Hey guys I noticed the other day if my glow plugs are on for more than like 10 seconds the truck won't start. Is this normal? It's about 70 degrees here this week. Any suggestions or thoughts?

 

That isn't really much to go on, but how old are your batteries? What happens if you just get in and turn the key to start without waiting for the WTS light, does it start?

 

Yes. It will start no problem even if I wait for the light to go out. But once it's off and I wait like 10 seconds or so it will just crank and crank but will not fire. Then I shut it off and turn the key don't wait and it fires right up.

 

Well, that is odd, isn't it. I'll think about what it could be, but right now I've got nothing.

 

Well I appreciate the effort man. I mean it really isn't a major problem but it would be nice to figure out lol

 

Do you have a traditional glow plug relay or a glow plug control module like the California trucks and the Excursions do?

 

As far as I know it's just a traditional. How would I tell otherwise?

 

If you have two identical relays under the hood next to each other it's traditional

 

Maybe the fuel pump is timing out and not restarting. Can you hear your fuel pump on the rail under your butt?

 

Rich, so once fuel pressure is at optimum, does that trigger pump shut-off or is it a timing function?

It would make more logical sense for the pump to be controlled by the PCM input from the fuel pressure sensor and a timeout feature. If that sensor is faulty or slow from plugging up or just beginning to fail, the pump could be erratic during start-up.

Once the engine is running, the demand for fuel would keep the pump running because the PCM timing cycle would not initiate due to the engines need for fuel. I believe that the pressure sensor is more likely to fail than the timer in the PCM. The fuel pump relay cannot be the problem, because Nick's description shows that the pump's operation is very predictable.
Larry

 

There is no fuel pressure sensor. The pump runs for 20 seconds when the ignition is turned on. If the engine is started after that time, the pump should restart when the engine is cranked. If the fuel system is in good order, there should still be residual pressure in the fuel filter housing for a couple seconds after the pump stops running. IIRC, as a safety feature, the FPR has a small orifice in it to bleed off pressure slowly after the pump stops to make it harder to remove the filter cap while the housing is still pressurized.

If the fuel pump circuit is commanded on by the PCM, and power is not detected, you should get a P0231 DTC. A quick test would be to turn the key on and listen for the fuel pump to run for 20 seconds. After it times out, quickly bump the key to start without turning it off first. The fuel pump should restart and time out again after another 20 seconds.

 

So, in the logic of this fuel pump command, what is necessary to make it run continuous, just the crank sensor signal?

 

It runs by default at key on and any time RPM is detected, so it seems the camshaft position sensor signal is in play. It would be kind of interesting for the next person who has a bad cam sensor to try the starter bump and see if the pump restarts after it times out.

 

Its reaching and would require a lot more thought & schematic chasing than I have right now but what about the collapsing field of the GPR causing either IDM or PCM relay (because of a bad diode) to quit working. It would cost nothing to check as you could swap one with the blower relay and keep swapping until you know that they have all been through each hole. Of course, you could check the diode in the relay with VOM as well.

 

But with a little more thought, the wts light is just an idiot light and does not really signal the GPR being done with its job.