The glow plug light indicator is staying on after a start. 1. Will this damage the glow plugs? 2. What do I need to look for to fix the problem? 3. Is the indicator a trouble light showing that one or more are out?
Anything else you can tell me would be appreciated.

 

When you say the glow plug indicator light do you mean the WTS light? Or you do have a GPR LED?

 

Does it go off after time? You can test the GPR to see if it is staying energized also.

 

OK Guys,
I don't know what you are talking about. The indicator is the one that you wait for before cranking the engine over on a cold day. Is it the GPR LED or the WTS? I can't tell you which one it is. Which ever one it is stays on while running. It never used to. After the engine started it went off.

 

The WTS light isn't hooked to your GP's, it gets a signal from the PCM, so more than likely your GP's aren't on. Wasn't there a TSB for the WTS light coming on when the engine's running?

 

Where in Texas are you Scott?

The WTS light is the "Wait to Start" light on the 99 - 01 trucks, and the squiggly line thing on the 02-03 trucks that lights up on the instrument panel when you first turn the key on. That light actually has nothing at all to do with the glow plugs being on or off, it's just a reminder signal from the truck computer.

Odds are, the glow plugs are not even coming on right now with the weather we're having around here, so the glow plugs should be safe. However, the dash light can be a signal of some wiring issues that may affect how the truck runs (or stalls) so you will want to get to the bottom of this.

First off, does the truck run any different when the light stays on?

 

The GPR Led is a mod that we do to tell you when and how long the glow plugs are actually on versus the light on the dash that is a predetermined amount tof time via the PCM.

I would test the GPR for power after the truck has been running a bit to see if it has actually shut off. If it has not shut off remove one of the small wires on the GPR and retest for power.

If you have power then the relay is stuck closed.
If no power then the PCM is giving it the signal that it is to cold and to stay energized.

 

Here is a screenshot of what the glow plugs are actually doing and what the "wait to start" light is doing.



As you can see, the glow plugs are ON for a lot longer than the light is on.
The WTS light time is based on EOT (engine oil temp) and battery voltage.
The glow plug on time is based on EOT.

Thankfully, both of these are changeable. I usually change the glow plug ON time to a maximum of 40 seconds instead of 120. Then I keep the WTS light OFF at anything above 50 degrees F so it's a turn the key and go affair without having to feel like I have to wait.

 

The glow plugs come on for 30 seconds with an EOT below 122 deg F?

That doesn't sound right. You shouldn't need any glow plugs at those temps. Does IAT not have anything to do with this? I guess I need to do a little research. If my glow plugs come on that long every time EOT is below 122, I probably have some burned up ones by now. Time to ohm the connectors before it gets cold outside.

 

We have different ideas on the cold though.

 

You're right Jim. I meant before the temps drop below 80

 

If it suits you better, the TDE1 programming for OBS automatics only runs the glow plugs for 30 seconds tops....and the time goes down sharply from there.

The glow plug strategy in the Super Duty trucks is due to emission regulations.

 

Well now. I didn't expect to start such a thread. I appreciate everyone's input. I also lied about the amount of time the WTS was on. Not intentionally. The WTS light comes on for a few seconds and then goes off to indicate that the engine is ready to start. Well, it quit going off. Now with the information y'all have provided, I can say that my problem is coming from the PCM. If that is the one responsible for turning the WTS on and off then I have to figure out why it leaves the light on.

Apparently the truck runs fine with the light just glowing annoyingly. I am not actually driving it, my daughter is. There is somewhat of a communication problem when talking to someone who doesn't want to know how things work, they just want a new truck. This could also be related to another problem. Intermittently, the truck blows a fuse that takes out something. The truck will run, start, drive, but only at idle and without gauges. I think I asked about this in a previous thread. Anyway it is something that requires my running the circuit to see where a short might be happening. I am beginning to suspect it is in the steering column. One other issue that she told me about was that the fuel gauge and the Miles To Empty indicator are not in sinc. Maybe that is connected to the problem. It sounds like the computer needs to be rebooted.

BTW there are no codes being thrown.

I live in Lake Jackson, South of Houston near the Gulf. My daughter is in College Station at A&M. I work near Livingston which is in East Texas. So it is difficult to make a solid diagnosis on a problem with a vehicle 100 miles away. And it is so hot, there is no need for a glow plug. I'll bet the EOT is about 80 in the morning and without running it is probably around 110 in the afternoon.