My GPR will not turn on when I start my truck when cold. My mechanic hooked up AE and the coolant temp sensor was reading 270 when cold. He replaced both CTS and oil temp sensor along with new connectors. He was able to get everything to spec both warm and cold, GPR cycling accordingly. The next day, I have the same issue so I have to either jump the GPR or have the truck plugged in.

Is there anything I can inspect, test??

Also, I replaced injectors this summer with casserly stages 2's and at that time I replaced all glow plugs, harnesses and GPR. Now I have 2 gp's out on each side. Harnesses check out fine. What could have caused this?

 

You sure your GPR is working? How have you tested it?

 

That would be a normal value for a truck with an automatic transmission. The 1999 models will have a coolant temp value that will increase from 50-300 degrees and then cycle over again and again.

On automatic transmission trucks, the engine coolant sensor is not monitored by the PCM so the value reported by AE is useless.

Just an FYI...

 

The GPR will still work if I jump the terminals. It will kick on and cycle if I attempt to crank it 2 times when cold

 

Because you can jump the terminals does not mean that your GPR is good. You need to test it with a volt meter by turning the key to ON and see what the volts reads on the GP side of the relay. Even if you hear it click does not mean that it is working.

 

I'm not following. Which four are "out" and how did you determine this?

 

How about you do EVERYONE a favor and get a new GPR. They are cheap, and often need replacing anyway. It is very possible that yours is bad, and is not throwing when energized. All bridging the terminals does it do the work of the GPR for it.

 

Replaced GPR with one from international. Worked fine for 4 days. Went to start my truck this morning, and nothing. Tried a few times today and it would not turn on

 

TTT

Still having GPR/GP issues.

Seems like the gpr will only turn on when the truck is plugged in, and outside temp is 32 or warmer. Noticed this week it will not turn on even with the truck plugged in. Assuming because it has been in the well below 0 degrees(like 2-10 degrees F) this may be something to do with air temp/oil temp???

After the truck is started, the gpr will turn on. I am still thinking this is not the GPR itself. And I just installed a new oil temp sensor 3 weeks ago and AE showed it reading dead on.

 

All i can offer on this one is a bump

 

Quote from my Ford manual,
"The 7.3L diesel engine uses a glow plug system that preheats air in the combustion chamber to improve cold engine starting.

The system consists of:
glow plugs (12A342).
glow plug relay (12A343).
glow plug module (if equipped).
powertrain control module (PCM) (12A650).
engine oil temperature (EOT) sensor.
barometric pressure sensor (BARO sensor) (12A644).

The glow plug system is electronically controlled by the PCM. If the temperature is below 55°C (131°F) the PCM will energize the glow plugs immediately after the key is placed in the ON position. Then, depending on the readings from the engine oil temperature (EOT) sensor and the barometric pressure (BARO) sensor, the PCM determines how long the glow plugs will be on"


Using the block heater will raise the EOT. If it is still below 131*, the GPR should still activate.
You may want to look into your Barometric Pressure reading. I'm not sure how much altitude plays in determining glow plug timing, but could be a factor if not read correctly by the PCM.

 

How are you determining that the GPR is not "turning on"? Do you have a GPR LED hooked up?

 

Have you checked the battery voltage while cranking, If the voltage falls below 10.5 volts the PCM will not allow it to start. Just something to check.

 

I do have a GPR led.

What confuses me is that it's acting the exact opposite of what it should( eot cold, doesn't turn on. Eot somewhat warmer, it will turn on)

FYI. I run 7000 15-40.

 

Mitt want to post in your local chapter to see if someone with AE and knows what there looking at can help you out. This all seems fishy to me. Its got to be a relay or sensor or some kind. And if you really got two glows plugs out its not going to start very well at all. So two on both sides, its hard to believe it will start at all in the cold of MN. Please keep us posted, I'm just trying to post what I have learned over the years on here so please don't take this the wrong way.