS IS A VERY IMPORTANT DETAIL. The metallic glow plugs are a "spray-on" design and work best if aligned with one hole on the injector nozzle.

So we have a colder plug that is not getting a direct blast of fuel and it takes longer crank times to build sufficient heat for stable combustion. The best work around in cold weather is a good charged battery with high CCA rating and usage of the block heater.

LMWatBullRun · **Posted:** Wed Feb 12, 2014 10:26 am

Time for the hair dryer!

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

An aftermarket air grid heater would be a nice option for sure!

MRausch82 · **Posted:** Wed Feb 12, 2014 12:24 pm

GreenDieselEngineering wrote:

There is one other major design consideration that cannot be fixed when changing from ceramic gp to metallic gp. The original ceramic glow plugs were positioned directly between the spray pattern on the injector nozzle. This means fuel sprays around the glow plug and not directly on it. THIS IS A VERY IMPORTANT DETAIL. The metallic glow plugs are a "spray-on" design and work best if aligned with one hole on the injector nozzle.

So we have a colder plug that is not getting a direct blast of fuel and it takes longer crank times to build sufficient heat for stable combustion. The best work around in cold weather is a good charged battery with high CCA rating and usage of the block heater.

Interesting! I had not considered this previously. Have you, or anyone else heard of failures with the 5v Bosch metallic (updated) plugs? I have not, yet. Seems to be mainly with the Etecno plugs so far. One reason I suspect *might* be a cause for failure on the Etecno plugs is that folks are using the original glow plug control relay. I have seen these relays fail on VW's and other small diesels resulting in a much lower life of the glow plugs, among other catastrophic glow plug related failures. It is just a theory that I have on the CRD... That said, I wonder if it is worth "experimenting" with longer pulse and glow times?

LMWatBullRun · **Posted:** Wed Feb 12, 2014 12:44 pm

GreenDieselEngineering wrote:

An aftermarket air grid heater would be a nice option for sure!

What is presently commercially available?

CGman · **Posted:** Wed Feb 12, 2014 1:26 pm

So is there anything else that should be changed when switching to the 7v steel plugs? I asked the question on the idparts website and they only talked about ecu flash. Any advantages to going to New glow plug module?

mark2m · **Posted:** Wed Feb 12, 2014 1:39 pm

I had one glow plug fail from the new 5v ones after about 2 years. Fixed now. I do have problems with it starting when it gets down to the single digits. It will fire off and seem like it will catch on the first try but the next few tries it seems to struggle more and more to catch and this is with a good battery. I have found what works for me is pumping the gas a little. I don't know if there is some other problem but when I pump the pedal when cranking I can keep it running and it will catch and settle down a lot quicker than if I do nothing.

MRausch82 · **Posted:** Wed Feb 12, 2014 1:58 pm

mark2m wrote:

I do have problems with it starting when it gets down to the single digits. It will fire off and seem like it will catch on the first try but the next few tries it seems to struggle more and more to catch and this is with a good battery. I have found what works for me is pumping the gas a little. I don't know if there is some other problem but when I pump the pedal when cranking I can keep it running and it will catch and settle down a lot quicker than if I do nothing.

Sounds like the same issue I am experiencing. Pumping the gas "seems" to help, but the last time I tried that, it did nothing. Had it plugged in for 3 hours this AM while it was -15ºF. It warmed up to about 5ºF by the time I went to start it. Started right up without so much as a hiccup.

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

I have the 5V Bosch plugs in mine. I am in Minnesota, so it's pretty cold here in the winter. I have it plugged in at night but not during the day. I only have starting issues when it's below zero and it has sat for 6-8+ hours (usually have to crank it a few times and then I get lots of smoke out the tailpipe). Otherwise, it starts up just fine.

I would definitely be interesting in a recalibration of the glow plug duty cycle higher pulse width, but only if it didn't degrade the lifetime of the glow plugs. It sounds like the switch to a "spray-on" design is the real culprit here.

thermorex · **Posted:** Wed Feb 12, 2014 7:13 pm

wonder how hard is to put a heater (glow plug) to replace the fcv, that may be the easiest option...

bugnout · **Posted:** Wed Feb 12, 2014 7:18 pm

Weeks101, how about incorporating one of these into your EGR delete pipe

http://www.straptperformance.com/product/1608/Shibby-Engineering-Throttle-Valve-with-Grid-heater/

Mike92104 · **Posted:** Wed Feb 12, 2014 8:16 pm

One of these:

http://www.webasto.com/us/markets-produ ... ro-50-eco/

would be awesome. I love the idea of not having to plug anything in, or worry about having power available. Of course, I live in San Diego, so I've never really had to deal with it, but I like the idea.

Mike

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

bugnout wrote:

Weeks101, how about incorporating one of these into your EGR delete pipe
http://www.straptperformance.com/product/1608/Shibby-Engineering-Throttle-Valve-with-Grid-heater/

That did cross my mind. I'd probably be willing to produce a run of them if there is enough interest.

But I do wonder if our batteries could handle the power draw from an air intake heater since these systems are usually used in full-size trucks that often have dual battery set-ups. If the battery voltage is low, glow plug performance and starter performance could be reduced, and the ECU might not even function. It needs a minimum voltage reading to function, even if the battery has enough juice to crank the engine.

Anyway, if the electrical questions were answered, something like this unit, hooked up via the proper relay to a momentary switch, would be more economical and straightforward to integrate into the kit:

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

Or this...

thermorex · **Posted:** Wed Feb 12, 2014 9:35 pm

Weeks, I think we can go with dual batteries if power juice would be an issue, a conversion is not hard, I did it on the Cherokee, plus it frees up some space under the hood if batteries are placed in the rear/trunk. I would be interested for sure in a kit, the first one you posted seems nice since if that would restrict the airflow it can be taken out relatively easy and replaced by a short bolt. The only issue I can see is to have a heater that won't crack and mess up the valves. You can count me in

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

This could be promising...

65Corvair · **Posted:** Thu Feb 13, 2014 12:24 am

If we could use 12V for the preheat then maybe drop down to 7V (glow plug voltage) while cranking, it might not eat all of the cranking power.

thermorex · **Posted:** Thu Feb 13, 2014 7:15 am

weeks101 wrote:

This could be promising...

It's funny, just looked at it yesterday... It's a diesel tractor intake heater, right? Anyways, if you end up building the intake elbow for it, please count me in, I can send you a payment anytime.

mark2m · **Posted:** Thu Feb 13, 2014 11:01 am

MRausch82 wrote:

mark2m wrote:

I do have problems with it starting when it gets down to the single digits. It will fire off and seem like it will catch on the first try but the next few tries it seems to struggle more and more to catch and this is with a good battery. I have found what works for me is pumping the gas a little. I don't know if there is some other problem but when I pump the pedal when cranking I can keep it running and it will catch and settle down a lot quicker than if I do nothing.

Sounds like the same issue I am experiencing. Pumping the gas "seems" to help, but the last time I tried that, it did nothing. Had it plugged in for 3 hours this AM while it was -15ºF. It warmed up to about 5ºF by the time I went to start it. Started right up without so much as a hiccup.

Oh yeah when it's plugged in starts right away. Hasn't failed me yet with pumping the pedal a little.

Mark

weeks101 · **Joined:** Mon Jul 30, 2012 3:29 pm **Posts:** 747

thermorex wrote:

Anyways, if you end up building the intake elbow for it, please count me in, I can send you a payment anytime.

Sent you a PM.

Why all the cold start issues...

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