Glow Plug Failure and Electronic Throttle Control

[Auberon]

Crashman,

This is a very serious post.

I have what I was told was the last 06 manufactured crd to come into the country DC regard it as an early '07...go figure.
When warranty ran out, during the first winter, the ETC light came on occasionally - never summer, autumn or spring. No odd resistances, temperaures with remote lasers, thermocouples etc can ID a common temp. The resistances seem OK.
I have not tried glow plugs tho. I will explain.

My ETC comes on sometimes (emphasise sometimes) only when the ambient air is cold and everything is running hot enough to get TC lockup etc. No trouble codes shown.
This only glitch is that my ETC light MIGHT come on.
Never happens in summer, autumn or spring.
Starts perfectly even really cold.

I hadn't considered glow plugs and have been studying the manual.
I have two possibilities. The first is least likely.

My truck has the original red top optima - this can cause the odd behaviours of the sensors....but I have load tested it and tests fine.

The ETC light goes out each time so I enterpret this as a very "soft" code.
Hope this helps.

The STRONGEST other thought I have had is that I don't believe we get real winter diesel in Sydney. I have the thought in the back of my mind that we get slightly waxy in the colder weather as this is a normal year we just haven't had one like this for a few years.

I have been thinking very hard on this. I believe we have this situation and I am not confident in Jeep knowing diesels for diesel characteristics. Sorry to say it but I do. I don't think it is a glow-plug issue.

In all candour, my strongest suspicion (as we have not had a year this cold since I have had this truck) and it is VERY TYPICAL of a diesel truck not getting winter grade fuel. I don't believe we do get it in Sydney. It is a classic running style for any diesel motor that doesn't have winter grade fuel in it - start - run - stop or run like crap or show A MINOR SENSOR FAULT? - hesitate a bit or leave you stranded just down the road.

It doesn't matter if the motor is hot - the motor will die or do any of the above as wax (or more correctly thickened fuel) will do what wax does. It only has to become a tad more viscous due to the temperature change, and that will cause this, I believe.

Good luck.
Auberon

[Crashman]

I have looked into it a bit more, What I have found is the glow plug light doenn't appear on the instrument pannel when starting and everything else seems to be ok. I have checked what i can at home but it appears it is just not kicking in at ignition. The manual details a control modual mounted next to the battery. I am going to have the auto electrician take a look as this modual may just be acting up.

[dazzer01]

Originally Posted by Crashman

I have looked into it a bit more, What I have found is the glow plug light doenn't appear on the instrument pannel when starting and everything else seems to be ok. I have checked what i can at home but it appears it is just not kicking in at ignition. The manual details a control modual mounted next to the battery. I am going to have the auto electrician take a look as this modual may just be acting up.

I have an 07 KJ and I've had this problem for the last 3 services. The dealer has checked it each time and also a special trip there for that problem, but when I leave it Murphy intervenes and they can't replicate the problem. Since the last service in April it's become much more persistent, on better than 50% of trips, but like you say it doesn't light during startup but maybe 10 seconds later. We've done 57k so age and distance is about similar. I had it in mind to call the dealer again about it and remind them that I'd brought this to their attention during the original warranty period (I lashed out and paid for the Jeep extended warranty because I get really concerned at some of the horror stories on here, wimp that I am )
Anyway I'll follow this thread and if I get a resolution from the dealer I'll post about it here.
(EDIT: Oh, it's mentioned in my manual under the Dash Lights section for CRD's as an ETC problem, and suggests that the brake and or throttle may be sticking or stuck. Also suggests IMMEDIATE dealer attention, but the dealer says if no loss of power or rough running or anything else then just mention it again at next service, which I have done, and we've probably done 15k. since the problem first appeared.)

[dazzer01]

Originally Posted by Auberon

It doesn't matter if the motor is hot - the motor will die or do any of the above as wax (or more correctly thickened fuel) will do what wax does. It only has to become a tad more viscous due to the temperature change, and that will cause this, I believe.

Good luck.
Auberon

No mechanical genius, me, but, I seem to recall that the KJ's have a "diesel pre-heat" element or something in the fuel line, being designed in North America and all. Am I right that this would abate the "wax" effect you talk of here?

[Muskrat]

Dazzer - I had a look in the Service Manual and the only pre-heat it talks about is related to the Glow Plugs. Also, according to the manual, "The glow plug module is mounted to the inner fender between the battery and the master cylinder in the engine compartment" - looks easy to replace as well. I am sure that there is an easy troubleshooting procedure for this because I have read it before. I seem to recall it runs on 7 volts not 12 as you would expect..

[Crashman]

It is a 7volt system and as far as testing I have only found in manual how to test the plugs not the module. there is instructions on how to remove it as well.

[Auberon]

The wax is a symptom of fuel. It relates to the fuel companies supplying the right fuel at the right tinme of the year. It is though that modern, more sophistacated diesels throw codes to it more readily than older diesels but the signs and symptoms are exactly the same in their presentation.
Diesel pre-heat awlways operates - it is just so short for our purposes for the most part that we don't have to go through holding the glow-plugs on gor a certain number of seconds like in days gone by.

The fuel manufacturers have to include additives or reformulate for winter and they are supposed to supply different formulary incase one of us drives to the snow. As was correctly noted it is not solved by any pre-heating sytem - this is to aid ignition of the fuel. With economy of the CRD we can easiliy get to the snow, have a wax-up and heaps of cost associated. So you should travel to the snow so that you are getting empty and fill up down there with WINTER GRADE fuel. This is why recently on 4wd TV they strongly suggested we all keep our fuel receipts...the onus is on the fuel company unless you mismanage. Preheat happens whether you know about it or not. It must.

IMPORTANTLY:
I understand that we only run 2 voltage systems. 12 V for lights etc and 5 V clamped rail for all other sensors and computers. 7V would read high in any terms for any sensor, would it not?

The ETC is at the pedal and is a sensor based on a hall-effect device and is refered to on page 4376 of the FSM makes reference to the "reference voltage" to which I refer.

I have never read of 7V in the KJ systems nor any other of my computer diagnostics dealings.
Auberon