Bypassing the glow plug controller...

Drewd · **Joined:** Mon Feb 06, 2006 12:24 pm **Posts:** 902

Durangotang,
Based on my hard start experience, have you looked at your glow plug wiring harness? Mine had bare wire showing (insulation worn off). Could something like this be causing your controller to fry? The wiring harness is only 44 bucks and a small PITA to replace but worth it for me. I don't recall but are you still on the original set of glow plugs but a change couldn't hurt if you are over 60k miles. I've seen some weird things over the years with electrical stuff as a former military maintenance test pilot....weirdest example was having to replace a master caution panel (just a panel of warning lights that turn on when something goes wrong) because my APU (auxiliary power unit) wouldn't start. We would have never figured this one out because the APU start and run sequence had nothing to do with lights on the panel except for one light that would turn on when the APU was running. A Vietnam era maintenance test pilot who had had many years of experience advised us to replace it....we thought he was nuts but it worked but no one could explain why.

Now, if I can only find out why my ABS/Cruise/ESP aren't working still. I got a code for right rear wheels sensor that I just replaced this morning. I still have the code and warning lights :-(

RJM · **Posted:** Sun Feb 14, 2010 5:26 pm

Drewd wrote:

Durangotang,
Based on my hard start experience, have you looked at your glow plug wiring harness? Mine had bare wire showing (insulation worn off). Could something like this be causing your controller to fry? The wiring harness is only 44 bucks and a small PITA to replace but worth it for me. I don't recall but are you still on the original set of glow plugs but a change couldn't hurt if you are over 60k miles. I've seen some weird things over the years with electrical stuff as a former military maintenance test pilot....weirdest example was having to replace a master caution panel (just a panel of warning lights that turn on when something goes wrong) because my APU (auxiliary power unit) wouldn't start. We would have never figured this one out because the APU start and run sequence had nothing to do with lights on the panel except for one light that would turn on when the APU was running. A Vietnam era maintenance test pilot who had had many years of experience advised us to replace it....we thought he was nuts but it worked but no one could explain why.

Now, if I can only find out why my ABS/Cruise/ESP aren't working still. I got a code for right rear wheels sensor that I just replaced this morning. I still have the code and warning lights

Check the wires in the loom for the RR sensor above the diff gear housing , they rub through and short out. throwing a sensor code

RJM · **Posted:** Sun Feb 14, 2010 5:29 pm

"Bubba" is a good guy in my books.

tonycrd · **Posted:** Tue Feb 16, 2010 1:35 pm

I don't know how you 05+ guys have it, but I would just paperclip the 2 relay connections...in the relaybox in front of the battery.

Drewd · **Joined:** Mon Feb 06, 2006 12:24 pm **Posts:** 902

Would that work? Doesn't the relay just switch on/off the 7v voltager coming from the controller (assuming it is the controller that steps the voltage down from 12v to 7 v).

BVCRD · **Posted:** Wed Feb 24, 2010 6:20 pm

Goglio704 wrote:

The following is the most relevant part of a post I made a while back in the tech section. It is based on some testing I did to satisfy my curiosity and have some baseline numbers:

"1. With the engine at about 30F, the glowplugs were showing about 1 ohm of resistance each. This was measured at the connector for the Bosch glowplug control just behind the battery.

2. At this temperature, the glowplugs initially are powered at 7 volts or just under. They drop to about 4 or 4.5 volts at about the same time the glow plug light goes out and float around at this voltage for 15 or 20 seconds before turning off if the engine is not started. If the engine is started, they float around between 3 and 5 volts for a long time. I'll try to define this time more closely, but I know it was at least 30 to 45 seconds. It may be dependent on either coolant or charge air temperature."

It seems to me the controller can vary the voltage, but if it only has a 7 volt supply, that would make bypass possibilities much safer to be sure.

Looking at the chart, the "initial" on time is around 3 minutes after the engine starts. Depending on the ambient temp reading taken by the ECU, they come on for 16-26 seconds. Like....20 seconds if it is 15* F before going to a "helper" stage.

BVCRD · **Posted:** Wed Feb 24, 2010 6:30 pm

nursecosmo wrote:

If anyone thinks that it is a bad idea, then don't do it. You probably don't have enough thumb control for safe use. I have used it all my life and have never had an engine damaged by it yet. I have seen others damage their engines by foolishly spraying too much into the intake, or who have used it when the temperature was too warm. If it is used judiciously when the temperature is very cold, it will NOT damage the engine. This is what it was designed for. Also, it is not recommended for engines which use grid heaters i.e. Cummins Ram trucks.

We should all try and give advice from our own personal experience and not just repeat things we read on the Internet, or what "Bubba", down at the corner Quick lube told us.

Shop manual says NO liquids in the intake.

nursecosmo · **Posted:** Wed Feb 24, 2010 11:28 pm

BVCRD wrote:

nursecosmo wrote:

If anyone thinks that it is a bad idea, then don't do it. You probably don't have enough thumb control for safe use. I have used it all my life and have never had an engine damaged by it yet. I have seen others damage their engines by foolishly spraying too much into the intake, or who have used it when the temperature was too warm. If it is used judiciously when the temperature is very cold, it will NOT damage the engine. This is what it was designed for. Also, it is not recommended for engines which use grid heaters i.e. Cummins Ram trucks.

We should all try and give advice from our own personal experience and not just repeat things we read on the Internet, or what "Bubba", down at the corner Quick lube told us.

Shop manual says NO liquids in the intake.

Someone should mention that to the engineers who designed the PCV valve.

BVCRD · **Posted:** Wed Feb 24, 2010 11:39 pm

Exactly. I think they meant....well....you know.

Bypassing the glow plug controller...

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