Strange starting issue - 2006 Jeep Liberty CRD

justinmc · **Posted:** Tue Oct 18, 2016 11:35 am

geordi wrote:

You don't need to measure anything - it will be engraved on the side of the plug. If you have ceramic, then they are 7V and the Etechno plugs are a drop-in replacement.

As far as what mileage they might fail at... What is the sound of one hand clapping? It cannot be known, they don't seem to be predictable, but they are ALL aging if they are still in service. Better safe than sorry. When they start to die, the resistance increases and the computer can detect this and throw a code. However it also still supplies voltage, which makes the plug hotter (higher resistance = more heat) until they overheat completely and shatter. VERY BAD.

My point was if there was a voltage to measure it would be easier than pulling a plug to check it. Thanks.

GordnadoCRD · **Posted:** Wed Oct 19, 2016 1:56 am

justinmc wrote:

My point was if there was a voltage to measure it would be easier than pulling a plug to check it. Thanks.

Look, friend.

No one here is trying to inconvenience you, nor cause you any extra work or grief. We are only relating to a situation of your description, as it pertains to our individual experience, none of which is entirely perfect, whole, or complete. (at least I know mine isn't)

Whether you heed anyone's advice is entirely up to you. You have many possible ways of addressing your situation

Whether you have instant access to someone with a proper oscilloscope to measure the glow plug circuit voltage wave, and whether they have the knowledge to interpret what it means; None of us know. For us "average Joe's" the simplest way that we would address the problem were we in your shoes, would most likely start with flipping the serpentine belt off of the alternator pulley, setting the alternator aside, pulling out #1 glow plug and having a look. We would then have one less "unknown" to worry about, and could move forward, knowing more truth about the situation wherein we stand.

justinmc · **Posted:** Wed Oct 19, 2016 6:17 pm

GordnadoCRD wrote:

Look, friend.

No one here is trying to inconvenience you, nor cause you any extra work or grief. We are only relating to a situation of your description, as it pertains to our individual experience, none of which is entirely perfect, whole, or complete. (at least I know mine isn't)

Whether you heed anyone's advice is entirely up to you. You have many possible ways of addressing your situation

Whether you have instant access to someone with a proper oscilloscope to measure the glow plug circuit voltage wave, and whether they have the knowledge to interpret what it means; None of us know. For us "average Joe's" the simplest way that we would address the problem were we in your shoes, would most likely start with flipping the serpentine belt off of the alternator pulley, setting the alternator aside, pulling out #1 glow plug and having a look. We would then have one less "unknown" to worry about, and could move forward, knowing more truth about the situation wherein we stand.

Interesting response you wrote here. I'm not sure if you're having trouble understanding what I am saying but at no point did I suggest anyone was trying to inconvenience me. I asked very specific questions which should have very specific answers. I do have a couple of oscilloscopes so I could certainly do that if it's not something that can be measured with a simple volt meter. I just seems silly to me that a system supplying a voltage to a glow plug isn't more easily identifiable as to what voltage is being supplied or which plugs are being used. I don't think glow plugs are the problem of my original question about starting though since most people seem to think the ceramic plugs work better just that they are an accident waiting to happen. Anyway, I hope that clarifies things a bit and I appreciate your input.

geordi · **Posted:** Wed Oct 19, 2016 6:54 pm

He may have been a bit touchy with his reply, but he wasn't wrong about the procedure. You can't just measure the voltage to the plugs b/c the computer doesn't have a way to send only 7v or 5v. It uses pulse width modulation to create the voltage and b/c the plug is a resistive heater, hitting it with 11+ volts for milliseconds at a time doesn't blow it up. For a time.

justinmc · **Posted:** Wed Oct 19, 2016 7:42 pm

geordi wrote:

He may have been a bit touchy with his reply, but he wasn't wrong about the procedure. You can't just measure the voltage to the plugs b/c the computer doesn't have a way to send only 7v or 5v. It uses pulse width modulation to create the voltage and b/c the plug is a resistive heater, hitting it with 11+ volts for milliseconds at a time doesn't blow it up. For a time.

Thanks for the additional info. I'll look in the tech sections to see where to hook up a scope and see if that seems easier than pulling a plug. I'm used to working on vehicles with more clearance around the engine so something as "simple" as pulling a plug by loosening the serpentine belt with a tensioner 1/2 way down the engine with very littler clearance to take the belt off to remove the alternator seems like a lot of trouble. Sometimes I think they add too much technology and complication to simple things under the guise of "improvement".

justinmc · **Posted:** Wed Oct 19, 2016 8:00 pm

flash7210 wrote:

Quote:

56044671AA: factory glow plug module for 7v ceramic

56044671AC: updated glow plug module - included as part of 5v conversion

Those part numbers are for the glow plug relay.
They both have the exact same Bosch #.

Okay, after looking at that thread again they mention that's the number on the side of the Bosch glow plug relay (0 281 003 034) and mine has that AC version on it not AA so according to that thread it means it was replaced during the 5v glow plug conversion. So I should have 5v glow plugs. Does that make sense?

flash7210 · **Posted:** Wed Oct 19, 2016 8:21 pm

justinmc wrote:

flash7210 wrote:

Quote:

56044671AA: factory glow plug module for 7v ceramic

56044671AC: updated glow plug module - included as part of 5v conversion

Those part numbers are for the glow plug relay.
They both have the exact same Bosch #.

Okay, after looking at that thread again they mention that's the number on the side of the Bosch glow plug relay (0 281 003 034) and mine has that AC version on it not AA so according to that thread it means it was replaced during the 5v glow plug conversion. So I should have 5v glow plugs. Does that make sense?

Its certainly possible.
Its also possible that the relay was replaced simply because a new one was needed and no 5v upgrade was performed.

justinmc · **Posted:** Wed Oct 19, 2016 9:12 pm

flash7210 wrote:

Its certainly possible.
Its also possible that the relay was replaced simply because a new one was needed and no 5v upgrade was performed.

If I ever get my MPPS working then I can check the ECU programming and confirm. Thanks.

geordi · **Posted:** Wed Oct 19, 2016 9:45 pm

The physical relays are also exactly the same - I don't know why they replaced the Mopar part number, but the part under it hasn't changed a bit. That is why it still has the same Bosch part number.

justinmc · **Posted:** Mon Dec 05, 2016 2:00 pm

My jeep was starting fine for the past couple of months (other than the long cranking of 4-5 seconds) but yesterday it wouldn't start at minus 5C (23F). Today at minus 8C it started right away no problem. I had to jump start it several times yesterday to get it going . It would start and idle roughly for a few seconds then stall over and over again.

Somewhere between -5C and +8C (23F and 46F) it has trouble. It always starts fine if the engine is warm. During cranking the voltage is usually 11v or more but it has started with the voltage as low as 10.5v. The battery tested fine for CCA with an electronic battery tester.

It seems like it's electrical related but also maybe glow plug related since it starts better when colder.

Does anyone have any further insight into this strange problem?

flash7210 · **Posted:** Mon Dec 05, 2016 3:22 pm

Does using the block heater help with cold starting?

Maybe the problem is fuel gelling. Have you tried any winter fuel additive?
PowerService in the white bottle is most common.

geordi · **Posted:** Mon Dec 05, 2016 3:31 pm

Could be the temperature sensor in the grille that (IIRC) is used to control the glow timing. Perhaps there is a dead spot in it that it isn't activating the plugs at all? That behavior that you describe sounds like the plugs weren't even being tried, which is unusual given the temperature.

justinmc · **Posted:** Mon Dec 05, 2016 3:57 pm

geordi wrote:

Could be the temperature sensor in the grille that (IIRC) is used to control the glow timing. Perhaps there is a dead spot in it that it isn't activating the plugs at all? That behavior that you describe sounds like the plugs weren't even being tried, which is unusual given the temperature.

How would I go about checking the temp sensor in the grill? I was leaning towards the glow plugs working since it started better when colder.

geordi · **Posted:** Mon Dec 05, 2016 6:16 pm

Not sure if you can inspect it electronically, but it should be a resistance type device just like most other sensors. Hopefully there is an ohm range in the service manual.

Only other thought is trying to swap it with a known-good and see if the performance changes.

justinmc · **Posted:** Mon Dec 05, 2016 6:55 pm

geordi wrote:

Not sure if you can inspect it electronically, but it should be a resistance type device just like most other sensors. Hopefully there is an ohm range in the service manual.

Only other thought is trying to swap it with a known-good and see if the performance changes.

If you're talking about the ambient air sensor which shows the temp on the trip computer it's working fine.

mass-hole · **Posted:** Mon Dec 05, 2016 9:30 pm

You can tell what plugs you have by pulling the connector off and looking at the ring of insulation at the base of the tip. Red = 5V, white =7V ceramic, none=most likely etechno 7V. At least this is what GDE told me.

You should be able to get to at least one of them without removing anything.

WWDiesel · **Posted:** Mon Dec 05, 2016 9:56 pm

mass-hole wrote:

You can tell what plugs you have by pulling the connector off and looking at the ring of insulation at the base of the tip. Red = 5V, white =7V ceramic, none=most likely etechno 7V. At least this is what GDE told me.
You should be able to get to at least one of them without removing anything.

Unfortunately not always entirely true, in my case I tried that before ordering new glow plugs and could find no color markings! So I pulled the no. 1 GP and deturmined it indeed was a 7v glow plug and ordered the 7v Etechnos...

So when I removed all four Bosch 7v ceramics, none of them had any colored rings, only the stamped markings visible after removing them identified what they actually were... :shock:

see picture:

joelukex4 · **Joined:** Thu Sep 29, 2011 4:54 pm **Posts:** 386

WWDiesel,
It looks like your third plug from the left has the black ring marking. I surprised the others do not unless from the heat the ring degraded and fell off.
Your glow plugs look to be in good shape. When did you remove & why? Just concern that they would break?

WWDiesel · **Posted:** Tue Dec 06, 2016 4:04 pm

joelukex4 wrote:

WWDiesel,
It looks like your third plug from the left has the black ring marking. I surprised the others do not unless from the heat the ring degraded and fell off.
Your glow plugs look to be in good shape. When did you remove & why? Just concern that they would break?

Actually they had no colored ring at all; I was surprised! :shock:

They should have had a white ring according to the stamped markings on the barrel. Bosch 7v

I replaced them at 155k. They were working just fine with no error codes or cold weather starting issues.
I just plain got scared of one of them breaking off and wreaking havoc in the engine.
Figured it was cheap insurance to change them now before they could do any expensive damage!!!

ps. Geordi helped convince me due to some of his dire warnings on this forum... :grim:

Guess it is better to have poor cold weather performance than a DEAD engine? :juggle:

justinmc · **Posted:** Wed Dec 07, 2016 2:53 pm

flash7210 wrote:

Does using the block heater help with cold starting?

Maybe the problem is fuel gelling. Have you tried any winter fuel additive?
PowerService in the white bottle is most common.

I thought it had to be colder for the fuel gelling to occur and don't the fuel stations add that automatically this time of year? I guess it wouldn't hurt to add some anyway?

I tried starting it earlier today at minus 10C (14F) and it didn't start. Then I plugged the block heater in for a couple of hours still no start. I'm just charging the battery now and then I'll try again or jump it. It's warmed up to minus 7C now.

EDIT: I opened up the bleeder on the fuel filter head and it didn't seem to be gelled at all. Still having trouble starting it with jumping. Starts and then stalls.

Strange starting issue - 2006 Jeep Liberty CRD

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