'96 F-250 purchased new, Aug. '96
255,XXX original except other day swapped out 3 bad glow plugs with good used ones. And of course 140V IDM etc. Never change or re flash PCM.

NEW GPR, no change.

All top wiring harness changed out in Feb. '10 with factory replacement. No burned pins at gasket, amp draw down consistent with good glow plugs. When working.

There has been a problem for a few years. You go to start the truck and in the warmer months, warm engine, turn key-start and then realize you have no power at the radio. If you turn the key and wait, after a few seconds the radio comes on, then you start.

Never noticed it affecting glow plugs before but last week was a first hard start with good relay. Swapped out 3 defective plugs with good used ones from my spare stuff.

Now, hard starts again, and sometimes with an assistant cycling key switch, "WTS" light comes on (always), cycles off but the GPR does not cycle on. There seems to be no pattern. Sometimes works, sometimes no.

Assistant could not keep up with whether radio was on or not. I am just not sure where to even start looking. This morning, last several days, 3 degrees.

Where would ya'll start looking? Sorry for the long post but trying to keep from having endless questions back and forth.

 

Sounds like something electrical is loose. Check all fuses and grounds. Other then that someone will come along.

 

I don't know much about electrical issues, but would putting only a few new glow plugs in while the rest are the older ones cause an issue? I have not heard of somebody only replacing a few at one time, generally because they get used, in theory, evenly. So if 3 are good but one or more of the older ones aren't, that could be an issue. Not sure if that would cause an intermittent electrical as well, but these powerstrokes have some weird electoral issues sometimes.

 

Normal with some aftermarket radios, nothing to do with GPR. Turn the key to start and the radio is booting up but starting immediately it has not fully powered up yet. Then when cranking the radio looses power and basically shuts OFF. I've never seen it on factory radios but have seen it with aftermarket radios. I just wait for a few seconds until the radio is fully powered up then crank. When cranking the radio looses power but reboots when key it turned back to run position.

Use a volt meter or trouble light on the two small wires on the GPR. A volt meter will show battery voltage across the two wires and trouble light will illuminate when the PCM commands the GPR to turn ON. Hope that gets you going in the right direction.

 

@Hussler, I can tell when the GPR pulls in with either a test light or DVM but the problem is it sends the signal intermittently. So, there seems to me some circuit only closing intermittently. I will study on the radio issue with this in mind. Perhaps a relay?

@Rad, All the other glow plugs tested good so I went with the spares. I hope to change them all later. I don't see how that would cause an intermittent signal at the GPR. I will ohm them out again.

Thanks!

 

The glow plug relay can stay on for up top 2 minutes after the WTS light goes out so don't let the fact that the signal from the PCM stays on confuse you. Cycling the key won't do you any good, as the PCM should be holding the glow plug relay in (on) regardless, so long as it is cold enough to need it. The amount of time the PCM wants to see the glow plugs on varies with the engine temperature as sensed by the EOT (Engine Oil Temperature) Sensor. If the EOT is bad the PCM won't know what the temperature is. Do you have a scanner or Torque app or something that you can use to see if the EOT sensor is working?

 

I have a Autoenginuity. I do not know if I can test the EOT but I am pretty sure I can look up live feed and see what it shows. I'm not sure I articulated the problem. The WTS light always comes on, however, not every cold start will it actually send the signal to energize and pull in the GPR. I have no way inside the truck to know that, only outside with a tester.

No glow plugs hot, no start.

 

Check the EOT and see what it says. An intermittent connection or bad EOT sensor could do this.

If that's not the issue, I think glow plug relay and wiring is the next test.

Can you not tell the GP's are running by the position of the needle on the volt gauge? I know on my truck, even with new batteries, it pulls WAY over to the left when the GP's are on, regardless of whether the engine is running or not.

 

^^^^^ That, plus AE can tell you when the GP relay is energized (well, when the PCM THINKS it is).

 

OK, went to start up today, key on, WTS light on, cycle off and waited a few more seconds. No start, un burnt diesel smoke all around. Did not think to watch gauge on dash. Waited, key on, WTS light and watched gauge and it swung way to left of center. WTS goes out, start like a brand new one. .???????

It's a real shame a powerstroke has be be left of center to start, don't seem right somehow?

Anyway, the first time I tried it definitely acted like bad GPR. This one is brand new maybe two,weeks old. Again, it is an intermittent problem.

 

What brand of Gpr did you put in?

Red

 

And what brand of GPs are installed?

 

This one is Durlast from Autozone. Perhaps not the best quality but they simply hand me a new one when they go bad. When you are running 4-5 trucks stuff like that helps. This particular problem started before swapping the GPR. I just changed after switching the bad glow plugs. I had planned to swap them out new but only changed the defective ones this time.

New glow plugs will not help if the GPR does not pull in, so I am stumped.

 

How are you determining that the GP relay is not closing?

 

All original from Ford. (?) I purchased this truck new and first time they have been fooled with. The others came out of my '95 when I changed the injectors and glow plugs at 125,XXX. I bought that used and assume they were factory.

Changed 3 from the '95. All others good.