Easy glow plug manual control mod

[glenlloyd]

After studying the wiring schematic for the system I elected to install a manual control system that utilizes the existing components rather than installing another glow relay and underhood wiring.

In fact, this install results in no modifications outside the cabin and is really pretty simple. It takes power from the glow plug controller power supply, which is already fused in the main fuse box, and redirects that power, via my dashboard push button switch, to the OE glow relay #1, through the OE wiring going to the #1 relay from the controller.

It does however assume that the #1 relay is working properly and that power is actually reaching the glow plugs, something that should be verified before you pursue this install.

The problem this solution addresses is the repeated claim that perhaps the OE system doesn’t heat long enough under certain conditions. Those conditions can be either the warm start problem that has been voiced by other members or the severe cold start where the plugs don’t operate for quite as long as we think they should.

My issue was that although my water temp sensor tested good, the system failed to glow for as long as it should have during the winter months. I may have fixed the problem with the water temp sensor by replacing the corroded bullet connectors which could have given the system false readings, but it was more important to me to put control of the glow system in the hands of the driver.

For 1982-83 vehicles this is the primary area where you’ll be working. You’ll need to remove the lower dash panel (three turn buttons) and the passenger kick panel (one screw) in order to get behind the carpet where you’ll want to run your wiring to the controller, which sits under the passenger seat. You’ll also want to remove the passenger seat, which isn’t a big deal, only four bolts.

The controller for 1981 MY is behind the drivers kick panel which would result is a lot less wiring and work IMO.



Once you have the above out of the way you can easily see the controller. Unplug the connector from the controller and notice the white/black wire (12v to controller) and the blue/yellow wire (power from controller to #1 relay).

You’ll have to cut these two wires (make sure your battery is disconnected and the key is in the off position for good measure).



With the wires cut you can split the sheathing back away from the end in preparation for attaching connectors and soldering. I used crimp connectors without the plastic covers and then soldered the connectors and used heat shrink tubing to cover all exposed parts.



I used male spade connectors at the plug side and a male / female (dual) connector at the harness side. This way I would be able to attach my manual wires with an additional female connector.



Once I had the connections established at the controller, I removed an existing switch that had been used by the PO to operated a now defunct GP controller system. I tested this switch to make sure that it was still operational. Had it not been usable I had another push button switch ready to take its place. Since I already had a ¾” round hole in the dash I elected to get a replacement switch that would utilize the same opening.



Next I built my two wire harness and fed it across the dash, behind the radio and over to the passenger kick panel area where there were some wire straps that I could neatly tuck my two wire harness into. From there it goes down and under the carpet alongside the main body harness that runs next to the GP controller.





Next I soldered on the two remaining female spade connectors, heat shrinked them and attached them to the GP harness. I taped the two connections for good measure.




Back on the driver side the only thing left to do is to solder two loop connectors (or whatever connector your switch needs) and (re)install the switch into the lower dashboard.




When this is all complete you can reconnect your battery and give it a test. Because it’s been warm here the GP system doesn’t operate for very long so when the #1 relay kicked off (audible thunk) I pushed the button in and it supplied power to the #1 relay again, making another thunk.

Once you’ve established that your #1 relay operates by pressing the button or flipping whatever switch you’ve selected, your done and ready to clean up!

Hope this helps some folks take the plunge on this needed mod.

steve a

[goglio704]

Nice work, both on the Mod and the informative post. I did something similar which fools the GP controller into thinking the engine is cranking. This forces the reduced voltage relay to engage. If I'm reading you right, your mod forces the full voltage relay to engage?

BTW, it's good to see you back.

[83_maxima]

Very nice post (and idea) Steve! Nice to have you posting again!

I may go ahead and do this too, seeing as how I am experiencing the warm start problems now - as my GP system is funtioning properly again. I am noticing it an hour, up to two, after I shut it off. I let the #1 relay "thunk" off, then turn the key and it has to spin quite a few revolutions to fire up.

I even found the perfect momentary micro switch for this last week - sh-weet!

[glenlloyd]

If I'm reading you right, your mod forces the full voltage relay to engage?

You're correct, I'm forcing full voltage because what I've experienced in the past is a problem with short pre-glow cycle on cold starts.

Now as I said in the post, that may have been due to bad readings from the water temp sensor because of bad bullet connectors, but I can't say for sure, so just in case I hadn't solved the problem with the connectors I wanted to make sure that I had the option of additional pre-glow in case I needed it. My relay has always cut power to the glow plugs at about 8 seconds, and since mine is the early system (pre 12/81) I always thought it should glow longer.

Good to be back and posting again!

steve a

[LD28 Owner]

A caution on overriding the controller: I'm not sure about this, but it appears on some parts sites that some 1981 910's with "non-controller" systems used 11 volt glow plugs while later 910's with "controller" systems used 7 to 9 volt glow plugs.

If one loads these lower voltage glow plugs with a full 12 volts, the glow plugs will fry quickly -- I've experienced this problem on my 6.9 Ford F-250 when I replaced bad glow plugs without replacing a bad controller and I very quickly had yet another set of shot glow plugs. Since that experience, I've replaced the controller whenever I've replaced the glow plugs (about every 10 years).

I've been looking into this glow plug voltage issue since it appear that some industrial/marine LD28's came with controllers and others do not. Both 11 volt and 7-9 volt glow plugs come up as the "proper" ones to use???

The marine engines that appear not to have controllers have a key switch that is operated in a preheat position for 10 - 15 seconds and is then turned to the start position.

[glenlloyd]

The way this setup works the plugs get no more voltage then would normally be applied if the controller were handling the operation. All I'm doing is activating the relay manually, everything else is the same.

Now I'm no expert on glow plugs, but my understanding of the voltage rating is that it doesn't necessarily mean that it's the amount of voltage applied to the plug. Take for instance in our glow plug cross-ref, where several plugs that work for the same year vehicle have different voltage ratings. Others may be able to convey this more clearly.

At any length, this modification shouldn't be a problem. It only activates the mechanism that supplies the voltage, it doesn't supply any voltage on its own.

If one were to have a 810 / 910 without a controller then obviously this modification wouldn't work, then again I've never heard of the controllerless 810/910 before either. That doesn't mean that it isn't out there. My car has the earlier of the two systems that I'm aware of, it was built before 12/'81

thanks for the comments

steve a

[asavage]

Great job, Steve! I esp. like the pics.

The IDI Ford (IH) 6.9l and early 7.3l have a balky and somewhat failure-prone GPC. The same GPC was used on the GM 6.2l. I've owned one of each, and both have crapped the GPC, the GM twice in seven years.

On the Ford, it tends to wipe out all the GPs. On the 6.2l, I never had to change them, though they would run continuously.

I do not know the pain threshold of the Maxima's GPs, but I do assume that somewhere over fifteen seconds is getting there. The OEM eight to ten seconds does not seem like enough time on my '82.

The '83 I just sold starts up cold better than my '82, and the '83 has 90k more miles on it! It cold glows about eight seconds. But I'm running B99 (which definitely is harder to start in my '82; I really notice when I travel out of state and have to fill with petrodiesel: starts are easier); the '83 is running PD with cetane booster. Not apples-to-apples.

[glenlloyd]

Very nice post (and idea) Steve! Nice to have you posting again!

I may go ahead and do this too, seeing as how I am experiencing the warm start problems now - as my GP system is funtioning properly again. I am noticing it an hour, up to two, after I shut it off. I let the #1 relay "thunk" off, then turn the key and it has to spin quite a few revolutions to fire up.

I even found the perfect momentary micro switch for this last week - sh-weet!

Thanks Ben, glad you found the post useful. I will admit, the switch that was installed was a bit antiquated, and as Al would put it kind of looks like the "door bell", but since the hole was there and the switch was working I elected to reuse it. If it fails I'll be replacing it with something more fashionable...and less spring tension...man that thing is hard to push in!!

steve a

[LD28 Owner]

Steve,
I read Al's last post and then re-read mine and I think Al made my point better than I did -- if you give the glow plugs full voltage for too long, they will fry (I think that is exactly what two bad Ford (IH) 6.9 controllers did to my 16 dead glow plugs over the last 15 years).

I was reading my "new" '83 FSM this AM and noticed that the Auto Glow control unit in "pre-glow" (full voltage) gives the plugs 4-12 seconds.

I also looked at my LD20/LD28 Industrial Service Manual and noted that a Type I Glow Controller in "pre-glow" mode gives the plugs 8V for 12 seconds and 10.5V for 6 seconds if coolant temp is below 122 F. The specs for "after-glow" (with the dropping resistor in the circuit) is 31 seconds if coolant is below -13 F, 11 seconds at 68 F, and 5 seconds between 86 and 122 F.

An industrial Type II controller (one w/o "after-glow") at 32 F delivers 10V for 16 seconds followed by 11V for 12 seconds. Between 32 and 122F, the Type II controller delivers 11V for 8 seconds.

All this seems to confirm Al's call that 15 seconds of full voltage may be pushing one's luck with the glow plugs (unless, of course, the coolant temp is below -13F when, I suspect you'd have difficulting counting to 15 anyhow while you are chattering in the cold).

[glenlloyd]

I'm not saying that too much voltage for too long a time isn't an issue here, that's not the case. What I am saying is that aside from buying a new third-party controller and doing a complete overhaul of the OE system this is the best way to deal with what Al also mentions; too short pre-glow cycling.

I don't plan on running this for any more than five seconds at a time. And that's only if the controller continues to full cycle at about eight seconds, and this only applies to cold weather operation.

I'm not trying to be argumentative, but one could claim that any manual control could potentially do harm to the plugs. All I've shown here is that there is a way to use the OE system to provide the manual control without having to invest in anything more than a little time, wiring and a switch. I think anyone in this forum would agree that any manual control would need to be used with restraint.

But, the fact that we discuss often the problems with the OE system and its failings suggests that in this case we cannot rely on it. I know personally in the past I have been unable to rely on the OE system and because of this modification I don't have to anymore.

Again, I thank you for commenting, it's only with discussion that we work through issues relevant to the forum

steve a

[asavage]

The early 720 (SD22) GPs seem to be indestructible, if one poster's claim is believed. He had a toggle switch for his GPs and left them on for something like an hour drive. They still worked the next day.

I don't think I'd try that, myself.

Because my '82 is an AT-equipped model, I am using a trick that Matt found: the GP system runs the GPs in afterglow mode while cranking. I have a 17 mi. drive followed by a 35 minutes stop every morning, and when I have to restart, on PD I have to crank maybe five seconds, but on BD I have to crank much longer. The GPs do not seem to get any pre-glow, but of course do afterglow during the cranking.

I am now putting the PRNDL into "D", then holding the key in the START position for a count of fifteen. Release the key to ON, move PRNDL to "N", crank. It always fires up in under two seconds.

The manual button as Steve has wired it would let me shorten that time to maybe a four second glow (at full voltage) and then crank. So I'd save eleven seconds every morning.

Additionally, we are now into frost weather here, and I'd like to avoid the double-cycle that I'm now doing for starts -- glow until the relay drops out, then cycle the key and get a few more seconds on the second cycle. I never get much time the second time around, and it comes up shakily and smoky. A manual button would be helpful.

[glenlloyd]

I am now putting the PRNDL into "D", then holding the key in the START position for a count of fifteen. Release the key to ON, move PRNDL to "N", crank. It always fires up in under two seconds.

That's an option that I hadn't really considered, mostly because I've been somewhat fixated on the pre-glow inadequacies.

Additionally, we are now into frost weather here, and I'd like to avoid the double-cycle that I'm now doing for starts -- glow until the relay drops out, then cycle the key and get a few more seconds on the second cycle. I never get much time the second time around, and it comes up shakily and smoky. A manual button would be helpful.

This is exactly what I experienced. When I would do a second cycle I wouldn't get enough extra pre-glow to really assist with the starting, and when it started it would be shaky and smokey.

That said, the conversation above about glow plugs types and voltages brings up what I think is an important point. Mixing of plugs of different voltage ratings is probably not a good thing. I know most here replace the plugs as a set, there are probably cases where one plug gets replaced and if it is a different brand it might have a different voltage rating.

Additionally, the use of the manual override again should be done with caution. When using the manual override switch you'll have to feel out the proper amount of additional glow based on your experience using it.

steve a

[glenlloyd]

Al, and or Matt
Do you think the afterglow technique for AT cars will be sufficient if the temps outside are 20F or less?

Additionally, I did notice a change this morning in the controller timing. I assume because I replaced the bullet connectors at the water temp sensor the controller might actually bet getting good information from the sensor. That said, it was 46F and sunny, the controller only maintained operation of the relay for six seconds (hard to count with chime ringing and I didn't have a watch with second hand).

steve a

[goglio704]

I think forcing the afterglow is most useful for the warm restart range of temperatures. It would be better than nothing for a cold start, but a lot of valuable juice would be lost to the dropping resistor. When I did my mod I was trying to do something which would be useful, but completely safe. I think you could run the plugs for a very long time on afterglow without hurting them. Full voltage will require restraint from the driver(s). If you fare OK this winter with the full voltage approach, I'll likely change mine (Mom's daily driver) to be like yours. Consider yourself the guinea pig.

[Carimbo]

I did a similar yet different mod to mine about 1-1/2 years ago-- appears to be working fine still. This thread. Wired a switch in series into one of the temp sensor leads next to the connector at the GPC, same location as glenlloyd photo above. Esentially the same topography as glenlloyd's. Have since upgraded the simple toggle switch to a momentary off switch (cannibalized from a junk refrigerator; the door light switch. Fits nicely, easy to press, same location as glenlloyd shows above, next to coin tray).

Depressing the switch cuts the voltage from the temp sensor signal, tricking the GPC into thinking the engine is cold cold. I press the MO switch just prior to turning the key to run position, hold 2-3 seconds, turn key to start position, release the button. Have not yet tested how long the GPC would keep the GPs lit if you left the switch on; I never keep the MO switch depressed.

Works well, apparently no ill effects on either the GPC, relays, or GPs yet (over 1-1/2 yrs), has had a beneficial effect on the starter and embarrassment factor (no more crank crank crank crank crank POOF everyone lost in a dense cloud of white smoke).

Can we agree the base problem is caused by the GPC's interpretation of the temp sensor voltage is not properly tuned to what the engine needs in the way of GP operation in the middle temps (say, 100-140 deg. F.)?

Some have mentioned inserting a resistor in series w/ the temp sensor signal but if the EGR also uses the temp sensor signal how would it be affected?